[Python手撕]用队列实现栈/用栈实现队列

用队列实现栈

class MyStack:

    def __init__(self):
        self.length = 0
        self.queue1 = []
        self.queue2 = []


    def push(self, x: int) -> None:
        self.queue1.append(x)
        self.length += 1


    def pop(self) -> int:
        for _ in range(self.length-1):
            self.queue2.append(self.queue1.pop(0))
        t = self.queue1.pop(0)
        for _ in range(self.length-1):
            self.queue1.append(self.queue2.pop(0))
        self.length -= 1
        return t


    def top(self) -> int:
        for _ in range(self.length-1):
            self.queue2.append(self.queue1.pop(0))
        t = self.queue1.pop(0)
        for _ in range(self.length-1):
            self.queue1.append(self.queue2.pop(0))
        self.queue1.append(t)
        return t


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



# 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()

用栈实现队列

class MyQueue:

    def __init__(self):
        self.stack1 = []
        self.stack2 = []
        self.length = 0


    def push(self, x: int) -> None:
        self.stack1.append(x)
        self.length += 1


    def pop(self) -> int:
        for _ in range(self.length-1):
            self.stack2.append(self.stack1.pop(-1))
        t = self.stack1.pop(-1)
        for _ in range(self.length-1):
            self.stack1.append(self.stack2.pop(-1))
        self.length -= 1
        return t


    def peek(self) -> int:
        for _ in range(self.length-1):
            self.stack2.append(self.stack1.pop(-1))
        t = self.stack1.pop(-1)
        self.stack1.append(t)
        for _ in range(self.length-1):
            self.stack1.append(self.stack2.pop(-1))
        
        return t


    def empty(self) -> bool:
        return self.length == 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()