算法编程12：栈实现队列

题目描述：

push(x) -- 将一个元素放入队列的尾部。
pop() -- 从队列首部移除元素。
peek() -- 返回队列首部的元素。
empty() -- 返回队列是否为空。

题目解析：在python中，利用列表可以实现上述功能

python代码如下：

class MyQueue:

    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.__list=[]

    def push(self, x: int) -> None:
        """
        Push element x to the back of queue.
        """
        self.__list.append(x)

    def pop(self) -> int:
        """
        Removes the element from in front of queue and returns that element.
        """
        if self.__list:
            return self.__list.pop(0)
        else:
            return None
    def peek(self) -> int:
        """
        Get the front element.
        """
        if self.__list:
            return self.__list[0]
        else:
            return None

    def empty(self) -> bool:
        """
        Returns whether the queue is empty.
        """
        if self.__list:
            return False
        else:
            return True


# 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()

leetcode执行情况：