diff --git a/.autotest b/.autotest
index 1236395..0857ef3 100644
--- a/.autotest
+++ b/.autotest
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rubygems'
 
-# vim: syntax=ruby
+# vim: ft=ruby
diff --git a/.fasterer.yml b/.fasterer.yml
new file mode 100644
index 0000000..821e02d
--- /dev/null
+++ b/.fasterer.yml
@@ -0,0 +1,4 @@
+exclude_paths:
+  - lib/diff/lcs.rb # sort_vs_sort_by on priority_compare
+  - Rakefile # each_with_index vs while
+  - spec/spec_helper.rb
diff --git a/.hoerc b/.hoerc
index 7922c87..1d8fb44 100644
--- a/.hoerc
+++ b/.hoerc
@@ -1,30 +1,11 @@
 ---
 exclude: !ruby/regexp '/
   \.(?:
-      tmp |
-      swp
-    )$
+    tmp |
+    swp
+  )$
   |
   \.(?:
-      autotest |
-      byebug_history |
-      gemtest |
-      gitignore |
-      hoerc |
-      minitest.rb |
-      simplecov-prelude.rb)$
-  |
-  \.(?:
-      coveralls |
-      pullreview |
-      travis |
-      appveyor
-     )\.yml$
-  |
-  (?i:TAGS)$
-  |
-  \.(?:
-      DS_Store|
       bundle|
       git|
       hg|
@@ -35,11 +16,36 @@ exclude: !ruby/regexp '/
   |
   [gG]emfile(?:\.lock)?
   |
-  support\/
+  (?:
+    support |
+    research
+  )\/
   |
-  research\/
+  \.(?:
+    appveyor |
+    coveralls |
+    fasterer |
+    pullreview |
+    rubocop.* |
+    travis |
+    unused
+    )\.yml$
+  |
+  (?i:TAGS)$
+  |
+  \.(?:
+      DS_Store |
+      autotest |
+      byebug_history |
+      gemtest |
+      gitattributes |
+      gitignore |
+      hoerc |
+      minitest.rb |
+      simplecov-prelude.rb
+  )$
   |
   \.gemspec$
   |
-  Vagrantfile
+  ^Vagrantfile$
   /x'
diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..de2cbc6
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,120 @@
+---
+AllCops:
+  DisplayCopNames: true
+  DisplayStyleGuide: true
+  ExtraDetails: true
+  Exclude:
+    - diff-lcs.gemspec
+    - research/**/*
+
+Layout/AlignParameters:
+  EnforcedStyle: with_fixed_indentation
+
+Layout/DotPosition:
+  EnforcedStyle: trailing
+
+Layout/ExtraSpacing:
+  Exclude:
+   - spec/**/*
+
+Layout/MultilineMethodCallIndentation:
+  EnforcedStyle: indented
+
+Metrics/LineLength:
+  Max: 110
+
+Naming/FileName:
+  Exclude:
+    - lib/diff-lcs.rb
+
+Naming/MemoizedInstanceVariableName:
+  Exclude: []
+
+Naming/UncommunicativeMethodParamName:
+  Exclude:
+    - lib/diff/lcs/internals.rb
+    - spec/spec_helper.rb
+
+Naming/VariableNumber:
+  Exclude: []
+
+Performance/Caller:
+  Exclude: []
+
+Security/MarshalLoad:
+  Exclude: []
+
+Security/YAMLLoad:
+  Exclude: []
+
+Style/BlockDelimiters:
+  EnforcedStyle: semantic
+  ProceduralMethods:
+    - trace
+    - assert_raises
+    - spec
+  FunctionalMethods:
+    - let
+    - subject
+    - add_discovery
+    - require_do
+    - it
+  IgnoredMethods:
+    - expect
+
+Style/Documentation:
+  Exclude:
+    - lib/diff/lcs/array.rb
+    - lib/diff/lcs/string.rb
+    - spec/spec_helper.rb
+
+# Until there is a hard drop of Ruby 1.8
+Style/HashSyntax:
+  Enabled: false
+
+Style/PercentLiteralDelimiters:
+  PreferredDelimiters:
+    default: ()
+    '%i': '()'
+    '%I': '()'
+    '%r': '{}'
+    '%w': '()'
+    '%W': '()'
+
+Style/RescueModifier:
+  Enabled: false
+
+Style/RescueStandardError:
+  EnforcedStyle: implicit
+
+Style/SignalException:
+  EnforcedStyle: semantic
+
+Layout/IndentHeredoc: { Enabled: false }
+Metrics/AbcSize: { Enabled: false }
+Metrics/BlockLength: { Enabled: false }
+Metrics/BlockNesting: { Enabled: false }
+Metrics/ClassLength: { Enabled: false }
+Metrics/CyclomaticComplexity: { Enabled: false }
+Metrics/MethodLength: { Enabled: false}
+Metrics/ModuleLength: { Enabled: false}
+Metrics/PerceivedComplexity: { Enabled: false }
+Style/AccessModifierDeclarations: { Enabled: false }
+Style/AndOr: { Enabled: false }
+Style/AsciiComments: { Enabled: false }
+Style/BarePercentLiterals: { Enabled: false }
+Style/ClassAndModuleChildren: { Enabled: false }
+Style/ClassCheck: { Enabled: false }
+Style/CommentedKeyword: { Enabled: false }
+Style/DoubleNegation: { Enabled: false }
+Style/EmptyMethod: { Enabled: false }
+Style/ExpandPathArguments: { Enabled: false }
+Style/FormatString: { Enabled: false }
+Style/FormatStringToken: { Enabled: false }
+Style/MultilineBlockChain: { Enabled: false }
+Style/ParallelAssignment: { Enabled: false }
+Style/SafeNavigation: { Enabled: false }
+Style/SpecialGlobalVars: { Enabled: false }
+Style/SymbolArray: { Enabled: false }
+Style/SymbolProc: { Enabled: false }
+Style/WordArray: { Enabled: false }
diff --git a/.travis.yml b/.travis.yml
index 03e800e..deafbb8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,22 +1,20 @@
 ---
 language: ruby
 rvm:
-  - 2.5.0
-  - 2.4.3
-  - 2.3.6
-  - 2.2.9
-  - 2.1.10
-  - 2.0.0
-  - 1.9.3
-  - 1.8.7
-  - ree
+  - 2.6.0
+  - 2.5.3
+  - 2.4.5
+  - 2.3.8
+  - jruby-9.2.5.0
+  - jruby-9.1.17.0
+  - jruby-9.0.5.0
+  - jruby-head
   - ruby-head
-  - jruby-19mode
 matrix:
   allow_failures:
+    - rvm: jruby-head
     - rvm: ruby-head
-    - rvm: 1.8.7
-    - rvm: ree
+  fast_finish: true
 gemfile:
   - Gemfile
 before_script:
@@ -24,10 +22,4 @@ before_script:
 script: bundle exec rake travis
 after_script:
   - bundle exec rake travis:after -t
-notifications:
-  email:
-    recipients:
-      - austin@rubyforge.org
-    on_success: change
-    on_failure: always
 sudo: false
diff --git a/Gemfile b/Gemfile
index b5a72e4..ccc6276 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,20 +1,20 @@
-# -*- ruby -*-
+# frozen_string_literal: true
 
 # NOTE: This file is present to keep Travis CI happy. Edits to it will not
 # be accepted.
 
-source "https://rubygems.org/"
+source 'https://rubygems.org/'
 
 if RUBY_VERSION < '1.9'
-  gem 'rdoc', '< 4'
   gem 'rake', '< 11'
+  gem 'rdoc', '< 4'
 elsif RUBY_VERSION >= '2.0'
   if RUBY_ENGINE == 'ruby'
-    gem 'simplecov', '~> 0.7'
     gem 'coveralls', '~> 0.7'
+    gem 'simplecov', '~> 0.7'
   end
 end
 
 gemspec
 
-# vim: syntax=ruby
+# vim: ft=ruby
diff --git a/History.md b/History.md
index 0db6448..36e976e 100644
--- a/History.md
+++ b/History.md
@@ -1,3 +1,8 @@
+## 1.NEXT / 2019-MM-DD
+
+*   Ruby versions lower than 2.3 are soft-deprecated and will not be run as part
+    of the CI process any longer.
+
 ## 1.3 / 2017-01-18
 
 *   Bugs fixed:
diff --git a/Manifest.txt b/Manifest.txt
index 955bec0..f583076 100644
--- a/Manifest.txt
+++ b/Manifest.txt
@@ -14,6 +14,7 @@ docs/artistic.txt
 lib/diff-lcs.rb
 lib/diff/lcs.rb
 lib/diff/lcs/array.rb
+lib/diff/lcs/backports.rb
 lib/diff/lcs/block.rb
 lib/diff/lcs/callbacks.rb
 lib/diff/lcs/change.rb
diff --git a/Rakefile b/Rakefile
index ab244ac..24edf0c 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'rubygems'
 require 'rspec'
@@ -11,14 +11,14 @@ Hoe.plugin :gemspec2
 Hoe.plugin :git
 Hoe.plugin :travis
 
-spec = Hoe.spec 'diff-lcs' do
+_spec = Hoe.spec 'diff-lcs' do
   developer('Austin Ziegler', 'halostatue@gmail.com')
 
   require_ruby_version '>= 1.8'
 
   self.history_file = 'History.md'
   self.readme_file = 'README.rdoc'
-  self.licenses = [ 'MIT', 'Artistic-2.0', 'GPL-2.0+' ]
+  self.licenses = ['MIT', 'Artistic-2.0', 'GPL-2.0+']
 
   extra_dev_deps << ['hoe-doofus', '~> 1.0']
   extra_dev_deps << ['hoe-gemspec2', '~> 1.1']
diff --git a/autotest/discover.rb b/autotest/discover.rb
index cd6892c..0ac9c8a 100644
--- a/autotest/discover.rb
+++ b/autotest/discover.rb
@@ -1 +1,3 @@
-Autotest.add_discovery { "rspec2" }
+# frozen_string_literal: true
+
+Autotest.add_discovery { 'rspec2' }
diff --git a/bin/htmldiff b/bin/htmldiff
index 1e4efe7..14114a7 100755
--- a/bin/htmldiff
+++ b/bin/htmldiff
@@ -1,4 +1,5 @@
-#!ruby -w
+#! /usr/bin/env ruby -w
+# frozen_string_literal: true
 
 require 'diff/lcs'
 require 'diff/lcs/htmldiff'
@@ -10,8 +11,8 @@ rescue LoadError
 end
 
 if ARGV.size < 2 or ARGV.size > 3
-  $stderr.puts "usage: #{File.basename($0)} old new [output.html]"
-  $stderr.puts "       #{File.basename($0)} old new > output.html"
+  warn "usage: #{File.basename($0)} old new [output.html]"
+  warn "       #{File.basename($0)} old new > output.html"
   exit 127
 end
 
@@ -23,10 +24,12 @@ options = { :title => "diff #{ARGV[0]} #{ARGV[1]}" }
 htmldiff = Diff::LCS::HTMLDiff.new(left, right, options)
 
 if ARGV[2]
-  File.open(ARGV[2], "w") do |f|
+  File.open(ARGV[2], 'w') do |f|
     htmldiff.options[:output] = f
     htmldiff.run
   end
 else
   htmldiff.run
 end
+
+# vim: ft=ruby
diff --git a/bin/ldiff b/bin/ldiff
index a9b876f..f4734f5 100755
--- a/bin/ldiff
+++ b/bin/ldiff
@@ -1,6 +1,9 @@
-#!ruby -w
+#! /usr/bin/env ruby -w
+# frozen_string_literal: true
 
 require 'diff/lcs'
 require 'diff/lcs/ldiff'
 
 exit Diff::LCS::Ldiff.run(ARGV)
+
+# vim: ft=ruby
diff --git a/diff-lcs.gemspec b/diff-lcs.gemspec
index 4c2c516..7407c06 100644
--- a/diff-lcs.gemspec
+++ b/diff-lcs.gemspec
@@ -2,58 +2,58 @@
 # stub: diff-lcs 1.3 ruby lib
 
 Gem::Specification.new do |s|
-  s.name = "diff-lcs"
+  s.name = "diff-lcs".freeze
   s.version = "1.3"
 
-  s.required_rubygems_version = Gem::Requirement.new(">= 0") if s.respond_to? :required_rubygems_version=
-  s.require_paths = ["lib"]
-  s.authors = ["Austin Ziegler"]
-  s.date = "2017-01-18"
-  s.description = "Diff::LCS computes the difference between two Enumerable sequences using the\nMcIlroy-Hunt longest common subsequence (LCS) algorithm. It includes utilities\nto create a simple HTML diff output format and a standard diff-like tool.\n\nThis is release 1.3, providing a tentative fix to a long-standing issue related\nto incorrect detection of a patch direction. Also modernizes the gem\ninfrastructure, testing infrastructure, and provides a warning-free experience\nto Ruby 2.4 users."
-  s.email = ["halostatue@gmail.com"]
-  s.executables = ["htmldiff", "ldiff"]
-  s.extra_rdoc_files = ["Code-of-Conduct.md", "Contributing.md", "History.md", "License.md", "Manifest.txt", "README.rdoc", "docs/COPYING.txt", "docs/artistic.txt"]
-  s.files = [".rspec", "Code-of-Conduct.md", "Contributing.md", "History.md", "License.md", "Manifest.txt", "README.rdoc", "Rakefile", "autotest/discover.rb", "bin/htmldiff", "bin/ldiff", "docs/COPYING.txt", "docs/artistic.txt", "lib/diff-lcs.rb", "lib/diff/lcs.rb", "lib/diff/lcs/array.rb", "lib/diff/lcs/block.rb", "lib/diff/lcs/callbacks.rb", "lib/diff/lcs/change.rb", "lib/diff/lcs/htmldiff.rb", "lib/diff/lcs/hunk.rb", "lib/diff/lcs/internals.rb", "lib/diff/lcs/ldiff.rb", "lib/diff/lcs/string.rb", "spec/change_spec.rb", "spec/diff_spec.rb", "spec/fixtures/ds1.csv", "spec/fixtures/ds2.csv", "spec/hunk_spec.rb", "spec/issues_spec.rb", "spec/lcs_spec.rb", "spec/ldiff_spec.rb", "spec/patch_spec.rb", "spec/sdiff_spec.rb", "spec/spec_helper.rb", "spec/traverse_balanced_spec.rb", "spec/traverse_sequences_spec.rb"]
-  s.homepage = "https://github.com/halostatue/diff-lcs"
-  s.licenses = ["MIT", "Artistic-2.0", "GPL-2.0+"]
-  s.rdoc_options = ["--main", "README.rdoc"]
-  s.required_ruby_version = Gem::Requirement.new(">= 1.8")
-  s.rubygems_version = "2.5.1"
-  s.summary = "Diff::LCS computes the difference between two Enumerable sequences using the McIlroy-Hunt longest common subsequence (LCS) algorithm"
+  s.required_rubygems_version = Gem::Requirement.new(">= 0".freeze) if s.respond_to? :required_rubygems_version=
+  s.require_paths = ["lib".freeze]
+  s.authors = ["Austin Ziegler".freeze]
+  s.date = "2019-01-28"
+  s.description = "Diff::LCS computes the difference between two Enumerable sequences using the\nMcIlroy-Hunt longest common subsequence (LCS) algorithm. It includes utilities\nto create a simple HTML diff output format and a standard diff-like tool.\n\nThis is release 1.3, providing a tentative fix to a long-standing issue related\nto incorrect detection of a patch direction. Also modernizes the gem\ninfrastructure, testing infrastructure, and provides a warning-free experience\nto Ruby 2.4 users.".freeze
+  s.email = ["halostatue@gmail.com".freeze]
+  s.executables = ["htmldiff".freeze, "ldiff".freeze]
+  s.extra_rdoc_files = ["Code-of-Conduct.md".freeze, "Contributing.md".freeze, "History.md".freeze, "License.md".freeze, "Manifest.txt".freeze, "README.rdoc".freeze, "docs/COPYING.txt".freeze, "docs/artistic.txt".freeze]
+  s.files = [".rspec".freeze, "Code-of-Conduct.md".freeze, "Contributing.md".freeze, "History.md".freeze, "License.md".freeze, "Manifest.txt".freeze, "README.rdoc".freeze, "Rakefile".freeze, "autotest/discover.rb".freeze, "bin/htmldiff".freeze, "bin/ldiff".freeze, "docs/COPYING.txt".freeze, "docs/artistic.txt".freeze, "lib/diff-lcs.rb".freeze, "lib/diff/lcs.rb".freeze, "lib/diff/lcs/array.rb".freeze, "lib/diff/lcs/block.rb".freeze, "lib/diff/lcs/callbacks.rb".freeze, "lib/diff/lcs/change.rb".freeze, "lib/diff/lcs/htmldiff.rb".freeze, "lib/diff/lcs/hunk.rb".freeze, "lib/diff/lcs/internals.rb".freeze, "lib/diff/lcs/ldiff.rb".freeze, "lib/diff/lcs/string.rb".freeze, "spec/change_spec.rb".freeze, "spec/diff_spec.rb".freeze, "spec/fixtures/ds1.csv".freeze, "spec/fixtures/ds2.csv".freeze, "spec/hunk_spec.rb".freeze, "spec/issues_spec.rb".freeze, "spec/lcs_spec.rb".freeze, "spec/ldiff_spec.rb".freeze, "spec/patch_spec.rb".freeze, "spec/sdiff_spec.rb".freeze, "spec/spec_helper.rb".freeze, "spec/traverse_balanced_spec.rb".freeze, "spec/traverse_sequences_spec.rb".freeze]
+  s.homepage = "https://github.com/halostatue/diff-lcs".freeze
+  s.licenses = ["MIT".freeze, "Artistic-2.0".freeze, "GPL-2.0+".freeze]
+  s.rdoc_options = ["--main".freeze, "README.rdoc".freeze]
+  s.required_ruby_version = Gem::Requirement.new(">= 1.8".freeze)
+  s.rubygems_version = "2.7.7".freeze
+  s.summary = "Diff::LCS computes the difference between two Enumerable sequences using the McIlroy-Hunt longest common subsequence (LCS) algorithm".freeze
 
