232.implement-queue-using-stacks.py

#
# @lc app=leetcode id=232 lang=python3
#
# [232] Implement Queue using Stacks
#

# @lc code=start
from collections import deque


class MyQueue:

    def __init__(self):
        self.inStack = deque()
        self.outStack = deque()

    def push(self, x: int) -> None:
        self.inStack.append(x)

    def pop(self) -> int:
        self.peek()
        return self.outStack.pop()

    def peek(self) -> int:
        if not self.outStack:
            while self.inStack:
                self.outStack.append(self.inStack.pop())
        return self.outStack[-1]

    def empty(self) -> bool:
        return len(self.inStack) + len(self.outStack) == 0


# Your MyQueue object will be instantiated and called as such:
# obj = MyQueue()
# obj.push(x)
# param_2 = obj.pop()
# param_3 = obj.peek()
# param_4 = obj.empty()
# @lc code=end