Sockets - Grace

lib/problems.rb

@@ -1,9 +1,38 @@
 require_relative './stack.rb'
 
 def balanced(string)
-  raise NotImplementedError, "Not implemented yet"
+  pairs = { ")" => "(", "]" => "[", "}" => "{" }
+  stack = Stack.new
+
+  string.each_char do |char|
+    if pairs.values.include?(char)
+      stack.push(char)
+    else
+      return false if stack.empty? or pairs[char] != stack.pop()
+    end
+  end
+  return stack.empty?
 end
 
 def evaluate_postfix(postfix_expression)
-  raise NotImplementedError, "Not implemented yet"
-end
+  stack = Stack.new
+  postfix_expression.split("").each do |char|
+    if char == char.to_i.to_s
+      stack.push(char.to_i)
+    else
+      num1 = stack.pop()
+      num2 = stack.pop()
+      case(char)
+      when "+"
+        stack.push(num2 + num1)
+      when "-"
+        stack.push(num2 - num1)
+      when "/"
+        stack.push(num2 / num1)
+      when "*"
+        stack.push(num2 * num1)
+      end
+    end
+  end
+  return stack.pop()
+end

lib/queue.rb

@@ -1,31 +1,55 @@
 class Queue
+  QUEUE = 20
 
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = Array.new(QUEUE)
+    @front = @rear = -1
   end
 
   def enqueue(element)
-    raise NotImplementedError, "Not yet implemented"
+    if @front == -1 
+      @rear = 1
+      @front = 0
+      @store[@front] = element
+    elsif @front == @rear
+      raise Error, "Queue Full"
+    else
+      new_rear = (@rear + 1) % QUEUE
+      @store[@rear] = element
+      @rear = new_rear
+    end
   end
 
   def dequeue
-    raise NotImplementedError, "Not yet implemented"
+    raise Error, "Queue Empty" if @front == -1
+    value = @store[@front]
+    @store[@front] = nil
+    @front = (@front + 1) % QUEUE
+    @front = @rear = -1 if @front == @rear
+    return value
   end
 
   def front
-    raise NotImplementedError, "Not yet implemented"
+    rreturn @store[@head]
   end
 
   def size
-    raise NotImplementedError, "Not yet implemented"
+    if (@head == @tail && !empty?)
+      return @capacity 
+    elsif @head == @tail
+      return 0
+    elsif @tail > @head
+      return @tail - @head
+    elsif @tail < @head
+      return @capacity - (@head - @tail)
+    end
   end
 
   def empty?
-    raise NotImplementedError, "Not yet implemented"
+    return @rear == -1
   end
 
   def to_s
-    return @store.to_s
+    return @store[@front...@rear].to_s
   end
 end

lib/stack.rb

@@ -1,19 +1,18 @@
 class Stack
   def initialize
-    # @store = ...
-    raise NotImplementedError, "Not yet implemented"
+    @store = LinkedList.new()
   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"
+    return @store.empty?()
   end
 
   def to_s