   if s.respond_to? :specification_version then
     s.specification_version = 4
 
     if Gem::Version.new(Gem::VERSION) >= Gem::Version.new('1.2.0') then
-      s.add_development_dependency(%q<hoe-doofus>, ["~> 1.0"])
-      s.add_development_dependency(%q<hoe-gemspec2>, ["~> 1.1"])
-      s.add_development_dependency(%q<hoe-git>, ["~> 1.6"])
-      s.add_development_dependency(%q<hoe-rubygems>, ["~> 1.0"])
-      s.add_development_dependency(%q<hoe-travis>, ["~> 1.2"])
-      s.add_development_dependency(%q<rspec>, ["< 4", ">= 2.0"])
-      s.add_development_dependency(%q<rake>, ["< 12", ">= 10.0"])
-      s.add_development_dependency(%q<rdoc>, [">= 0"])
-      s.add_development_dependency(%q<hoe>, ["~> 3.16"])
+      s.add_development_dependency(%q<hoe-doofus>.freeze, ["~> 1.0"])
+      s.add_development_dependency(%q<hoe-gemspec2>.freeze, ["~> 1.1"])
+      s.add_development_dependency(%q<hoe-git>.freeze, ["~> 1.6"])
+      s.add_development_dependency(%q<hoe-rubygems>.freeze, ["~> 1.0"])
+      s.add_development_dependency(%q<hoe-travis>.freeze, ["~> 1.2"])
+      s.add_development_dependency(%q<rspec>.freeze, ["< 4", ">= 2.0"])
+      s.add_development_dependency(%q<rake>.freeze, ["< 12", ">= 10.0"])
+      s.add_development_dependency(%q<rdoc>.freeze, [">= 0"])
+      s.add_development_dependency(%q<hoe>.freeze, ["~> 3.17"])
     else
-      s.add_dependency(%q<hoe-doofus>, ["~> 1.0"])
-      s.add_dependency(%q<hoe-gemspec2>, ["~> 1.1"])
-      s.add_dependency(%q<hoe-git>, ["~> 1.6"])
-      s.add_dependency(%q<hoe-rubygems>, ["~> 1.0"])
-      s.add_dependency(%q<hoe-travis>, ["~> 1.2"])
-      s.add_dependency(%q<rspec>, ["< 4", ">= 2.0"])
-      s.add_dependency(%q<rake>, ["< 12", ">= 10.0"])
-      s.add_dependency(%q<rdoc>, [">= 0"])
-      s.add_dependency(%q<hoe>, ["~> 3.16"])
+      s.add_dependency(%q<hoe-doofus>.freeze, ["~> 1.0"])
+      s.add_dependency(%q<hoe-gemspec2>.freeze, ["~> 1.1"])
+      s.add_dependency(%q<hoe-git>.freeze, ["~> 1.6"])
+      s.add_dependency(%q<hoe-rubygems>.freeze, ["~> 1.0"])
+      s.add_dependency(%q<hoe-travis>.freeze, ["~> 1.2"])
+      s.add_dependency(%q<rspec>.freeze, ["< 4", ">= 2.0"])
+      s.add_dependency(%q<rake>.freeze, ["< 12", ">= 10.0"])
+      s.add_dependency(%q<rdoc>.freeze, [">= 0"])
+      s.add_dependency(%q<hoe>.freeze, ["~> 3.17"])
     end
   else
-    s.add_dependency(%q<hoe-doofus>, ["~> 1.0"])
-    s.add_dependency(%q<hoe-gemspec2>, ["~> 1.1"])
-    s.add_dependency(%q<hoe-git>, ["~> 1.6"])
-    s.add_dependency(%q<hoe-rubygems>, ["~> 1.0"])
-    s.add_dependency(%q<hoe-travis>, ["~> 1.2"])
-    s.add_dependency(%q<rspec>, ["< 4", ">= 2.0"])
-    s.add_dependency(%q<rake>, ["< 12", ">= 10.0"])
-    s.add_dependency(%q<rdoc>, [">= 0"])
-    s.add_dependency(%q<hoe>, ["~> 3.16"])
+    s.add_dependency(%q<hoe-doofus>.freeze, ["~> 1.0"])
+    s.add_dependency(%q<hoe-gemspec2>.freeze, ["~> 1.1"])
+    s.add_dependency(%q<hoe-git>.freeze, ["~> 1.6"])
+    s.add_dependency(%q<hoe-rubygems>.freeze, ["~> 1.0"])
+    s.add_dependency(%q<hoe-travis>.freeze, ["~> 1.2"])
+    s.add_dependency(%q<rspec>.freeze, ["< 4", ">= 2.0"])
+    s.add_dependency(%q<rake>.freeze, ["< 12", ">= 10.0"])
+    s.add_dependency(%q<rdoc>.freeze, [">= 0"])
+    s.add_dependency(%q<hoe>.freeze, ["~> 3.17"])
   end
 end
diff --git a/lib/diff-lcs.rb b/lib/diff-lcs.rb
index 10d6e8a..250392f 100644
--- a/lib/diff-lcs.rb
+++ b/lib/diff-lcs.rb
@@ -1,3 +1,3 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'diff/lcs'
diff --git a/lib/diff/lcs.rb b/lib/diff/lcs.rb
index 34ddf0f..d3a75fd 100644
--- a/lib/diff/lcs.rb
+++ b/lib/diff/lcs.rb
@@ -1,6 +1,7 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
+
+module Diff; end unless defined? Diff # rubocop:disable Style/Documentation
 
-module Diff; end unless defined? Diff
 # == How Diff Works (by Mark-Jason Dominus)
 #
 # I once read an article written by the authors of +diff+; they said that
@@ -55,7 +56,7 @@ module Diff::LCS
 require 'diff/lcs/callbacks'
 require 'diff/lcs/internals'
 
-module Diff::LCS
+module Diff::LCS # rubocop:disable Style/Documentation
   # Returns an Array containing the longest common subsequence(s) between
   # +self+ and +other+. See Diff::LCS#LCS.
   #
@@ -97,7 +98,7 @@ def traverse_balanced(other, callbacks = nil, &block)
   def patch(patchset)
     Diff::LCS.patch(self, patchset)
   end
-  alias_method :unpatch, :patch
+  alias unpatch patch
 
   # Attempts to patch +self+ with the provided +patchset+. A new sequence
   # based on +self+ and the +patchset+ will be created. See Diff::LCS#patch.
@@ -142,16 +143,16 @@ def lcs(seq1, seq2, &block) #:yields seq1[i] for each matched:
     matches = Diff::LCS::Internals.lcs(seq1, seq2)
     ret = []
     string = seq1.kind_of? String
-    matches.each_with_index do |e, i|
-      unless matches[i].nil?
-        v = string ? seq1[i, 1] : seq1[i]
-        v = block[v] if block
-        ret << v
-      end
+    matches.each_with_index do |_e, i|
+      next if matches[i].nil?
+
+      v = string ? seq1[i, 1] : seq1[i]
+      v = block[v] if block
+      ret << v
     end
     ret
   end
-  alias_method :LCS, :lcs
+  alias LCS lcs
 
   # #diff computes the smallest set of additions and deletions necessary to
   # turn the first sequence into the second, and returns a description of
@@ -163,8 +164,7 @@ def lcs(seq1, seq2, &block) #:yields seq1[i] for each matched:
   # initialise it. If the +callbacks+ object (possibly initialised) responds
   # to #finish, it will be called.
   def diff(seq1, seq2, callbacks = nil, &block) # :yields diff changes:
-    diff_traversal(:diff, seq1, seq2, callbacks || Diff::LCS::DiffCallbacks,
-                   &block)
+    diff_traversal(:diff, seq1, seq2, callbacks || Diff::LCS::DiffCallbacks, &block)
   end
 
   # #sdiff computes all necessary components to show two sequences and their
@@ -182,8 +182,7 @@ def diff(seq1, seq2, callbacks = nil, &block) # :yields diff changes:
   # initialise it. If the +callbacks+ object (possibly initialised) responds
   # to #finish, it will be called.
   def sdiff(seq1, seq2, callbacks = nil, &block) #:yields diff changes:
-    diff_traversal(:sdiff, seq1, seq2, callbacks || Diff::LCS::SDiffCallbacks,
-                   &block)
+    diff_traversal(:sdiff, seq1, seq2, callbacks || Diff::LCS::SDiffCallbacks, &block)
   end
 
   # #traverse_sequences is the most general facility provided by this
@@ -267,7 +266,7 @@ def sdiff(seq1, seq2, callbacks = nil, &block) #:yields diff changes:
   # <tt>callbacks#discard_b</tt> will be called after the end of the
   # sequence is reached, if +a+ has not yet reached the end of +A+ or +b+
   # has not yet reached the end of +B+.
-  def traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks, &block) #:yields change events:
+  def traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks) #:yields change events:
     callbacks ||= Diff::LCS::SequenceCallbacks
     matches = Diff::LCS::Internals.lcs(seq1, seq2)
 
@@ -293,6 +292,7 @@ def traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks, &bl
       else
         loop do
           break unless bj < b_line
+
           bx = string ? seq2[bj, 1] : seq2[bj]
           event = Diff::LCS::ContextChange.new('+', i, ax, bj, bx)
           event = yield event if block_given?
@@ -314,7 +314,7 @@ def traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks, &bl
     while (ai < a_size) or (bj < b_size)
       # last A?
       if ai == a_size and bj < b_size
-        if callbacks.respond_to?(:finished_a) and not run_finished_a
+        if callbacks.respond_to?(:finished_a) and !run_finished_a
           ax = string ? seq1[-1, 1] : seq1[-1]
           bx = string ? seq2[bj, 1] : seq2[bj]
           event = Diff::LCS::ContextChange.new('>', (a_size - 1), ax, bj, bx)
@@ -336,7 +336,7 @@ def traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks, &bl
 
       # last B?
       if bj == b_size and ai < a_size
-        if callbacks.respond_to?(:finished_b) and not run_finished_b
+        if callbacks.respond_to?(:finished_b) and !run_finished_b
           ax = string ? seq1[ai, 1] : seq1[ai]
           bx = string ? seq2[-1, 1] : seq2[-1]
           event = Diff::LCS::ContextChange.new('<', ai, ax, (b_size - 1), bx)
@@ -365,14 +365,14 @@ def traverse_sequences(seq1, seq2, callbacks = Diff::LCS::SequenceCallbacks, &bl
         ai += 1
       end
 
-      if bj < b_size
-        ax = string ? seq1[ai, 1] : seq1[ai]
-        bx = string ? seq2[bj, 1] : seq2[bj]
-        event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx)
-        event = yield event if block_given?
-        callbacks.discard_b(event)
-        bj += 1
-      end
+      next unless bj < b_size
+
+      ax = string ? seq1[ai, 1] : seq1[ai]
+      bx = string ? seq2[bj, 1] : seq2[bj]
+      event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx)
+      event = yield event if block_given?
+      callbacks.discard_b(event)
+      bj += 1
     end
   end
 
@@ -475,6 +475,7 @@ def traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks)
       end
 
       break if ma >= matches.size # end of matches?
+
       mb = matches[ma]
 
       # Change(seq2)
@@ -489,7 +490,6 @@ def traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks)
             event = yield event if block_given?
             callbacks.change(event)
             ai += 1
-            bj += 1
           else
             event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx)
             event = yield event if block_given?
@@ -499,8 +499,9 @@ def traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks)
             event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx)
             event = yield event if block_given?
             callbacks.discard_b(event)
-            bj += 1
           end
+
+          bj += 1
         when [true, false]
           event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx)
           event = yield event if block_given?
@@ -535,7 +536,6 @@ def traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks)
           event = yield event if block_given?
           callbacks.change(event)
           ai += 1
-          bj += 1
         else
           event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx)
           event = yield event if block_given?
@@ -545,8 +545,9 @@ def traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks)
           event = Diff::LCS::ContextChange.new('+', ai, ax, bj, bx)
           event = yield event if block_given?
           callbacks.discard_b(event)
-          bj += 1
         end
+
+        bj += 1
       when [true, false]
         event = Diff::LCS::ContextChange.new('-', ai, ax, bj, bx)
         event = yield event if block_given?
@@ -562,9 +563,9 @@ def traverse_balanced(seq1, seq2, callbacks = Diff::LCS::BalancedCallbacks)
   end
 
   PATCH_MAP = { #:nodoc:
-    :patch => { '+' => '+', '-' => '-', '!' => '!', '=' => '=' },
-    :unpatch => { '+' => '-', '-' => '+', '!' => '!', '=' => '=' }
-  }
+    :patch => { '+' => '+', '-' => '-', '!' => '!', '=' => '=' }.freeze,
+    :unpatch => { '+' => '-', '-' => '+', '!' => '!', '=' => '=' }.freeze
+  }.freeze
 
   # Applies a +patchset+ to the sequence +src+ according to the +direction+
   # (<tt>:patch</tt> or <tt>:unpatch</tt>), producing a new sequence.
@@ -610,10 +611,7 @@ def patch(src, patchset, direction = nil)
     # Normalize the patchset.
     has_changes, patchset = Diff::LCS::Internals.analyze_patchset(patchset)
 
-    if not has_changes
-      return src.dup if src.respond_to? :dup
-      return src
-    end
+    return src.respond_to?(:dup) ? src.dup : src unless has_changes
 
     string = src.kind_of?(String)
     # Start with a new empty type of the source's class
@@ -657,8 +655,8 @@ def patch(src, patchset, direction = nil)
             bj += 1
           end
 
-        res << el
-        bj += 1
+          res << el
+          bj += 1
         when '='
           # This only appears in sdiff output with the SDiff callback.
           # Therefore, we only need to worry about dealing with a single
@@ -674,10 +672,10 @@ def patch(src, patchset, direction = nil)
             bj += 1
           end
 
-        bj += 1
-        ai += 1
+          bj += 1
+          ai += 1
 
-        res << el
+          res << el
         end
       when Diff::LCS::Change
         case action
@@ -723,3 +721,5 @@ def patch!(src, patchset)
     patch(src, patchset, :patch)
   end
 end
+
+require 'diff/lcs/backports'
diff --git a/lib/diff/lcs/array.rb b/lib/diff/lcs/array.rb
index 1acd8c9..5c250f6 100644
--- a/lib/diff/lcs/array.rb
+++ b/lib/diff/lcs/array.rb
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'diff/lcs'
 
diff --git a/lib/diff/lcs/backports.rb b/lib/diff/lcs/backports.rb
new file mode 100644
index 0000000..214a59a
--- /dev/null
+++ b/lib/diff/lcs/backports.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+unless 0.respond_to?(:positive?)
+  class Fixnum # rubocop:disable Lint/UnifiedInteger, Style/Documentation
+    def positive?
+      self > 0 # rubocop:disable Styel/NumericPredicate
+    end
+  end
+end
diff --git a/lib/diff/lcs/block.rb b/lib/diff/lcs/block.rb
index 8518727..430702d 100644
--- a/lib/diff/lcs/block.rb
+++ b/lib/diff/lcs/block.rb
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 # A block is an operation removing, adding, or changing a group of items.
 # Basically, this is just a list of changes, where each change adds or
diff --git a/lib/diff/lcs/callbacks.rb b/lib/diff/lcs/callbacks.rb
index 8eec5fc..93c860d 100644
--- a/lib/diff/lcs/callbacks.rb
+++ b/lib/diff/lcs/callbacks.rb
@@ -1,8 +1,8 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'diff/lcs/change'
 
