代码随想录算法训练营第十天 | 232.用栈实现队列、 225. 用队列实现栈

第一题 用栈实现队列

题目描述：
   https://leetcode.cn/problems/implement-queue-using-stacks/
思路：
   具体代码如下：

class MyQueue:

    def __init__(self):
        self.front = list()
        self.rear = list()

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

    def pop(self) -> int:

        if self.empty():
            return None

        if not self.front:
            for i in range(len(self.rear)):
                self.front.append(self.rear.pop())

        return self.front.pop()

    def peek(self) -> int:
        ans = self.pop()
        self.front.append(ans)
        return ans

    def empty(self) -> bool:
        return not (self.front or self.rear)

if __name__ == '__main__':

    obj = MyQueue()

    for i in range(1,6):
        obj.push(i)

    print(obj.pop())
    print(obj.peek())
    print(obj.empty())

第二题 用队列实现栈

题目描述：
   https://leetcode.cn/problems/implement-stack-using-queues/
思路：
   具体代码如下：

from collections import deque

class MyStack:

    def __init__(self):
        self.stack = deque()


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

    def pop(self) -> int:
        if self.empty():
            return None

        for i in range(len(self.stack)-1):
            self.push(self.stack.popleft())

        return self.stack.popleft()

    def top(self) -> int:
        ans = self.pop()
        self.push(ans)
        return ans

    def empty(self) -> bool:
        return len(self.stack) == 0



if __name__ == '__main__':
    obj = MyStack()
    for x in range(1,6):
        obj.push(x)
    print(obj.pop())
    print(obj.top())
    print(obj.empty())