Charlotte:Space

lib/problems.rb

@@ -1,13 +1,61 @@
 require_relative './stack.rb'
-
-# Time Complexity: ?
-# Space Complexity: ?
+# time complexity: 0(n) where n is the legth
+# space complexity: 0(n) - creates a new stack
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
+  return false if string.length.odd?
+
+# create hash for quick look up
+  brackets = {
+                "(" => ")", "{" => "}", "[" => "]"
+              }
+  stack = Stack.new
+
+  string.chars.each do |char|
+    if brackets[char]
+      element = brackets[char]
+      stack.push(element)
+    else
+      if stack.pop != char
+        return false
+      end
+    end
+  end
+  return stack.empty?
 end
 
+# Time Complexity: 0(n) where n is the length
+# Space Complexity: 0(n)
+# def balanced(string)
+#   # string length must be even
+#     return false if string.length.odd?
+
+#     stack = Stack.new
+
+#     # loop through each char in the string
+#     string.each_char do |char|
+#       if char == "[" 
+#         stack.push("]")
+#       elsif char == "{"
+#         stack.push("}")
+#       elsif char == "("
+#         stack.push(")")
+#       # if current char is the same as the last inserted char on stack, remove last inserted char
+#       elsif !stack.empty? && stack.top == char
+#         stack.pop
+#       # if stack is empty or last char is not 'opening' pair
+#       else 
+#         return false
+#       end
+#     end
+#     # finally if you get here and stack is empty - string is balanced
+#     return stack.empty?
+# end
+
+
 # Time Complexity: ?
 # Space Complexity: ?
-def evaluate_postfix(postfix_expression)
-  raise NotImplementedError, "Not implemented yet"
+# optional wave 4
+def evaluate_postfix(postfix_expression) 
+    raise NotImplementedError, "Not implemented yet"
+
 end

lib/queue.rb

@@ -1,31 +1,94 @@
 class Queue
-
+  
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new(20)
+    @size = 20
+    @front = -1
+    @back = -1
   end
-
-  def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+
+  # add element to rear
+  def enqueue(value)
+    if @front == -1
+      @front = 0
+      @back = 1
+      @store[@front] = value
+    elsif @store.empty?
+      raise ArgumentError, "Full"
+    else
+      @store[@back] = value
+      @back = (@back + 1) % @size
+    end
   end
 
+  # remove element from front and return it
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
-  end
-
-  def front
-    raise NotImplementedError, "Not yet implemented"
+    if @front == -1
+      raise ArgumentError, "Empty"
+    else
+      data = @store[@front]
+      @front = (@front + 1) % @size
+      if @store.empty?
+        @front = back = -1
+      end
+      return data
+    end
   end
-
-  def size
-    raise NotImplementedError, "Not yet implemented"
-  end
-
+
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @front == @back
   end
 
   def to_s
-    return @store.to_s
+    list = []
+    current = @front
+
+    while current != @back
+      list << @store[current]
+      current = (current + 1) % @size
+    end
+    return list.to_s
   end
 end
+
+# class Queue
+# passes all tests but not made with a circular buffer. 
+#   attr_accessor :front, :rear, :store
+#   attr_reader :size
+
+#   def initialize(size=20)
+#     @size = size
+#     @store = Array.new()
+#     @front = 0
+#     @rear = -1
+#   end
+
+#   # add element to rear
+#   def enqueue(element)
+#     return @store.push(element)
+#   end
+
+#   # remove element from front
+#   def dequeue
+#    return nil if @store.empty?
+#    return @store.shift()
+#   end
+
+#   def front(queue) 
+#     return @front == -1
+#   end
+
+#   def size
+#     return @store.size
+#   end
+
+#   def empty?
+#     if @front == 0 && @rear == -1
+#     return @store.empty?
+#     end
+#   end
+
+#   def to_s
+#     return @store.to_s
+#   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"
+    @store.remove_first
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    @store.empty?
+  end
+
+  def top
+    @store.get_first
   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
 
@@ -33,7 +33,7 @@
     end
   end
 
-  describe "postfix" do
+  xdescribe "postfix" do
     it "can add a 2 numbers together" do
 
       expect(evaluate_postfix("34+")).must_equal 7

test/test_helper.rb

@@ -10,4 +10,4 @@
 require_relative "../lib/queue.rb"
 require_relative "../lib/stack.rb"
 # Extra exercises
-# require_relative "../lib/problems.rb"
+require_relative "../lib/problems.rb"