-module Diff::LCS
+module Diff::LCS # rubocop:disable Style/Documentation
   # This callback object implements the default set of callback events,
   # which only returns the event itself. Note that #finished_a and
   # #finished_b are not implemented -- I haven't yet figured out where they
@@ -17,14 +17,17 @@ class << self
       def match(event)
         event
       end
+
       # Called when the old value is discarded in favour of the new value.
       def discard_a(event)
         event
       end
+
       # Called when the new value is discarded in favour of the old value.
       def discard_b(event)
         event
       end
+
       # Called when both the old and new values have changed.
       def change(event)
         event
@@ -108,12 +111,12 @@ def initialize # :yields self:
     @hunk = []
     @diffs = []
 
-    if block_given?
-      begin
-        yield self
-      ensure
-        self.finish
-      end
+    return unless block_given?
+
+    begin
+      yield self
+    ensure
+      finish
     end
   end
 
@@ -123,7 +126,7 @@ def finish
     finish_hunk
   end
 
-  def match(event)
+  def match(_event)
     finish_hunk
   end
 
@@ -241,7 +244,7 @@ def change(event)
 # will compute and display the necessary components to show two sequences
 # and their minimized differences side by side, just like the Unix utility
 # +sdiff+.
-# 
+#
 #     same             same
 #     before     |     after
 #     old        <     -
diff --git a/lib/diff/lcs/change.rb b/lib/diff/lcs/change.rb
index 9229069..75e1f84 100644
--- a/lib/diff/lcs/change.rb
+++ b/lib/diff/lcs/change.rb
@@ -1,16 +1,16 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 # Represents a simplistic (non-contextual) change. Represents the removal or
 # addition of an element from either the old or the new sequenced
 # enumerable.
 class Diff::LCS::Change
-  IntClass = 1.class # Fixnum is deprecated in Ruby 2.4
+  IntClass = 1.class # Fixnum is deprecated in Ruby 2.4 # rubocop:disable Naming/ConstantName
 
   # The only actions valid for changes are '+' (add), '-' (delete), '='
   # (no change), '!' (changed), '<' (tail changes from first sequence), or
   # '>' (tail changes from second sequence). The last two ('<>') are only
   # found with Diff::LCS::diff and Diff::LCS::sdiff.
-  VALID_ACTIONS = %W(+ - = ! > <)
+  VALID_ACTIONS = %w(+ - = ! > <).freeze
 
   def self.valid_action?(action)
     VALID_ACTIONS.include? action
@@ -27,18 +27,16 @@ def self.valid_action?(action)
   def initialize(*args)
     @action, @position, @element = *args
 
-    unless Diff::LCS::Change.valid_action?(@action)
-      raise "Invalid Change Action '#{@action}'"
-    end
-    raise "Invalid Position Type" unless @position.kind_of? IntClass
+    fail "Invalid Change Action '#{@action}'" unless Diff::LCS::Change.valid_action?(@action)
+    fail 'Invalid Position Type' unless @position.kind_of? IntClass
   end
 
-  def inspect
-    to_a.inspect
+  def inspect(*_args)
+    "#<#{self.class}: #{to_a.inspect}>"
   end
 
   def to_a
-    [ @action, @position, @element ]
+    [@action, @position, @element]
   end
 
   def self.from_a(arr)
@@ -49,7 +47,7 @@ def self.from_a(arr)
     when 3
       Diff::LCS::Change.new(*(arr[0...3]))
     else
-      raise "Invalid change array format provided."
+      fail 'Invalid change array format provided.'
     end
   end
 
@@ -57,15 +55,15 @@ def self.from_a(arr)
 
   def ==(other)
     (self.class == other.class) and
-    (self.action == other.action) and
-    (self.position == other.position) and
-    (self.element == other.element)
+      (action == other.action) and
+      (position == other.position) and
+      (element == other.element)
   end
 
   def <=>(other)
-    r = self.action <=> other.action
-    r = self.position <=> other.position if r.zero?
-    r = self.element <=> other.element if r.zero?
+    r = action <=> other.action
+    r = position <=> other.position if r.zero?
+    r = element <=> other.element if r.zero?
     r
   end
 
@@ -114,28 +112,19 @@ class Diff::LCS::ContextChange < Diff::LCS::Change
   def initialize(*args)
     @action, @old_position, @old_element, @new_position, @new_element = *args
 
-    unless Diff::LCS::Change.valid_action?(@action)
-      raise "Invalid Change Action '#{@action}'"
-    end
-    unless @old_position.nil? or @old_position.kind_of? IntClass
-      raise "Invalid (Old) Position Type"
-    end
-    unless @new_position.nil? or @new_position.kind_of? IntClass
-      raise "Invalid (New) Position Type"
-    end
+    fail "Invalid Change Action '#{@action}'" unless Diff::LCS::Change.valid_action?(@action)
+    fail 'Invalid (Old) Position Type' unless @old_position.nil? or @old_position.kind_of? IntClass
+    fail 'Invalid (New) Position Type' unless @new_position.nil? or @new_position.kind_of? IntClass
   end
 
   def to_a
-    [ @action,
-      [ @old_position, @old_element ],
-      [ @new_position, @new_element ]
+    [
+      @action,
+      [@old_position, @old_element],
+      [@new_position, @new_element]
     ]
   end
 
-  def inspect(*args)
-    to_a.inspect
-  end
-
   def self.from_a(arr)
     Diff::LCS::Change.from_a(arr)
   end
@@ -163,11 +152,11 @@ def self.simplify(event)
 
   def ==(other)
     (self.class == other.class) and
-    (@action == other.action) and
-    (@old_position == other.old_position) and
-    (@new_position == other.new_position) and
-    (@old_element == other.old_element) and
-    (@new_element == other.new_element)
+      (@action == other.action) and
+      (@old_position == other.old_position) and
+      (@new_position == other.new_position) and
+      (@old_element == other.old_element) and
+      (@new_element == other.new_element)
   end
 
   def <=>(other)
diff --git a/lib/diff/lcs/htmldiff.rb b/lib/diff/lcs/htmldiff.rb
index 8b79994..f12220b 100644
--- a/lib/diff/lcs/htmldiff.rb
+++ b/lib/diff/lcs/htmldiff.rb
@@ -1,14 +1,15 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'cgi'
 
+# Produce a simple HTML diff view.
 class Diff::LCS::HTMLDiff
   class << self
     attr_accessor :can_expand_tabs #:nodoc:
   end
   self.can_expand_tabs = true
 
-  class Callbacks
+  class Callbacks #:nodoc:
     attr_accessor :output
     attr_accessor :match_class
     attr_accessor :only_a_class
@@ -18,14 +19,14 @@ def initialize(output, options = {})
       @output = output
       options ||= {}
 
-      @match_class = options[:match_class] || "match"
-      @only_a_class = options[:only_a_class] || "only_a"
-      @only_b_class = options[:only_b_class] || "only_b"
+      @match_class = options[:match_class] || 'match'
+      @only_a_class = options[:only_a_class] || 'only_a'
+      @only_b_class = options[:only_b_class] || 'only_b'
     end
 
     def htmlize(element, css_class)
-      element = "&nbsp;" if element.empty?
-      %Q|<pre class="#{__send__(css_class)}">#{element}</pre>\n|
+      element = '&nbsp;' if element.empty?
+      %Q(<pre class="#{__send__(css_class)}">#{element}</pre>\n)
     end
     private :htmlize
 
@@ -49,8 +50,8 @@ def discard_b(event)
     :expand_tabs => nil,
     :output => nil,
     :css => nil,
-    :title => nil,
-  }
+    :title => nil
+  }.freeze
 
   DEFAULT_CSS = <<-CSS
 body { margin: 0; }
@@ -96,13 +97,13 @@ def initialize(left, right, options = nil)
 
   def verify_options
     @options[:expand_tabs] ||= 4
-    @options[:expand_tabs] = 4 if @options[:expand_tabs] < 0
+    @options[:expand_tabs] = 4 if @options[:expand_tabs].negative?
 
     @options[:output] ||= $stdout
 
     @options[:css] ||= DEFAULT_CSS.dup
 
-    @options[:title] ||= "diff"
+    @options[:title] ||= 'diff'
   end
   private :verify_options
 
@@ -111,16 +112,16 @@ def verify_options
   def run
     verify_options
 
-    if @options[:expand_tabs] > 0 && self.class.can_expand_tabs
+    if @options[:expand_tabs].positive? && self.class.can_expand_tabs
       formatter = Text::Format.new
       formatter.tabstop = @options[:expand_tabs]
 
-      @left.map! { |line| formatter.expand(line.chomp) }
-      @right.map! { |line| formatter.expand(line.chomp) }
+      @left.map! do |line| formatter.expand(line.chomp) end
+      @right.map! do |line| formatter.expand(line.chomp) end
     end
 
-    @left.map! { |line| CGI.escapeHTML(line.chomp) }
-    @right.map! { |line| CGI.escapeHTML(line.chomp) }
+    @left.map! do |line| CGI.escapeHTML(line.chomp) end
+    @right.map! do |line| CGI.escapeHTML(line.chomp) end
 
     @options[:output] << <<-OUTPUT
 <html>
diff --git a/lib/diff/lcs/hunk.rb b/lib/diff/lcs/hunk.rb
index 05c3fb6..58a68db 100644
--- a/lib/diff/lcs/hunk.rb
+++ b/lib/diff/lcs/hunk.rb
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'diff/lcs/block'
 
@@ -10,9 +10,9 @@ class Diff::LCS::Hunk
   # the piece of data.
   def initialize(data_old, data_new, piece, flag_context, file_length_difference)
     # At first, a hunk will have just one Block in it
-    @blocks = [ Diff::LCS::Block.new(piece) ]
+    @blocks = [Diff::LCS::Block.new(piece)]
     if String.method_defined?(:encoding)
-      @preferred_data_encoding = data_old.fetch(0, data_new.fetch(0,'') ).encoding
+      @preferred_data_encoding = data_old.fetch(0, data_new.fetch(0, '')).encoding
     end
     @data_old = data_old
     @data_new = data_new
@@ -55,19 +55,21 @@ def initialize(data_old, data_new, piece, flag_context, file_length_difference)
   # Change the "start" and "end" fields to note that context should be added
   # to this hunk.
   attr_accessor :flag_context
-  undef :flag_context=;
-  def flag_context=(context) #:nodoc:
+  undef :flag_context=
+  def flag_context=(context) #:nodoc: # rubocop:disable Lint/DuplicateMethods
     return if context.nil? or context.zero?
 
-    add_start = (context > @start_old) ? @start_old : context
+    add_start = context > @start_old ? @start_old : context
     @start_old -= add_start
     @start_new -= add_start
 
-    if (@end_old + context) > @data_old.size
-      add_end = @data_old.size - @end_old
-    else
-      add_end = context
-    end
+    add_end =
+      if (@end_old + context) > @data_old.size
+        @data_old.size - @end_old
+      else
+        context
+      end
+
     @end_old += add_end
     @end_new += add_end
   end
@@ -76,15 +78,13 @@ def flag_context=(context) #:nodoc:
   # a truthy value so that if there is no overlap, you can know the merge
   # was skipped.
   def merge(hunk)
-    if overlaps?(hunk)
-      @start_old = hunk.start_old
-      @start_new = hunk.start_new
-      blocks.unshift(*hunk.blocks)
-    else
-      nil
-    end
+    return unless overlaps?(hunk)
+
+    @start_old = hunk.start_old
+    @start_new = hunk.start_new
+    blocks.unshift(*hunk.blocks)
   end
-  alias_method :unshift, :merge
+  alias unshift merge
 
   # Determines whether there is an overlap between this hunk and the
   # provided hunk. This will be true if the difference between the two hunks
@@ -108,15 +108,15 @@ def diff(format)
     when :reverse_ed, :ed_finish
       ed_diff(format)
     else
-      raise "Unknown diff format #{format}."
+      fail "Unknown diff format #{format}."
     end
   end
 
   # Note that an old diff can't have any context. Therefore, we know that
   # there's only one block in the hunk.
   def old_diff
-    warn "Expecting only one block in an old diff hunk!" if @blocks.size > 1
-    op_act = { "+" => 'a', "-" => 'd', "!" => "c" }
+    warn 'Expecting only one block in an old diff hunk!' if @blocks.size > 1
+    op_act = { '+' => 'a', '-' => 'd', '!' => 'c' }
 
     block = @blocks[0]
 
@@ -126,9 +126,16 @@ def old_diff
     s = encode("#{context_range(:old)}#{op_act[block.op]}#{context_range(:new)}\n")
     # If removing anything, just print out all the remove lines in the hunk
     # which is just all the remove lines in the block.
-    @data_old[@start_old .. @end_old].each { |e| s << encode("< ") + e + encode("\n") } unless block.remove.empty?
-    s << encode("---\n") if block.op == "!"
-    @data_new[@start_new .. @end_new].each { |e| s << encode("> ") + e + encode("\n") } unless block.insert.empty?
+    unless block.remove.empty?
+      @data_old[@start_old..@end_old].each { |e| s << encode('< ') + e + encode("\n") }
+    end
+
+    s << encode("---\n") if block.op == '!'
+
+    unless block.insert.empty?
+      @data_new[@start_new..@end_new].each { |e| s << encode('> ') + e + encode("\n") }
+    end
+
     s
   end
   private :old_diff
@@ -148,7 +155,7 @@ def unified_diff
     # file -- don't take removed items into account.
     lo, hi, num_added, num_removed = @start_old, @end_old, 0, 0
 
-    outlist = @data_old[lo .. hi].map { |e| e.insert(0, encode(' ')) }
+    outlist = @data_old[lo..hi].map { |e| e.insert(0, encode(' ')) }
 
     @blocks.each do |block|
       block.remove.each do |item|
@@ -177,9 +184,9 @@ def context_diff
     # Print out file 1 part for each block in context diff format if there
     # are any blocks that remove items
     lo, hi = @start_old, @end_old
-    removes = @blocks.select { |e| not e.remove.empty? }
+    removes = @blocks.reject { |e| e.remove.empty? }
     if removes
-      outlist = @data_old[lo .. hi].map { |e| e.insert(0, encode(' ')) }
+      outlist = @data_old[lo..hi].map { |e| e.insert(0, encode(' ')) }
 
       removes.each do |block|
         block.remove.each do |item|
@@ -191,9 +198,9 @@ def context_diff
 
     s << encode("\n--- #{r} ----\n")
     lo, hi = @start_new, @end_new
-    inserts = @blocks.select { |e| not e.insert.empty? }
+    inserts = @blocks.reject { |e| e.insert.empty? }
     if inserts
-      outlist = @data_new[lo .. hi].collect { |e| e.insert(0, encode(' ')) }
+      outlist = @data_new[lo..hi].collect { |e| e.insert(0, encode(' ')) }
       inserts.each do |block|
         block.insert.each do |item|
           outlist[item.position - lo][0, 1] = encode(block.op) # + or !
@@ -206,17 +213,18 @@ def context_diff
   private :context_diff
 
   def ed_diff(format)
-    op_act = { "+" => 'a', "-" => 'd', "!" => "c" }
-    warn "Expecting only one block in an old diff hunk!" if @blocks.size > 1
-
-    if format == :reverse_ed
-      s = encode("#{op_act[@blocks[0].op]}#{context_range(:old)}\n")
-    else
-      s = encode("#{context_range(:old, ' ')}#{op_act[@blocks[0].op]}\n")
-    end
+    op_act = { '+' => 'a', '-' => 'd', '!' => 'c' }
+    warn 'Expecting only one block in an old diff hunk!' if @blocks.size > 1
+
+    s =
+      if format == :reverse_ed
+        encode("#{op_act[@blocks[0].op]}#{context_range(:old)}\n")
+      else
+        encode("#{context_range(:old, ' ')}#{op_act[@blocks[0].op]}\n")
+      end
 
     unless @blocks[0].insert.empty?
-      @data_new[@start_new .. @end_new].each { |e| s << e + encode("\n") }
+      @data_new[@start_new..@end_new].each do |e| s << e + encode("\n") end
       s << encode(".\n")
     end
     s
@@ -225,7 +233,7 @@ def ed_diff(format)
 
