Space - Sara

lib/problems.rb

@@ -1,13 +1,27 @@
 require_relative './stack.rb'
 
-# Time Complexity: ?
-# Space Complexity: ?
+# Time Complexity: O(n)
+# Space Complexity: O(n)
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
-end
+  return false if string.length.odd?
+  stack = []
+  brackets = { '{' => '}', '[' => ']', '(' => ')' }
+
+  string.each_char do |char|
+    if brackets.key?(char)
+      stack.push(char)
+    elsif brackets.values.include?(char)
+      return false if brackets.key(char) != stack.pop
+    end
+  end
 
-# Time Complexity: ?
-# Space Complexity: ?
-def evaluate_postfix(postfix_expression)
-  raise NotImplementedError, "Not implemented yet"
+  if stack.empty?
+    return true 
+  end 
 end
+
+# # Time Complexity: ?
+# # Space Complexity: ?
+# def evaluate_postfix(postfix_expression)
+#   raise NotImplementedError, "Not implemented yet"
+# end

lib/queue.rb

@@ -1,31 +1,64 @@
 class Queue
 
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @size = 20
+    @store = Array.new(@size)
+    @front, @rear = -1, -1 
   end
 
-  def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+  def enqueue(element) #move back to the next free position 
+    if @front == -1 && @rear -1 #first time 
+      @front = 0 
+      @rear = 1 
+      @store[@front] = element 
+      return element
+    end 
+
+    if @front == (@rear + 1) % @size #check if is full 
+     return nil 
+    else 
+      @store[@rear] = element #when not full add to the back 
+      @rear = (@rear + 1) % @size #keeping track of the next free index  
+    end 
   end
 
-  def dequeue
-    raise NotImplementedError, "Not yet implemented"
+  def dequeue #move front one position clockwise 
+    if @front == -1 && @rear == -1 #first time 
+      return nil 
+    end 
+
+    #remove first element 
+    element = @store[@front]
+    @front = (@front + 1) % @size
+    #after removing check if queue is empty to set front and back -1 
+    if @front == @rear
+      @front, @rear = -1, -1 
+    end  
+    return element
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    return nil if @front == @rear 
+    return @store[@front] 
   end
 
   def size
-    raise NotImplementedError, "Not yet implemented"
+    return 0 if @front == @rear #empty
+    return @rear - @front + 1 if @rear > @front # @back ahead of @front
+    return (@size - @front) + (@rear + 1)
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @front == @rear  
   end
 
   def to_s
-    return @store.to_s
+    return '[]' if @front == @rear
+    if @rear > @front
+      return @store[@front..@rear - 1].to_s
+    else 
+      return (@store[@front..@size - 1] + @store[0..@rear - 1]).to_s
+    end 
+
   end
-end
+end

lib/stack.rb

@@ -1,19 +1,22 @@
 class Stack
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = LinkedList.new
   end
 
   def push(element)
-    raise NotImplementedError, "Not yet implemented"
+    @store.add_first(element)
   end
 
   def pop
-    raise NotImplementedError, "Not yet implemented"
+    return nil if @store.empty?
+
+    item = @store.remove_first
+
+    return item
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @store.empty?
   end
 
   def to_s

test/problems_test.rb

@@ -2,7 +2,7 @@
 
 Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
 
-xdescribe "Test wave 3 problems" do
+describe "Test wave 3 problems" do
   describe "balanced" do
     it "Given balanced strings it should return true" do
 
@@ -33,23 +33,23 @@
     end
   end
 
-  describe "postfix" do
-    it "can add a 2 numbers together" do
+  # xdescribe "postfix" do
+  #   it "can add a 2 numbers together" do
 
-      expect(evaluate_postfix("34+")).must_equal 7
-      expect(evaluate_postfix("34*")).must_equal 12
-      expect(evaluate_postfix("34-")).must_equal(-1)
-      expect(evaluate_postfix("34/")).must_equal 0
-    end
+  #     expect(evaluate_postfix("34+")).must_equal 7
+  #     expect(evaluate_postfix("34*")).must_equal 12
+  #     expect(evaluate_postfix("34-")).must_equal(-1)
+  #     expect(evaluate_postfix("34/")).must_equal 0
+  #   end
 
-    it "can add a evaluate a more complicated expression" do
+  #   it "can add a evaluate a more complicated expression" do
 
-      expect(evaluate_postfix("34+2*")).must_equal 14
-      expect(evaluate_postfix("34*2/")).must_equal 6
-      expect(evaluate_postfix("34-1+")).must_equal 0
-      expect(evaluate_postfix("34/7-")).must_equal(-7)
-      expect(evaluate_postfix("35+6*")).must_equal 48
-      expect(evaluate_postfix("62/5+")).must_equal 8
-    end
-  end
+  #     expect(evaluate_postfix("34+2*")).must_equal 14
+  #     expect(evaluate_postfix("34*2/")).must_equal 6
+  #     expect(evaluate_postfix("34-1+")).must_equal 0
+  #     expect(evaluate_postfix("34/7-")).must_equal(-7)
+  #     expect(evaluate_postfix("35+6*")).must_equal 48
+  #     expect(evaluate_postfix("62/5+")).must_equal 8
+  #   end
+  # end
 end

test/test_helper.rb

@@ -9,5 +9,6 @@
 require_relative "../lib/linked_list.rb"
 require_relative "../lib/queue.rb"
 require_relative "../lib/stack.rb"
+
 # Extra exercises
-# require_relative "../lib/problems.rb"
+require_relative "../lib/problems.rb"