From 1d39f15e9c106a0d2b492793256ce086b828db79 Mon Sep 17 00:00:00 2001
From: Ngoc Le <ngocle@outlook.com>
Date: Thu, 2 May 2019 00:28:49 -0700
Subject: [PATCH] added solution

---
 lib/matrix_convert_to_zero.rb        | 55 ++++++++++++++++++++++++++--
 specs/matrix_convert_to_zero_spec.rb | 11 +++---
 2 files changed, 58 insertions(+), 8 deletions(-)

diff --git a/lib/matrix_convert_to_zero.rb b/lib/matrix_convert_to_zero.rb
index 4fb139c..ca2d608 100644
--- a/lib/matrix_convert_to_zero.rb
+++ b/lib/matrix_convert_to_zero.rb
@@ -3,8 +3,57 @@
 # If any number is found to be 0, the method updates all the numbers in the
 # corresponding row as well as the corresponding column to be 0.
 
-# Time complexity: ?
-# Space complexity: ?
+#Approach 1:
+# Time complexity: O(n^3) 3 nested loops
+# Space complexity: O(n^2) n is the number of rows and columns in the matrix being cloned
+
+def matrix_convert_to_zero_n_3(matrix)
+  clone = matrix.map(&:dup)
+  rows = matrix.length
+  columns = matrix[0].length
+  rows.times do |i|
+    columns.times do |j|
+      if matrix[i][j] == 0
+        columns.times do |jj|
+          clone[i][jj] = 0
+        end
+        rows.times do |ii|
+          clone[ii][j] = 0
+        end
+      end
+    end
+  end
+  rows.times do |i|
+    columns.times do |j|
+      matrix[i][j] = clone[i][j]
+    end
+  end
+end
+
+#Approach 2:
+# Time complexity: O(n^2) 2 nested loops
+# Space complexity: O(n) n is the number of affected rows and columns
 def matrix_convert_to_zero(matrix)
-  raise NotImplementedError
+  affected_rows = []
+  affected_columns = []
+  rows = matrix.length
+  columns = matrix[0].length
+  rows.times do |i|
+    columns.times do |j|
+      if matrix[i][j] == 0
+        affected_rows << i
+        affected_columns << j
+      end
+    end
+  end
+  affected_rows.each do |i|
+    columns.times do |j|
+      matrix[i][j] = 0
+    end
+  end
+  affected_columns.each do |j|
+    rows.times do |i|
+      matrix[i][j] = 0
+    end
+  end
 end
diff --git a/specs/matrix_convert_to_zero_spec.rb b/specs/matrix_convert_to_zero_spec.rb
index a21b0a6..9ef8e21 100644
--- a/specs/matrix_convert_to_zero_spec.rb
+++ b/specs/matrix_convert_to_zero_spec.rb
@@ -1,11 +1,11 @@
-require 'minitest/autorun'
-require 'minitest/reporters'
-require_relative '../lib/matrix_convert_to_zero'
+require "minitest/autorun"
+require "minitest/reporters"
+require_relative "../lib/matrix_convert_to_zero"
 
 # helper method for creating and initializing a matrix with all 1s
 def initialize_matrix(rows, columns)
   # create the matrix using the rows and columns
-  matrix = Array.new(rows){Array.new(columns)}
+  matrix = Array.new(rows) { Array.new(columns) }
 
   # initialize the matrix
   rows.times do |row|
@@ -47,8 +47,9 @@ def verify_matrix(matrix, rows_array, columns_array)
       columns_array = [3, 4]
 
       # method call
+      p matrix
       matrix_convert_to_zero(matrix)
-
+      p matrix
       # validation
       verify_matrix(matrix, rows_array, columns_array)
     end