   # Generate a range of item numbers to print. Only print 1 number if the
   # range has only one item in it. Otherwise, it's 'start,end'
-  def context_range(mode, op = ',')
+  def context_range(mode, op = ',') # rubocop:disable Naming/UncommunicativeMethodParamName
     case mode
     when :old
       s, e = (@start_old + 1), (@end_old + 1)
@@ -233,7 +241,7 @@ def context_range(mode, op = ',')
       s, e = (@start_new + 1), (@end_new + 1)
     end
 
-    (s < e) ? "#{s}#{op}#{e}" : "#{e}"
+    s < e ? "#{s}#{op}#{e}" : e.to_s
   end
   private :context_range
 
@@ -249,8 +257,8 @@ def unified_range(mode)
     end
 
     length = e - s + 1
-    first = (length < 2) ? e : s # "strange, but correct"
-    (length == 1) ? "#{first}" : "#{first},#{length}"
+    first = length < 2 ? e : s # "strange, but correct"
+    length == 1 ? first.to_s : "#{first},#{length}"
   end
   private :unified_range
 
@@ -263,10 +271,11 @@ def encode_as(string, *args)
       args.map { |arg| arg.encode(string.encoding) }
     end
   else
-    def encode(literal, target_encoding = nil)
+    def encode(literal, _target_encoding = nil)
       literal
     end
-    def encode_as(string, *args)
+
+    def encode_as(_string, *args)
       args
     end
   end
diff --git a/lib/diff/lcs/internals.rb b/lib/diff/lcs/internals.rb
index 17d1d06..c3360d5 100644
--- a/lib/diff/lcs/internals.rb
+++ b/lib/diff/lcs/internals.rb
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 class << Diff::LCS
   def diff_traversal(method, seq1, seq2, callbacks, &block)
@@ -45,8 +45,7 @@ def lcs(a, b)
     vector = []
 
     # Prune off any common elements at the beginning...
-    while ((a_start <= a_finish) and (b_start <= b_finish) and
-           (a[a_start] == b[b_start]))
+    while (a_start <= a_finish) and (b_start <= b_finish) and (a[a_start] == b[b_start])
       vector[a_start] = b_start
       a_start += 1
       b_start += 1
@@ -54,8 +53,7 @@ def lcs(a, b)
     b_start = a_start
 
     # Now the end...
-    while ((a_start <= a_finish) and (b_start <= b_finish) and
-           (a[a_finish] == b[b_finish]))
+    while (a_start <= a_finish) and (b_start <= b_finish) and (a[a_finish] == b[b_finish])
       vector[a_finish] = b_finish
       a_finish -= 1
       b_finish -= 1
@@ -68,7 +66,7 @@ def lcs(a, b)
     links  = []
     string = a.kind_of?(String)
 
-    (a_start .. a_finish).each do |i|
+    (a_start..a_finish).each do |i|
       ai = string ? a[i, 1] : a[i]
       bm = b_matches[ai]
       k = nil
@@ -78,13 +76,13 @@ def lcs(a, b)
         else
           k = replace_next_larger(thresh, j, k)
         end
-        links[k] = [ (k > 0) ? links[k - 1] : nil, i, j ] unless k.nil?
+        links[k] = [k.positive? ? links[k - 1] : nil, i, j] unless k.nil?
       end
     end
 
     unless thresh.empty?
       link = links[thresh.size - 1]
-      while not link.nil?
+      until link.nil?
         vector[link[1]] = link[2]
         link = link[0]
       end
@@ -98,7 +96,7 @@ def lcs(a, b)
   # Diff::LCS::Change objects to the object form of same) and detection of
   # whether the patchset represents changes to be made.
   def analyze_patchset(patchset, depth = 0)
-    raise "Patchset too complex" if depth > 1
+    fail 'Patchset too complex' if depth > 1
 
     has_changes = false
 
@@ -110,7 +108,7 @@ def analyze_patchset(patchset, depth = 0)
     #   ]
     # ]
 
-    patchset = patchset.map do |hunk|
+    patchset = patchset.map { |hunk|
       case hunk
       when Diff::LCS::Change
         has_changes ||= !hunk.unchanged?
@@ -128,11 +126,11 @@ def analyze_patchset(patchset, depth = 0)
           hunk.flatten
         end
       else
-        raise ArgumentError, "Cannot normalise a hunk of class #{hunk.class}."
+        fail ArgumentError, "Cannot normalise a hunk of class #{hunk.class}."
       end
-    end
+    }
 
-    [ has_changes, patchset.flatten(1) ]
+    [has_changes, patchset.flatten(1)]
   end
 
   # Examine the patchset and the source to see in which direction the
@@ -173,13 +171,11 @@ def intuit_diff_direction(src, patchset, limit = nil)
         when '!'
           if le == change.old_element
             left_match += 1
+          elsif re == change.new_element
+            right_match += 1
           else
-            if re == change.new_element
-              right_match += 1
-            else
-              left_miss += 1
-              right_miss += 1
-            end
+            left_miss += 1
+            right_miss += 1
           end
         end
       when Diff::LCS::Change
@@ -209,16 +205,16 @@ def intuit_diff_direction(src, patchset, limit = nil)
         end
       end
 
-      break if (not limit.nil?) && (count > limit)
+      break if !limit.nil? && (count > limit)
     end
 
-    no_left = (left_match == 0) && (left_miss > 0)
-    no_right = (right_match == 0) && (right_miss > 0)
+    no_left = left_match.zero? && left_miss.positive?
+    no_right = right_match.zero? && right_miss.positive?
 
-    case [ no_left, no_right ]
-    when [ false, true ]
+    case [no_left, no_right]
+    when [false, true]
       :patch
-    when [ true, false ]
+    when [true, false]
       :unpatch
     else
       case left_match <=> right_match
@@ -235,7 +231,8 @@ def intuit_diff_direction(src, patchset, limit = nil)
           :patch
         end
       else
-        raise "The provided patchset does not appear to apply to the provided enumerable as either source or destination value."
+        fail "The provided patchset does not appear to apply to the provided \
+enumerable as either source or destination value."
       end
     end
   end
@@ -258,14 +255,14 @@ def replace_next_larger(enum, value, last_index = nil)
     # Binary search for the insertion point
     last_index ||= enum.size
     first_index = 0
-    while (first_index <= last_index)
+    while first_index <= last_index
       i = (first_index + last_index) >> 1
 
       found = enum[i]
 
-      if value == found
-        return nil
-      elsif value > found
+      return nil if value == found
+
+      if value > found
         first_index = i + 1
       else
         last_index = i - 1
@@ -275,7 +272,7 @@ def replace_next_larger(enum, value, last_index = nil)
     # The insertion point is in first_index; overwrite the next larger
     # value.
     enum[first_index] = value
-    return first_index
+    first_index
   end
   private :replace_next_larger
 
diff --git a/lib/diff/lcs/ldiff.rb b/lib/diff/lcs/ldiff.rb
index c789f46..d385f72 100644
--- a/lib/diff/lcs/ldiff.rb
+++ b/lib/diff/lcs/ldiff.rb
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'optparse'
 require 'ostruct'
@@ -7,7 +7,7 @@
 module Diff::LCS::Ldiff #:nodoc:
   BANNER = <<-COPYRIGHT
 ldiff #{Diff::LCS::VERSION}
-  Copyright 2004-2014 Austin Ziegler
+  Copyright 2004-2019 Austin Ziegler
 
   Part of Diff::LCS.
   https://github.com/halostatue/diff-lcs
@@ -15,7 +15,7 @@ module Diff::LCS::Ldiff #:nodoc:
   This program is free software. It may be redistributed and/or modified under
   the terms of the GPL version 2 (or later), the Perl Artistic licence, or the
   MIT licence.
-COPYRIGHT
+  COPYRIGHT
 end
 
 class << Diff::LCS::Ldiff
@@ -23,33 +23,42 @@ class << Diff::LCS::Ldiff
   attr_reader :file_old, :file_new #:nodoc:
   attr_reader :data_old, :data_new #:nodoc:
 
-  def run(args, input = $stdin, output = $stdout, error = $stderr) #:nodoc:
+  def run(args, _input = $stdin, output = $stdout, error = $stderr) #:nodoc:
     @binary = nil
 
     args.options do |o|
       o.banner = "Usage: #{File.basename($0)} [options] oldfile newfile"
-      o.separator ""
-      o.on('-c', '-C', '--context [LINES]', Numeric, 'Displays a context diff with LINES lines', 'of context. Default 3 lines.') do |ctx|
+      o.separator ''
+      o.on(
+        '-c', '-C', '--context [LINES]', Numeric,
+        'Displays a context diff with LINES lines', 'of context. Default 3 lines.'
+      ) do |ctx|
         @format = :context
         @lines  = ctx || 3
       end
-      o.on('-u', '-U', '--unified [LINES]', Numeric, 'Displays a unified diff with LINES lines', 'of context. Default 3 lines.') do |ctx|
+      o.on(
+        '-u', '-U', '--unified [LINES]', Numeric,
+        'Displays a unified diff with LINES lines', 'of context. Default 3 lines.'
+      ) do |ctx|
         @format = :unified
         @lines  = ctx || 3
       end
-      o.on('-e', 'Creates an \'ed\' script to change', 'oldfile to newfile.') do |ctx|
+      o.on('-e', 'Creates an \'ed\' script to change', 'oldfile to newfile.') do |_ctx|
         @format = :ed
       end
-      o.on('-f', 'Creates an \'ed\' script to change', 'oldfile to newfile in reverse order.') do |ctx|
+      o.on('-f', 'Creates an \'ed\' script to change', 'oldfile to newfile in reverse order.') do |_ctx|
         @format = :reverse_ed
       end
-      o.on('-a', '--text', 'Treat the files as text and compare them', 'line-by-line, even if they do not seem', 'to be text.') do |txt|
+      o.on(
+        '-a', '--text',
+        'Treat the files as text and compare them', 'line-by-line, even if they do not seem', 'to be text.'
+      ) do |_txt|
         @binary = false
       end
-      o.on('--binary', 'Treats the files as binary.') do |bin|
+      o.on('--binary', 'Treats the files as binary.') do |_bin|
         @binary = true
       end
-      o.on('-q', '--brief', 'Report only whether or not the files', 'differ, not the details.') do |ctx|
+      o.on('-q', '--brief', 'Report only whether or not the files', 'differ, not the details.') do |_ctx|
         @format = :report
       end
       o.on_tail('--help', 'Shows this text.') do
@@ -60,7 +69,7 @@ def run(args, input = $stdin, output = $stdout, error = $stderr) #:nodoc:
         error << Diff::LCS::Ldiff::BANNER
         return 0
       end
-      o.on_tail ""
+      o.on_tail ''
       o.on_tail 'By default, runs produces an "old-style" diff, with output like UNIX diff.'
       o.parse!
     end
@@ -97,8 +106,7 @@ def run(args, input = $stdin, output = $stdout, error = $stderr) #:nodoc:
       if @binary.nil?
         old_txt = data_old[0, 4096].scan(/\0/).empty?
         new_txt = data_new[0, 4096].scan(/\0/).empty?
-        @binary = (not old_txt) or (not new_txt)
-        old_txt = new_txt = nil
+        @binary = !old_txt or !new_txt
       end
 
       unless @binary
@@ -143,12 +151,11 @@ def run(args, input = $stdin, output = $stdout, error = $stderr) #:nodoc:
 
     diffs.each do |piece|
       begin
-        hunk = Diff::LCS::Hunk.new(data_old, data_new, piece, @lines,
-                                   file_length_difference)
+        hunk = Diff::LCS::Hunk.new(data_old, data_new, piece, @lines, file_length_difference)
         file_length_difference = hunk.file_length_difference
 
         next unless oldhunk
-        next if (@lines > 0) and hunk.merge(oldhunk)
+        next if @lines.postive? and hunk.merge(oldhunk)
 
         output << oldhunk.diff(@format) << "\n"
       ensure
@@ -158,10 +165,8 @@ def run(args, input = $stdin, output = $stdout, error = $stderr) #:nodoc:
 
     output << oldhunk.diff(@format) << "\n"
 
-    if @format == :ed
-      output.reverse_each { |e| real_output << e.diff(:ed_finish) }
-    end
+    output.reverse_each { |e| real_output << e.diff(:ed_finish) } if @format == :ed
 
-    return 1
+    1
   end
 end
diff --git a/lib/diff/lcs/string.rb b/lib/diff/lcs/string.rb
index 8545bcf..9ab32e9 100644
--- a/lib/diff/lcs/string.rb
+++ b/lib/diff/lcs/string.rb
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 class String
   include Diff::LCS
diff --git a/spec/change_spec.rb b/spec/change_spec.rb
index dfe385f..b5ad0cb 100644
--- a/spec/change_spec.rb
+++ b/spec/change_spec.rb
@@ -1,9 +1,9 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
 describe Diff::LCS::Change do
-  describe "an add" do
+  describe 'an add' do
     subject { described_class.new('+', 0, 'element') }
     it { should_not be_deleting   }
     it { should     be_adding     }
@@ -13,7 +13,7 @@
     it { should_not be_finished_b }
   end
 
-  describe "a delete" do
+  describe 'a delete' do
     subject { described_class.new('-', 0, 'element') }
     it { should     be_deleting   }
     it { should_not be_adding     }
@@ -23,7 +23,7 @@
     it { should_not be_finished_b }
   end
 
-  describe "an unchanged" do
+  describe 'an unchanged' do
     subject { described_class.new('=', 0, 'element') }
     it { should_not be_deleting   }
     it { should_not be_adding     }
@@ -33,7 +33,7 @@
     it { should_not be_finished_b }
   end
 
-  describe "a changed" do
+  describe 'a changed' do
     subject { described_class.new('!', 0, 'element') }
     it { should_not be_deleting   }
     it { should_not be_adding     }
@@ -43,7 +43,7 @@
     it { should_not be_finished_b }
   end
 
-  describe "a finished_a" do
+  describe 'a finished_a' do
     subject { described_class.new('>', 0, 'element') }
     it { should_not be_deleting   }
     it { should_not be_adding     }
@@ -53,7 +53,7 @@
     it { should_not be_finished_b }
   end
 
-  describe "a finished_b" do
+  describe 'a finished_b' do
     subject { described_class.new('<', 0, 'element') }
     it { should_not be_deleting   }
     it { should_not be_adding     }
diff --git a/spec/diff_spec.rb b/spec/diff_spec.rb
index 020ff44..e7d632a 100644
--- a/spec/diff_spec.rb
+++ b/spec/diff_spec.rb
@@ -1,33 +1,37 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
-describe Diff::LCS, ".diff" do
+describe Diff::LCS, '.diff' do
   include Diff::LCS::SpecHelper::Matchers
 
-  it "correctly diffs seq1 to seq2" do
+  it 'correctly diffs seq1 to seq2' do
     diff_s1_s2 = Diff::LCS.diff(seq1, seq2)
     expect(change_diff(correct_forward_diff)).to eq(diff_s1_s2)
   end
 
-  it "correctly diffs seq2 to seq1" do
+  it 'correctly diffs seq2 to seq1' do
     diff_s2_s1 = Diff::LCS.diff(seq2, seq1)
     expect(change_diff(correct_backward_diff)).to eq(diff_s2_s1)
   end
 
-  it "correctly diffs against an empty sequence" do
+  it 'correctly diffs against an empty sequence' do
     diff = Diff::LCS.diff(word_sequence, [])
     correct_diff = [
-      [ [ '-', 0, 'abcd'           ],
-        [ '-', 1, 'efgh'           ],
-        [ '-', 2, 'ijkl'           ],
-        [ '-', 3, 'mnopqrstuvwxyz' ] ]
+      [
+        ['-', 0, 'abcd'],
+        ['-', 1, 'efgh'],
+        ['-', 2, 'ijkl'],
+        ['-', 3, 'mnopqrstuvwxyz']
+      ]
     ]
 
     expect(change_diff(correct_diff)).to eq(diff)
 
     diff = Diff::LCS.diff([], word_sequence)
-    correct_diff.each { |hunk| hunk.each { |change| change[0] = '+' } }
+    correct_diff.each do |hunk|
+      hunk.each do |change| change[0] = '+' end
+    end
     expect(change_diff(correct_diff)).to eq(diff)
   end
 
@@ -37,11 +41,11 @@
     expect(Diff::LCS.patch(left, Diff::LCS.diff(left, right))).to eq(right)
   end
 
-  it "returns an empty diff with (hello, hello)" do
+  it 'returns an empty diff with (hello, hello)' do
     expect(Diff::LCS.diff(hello, hello)).to be_empty
   end
 
