Faiza

lib/problems.rb

@@ -1,9 +1,65 @@
 require_relative './stack.rb'
 
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
+  if string == ""
+    return true
+  end
+
+  parens = {
+    "(" => ")",
+    "[" => "]",
+    "{" => "}",
+  }
+
+  stack = Stack.new
+  string.each_char do |element|
+    if parens[element]
+      stack.push(parens[element])
+    else
+      return false if element != stack.pop
+    end
+  end
+
+  return stack.empty?
+
+  # cannot do this either
+  # if stack.empty?
+  #   return
+  # end
+
+  #undefined method `length'
+  # if stack.length == 0
+  #   return true
+  # end
+
 end
 
+  # open_paren = []
+  # close_parens = []
+  # PUSH PARENS INTO ARRAYS
+  # string.each_char do |element|
+  #   if element == "(" || element == "{" || element == "["
+  #     open.push(element);
+  #   else
+  #     close.push(element);
+  #   end
+  # end
+  # if open.length != close.length
+  #   return false
+  # end
+  # is_balanced = false
+  # for index in (0...open.length)
+  #   if open[index] == "("  && close[(close.length - 1) - index] == ")" ||
+  #   open[index] == "{"  && close[(close.length - 1) - index] == "}" ||
+  #   open[index] == "["  && close[(close.length - 1) - index] == "]"
+  #     is_balanced = true
+  #   else
+  #     return is_balanced
+  #   end
+  # end
+  # return is_balanced
+
+
 def evaluate_postfix(postfix_expression)
   raise NotImplementedError, "Not implemented yet"
 end

lib/queue.rb

@@ -1,31 +1,76 @@
+QUEUE_SIZE = 20
+
 class Queue
 
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new(QUEUE_SIZE)
+    @front = @rear = -1
   end
 
+  # using circular buffer
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    if @front == -1 # Q is empty
+      @rear = 1
+      @front = 0
+      @store[@front] = element
+
+    elsif @front == @rear
+      raise Error, "Queue is full."
+
+    else # not empty
+       # if we reach the end of the array, rear will once again be pointed to 0
+      new_rear = (@rear + 1) % QUEUE_SIZE
+      @store[@rear] = element
+      @rear = new_rear
+    end
   end
 
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
+    if @front == -1 # Q is empty
+      return
+
+    elsif @front == @rear #  There's only 1 element
+      temp_node = @store[@front] # "remove" the element
+      @front = -1 # points to the empty bucket
+      @rear = -1 # points to the empty bucket
+      return temp_node
+
+    else # there's more than 1 element in the array
+      temp_node = @store[@front] # "remove" the element
+      @store[@front] = nil # store is now empty
+      @front = (@front + 1) % QUEUE_SIZE # wrap front around array
+      return temp_node
+    end
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    return @store[@front]
   end
 
   def size
-    raise NotImplementedError, "Not yet implemented"
+    if @front > @rear
+      return QUEUE_SIZE - @front + @rear
+    else
+      return @rear - @front
+    end
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+   if @store[@front].nil?
+      return true
+   else
+    return false
+   end
   end
 
   def to_s
-    return @store.to_s
+    array = []
+    @store.each_with_index do |element, i|
+      next if i < @front
+      break if element.nil?
+
+      array << element
+    end
+    return array.to_s
   end
 end

lib/stack.rb

@@ -1,22 +1,29 @@
+require_relative './linked_list.rb'
+
 class Stack
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = LinkedList.new
+    @top = nil
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    @store.add_last(element)
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    @store.remove_last
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    if @store.empty?
+      return true
+    else
+      return false
+    end
   end
 
   def to_s
     return @store.to_s
   end
 end
+

test/problems_test.rb

@@ -7,24 +7,25 @@
 describe "Test wave 3 problems" do
   describe "balanced" do
     it "Given balanced strings it should return true" do
-      skip
+      # skip
       expect(balanced('(({}))')).must_equal true
     end
 
     it "regards an empty string as balanced" do
-      skip
+      # skip
       expect(balanced('')).must_equal true
     end
 
     it "will return false for an unbalanced set of parens" do
-      skip
+      # skip
       expect(balanced('(()')).must_equal false
       expect(balanced('(()}')).must_equal false
       expect(balanced('([]]')).must_equal false
+      expect(balanced('({[}]')).must_equal false
     end
 
     it "also works for {} and []" do
-      skip
+      # skip
       expect(balanced('[]')).must_equal true
       expect(balanced('{}')).must_equal true
     end

test/queue_test.rb

@@ -11,14 +11,14 @@
   end
 
   it "adds something to an empty Queue" do
-    skip
+    # skip
     q = Queue.new
     q.enqueue(10)
     q.to_s.must_equal "[10]"
   end
 
   it "adds multiple somethings to a Queue" do
-    skip
+    # skip
     q = Queue.new
     q.enqueue(10)
     q.enqueue(20)
@@ -27,13 +27,13 @@
   end
 
   it "starts the size of a Queue at 0" do
-    skip
+    # skip
     q = Queue.new
     q.empty?.must_equal true
   end
 
   it "removes something from the Queue" do
-    skip
+    # skip
     q = Queue.new
     q.enqueue(5)
     removed = q.dequeue
@@ -42,7 +42,7 @@
   end
 
   it "removes the right something (LIFO)" do
-    skip
+    # skip
     q = Queue.new
     q.enqueue(5)
     q.enqueue(3)
@@ -53,7 +53,7 @@
   end
 
   it "properly adjusts the size with enqueueing and dequeueing" do
-    skip
+    # skip
     q = Queue.new
     q.empty?.must_equal true
     q.enqueue(-1)
@@ -65,7 +65,7 @@
   end
 
   it "returns the front element in the Queue" do
-    skip
+    # skip
     q = Queue.new
     q.enqueue(40)
     q.enqueue(22)

test/stack_test.rb

@@ -10,14 +10,14 @@
   end
 
   it "pushes something onto a empty Stack" do
-    skip
+    # skip
     s = Stack.new
     s.push(10)
     s.to_s.must_equal "[10]"
   end
 
   it "pushes multiple somethings onto a Stack" do
-    skip
+    # skip
     s = Stack.new
     s.push(10)
     s.push(20)
@@ -26,13 +26,13 @@
   end
 
   it "starts the stack empty" do
-    skip
+    # skip
     s = Stack.new
     s.empty?.must_equal true
   end
 
   it "removes something from the stack" do
-    skip
+    # skip
     s = Stack.new
     s.push(5)
     removed = s.pop
@@ -41,7 +41,7 @@
   end
 
   it "removes the right something (LIFO)" do
-    skip
+    # skip
     s = Stack.new
     s.push(5)
     s.push(3)