6/19/2017 - 9:49 AM

## 232. Implement Queue using Stacks

1. Implement Queue using Stacks
``````class Queue(object):
def __init__(self):
"""
"""
self.queue = []

def push(self, x):
"""
:type x: int
:rtype: nothing
"""
self.queue.append(x)

def pop(self):
"""
:rtype: nothing
"""
ele = self.queue[0]
del self.queue[0]
return ele

def peek(self):
"""
:rtype: int
"""
ele = self.queue[0]
return ele

def empty(self):
"""
:rtype: bool
"""
return len(self.queue) == 0``````

https://leetcode.com/problems/implement-queue-using-stacks/#/description

Implement the following operations of a queue using stacks.

• push(x) -- Push element x to the back of queue.
• pop() -- Removes the element from in front of queue.
• peek() -- Get the front element.
• empty() -- Return whether the queue is empty.

Notes:

• You must use only standard operations of a stack -- which means only `push to top`, `peek/pop from top`, `size`, and `is empty` operations are valid.
• Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
• You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).