-  it "returns an empty diff with (hello_ary, hello_ary)" do
+  it 'returns an empty diff with (hello_ary, hello_ary)' do
     expect(Diff::LCS.diff(hello_ary, hello_ary)).to be_empty
   end
 end
diff --git a/spec/hunk_spec.rb b/spec/hunk_spec.rb
index 0711e0d..5a45072 100644
--- a/spec/hunk_spec.rb
+++ b/spec/hunk_spec.rb
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
@@ -6,52 +6,52 @@
   require 'diff/lcs/hunk'
 
   describe Diff::LCS::Hunk do
-    let(:old_data) { ["Tu avec carté {count} itém has".encode('UTF-16LE')] }
-    let(:new_data) { ["Tu avec carte {count} item has".encode('UTF-16LE')] }
+    let(:old_data) { ['Tu avec carté {count} itém has'.encode('UTF-16LE')] }
+    let(:new_data) { ['Tu avec carte {count} item has'.encode('UTF-16LE')] }
     let(:pieces)   { Diff::LCS.diff old_data, new_data }
     let(:hunk)     { Diff::LCS::Hunk.new(old_data, new_data, pieces[0], 3, 0) }
 
     it 'produces a unified diff from the two pieces' do
-      expected = (<<-EOD.gsub(/^\s+/,'').encode('UTF-16LE').chomp)
+      expected = <<-EXPECTED.gsub(/^\s+/, '').encode('UTF-16LE').chomp
         @@ -1,2 +1,2 @@
         -Tu avec carté {count} itém has
         +Tu avec carte {count} item has
-      EOD
+      EXPECTED
 
       expect(hunk.diff(:unified)).to eq(expected)
     end
 
     it 'produces a context diff from the two pieces' do
-      expected = (<<-EOD.gsub(/^\s+/,'').encode('UTF-16LE').chomp)
+      expected = <<-EXPECTED.gsub(/^\s+/, '').encode('UTF-16LE').chomp
         ***************
         *** 1,2 ****
         !Tu avec carté {count} itém has
         --- 1,2 ----
         !Tu avec carte {count} item has
-      EOD
+      EXPECTED
 
       expect(hunk.diff(:context)).to eq(expected)
     end
 
     it 'produces an old diff from the two pieces' do
-      expected = (<<-EOD.gsub(/^ +/,'').encode('UTF-16LE').chomp)
+      expected = <<-EXPECTED.gsub(/^ +/, '').encode('UTF-16LE').chomp
         1,2c1,2
         < Tu avec carté {count} itém has
         ---
         > Tu avec carte {count} item has
 
-      EOD
+      EXPECTED
 
       expect(hunk.diff(:old)).to eq(expected)
     end
 
     it 'produces a reverse ed diff from the two pieces' do
-      expected = (<<-EOD.gsub(/^ +/,'').encode('UTF-16LE').chomp)
+      expected = <<-EXPECTED.gsub(/^ +/, '').encode('UTF-16LE').chomp
         c1,2
         Tu avec carte {count} item has
         .
 
-      EOD
+      EXPECTED
 
       expect(hunk.diff(:reverse_ed)).to eq(expected)
     end
@@ -60,10 +60,10 @@
       let(:old_data) { [] }
 
       it 'produces a unified diff' do
-        expected = (<<-EOD.gsub(/^\s+/,'').encode('UTF-16LE').chomp)
+        expected = <<-EXPECTED.gsub(/^\s+/, '').encode('UTF-16LE').chomp
           @@ -1 +1,2 @@
           +Tu avec carte {count} item has
-        EOD
+        EXPECTED
 
         expect(hunk.diff(:unified)).to eq(expected)
       end
diff --git a/spec/issues_spec.rb b/spec/issues_spec.rb
index 7638249..79ddd0b 100644
--- a/spec/issues_spec.rb
+++ b/spec/issues_spec.rb
@@ -1,8 +1,8 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
-describe "Diff::LCS Issues" do
+describe 'Diff::LCS Issues' do
   include Diff::LCS::SpecHelper::Matchers
 
   describe 'issue #1' do
@@ -26,23 +26,31 @@
 
     describe 'string' do
       it_has_behavior 'handles simple diffs', 'aX', 'bXaX', [
-        [ [ '+', 0, 'b' ],
-          [ '+', 1, 'X' ] ],
+        [
+          ['+', 0, 'b'],
+          ['+', 1, 'X']
+        ]
       ]
       it_has_behavior 'handles simple diffs', 'bXaX', 'aX', [
-        [ [ '-', 0, 'b' ],
-          [ '-', 1, 'X' ] ],
+        [
+          ['-', 0, 'b'],
+          ['-', 1, 'X']
+        ]
       ]
     end
 
     describe 'array' do
       it_has_behavior 'handles simple diffs', %w(a X), %w(b X a X), [
-        [ [ '+', 0, 'b' ],
-          [ '+', 1, 'X' ] ],
+        [
+          ['+', 0, 'b'],
+          ['+', 1, 'X']
+        ]
       ]
       it_has_behavior 'handles simple diffs', %w(b X a X), %w(a X), [
-        [ [ '-', 0, 'b' ],
-          [ '-', 1, 'X' ] ],
+        [
+          ['-', 0, 'b'],
+          ['-', 1, 'X']
+        ]
       ]
     end
   end
diff --git a/spec/lcs_spec.rb b/spec/lcs_spec.rb
index 28533e3..94428fd 100644
--- a/spec/lcs_spec.rb
+++ b/spec/lcs_spec.rb
@@ -1,11 +1,11 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
-describe Diff::LCS::Internals, ".lcs" do
+describe Diff::LCS::Internals, '.lcs' do
   include Diff::LCS::SpecHelper::Matchers
 
-  it "returns a meaningful LCS array with (seq1, seq2)" do
+  it 'returns a meaningful LCS array with (seq1, seq2)' do
     res = Diff::LCS::Internals.lcs(seq1, seq2)
     # The result of the LCS (less the +nil+ values) must be as long as the
     # correct result.
@@ -20,37 +20,37 @@
     expect(x_seq2).to eq(correct_lcs)
   end
 
-  it "returns all indexes with (hello, hello)" do
+  it 'returns all indexes with (hello, hello)' do
     expect(Diff::LCS::Internals.lcs(hello, hello)).to \
       eq((0...hello.size).to_a)
   end
 
-  it "returns all indexes with (hello_ary, hello_ary)" do
+  it 'returns all indexes with (hello_ary, hello_ary)' do
     expect(Diff::LCS::Internals.lcs(hello_ary, hello_ary)).to \
       eq((0...hello_ary.size).to_a)
   end
 end
 
-describe Diff::LCS, ".LCS" do
+describe Diff::LCS, '.LCS' do
   include Diff::LCS::SpecHelper::Matchers
 
-  it "returns the correct compacted values from Diff::LCS.LCS" do
+  it 'returns the correct compacted values from Diff::LCS.LCS' do
     res = Diff::LCS.LCS(seq1, seq2)
     expect(res).to eq(correct_lcs)
     expect(res.compact).to eq(res)
   end
 
-  it "is transitive" do
+  it 'is transitive' do
     res = Diff::LCS.LCS(seq2, seq1)
     expect(res).to eq(correct_lcs)
     expect(res.compact).to eq(res)
   end
 
-  it "returns %W(h e l l o) with (hello, hello)" do
+  it 'returns %W(h e l l o) with (hello, hello)' do
     expect(Diff::LCS.LCS(hello, hello)).to eq(hello.split(//))
   end
 
-  it "returns hello_ary with (hello_ary, hello_ary)" do
+  it 'returns hello_ary with (hello_ary, hello_ary)' do
     expect(Diff::LCS.LCS(hello_ary, hello_ary)).to eq(hello_ary)
   end
 end
diff --git a/spec/ldiff_spec.rb b/spec/ldiff_spec.rb
index ad1377f..113c0dd 100644
--- a/spec/ldiff_spec.rb
+++ b/spec/ldiff_spec.rb
@@ -1,8 +1,8 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
-describe "Diff::LCS.diff" do
+describe 'Diff::LCS.diff' do
   include Diff::LCS::SpecHelper::Matchers
 
   it 'correctly diffs seq1 to seq2' do
@@ -18,16 +18,20 @@
   it 'correctly diffs against an empty sequence' do
     diff = Diff::LCS.diff(word_sequence, [])
     correct_diff = [
-      [ [ '-', 0, 'abcd'           ],
-        [ '-', 1, 'efgh'           ],
-        [ '-', 2, 'ijkl'           ],
-        [ '-', 3, 'mnopqrstuvwxyz' ] ]
+      [
+        ['-', 0, 'abcd'],
+        ['-', 1, 'efgh'],
+        ['-', 2, 'ijkl'],
+        ['-', 3, 'mnopqrstuvwxyz']
+      ]
     ]
 
     expect(change_diff(correct_diff)).to eq(diff)
 
     diff = Diff::LCS.diff([], word_sequence)
-    correct_diff.each { |hunk| hunk.each { |change| change[0] = '+' } }
+    correct_diff.each do |hunk|
+      hunk.each do |change| change[0] = '+' end
+    end
     expect(change_diff(correct_diff)).to eq(diff)
   end
 
@@ -37,11 +41,11 @@
     expect(Diff::LCS.patch(left, Diff::LCS.diff(left, right))).to eq(right)
   end
 
-  it "returns an empty diff with (hello, hello)" do
+  it 'returns an empty diff with (hello, hello)' do
     expect(Diff::LCS.diff(hello, hello)).to eq([])
   end
 
-  it "returns an empty diff with (hello_ary, hello_ary)" do
+  it 'returns an empty diff with (hello_ary, hello_ary)' do
     expect(Diff::LCS.diff(hello_ary, hello_ary)).to eq([])
   end
 end
diff --git a/spec/patch_spec.rb b/spec/patch_spec.rb
index 9f1a4f1..11b0981 100644
--- a/spec/patch_spec.rb
+++ b/spec/patch_spec.rb
@@ -1,54 +1,54 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
-describe "Diff::LCS.patch" do
+describe 'Diff::LCS.patch' do
   include Diff::LCS::SpecHelper::Matchers
 
-  shared_examples "patch sequences correctly" do
-    it "correctly patches left-to-right (patch autodiscovery)" do
+  shared_examples 'patch sequences correctly' do
+    it 'correctly patches left-to-right (patch autodiscovery)' do
       expect(Diff::LCS.patch(s1, patch_set)).to eq(s2)
     end
 
-    it "correctly patches left-to-right (explicit patch)" do
+    it 'correctly patches left-to-right (explicit patch)' do
       expect(Diff::LCS.patch(s1, patch_set, :patch)).to eq(s2)
       expect(Diff::LCS.patch!(s1, patch_set)).to eq(s2)
     end
 
-    it "correctly patches right-to-left (unpatch autodiscovery)" do
+    it 'correctly patches right-to-left (unpatch autodiscovery)' do
       expect(Diff::LCS.patch(s2, patch_set)).to eq(s1)
     end
 
-    it "correctly patches right-to-left (explicit unpatch)" do
+    it 'correctly patches right-to-left (explicit unpatch)' do
       expect(Diff::LCS.patch(s2, patch_set, :unpatch)).to eq(s1)
       expect(Diff::LCS.unpatch!(s2, patch_set)).to eq(s1)
     end
   end
 
-  describe "using a Diff::LCS.diff patchset" do
-    describe "an empty patchset returns the source" do
-      it "works on a string (hello)" do
+  describe 'using a Diff::LCS.diff patchset' do
+    describe 'an empty patchset returns the source' do
+      it 'works on a string (hello)' do
         diff = Diff::LCS.diff(hello, hello)
-        expect(Diff::LCS::patch(hello, diff)).to eq(hello)
+        expect(Diff::LCS.patch(hello, diff)).to eq(hello)
       end
 
-      it "works on an array %W(h e l l o)" do
+      it 'works on an array %W(h e l l o)' do
         diff = Diff::LCS.diff(hello_ary, hello_ary)
-        expect(Diff::LCS::patch(hello_ary, diff)).to eq(hello_ary)
+        expect(Diff::LCS.patch(hello_ary, diff)).to eq(hello_ary)
       end
     end
 
-    describe "with default diff callbacks (DiffCallbacks)" do
-      describe "forward (s1 -> s2)" do
-        it_has_behavior "patch sequences correctly" do
+    describe 'with default diff callbacks (DiffCallbacks)' do
+      describe 'forward (s1 -> s2)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq1 }
           let(:s2) { seq2 }
           let(:patch_set) { Diff::LCS.diff(seq1, seq2) }
         end
       end
 
-      describe "reverse (s2 -> s1)" do
-        it_has_behavior "patch sequences correctly" do
+      describe 'reverse (s2 -> s1)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq2 }
           let(:s2) { seq1 }
           let(:patch_set) { Diff::LCS.diff(seq2, seq1) }
@@ -56,9 +56,9 @@
       end
     end
 
-    describe "with context diff callbacks (ContextDiffCallbacks)" do
-      describe "forward (s1 -> s2)" do
-        it_has_behavior "patch sequences correctly" do
+    describe 'with context diff callbacks (ContextDiffCallbacks)' do
+      describe 'forward (s1 -> s2)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq1 }
           let(:s2) { seq2 }
           let(:patch_set) {
@@ -67,8 +67,8 @@
         end
       end
 
-      describe "reverse (s2 -> s1)" do
-        it_has_behavior "patch sequences correctly" do
+      describe 'reverse (s2 -> s1)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq2 }
           let(:s2) { seq1 }
           let(:patch_set) {
@@ -78,9 +78,9 @@
       end
     end
 
-    describe "with sdiff callbacks (SDiffCallbacks)" do
-      describe "forward (s1 -> s2)" do
-        it_has_behavior "patch sequences correctly" do
+    describe 'with sdiff callbacks (SDiffCallbacks)' do
+      describe 'forward (s1 -> s2)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq1 }
           let(:s2) { seq2 }
           let(:patch_set) {
@@ -89,8 +89,8 @@
         end
       end
 
-      describe "reverse (s2 -> s1)" do
-        it_has_behavior "patch sequences correctly" do
+      describe 'reverse (s2 -> s1)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq2 }
           let(:s2) { seq1 }
           let(:patch_set) {
@@ -101,20 +101,20 @@
     end
   end
 
-  describe "using a Diff::LCS.sdiff patchset" do
-    describe "an empty patchset returns the source" do
-      it "works on a string (hello)" do
-        expect(Diff::LCS::patch(hello, Diff::LCS.sdiff(hello, hello))).to eq(hello)
+  describe 'using a Diff::LCS.sdiff patchset' do
+    describe 'an empty patchset returns the source' do
+      it 'works on a string (hello)' do
+        expect(Diff::LCS.patch(hello, Diff::LCS.sdiff(hello, hello))).to eq(hello)
       end
 
-      it "works on an array %W(h e l l o)" do
-        expect(Diff::LCS::patch(hello_ary, Diff::LCS.sdiff(hello_ary, hello_ary))).to eq(hello_ary)
+      it 'works on an array %W(h e l l o)' do
+        expect(Diff::LCS.patch(hello_ary, Diff::LCS.sdiff(hello_ary, hello_ary))).to eq(hello_ary)
       end
     end
 
-    describe "with default diff callbacks (DiffCallbacks)" do
-      describe "forward (s1 -> s2)" do
-        it_has_behavior "patch sequences correctly" do
+    describe 'with default diff callbacks (DiffCallbacks)' do
+      describe 'forward (s1 -> s2)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq1 }
           let(:s2) { seq2 }
           let(:patch_set) {
@@ -123,8 +123,8 @@
         end
       end
 
-      describe "reverse (s2 -> s1)" do
-        it_has_behavior "patch sequences correctly" do
+      describe 'reverse (s2 -> s1)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq2 }
           let(:s2) { seq1 }
           let(:patch_set) {
@@ -134,9 +134,9 @@
       end
     end
 
-    describe "with context diff callbacks (DiffCallbacks)" do
-      describe "forward (s1 -> s2)" do
-        it_has_behavior "patch sequences correctly" do
+    describe 'with context diff callbacks (DiffCallbacks)' do
+      describe 'forward (s1 -> s2)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq1 }
           let(:s2) { seq2 }
           let(:patch_set) {
@@ -145,8 +145,8 @@
         end
       end
 
-      describe "reverse (s2 -> s1)" do
-        it_has_behavior "patch sequences correctly" do
+      describe 'reverse (s2 -> s1)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq2 }
           let(:s2) { seq1 }
           let(:patch_set) {
@@ -156,17 +156,17 @@
       end
     end
 
-    describe "with sdiff callbacks (SDiffCallbacks)" do
-      describe "forward (s1 -> s2)" do
-        it_has_behavior "patch sequences correctly" do
+    describe 'with sdiff callbacks (SDiffCallbacks)' do
+      describe 'forward (s1 -> s2)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq1 }
           let(:s2) { seq2 }
           let(:patch_set) { Diff::LCS.sdiff(seq1, seq2) }
         end
       end
 
