Q4_QueueStack.py

#   Created by Elshad Karimov on 04/06/2020.
#   Copyright © 2020 AppMillers. All rights reserved.

# Implement a queue using two stacks.

class Stack():
  def __init__(self):
    self.list = []
  
  def __len__(self):
    return len(self.list)
   
  def push(self, item):
    self.list.append(item)
  
  def pop(self):
    if len(self.list) == 0:
      return None
    return self.list.pop()

class QueueviaStack():
  def __init__(self):
    self.inStack = Stack()
    self.outStack = Stack()
  
  def enqueue(self, item):
    self.inStack.push(item)
  
  def dequeue(self):
    while len(self.inStack):
      self.outStack.push(self.inStack.pop())
    result = self.outStack.pop()
    while len(self.outStack):
      self.inStack.push(self.outStack.pop())
    return result
  

customQueue = QueueviaStack()
customQueue.enqueue(1)
customQueue.enqueue(2)
customQueue.enqueue(3)
print(customQueue.dequeue())
customQueue.enqueue(4)
print(customQueue.dequeue())
print(customQueue.dequeue())
print(customQueue.dequeue())
print(customQueue.dequeue())