225 用队列实现栈

题目225 用队列实现栈

思路

两个方法：分别是一个队列模拟栈和两个队列模拟栈
一个队列模拟栈
当栈pop时，只要把队列的前size-1个元素依次放入到队列末尾即可

代码

class MyStack:
    # 使用一个队列实现栈
    def __init__(self):
        self.queue = []

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

    def pop(self) -> int:
        self.queue_len = len(self.queue)
        for i in range(self.queue_len - 1):
            self.queue.append(self.queue.pop(0))
        return self.queue.pop(0)

    def top(self) -> int:
        return self.queue[-1]

    def empty(self) -> bool:
        return self.queue == []

# Your MyStack object will be instantiated and called as such:
# obj = MyStack()
# obj.push(x)
# param_2 = obj.pop()
# param_3 = obj.top()
# param_4 = obj.empty()