-      describe "reverse (s2 -> s1)" do
-        it_has_behavior "patch sequences correctly" do
+      describe 'reverse (s2 -> s1)' do
+        it_has_behavior 'patch sequences correctly' do
           let(:s1) { seq2 }
           let(:s2) { seq1 }
           let(:patch_set) { Diff::LCS.sdiff(seq2, seq1) }
@@ -179,43 +179,43 @@
   # to s2 patches"), this cannot use the "patch sequences correctly" shared
   # set. Once the bug in autodiscovery is fixed, this can be converted as
   # above.
-  describe "fix bug 891: patchsets do not contain the last equal part" do
+  describe 'fix bug 891: patchsets do not contain the last equal part' do
     before :each do
-      @s1 = %w(a b c d   e f g h i j k)
+      @s1 = %w(a b c d   e f g h i j k) # rubocop:disable Layout/SpaceInsideArrayPercentLiteral
       @s2 = %w(a b c d D e f g h i j k)
     end
 
-    describe "using Diff::LCS.diff with default diff callbacks" do
+    describe 'using Diff::LCS.diff with default diff callbacks' do
       before :each do
         @patch_set_s1_s2 = Diff::LCS.diff(@s1, @s2)
         @patch_set_s2_s1 = Diff::LCS.diff(@s2, @s1)
       end
 
-      it "autodiscovers s1 to s2 patches" do
+      it 'autodiscovers s1 to s2 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s1_s2)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 patches" do
+      it 'autodiscovers s2 to s1 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s2_s1)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 the left-to-right patches" do
+      it 'autodiscovers s2 to s1 the left-to-right patches' do
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1)).to eq(@s1)
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2)).to eq(@s1)
       end
 
-      it "correctly patches left-to-right (explicit patch)" do
+      it 'correctly patches left-to-right (explicit patch)' do
         expect(Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch)).to eq(@s2)
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch)).to eq(@s1)
         expect(Diff::LCS.patch!(@s1, @patch_set_s1_s2)).to eq(@s2)
         expect(Diff::LCS.patch!(@s2, @patch_set_s2_s1)).to eq(@s1)
       end
 
-      it "correctly patches right-to-left (explicit unpatch)" do
+      it 'correctly patches right-to-left (explicit unpatch)' do
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch)).to eq(@s1)
         expect(Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch)).to eq(@s2)
         expect(Diff::LCS.unpatch!(@s2, @patch_set_s1_s2)).to eq(@s1)
@@ -223,39 +223,37 @@
       end
     end
 
-    describe "using Diff::LCS.diff with context diff callbacks" do
+    describe 'using Diff::LCS.diff with context diff callbacks' do
       before :each do
-        @patch_set_s1_s2 = Diff::LCS.diff(@s1, @s2,
-                                          Diff::LCS::ContextDiffCallbacks)
-        @patch_set_s2_s1 = Diff::LCS.diff(@s2, @s1,
-                                          Diff::LCS::ContextDiffCallbacks)
+        @patch_set_s1_s2 = Diff::LCS.diff(@s1, @s2, Diff::LCS::ContextDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.diff(@s2, @s1, Diff::LCS::ContextDiffCallbacks)
       end
 
-      it "autodiscovers s1 to s2 patches" do
+      it 'autodiscovers s1 to s2 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s1_s2)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 patches" do
+      it 'autodiscovers s2 to s1 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s2_s1)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 the left-to-right patches" do
+      it 'autodiscovers s2 to s1 the left-to-right patches' do
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1)).to eq(@s1)
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2)).to eq(@s1)
       end
 
-      it "correctly patches left-to-right (explicit patch)" do
+      it 'correctly patches left-to-right (explicit patch)' do
         expect(Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch)).to eq(@s2)
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch)).to eq(@s1)
         expect(Diff::LCS.patch!(@s1, @patch_set_s1_s2)).to eq(@s2)
         expect(Diff::LCS.patch!(@s2, @patch_set_s2_s1)).to eq(@s1)
       end
 
-      it "correctly patches right-to-left (explicit unpatch)" do
+      it 'correctly patches right-to-left (explicit unpatch)' do
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch)).to eq(@s1)
         expect(Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch)).to eq(@s2)
         expect(Diff::LCS.unpatch!(@s2, @patch_set_s1_s2)).to eq(@s1)
@@ -263,39 +261,37 @@
       end
     end
 
-    describe "using Diff::LCS.diff with sdiff callbacks" do
+    describe 'using Diff::LCS.diff with sdiff callbacks' do
       before(:each) do
-        @patch_set_s1_s2 = Diff::LCS.diff(@s1, @s2,
-                                          Diff::LCS::SDiffCallbacks)
-        @patch_set_s2_s1 = Diff::LCS.diff(@s2, @s1,
-                                          Diff::LCS::SDiffCallbacks)
+        @patch_set_s1_s2 = Diff::LCS.diff(@s1, @s2, Diff::LCS::SDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.diff(@s2, @s1, Diff::LCS::SDiffCallbacks)
       end
 
-      it "autodiscovers s1 to s2 patches" do
+      it 'autodiscovers s1 to s2 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s1_s2)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 patches" do
+      it 'autodiscovers s2 to s1 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s2_s1)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 the left-to-right patches" do
+      it 'autodiscovers s2 to s1 the left-to-right patches' do
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1)).to eq(@s1)
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2)).to eq(@s1)
       end
 
-      it "correctly patches left-to-right (explicit patch)" do
+      it 'correctly patches left-to-right (explicit patch)' do
         expect(Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch)).to eq(@s2)
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch)).to eq(@s1)
         expect(Diff::LCS.patch!(@s1, @patch_set_s1_s2)).to eq(@s2)
         expect(Diff::LCS.patch!(@s2, @patch_set_s2_s1)).to eq(@s1)
       end
 
-      it "correctly patches right-to-left (explicit unpatch)" do
+      it 'correctly patches right-to-left (explicit unpatch)' do
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch)).to eq(@s1)
         expect(Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch)).to eq(@s2)
         expect(Diff::LCS.unpatch!(@s2, @patch_set_s1_s2)).to eq(@s1)
@@ -303,37 +299,37 @@
       end
     end
 
-    describe "using Diff::LCS.sdiff with default sdiff callbacks" do
+    describe 'using Diff::LCS.sdiff with default sdiff callbacks' do
       before(:each) do
         @patch_set_s1_s2 = Diff::LCS.sdiff(@s1, @s2)
         @patch_set_s2_s1 = Diff::LCS.sdiff(@s2, @s1)
       end
 
-      it "autodiscovers s1 to s2 patches" do
+      it 'autodiscovers s1 to s2 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s1_s2)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 patches" do
+      it 'autodiscovers s2 to s1 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s2_s1)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 the left-to-right patches" do
+      it 'autodiscovers s2 to s1 the left-to-right patches' do
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1)).to eq(@s1)
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2)).to eq(@s1)
       end
 
-      it "correctly patches left-to-right (explicit patch)" do
+      it 'correctly patches left-to-right (explicit patch)' do
         expect(Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch)).to eq(@s2)
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch)).to eq(@s1)
         expect(Diff::LCS.patch!(@s1, @patch_set_s1_s2)).to eq(@s2)
         expect(Diff::LCS.patch!(@s2, @patch_set_s2_s1)).to eq(@s1)
       end
 
-      it "correctly patches right-to-left (explicit unpatch)" do
+      it 'correctly patches right-to-left (explicit unpatch)' do
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch)).to eq(@s1)
         expect(Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch)).to eq(@s2)
         expect(Diff::LCS.unpatch!(@s2, @patch_set_s1_s2)).to eq(@s1)
@@ -341,39 +337,37 @@
       end
     end
 
-    describe "using Diff::LCS.sdiff with context diff callbacks" do
+    describe 'using Diff::LCS.sdiff with context diff callbacks' do
       before(:each) do
-        @patch_set_s1_s2 = Diff::LCS.sdiff(@s1, @s2,
-                                           Diff::LCS::ContextDiffCallbacks)
-        @patch_set_s2_s1 = Diff::LCS.sdiff(@s2, @s1,
-                                           Diff::LCS::ContextDiffCallbacks)
+        @patch_set_s1_s2 = Diff::LCS.sdiff(@s1, @s2, Diff::LCS::ContextDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.sdiff(@s2, @s1, Diff::LCS::ContextDiffCallbacks)
       end
 
-      it "autodiscovers s1 to s2 patches" do
+      it 'autodiscovers s1 to s2 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s1_s2)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 patches" do
+      it 'autodiscovers s2 to s1 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s2_s1)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 the left-to-right patches" do
+      it 'autodiscovers s2 to s1 the left-to-right patches' do
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1)).to eq(@s1)
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2)).to eq(@s1)
       end
 
-      it "correctly patches left-to-right (explicit patch)" do
+      it 'correctly patches left-to-right (explicit patch)' do
         expect(Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch)).to eq(@s2)
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch)).to eq(@s1)
         expect(Diff::LCS.patch!(@s1, @patch_set_s1_s2)).to eq(@s2)
         expect(Diff::LCS.patch!(@s2, @patch_set_s2_s1)).to eq(@s1)
       end
 
-      it "correctly patches right-to-left (explicit unpatch)" do
+      it 'correctly patches right-to-left (explicit unpatch)' do
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch)).to eq(@s1)
         expect(Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch)).to eq(@s2)
         expect(Diff::LCS.unpatch!(@s2, @patch_set_s1_s2)).to eq(@s1)
@@ -381,37 +375,37 @@
       end
     end
 
-    describe "using Diff::LCS.sdiff with default diff callbacks" do
+    describe 'using Diff::LCS.sdiff with default diff callbacks' do
       before(:each) do
         @patch_set_s1_s2 = Diff::LCS.sdiff(@s1, @s2, Diff::LCS::DiffCallbacks)
         @patch_set_s2_s1 = Diff::LCS.sdiff(@s2, @s1, Diff::LCS::DiffCallbacks)
       end
 
-      it "autodiscovers s1 to s2 patches" do
+      it 'autodiscovers s1 to s2 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s1_s2)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 patches" do
+      it 'autodiscovers s2 to s1 patches' do
         expect do
           expect(Diff::LCS.patch(@s1, @patch_set_s2_s1)).to eq(@s2)
         end.to_not raise_error
       end
 
-      it "autodiscovers s2 to s1 the left-to-right patches" do
+      it 'autodiscovers s2 to s1 the left-to-right patches' do
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1)).to eq(@s1)
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2)).to eq(@s1)
       end
 
-      it "correctly patches left-to-right (explicit patch)" do
+      it 'correctly patches left-to-right (explicit patch)' do
         expect(Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch)).to eq(@s2)
         expect(Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch)).to eq(@s1)
         expect(Diff::LCS.patch!(@s1, @patch_set_s1_s2)).to eq(@s2)
         expect(Diff::LCS.patch!(@s2, @patch_set_s2_s1)).to eq(@s1)
       end
 
-      it "correctly patches right-to-left (explicit unpatch)" do
+      it 'correctly patches right-to-left (explicit unpatch)' do
         expect(Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch)).to eq(@s1)
         expect(Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch)).to eq(@s2)
         expect(Diff::LCS.unpatch!(@s2, @patch_set_s1_s2)).to eq(@s1)
diff --git a/spec/sdiff_spec.rb b/spec/sdiff_spec.rb
index d619eb4..06d39d6 100644
--- a/spec/sdiff_spec.rb
+++ b/spec/sdiff_spec.rb
@@ -1,214 +1,214 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
-describe "Diff::LCS.sdiff" do
+describe 'Diff::LCS.sdiff' do
   include Diff::LCS::SpecHelper::Matchers
 
-  shared_examples "compare sequences correctly" do
-    it "compares s1 -> s2 correctly" do
+  shared_examples 'compare sequences correctly' do
+    it 'compares s1 -> s2 correctly' do
       expect(Diff::LCS.sdiff(s1, s2)).to eq(context_diff(result))
     end
 
-    it "compares s2 -> s1 correctly" do
+    it 'compares s2 -> s1 correctly' do
       expect(Diff::LCS.sdiff(s2, s1)).to eq(context_diff(reverse_sdiff(result)))
     end
   end
 
-  describe "using seq1 & seq2" do
+  describe 'using seq1 & seq2' do
     let(:s1) { seq1 }
     let(:s2) { seq2 }
     let(:result) { correct_forward_sdiff }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(abc def yyy xxx ghi jkl) & %w(abc dxf xxx ghi jkl)" do
+  describe 'using %w(abc def yyy xxx ghi jkl) & %w(abc dxf xxx ghi jkl)' do
     let(:s1) { %w(abc def yyy xxx ghi jkl) }
     let(:s2) { %w(abc dxf xxx ghi jkl) }
     let(:result) {
       [
-        [ '=', [ 0, 'abc' ], [ 0, 'abc' ] ],
-        [ '!', [ 1, 'def' ], [ 1, 'dxf' ] ],
-        [ '-', [ 2, 'yyy' ], [ 2,  nil  ] ],
-        [ '=', [ 3, 'xxx' ], [ 2, 'xxx' ] ],
-        [ '=', [ 4, 'ghi' ], [ 3, 'ghi' ] ],
-        [ '=', [ 5, 'jkl' ], [ 4, 'jkl' ] ]
+        ['=', [0, 'abc'], [0, 'abc']],
+        ['!', [1, 'def'], [1, 'dxf']],
+        ['-', [2, 'yyy'], [2,  nil]],
+        ['=', [3, 'xxx'], [2, 'xxx']],
+        ['=', [4, 'ghi'], [3, 'ghi']],
+        ['=', [5, 'jkl'], [4, 'jkl']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(a b c d e) & %w(a e)" do
+  describe 'using %w(a b c d e) & %w(a e)' do
     let(:s1) { %w(a b c d e) }
     let(:s2) { %w(a e) }
     let(:result) {
       [
-        [ '=', [ 0, 'a' ], [ 0, 'a' ] ],
-        [ '-', [ 1, 'b' ], [ 1, nil ] ],
-        [ '-', [ 2, 'c' ], [ 1, nil ] ],
-        [ '-', [ 3, 'd' ], [ 1, nil ] ],
-        [ '=', [ 4, 'e' ], [ 1, 'e' ] ]
+        ['=', [0, 'a'], [0, 'a']],
+        ['-', [1, 'b'], [1, nil]],
+        ['-', [2, 'c'], [1, nil]],
+        ['-', [3, 'd'], [1, nil]],
+        ['=', [4, 'e'], [1, 'e']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(a e) & %w(a b c d e)" do
+  describe 'using %w(a e) & %w(a b c d e)' do
     let(:s1) { %w(a e) }
     let(:s2) { %w(a b c d e) }
     let(:result) {
       [
-        [ '=', [ 0, 'a' ], [ 0, 'a' ] ],
-        [ '+', [ 1, nil ], [ 1, 'b' ] ],
-        [ '+', [ 1, nil ], [ 2, 'c' ] ],
-        [ '+', [ 1, nil ], [ 3, 'd' ] ],
-        [ '=', [ 1, 'e' ], [ 4, 'e' ] ]
+        ['=', [0, 'a'], [0, 'a']],
+        ['+', [1, nil], [1, 'b']],
+        ['+', [1, nil], [2, 'c']],
+        ['+', [1, nil], [3, 'd']],
+        ['=', [1, 'e'], [4, 'e']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(v x a e) & %w(w y a b c d e)" do
+  describe 'using %w(v x a e) & %w(w y a b c d e)' do
     let(:s1) { %w(v x a e) }
     let(:s2) { %w(w y a b c d e) }
     let(:result) {
       [
-        [ '!', [ 0, 'v' ], [ 0, 'w' ] ],
-        [ '!', [ 1, 'x' ], [ 1, 'y' ] ],
-        [ '=', [ 2, 'a' ], [ 2, 'a' ] ],
-        [ '+', [ 3, nil ], [ 3, 'b' ] ],
-        [ '+', [ 3, nil ], [ 4, 'c' ] ],
-        [ '+', [ 3, nil ], [ 5, 'd' ] ],
-        [ '=', [ 3, 'e' ], [ 6, 'e' ] ]
+        ['!', [0, 'v'], [0, 'w']],
+        ['!', [1, 'x'], [1, 'y']],
+        ['=', [2, 'a'], [2, 'a']],
+        ['+', [3, nil], [3, 'b']],
+        ['+', [3, nil], [4, 'c']],
+        ['+', [3, nil], [5, 'd']],
+        ['=', [3, 'e'], [6, 'e']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(x a e) & %w(a b c d e)" do
+  describe 'using %w(x a e) & %w(a b c d e)' do
     let(:s1) { %w(x a e) }
     let(:s2) { %w(a b c d e) }
     let(:result) {
       [
-        [ '-', [ 0, 'x' ], [ 0, nil ] ],
-        [ '=', [ 1, 'a' ], [ 0, 'a' ] ],
-        [ '+', [ 2, nil ], [ 1, 'b' ] ],
-        [ '+', [ 2, nil ], [ 2, 'c' ] ],
-        [ '+', [ 2, nil ], [ 3, 'd' ] ],
-        [ '=', [ 2, 'e' ], [ 4, 'e' ] ]
+        ['-', [0, 'x'], [0, nil]],
+        ['=', [1, 'a'], [0, 'a']],
+        ['+', [2, nil], [1, 'b']],
+        ['+', [2, nil], [2, 'c']],
+        ['+', [2, nil], [3, 'd']],
+        ['=', [2, 'e'], [4, 'e']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(a e) & %w(x a b c d e)" do
+  describe 'using %w(a e) & %w(x a b c d e)' do
     let(:s1) { %w(a e) }
     let(:s2) { %w(x a b c d e) }
     let(:result) {
       [
-        [ '+', [ 0, nil ], [ 0, 'x' ] ],
-        [ '=', [ 0, 'a' ], [ 1, 'a' ] ],
-        [ '+', [ 1, nil ], [ 2, 'b' ] ],
-        [ '+', [ 1, nil ], [ 3, 'c' ] ],
-        [ '+', [ 1, nil ], [ 4, 'd' ] ],
-        [ '=', [ 1, 'e' ], [ 5, 'e' ] ]
+        ['+', [0, nil], [0, 'x']],
+        ['=', [0, 'a'], [1, 'a']],
+        ['+', [1, nil], [2, 'b']],
+        ['+', [1, nil], [3, 'c']],
+        ['+', [1, nil], [4, 'd']],
+        ['=', [1, 'e'], [5, 'e']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(a e v) & %w(x a b c d e w x)" do
+  describe 'using %w(a e v) & %w(x a b c d e w x)' do
     let(:s1) { %w(a e v) }
     let(:s2) { %w(x a b c d e w x) }
     let(:result) {
       [
-        [ '+', [ 0, nil ], [ 0, 'x' ] ],
-        [ '=', [ 0, 'a' ], [ 1, 'a' ] ],
-        [ '+', [ 1, nil ], [ 2, 'b' ] ],
-        [ '+', [ 1, nil ], [ 3, 'c' ] ],
-        [ '+', [ 1, nil ], [ 4, 'd' ] ],
-        [ '=', [ 1, 'e' ], [ 5, 'e' ] ],
-        [ '!', [ 2, 'v' ], [ 6, 'w' ] ],
-        [ '+', [ 3, nil ], [ 7, 'x' ] ]
+        ['+', [0, nil], [0, 'x']],
+        ['=', [0, 'a'], [1, 'a']],
+        ['+', [1, nil], [2, 'b']],
+        ['+', [1, nil], [3, 'c']],
+        ['+', [1, nil], [4, 'd']],
+        ['=', [1, 'e'], [5, 'e']],
+        ['!', [2, 'v'], [6, 'w']],
+        ['+', [3, nil], [7, 'x']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w() & %w(a b c)" do
+  describe 'using %w() & %w(a b c)' do
     let(:s1) { %w() }
     let(:s2) { %w(a b c) }
     let(:result) {
       [
-        [ '+', [ 0, nil ], [ 0, 'a' ] ],
-        [ '+', [ 0, nil ], [ 1, 'b' ] ],
-        [ '+', [ 0, nil ], [ 2, 'c' ] ]
+        ['+', [0, nil], [0, 'a']],
+        ['+', [0, nil], [1, 'b']],
+        ['+', [0, nil], [2, 'c']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(a b c) & %w(1)" do
+  describe 'using %w(a b c) & %w(1)' do
     let(:s1) { %w(a b c) }
     let(:s2) { %w(1) }
     let(:result) {
       [
-        [ '!', [ 0, 'a' ], [ 0, '1' ] ],
-        [ '-', [ 1, 'b' ], [ 1, nil ] ],
-        [ '-', [ 2, 'c' ], [ 1, nil ] ]
+        ['!', [0, 'a'], [0, '1']],
+        ['-', [1, 'b'], [1, nil]],
+        ['-', [2, 'c'], [1, nil]]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(a b c) & %w(c)" do
+  describe 'using %w(a b c) & %w(c)' do
     let(:s1) { %w(a b c) }
     let(:s2) { %w(c) }
     let(:result) {
       [
-        [ '-', [ 0, 'a' ], [ 0, nil ] ],
-        [ '-', [ 1, 'b' ], [ 0, nil ] ],
-        [ '=', [ 2, 'c' ], [ 0, 'c' ] ]
+        ['-', [0, 'a'], [0, nil]],
+        ['-', [1, 'b'], [0, nil]],
+        ['=', [2, 'c'], [0, 'c']]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using %w(abcd efgh ijkl mnop) & []" do
+  describe 'using %w(abcd efgh ijkl mnop) & []' do
     let(:s1) { %w(abcd efgh ijkl mnop) }
     let(:s2) { [] }
     let(:result) {
       [
-        [ '-', [ 0, 'abcd' ], [ 0, nil ] ],
-        [ '-', [ 1, 'efgh' ], [ 0, nil ] ],
-        [ '-', [ 2, 'ijkl' ], [ 0, nil ] ],
-        [ '-', [ 3, 'mnop' ], [ 0, nil ] ]
+        ['-', [0, 'abcd'], [0, nil]],
+        ['-', [1, 'efgh'], [0, nil]],
+        ['-', [2, 'ijkl'], [0, nil]],
+        ['-', [3, 'mnop'], [0, nil]]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 
-  describe "using [[1,2]] & []" do
-    let(:s1) { [ [ 1, 2 ] ] }
+  describe 'using [[1,2]] & []' do
+    let(:s1) { [[1, 2]] }
     let(:s2) { [] }
     let(:result) {
       [
-        [ '-', [ 0, [ 1, 2 ] ], [ 0, nil ] ]
+        ['-', [0, [1, 2]], [0, nil]]
       ]
     }
 
-    it_has_behavior "compare sequences correctly"
+    it_has_behavior 'compare sequences correctly'
   end
 end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 27298c4..4899c49 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,4 +1,4 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'rubygems'
 require 'pathname'
@@ -10,14 +10,14 @@
 elsif ENV['COVERAGE']
   require 'simplecov'
 
-  def require_do(resource, &block)
+  def require_do(resource)
     require resource
-    block.call
+    yield if block_given?
   rescue LoadError
     nil
   end
 
-  formatters = [ SimpleCov::Formatter::HTMLFormatter ]
+  formatters = [SimpleCov::Formatter::HTMLFormatter]
 
   require_do('simplecov-rcov') {
     formatters << SimpleCov::Formatter::RcovFormatter
@@ -44,11 +44,11 @@ def require_do(resource, &block)
 
 module Diff::LCS::SpecHelper
   def hello
-    "hello"
+    'hello'
   end
 
   def hello_ary
-    %W(h e l l o)
+    %w(h e l l o)
   end
 
   def seq1
@@ -77,50 +77,69 @@ def correct_lcs
 
   def correct_forward_diff
     [
-      [ [ '-',  0, 'a' ] ],
-      [ [ '+',  2, 'd' ] ],
-      [ [ '-',  4, 'h' ],
-        [ '+',  4, 'f' ] ],
-      [ [ '+',  6, 'k' ] ],
-      [ [ '-',  8, 'n' ],
-        [ '-',  9, 'p' ],
-        [ '+',  9, 'r' ],
-        [ '+', 10, 's' ],
-        [ '+', 11, 't' ] ]
+      [
+        ['-',  0, 'a']
+      ],
+      [
+        ['+',  2, 'd']
+      ],
+      [
+        ['-',  4, 'h'],
+        ['+',  4, 'f']
+      ],
+      [
+        ['+',  6, 'k']
+      ],
+      [
+        ['-',  8, 'n'],
+        ['-',  9, 'p'],
+        ['+',  9, 'r'],
+        ['+', 10, 's'],
+        ['+', 11, 't']
+      ]
     ]
   end
 
   def correct_backward_diff
     [
-      [ [ '+',  0, 'a' ] ],
-      [ [ '-',  2, 'd' ] ],
-      [ [ '-',  4, 'f' ],
-        [ '+',  4, 'h' ] ],
-      [ [ '-',  6, 'k' ] ],
       [
-        [ '-',  9, 'r' ],
-        [ '-', 10, 's' ],
-        [ '+',  8, 'n' ],
-        [ '-', 11, 't' ],
-        [ '+',  9, 'p' ] ]
+        ['+',  0, 'a']
+      ],
+      [
+        ['-',  2, 'd']
+      ],
+      [
+        ['-',  4, 'f'],
+        ['+',  4, 'h']
+      ],
+      [
+        ['-',  6, 'k']
+      ],
+      [
+        ['-',  9, 'r'],
+        ['-', 10, 's'],
+        ['+',  8, 'n'],
+        ['-', 11, 't'],
+        ['+',  9, 'p']
+      ]
     ]
   end
 
   def correct_forward_sdiff
     [
-      [ '-', [  0, 'a' ], [  0, nil ] ],
-      [ '=', [  1, 'b' ], [  0, 'b' ] ],
-      [ '=', [  2, 'c' ], [  1, 'c' ] ],
-      [ '+', [  3, nil ], [  2, 'd' ] ],
-      [ '=', [  3, 'e' ], [  3, 'e' ] ],
-      [ '!', [  4, 'h' ], [  4, 'f' ] ],
-      [ '=', [  5, 'j' ], [  5, 'j' ] ],
-      [ '+', [  6, nil ], [  6, 'k' ] ],
-      [ '=', [  6, 'l' ], [  7, 'l' ] ],
-      [ '=', [  7, 'm' ], [  8, 'm' ] ],
-      [ '!', [  8, 'n' ], [  9, 'r' ] ],
-      [ '!', [  9, 'p' ], [ 10, 's' ] ],
-      [ '+', [ 10, nil ], [ 11, 't' ] ]
+      ['-', [0, 'a'], [0, nil]],
+      ['=', [1, 'b'], [0, 'b']],
+      ['=', [2, 'c'], [1, 'c']],
+      ['+', [3, nil], [2, 'd']],
+      ['=', [3, 'e'], [3, 'e']],
+      ['!', [4, 'h'], [4, 'f']],
+      ['=', [5, 'j'], [5, 'j']],
+      ['+', [6, nil], [6, 'k']],
+      ['=', [6, 'l'], [7, 'l']],
+      ['=', [7, 'm'], [8, 'm']],
+      ['!', [8, 'n'], [9, 'r']],
+      ['!', [9, 'p'], [10, 's']],
+      ['+', [10, nil], [11, 't']]
     ]
   end
 
@@ -144,13 +163,13 @@ def context_diff(diff)
   end
 
   def format_diffs(diffs)
-    diffs.map do |e|
+    diffs.map { |e|
       if e.kind_of?(Array)
-        e.map { |f| f.to_a.join }.join(", ")
+        e.map { |f| f.to_a.join }.join(', ')
       else
         e.to_a.join
       end
-    end.join("\n")
+    }.join("\n")
   end
 
   def map_diffs(diffs, klass = Diff::LCS::ContextChange)
@@ -171,8 +190,8 @@ def balanced_traversal(s1, s2, callback_type)
 
   def balanced_reverse(change_result)
     new_result = []
-    change_result.each { |line|
-      line = [ line[0], line[2], line[1] ]
+    change_result.each do |line|
+      line = [line[0], line[2], line[1]]
       case line[0]
       when '<'
         line[0] = '>'
@@ -180,21 +199,21 @@ def balanced_reverse(change_result)
         line[0] = '<'
       end
       new_result << line
-    }
-    new_result.sort_by { |line| [ line[1], line[2] ] }
+    end
+    new_result.sort_by { |line| [line[1], line[2]] }
   end
 
   def map_to_no_change(change_result)
     new_result = []
-    change_result.each { |line|
+    change_result.each do |line|
       case line[0]
       when '!'
-        new_result << [ '<', line[1], line[2] ]
-        new_result << [ '>', line[1] + 1, line[2] ]
+        new_result << ['<', line[1], line[2]]
+        new_result << ['>', line[1] + 1, line[2]]
       else
         new_result << line
       end
-    }
+    end
     new_result
   end
 
@@ -231,14 +250,18 @@ def discard_a(event)
       end
 
       def finished_a(event)
-        @done_a << [event.old_element, event.old_position,
-          event.new_element, event.new_position]
+        @done_a << [
+          event.old_element, event.old_position,
+          event.new_element, event.new_position
+        ]
       end
 
       def finished_b(event)
-        p "called #finished_b"
-        @done_b << [event.old_element, event.old_position,
-          event.new_element, event.new_position]
+        p 'called #finished_b'
+        @done_b << [
+          event.old_element, event.old_position,
+          event.new_element, event.new_position
+        ]
       end
     end
     callbacks.reset
@@ -264,19 +287,19 @@ def reset
       end
 
       def match(event)
-        @result << [ "=", event.old_position, event.new_position ]
+        @result << ['=', event.old_position, event.new_position]
       end
 
       def discard_a(event)
-        @result << [ "<", event.old_position, event.new_position ]
+        @result << ['<', event.old_position, event.new_position]
       end
 
       def discard_b(event)
-        @result << [ ">", event.old_position, event.new_position ]
+        @result << ['>', event.old_position, event.new_position]
       end
 
       def change(event)
-        @result << [ "!", event.old_position, event.new_position ]
+        @result << ['!', event.old_position, event.new_position]
       end
     end
     cb.reset
diff --git a/spec/traverse_balanced_spec.rb b/spec/traverse_balanced_spec.rb
index 95e60ec..9ee68ea 100644
--- a/spec/traverse_balanced_spec.rb
+++ b/spec/traverse_balanced_spec.rb
@@ -1,310 +1,310 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
-describe "Diff::LCS.traverse_balanced" do
+describe 'Diff::LCS.traverse_balanced' do
   include Diff::LCS::SpecHelper::Matchers
 
-  shared_examples "with a #change callback" do |s1, s2, result|
-    it "traverses s1 -> s2 correctly" do
+  shared_examples 'with a #change callback' do |s1, s2, result|
+    it 'traverses s1 -> s2 correctly' do
       traversal = balanced_traversal(s1, s2, :balanced_callback)
       expect(traversal.result).to eq(result)
     end
 
-    it "traverses s2 -> s1 correctly" do
+    it 'traverses s2 -> s1 correctly' do
       traversal = balanced_traversal(s2, s1, :balanced_callback)
       expect(traversal.result).to eq(balanced_reverse(result))
     end
   end
 
-  shared_examples "without a #change callback" do |s1, s2, result|
-    it "traverses s1 -> s2 correctly" do
+  shared_examples 'without a #change callback' do |s1, s2, result|
+    it 'traverses s1 -> s2 correctly' do
       traversal = balanced_traversal(s1, s2, :balanced_callback_no_change)
       expect(traversal.result).to eq(map_to_no_change(result))
     end
 
-    it "traverses s2 -> s1 correctly" do
+    it 'traverses s2 -> s1 correctly' do
       traversal = balanced_traversal(s2, s1, :balanced_callback_no_change)
       expect(traversal.result).to eq(map_to_no_change(balanced_reverse(result)))
     end
   end
 
   describe "identical string sequences ('abc')" do
-    s1 = s2 = "abc"
+    s1 = s2 = 'abc'
 
     result = [
-      [ '=', 0, 0 ],
-      [ '=', 1, 1 ],
-      [ '=', 2, 2 ]
+      ['=', 0, 0],
+      ['=', 1, 1],
+      ['=', 2, 2]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "identical array sequences %w(a b c)" do
+  describe 'identical array sequences %w(a b c)' do
     s1 = s2 = %w(a b c)
 
     result = [
-      [ '=', 0, 0 ],
-      [ '=', 1, 1 ],
-      [ '=', 2, 2 ]
+      ['=', 0, 0],
+      ['=', 1, 1],
+      ['=', 2, 2]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "sequences %w(a b c) & %w(a x c)" do
+  describe 'sequences %w(a b c) & %w(a x c)' do
     s1 = %w(a b c)
     s2 = %w(a x c)
 
     result = [
-      [ '=', 0, 0 ],
-      [ '!', 1, 1 ],
-      [ '=', 2, 2 ]
+      ['=', 0, 0],
+      ['!', 1, 1],
+      ['=', 2, 2]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "sequences %w(a x y c) & %w(a v w c)" do
+  describe 'sequences %w(a x y c) & %w(a v w c)' do
     s1 = %w(a x y c)
     s2 = %w(a v w c)
 
     result = [
-      [ '=', 0, 0 ],
-      [ '!', 1, 1 ],
-      [ '!', 2, 2 ],
-      [ '=', 3, 3 ]
+      ['=', 0, 0],
+      ['!', 1, 1],
+      ['!', 2, 2],
+      ['=', 3, 3]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "sequences %w(x y c) & %w(v w c)" do
+  describe 'sequences %w(x y c) & %w(v w c)' do
     s1 = %w(x y c)
     s2 = %w(v w c)
     result = [
-      [ '!', 0, 0 ],
-      [ '!', 1, 1 ],
-      [ '=', 2, 2 ]
+      ['!', 0, 0],
+      ['!', 1, 1],
+      ['=', 2, 2]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "sequences %w(a x y z) & %w(b v w)" do
+  describe 'sequences %w(a x y z) & %w(b v w)' do
     s1 = %w(a x y z)
     s2 = %w(b v w)
     result = [
-      [ '!', 0, 0 ],
-      [ '!', 1, 1 ],
-      [ '!', 2, 2 ],
-      [ '<', 3, 3 ]
+      ['!', 0, 0],
+      ['!', 1, 1],
+      ['!', 2, 2],
+      ['<', 3, 3]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "sequences %w(a z) & %w(a)" do
+  describe 'sequences %w(a z) & %w(a)' do
     s1 = %w(a z)
     s2 = %w(a)
     result = [
-      [ '=', 0, 0 ],
-      [ '<', 1, 1 ]
+      ['=', 0, 0],
+      ['<', 1, 1]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "sequences %w(z a) & %w(a)" do
+  describe 'sequences %w(z a) & %w(a)' do
     s1 = %w(z a)
     s2 = %w(a)
     result = [
-      [ '<', 0, 0 ],
-      [ '=', 1, 0 ]
+      ['<', 0, 0],
+      ['=', 1, 0]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "sequences %w(a b c) & %w(x y z)" do
+  describe 'sequences %w(a b c) & %w(x y z)' do
     s1 = %w(a b c)
     s2 = %w(x y z)
     result = [
-      [ '!', 0, 0 ],
-      [ '!', 1, 1 ],
-      [ '!', 2, 2 ]
+      ['!', 0, 0],
+      ['!', 1, 1],
+      ['!', 2, 2]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "sequences %w(abcd efgh ijkl mnoopqrstuvwxyz) & []" do
+  describe 'sequences %w(abcd efgh ijkl mnoopqrstuvwxyz) & []' do
     s1 = %w(abcd efgh ijkl mnopqrstuvwxyz)
     s2 = []
     result = [
-      [ '<', 0, 0 ],
-      [ '<', 1, 0 ],
-      [ '<', 2, 0 ],
-      [ '<', 3, 0 ]
+      ['<', 0, 0],
+      ['<', 1, 0],
+      ['<', 2, 0],
+      ['<', 3, 0]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "strings %Q(a b c) & %Q(a x c)" do
-    s1 = %Q(a b c)
-    s2 = %Q(a x c)
+  describe 'strings %q(a b c) & %q(a x c)' do
+    s1 = 'a b c'
+    s2 = 'a x c'
 
     result = [
-      [ '=', 0, 0 ],
-      [ '=', 1, 1 ],
-      [ '!', 2, 2 ],
-      [ '=', 3, 3 ],
-      [ '=', 4, 4 ]
+      ['=', 0, 0],
+      ['=', 1, 1],
+      ['!', 2, 2],
+      ['=', 3, 3],
+      ['=', 4, 4]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "strings %Q(a x y c) & %Q(a v w c)" do
-    s1 = %Q(a x y c)
-    s2 = %Q(a v w c)
+  describe 'strings %q(a x y c) & %q(a v w c)' do
+    s1 = 'a x y c'
+    s2 = 'a v w c'
 
     result = [
-      [ '=', 0, 0 ],
-      [ '=', 1, 1 ],
-      [ '!', 2, 2 ],
-      [ '=', 3, 3 ],
-      [ '!', 4, 4 ],
-      [ '=', 5, 5 ],
-      [ '=', 6, 6 ]
+      ['=', 0, 0],
+      ['=', 1, 1],
+      ['!', 2, 2],
+      ['=', 3, 3],
+      ['!', 4, 4],
+      ['=', 5, 5],
+      ['=', 6, 6]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "strings %Q(x y c) & %Q(v w c)" do
-    s1 = %Q(x y c)
-    s2 = %Q(v w c)
+  describe 'strings %q(x y c) & %q(v w c)' do
+    s1 = 'x y c'
+    s2 = 'v w c'
     result = [
-      [ '!', 0, 0 ],
-      [ '=', 1, 1 ],
-      [ '!', 2, 2 ],
-      [ '=', 3, 3 ],
-      [ '=', 4, 4 ]
+      ['!', 0, 0],
+      ['=', 1, 1],
+      ['!', 2, 2],
+      ['=', 3, 3],
+      ['=', 4, 4]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "strings %Q(a x y z) & %Q(b v w)" do
-    s1 = %Q(a x y z)
-    s2 = %Q(b v w)
+  describe 'strings %q(a x y z) & %q(b v w)' do
+    s1 = 'a x y z'
+    s2 = 'b v w'
     result = [
-      [ '!', 0, 0 ],
-      [ '=', 1, 1 ],
-      [ '!', 2, 2 ],
-      [ '=', 3, 3 ],
-      [ '!', 4, 4 ],
-      [ '<', 5, 5 ],
-      [ '<', 6, 5 ]
+      ['!', 0, 0],
+      ['=', 1, 1],
+      ['!', 2, 2],
+      ['=', 3, 3],
+      ['!', 4, 4],
+      ['<', 5, 5],
+      ['<', 6, 5]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "strings %Q(a z) & %Q(a)" do
-    s1 = %Q(a z)
-    s2 = %Q(a)
+  describe 'strings %q(a z) & %q(a)' do
+    s1 = 'a z'
+    s2 = 'a'
     result = [
-      [ '=', 0, 0 ],
-      [ '<', 1, 1 ],
-      [ '<', 2, 1 ]
+      ['=', 0, 0],
+      ['<', 1, 1],
+      ['<', 2, 1]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "strings %Q(z a) & %Q(a)" do
-    s1 = %Q(z a)
-    s2 = %Q(a)
+  describe 'strings %q(z a) & %q(a)' do
+    s1 = 'z a'
+    s2 = 'a'
     result = [
-      [ '<', 0, 0 ],
-      [ '<', 1, 0 ],
-      [ '=', 2, 0 ]
+      ['<', 0, 0],
+      ['<', 1, 0],
+      ['=', 2, 0]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "strings %Q(a b c) & %Q(x y z)" do
-    s1 = %Q(a b c)
-    s2 = %Q(x y z)
+  describe 'strings %q(a b c) & %q(x y z)' do
+    s1 = 'a b c'
+    s2 = 'x y z'
     result = [
-      [ '!', 0, 0 ],
-      [ '=', 1, 1 ],
-      [ '!', 2, 2 ],
-      [ '=', 3, 3 ],
-      [ '!', 4, 4 ]
+      ['!', 0, 0],
+      ['=', 1, 1],
+      ['!', 2, 2],
+      ['=', 3, 3],
+      ['!', 4, 4]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 
-  describe "strings %Q(abcd efgh ijkl mnopqrstuvwxyz) & %Q()" do
-    s1 = %Q(abcd efgh ijkl mnopqrstuvwxyz)
-    s2 = ""
+  describe 'strings %q(abcd efgh ijkl mnopqrstuvwxyz) & %q()' do
+    s1 = 'abcd efgh ijkl mnopqrstuvwxyz'
+    s2 = ''
     result = [
-      [ '<',  0, 0 ],
-      [ '<',  1, 0 ],
-      [ '<',  2, 0 ],
-      [ '<',  3, 0 ],
-      [ '<',  4, 0 ],
-      [ '<',  5, 0 ],
-      [ '<',  6, 0 ],
-      [ '<',  7, 0 ],
-      [ '<',  8, 0 ],
-      [ '<',  9, 0 ],
-      [ '<', 10, 0 ],
-      [ '<', 11, 0 ],
-      [ '<', 12, 0 ],
-      [ '<', 13, 0 ],
-      [ '<', 14, 0 ],
-      [ '<', 15, 0 ],
-      [ '<', 16, 0 ],
-      [ '<', 17, 0 ],
-      [ '<', 18, 0 ],
-      [ '<', 19, 0 ],
-      [ '<', 20, 0 ],
-      [ '<', 21, 0 ],
-      [ '<', 22, 0 ],
-      [ '<', 23, 0 ],
-      [ '<', 24, 0 ],
-      [ '<', 25, 0 ],
-      [ '<', 26, 0 ],
-      [ '<', 27, 0 ],
-      [ '<', 28, 0 ],
+      ['<',  0, 0],
+      ['<',  1, 0],
+      ['<',  2, 0],
+      ['<',  3, 0],
+      ['<',  4, 0],
+      ['<',  5, 0],
+      ['<',  6, 0],
+      ['<',  7, 0],
+      ['<',  8, 0],
+      ['<',  9, 0],
+      ['<', 10, 0],
+      ['<', 11, 0],
+      ['<', 12, 0],
+      ['<', 13, 0],
+      ['<', 14, 0],
+      ['<', 15, 0],
+      ['<', 16, 0],
+      ['<', 17, 0],
+      ['<', 18, 0],
+      ['<', 19, 0],
+      ['<', 20, 0],
+      ['<', 21, 0],
+      ['<', 22, 0],
+      ['<', 23, 0],
+      ['<', 24, 0],
+      ['<', 25, 0],
+      ['<', 26, 0],
+      ['<', 27, 0],
+      ['<', 28, 0]
     ]
 
-    it_has_behavior "with a #change callback", s1, s2, result
-    it_has_behavior "without a #change callback", s1, s2, result
+    it_has_behavior 'with a #change callback', s1, s2, result
+    it_has_behavior 'without a #change callback', s1, s2, result
   end
 end
diff --git a/spec/traverse_sequences_spec.rb b/spec/traverse_sequences_spec.rb
index 1252d53..ea7a129 100644
--- a/spec/traverse_sequences_spec.rb
+++ b/spec/traverse_sequences_spec.rb
@@ -1,10 +1,10 @@
-# -*- ruby encoding: utf-8 -*-
+# frozen_string_literal: true
 
 require 'spec_helper'
 
-describe "Diff::LCS.traverse_sequences" do
-  describe "callback with no finishers" do
-    describe "over (seq1, seq2)" do
+describe 'Diff::LCS.traverse_sequences' do
+  describe 'callback with no finishers' do
+    describe 'over (seq1, seq2)' do
       before(:each) do
         @callback_s1_s2 = simple_callback_no_finishers
         Diff::LCS.traverse_sequences(seq1, seq2, @callback_s1_s2)
@@ -13,27 +13,27 @@
         Diff::LCS.traverse_sequences(seq2, seq1, @callback_s2_s1)
       end
 
-      it "has the correct LCS result on left-matches" do
+      it 'has the correct LCS result on left-matches' do
         expect(@callback_s1_s2.matched_a).to eq(correct_lcs)
         expect(@callback_s2_s1.matched_a).to eq(correct_lcs)
       end
 
-      it "has the correct LCS result on right-matches" do
+      it 'has the correct LCS result on right-matches' do
         expect(@callback_s1_s2.matched_b).to eq(correct_lcs)
         expect(@callback_s2_s1.matched_b).to eq(correct_lcs)
       end
 
-      it "has the correct skipped sequences with the left sequence" do
+      it 'has the correct skipped sequences with the left sequence' do
         expect(@callback_s1_s2.discards_a).to eq(skipped_seq1)
         expect(@callback_s2_s1.discards_a).to eq(skipped_seq2)
       end
 
-      it "has the correct skipped sequences with the right sequence" do
+      it 'has the correct skipped sequences with the right sequence' do
         expect(@callback_s1_s2.discards_b).to eq(skipped_seq2)
         expect(@callback_s2_s1.discards_b).to eq(skipped_seq1)
       end
 
-      it "does not have anything done markers from the left or right sequences" do
+      it 'does not have anything done markers from the left or right sequences' do
         expect(@callback_s1_s2.done_a).to be_empty
         expect(@callback_s1_s2.done_b).to be_empty
         expect(@callback_s2_s1.done_a).to be_empty
@@ -41,64 +41,64 @@
       end
     end
 
-    describe "over (hello, hello)" do
+    describe 'over (hello, hello)' do
       before(:each) do
         @callback = simple_callback_no_finishers
         Diff::LCS.traverse_sequences(hello, hello, @callback)
       end
 
-      it "has the correct LCS result on left-matches" do
+      it 'has the correct LCS result on left-matches' do
         expect(@callback.matched_a).to eq(hello.split(//))
       end
 
-      it "has the correct LCS result on right-matches" do
+      it 'has the correct LCS result on right-matches' do
         expect(@callback.matched_b).to eq(hello.split(//))
       end
 
-      it "has the correct skipped sequences with the left sequence", :only => true do
+      it 'has the correct skipped sequences with the left sequence', :only => true do
         expect(@callback.discards_a).to be_empty
       end
 
-      it "has the correct skipped sequences with the right sequence" do
+      it 'has the correct skipped sequences with the right sequence' do
         expect(@callback.discards_b).to be_empty
       end
 
-      it "does not have anything done markers from the left or right sequences" do
+      it 'does not have anything done markers from the left or right sequences' do
         expect(@callback.done_a).to be_empty
         expect(@callback.done_b).to be_empty
       end
     end
 
-    describe "over (hello_ary, hello_ary)" do
+    describe 'over (hello_ary, hello_ary)' do
       before(:each) do
         @callback = simple_callback_no_finishers
         Diff::LCS.traverse_sequences(hello_ary, hello_ary, @callback)
       end
 
-      it "has the correct LCS result on left-matches" do
+      it 'has the correct LCS result on left-matches' do
         expect(@callback.matched_a).to eq(hello_ary)
       end
 
-      it "has the correct LCS result on right-matches" do
+      it 'has the correct LCS result on right-matches' do
         expect(@callback.matched_b).to eq(hello_ary)
       end
 
-      it "has the correct skipped sequences with the left sequence" do
+      it 'has the correct skipped sequences with the left sequence' do
         expect(@callback.discards_a).to be_empty
       end
 
-      it "has the correct skipped sequences with the right sequence" do
+      it 'has the correct skipped sequences with the right sequence' do
         expect(@callback.discards_b).to be_empty
       end
 
-      it "does not have anything done markers from the left or right sequences" do
+      it 'does not have anything done markers from the left or right sequences' do
         expect(@callback.done_a).to be_empty
         expect(@callback.done_b).to be_empty
       end
     end
   end
 
-  describe "callback with finisher" do
+  describe 'callback with finisher' do
     before(:each) do
       @callback_s1_s2 = simple_callback
       Diff::LCS.traverse_sequences(seq1, seq2, @callback_s1_s2)
@@ -106,28 +106,28 @@
       Diff::LCS.traverse_sequences(seq2, seq1, @callback_s2_s1)
     end
 
-    it "has the correct LCS result on left-matches" do
+    it 'has the correct LCS result on left-matches' do
       expect(@callback_s1_s2.matched_a).to eq(correct_lcs)
       expect(@callback_s2_s1.matched_a).to eq(correct_lcs)
     end
 
-    it "has the correct LCS result on right-matches" do
+    it 'has the correct LCS result on right-matches' do
       expect(@callback_s1_s2.matched_b).to eq(correct_lcs)
       expect(@callback_s2_s1.matched_b).to eq(correct_lcs)
     end
 
-    it "has the correct skipped sequences for the left sequence" do
+    it 'has the correct skipped sequences for the left sequence' do
       expect(@callback_s1_s2.discards_a).to eq(skipped_seq1)
       expect(@callback_s2_s1.discards_a).to eq(skipped_seq2)
     end
 
-    it "has the correct skipped sequences for the right sequence" do
+    it 'has the correct skipped sequences for the right sequence' do
       expect(@callback_s1_s2.discards_b).to eq(skipped_seq2)
       expect(@callback_s2_s1.discards_b).to eq(skipped_seq1)
     end
 
-    it "has done markers differently-sized sequences" do
-      expect(@callback_s1_s2.done_a).to eq([[ "p", 9, "s", 10 ]])
+    it 'has done markers differently-sized sequences' do
+      expect(@callback_s1_s2.done_a).to eq([['p', 9, 's', 10]])
       expect(@callback_s1_s2.done_b).to be_empty
 
       # 20110731 I don't yet understand why this particular behaviour