栈与队列232|225

232用栈实现队列

class MyQueue:

    def __init__(self):
        self.listin = []
        self.listout = []

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

    def pop(self) -> int:
        if not self.listin and  not self.listout:
            return None
        if self.listout:
            return self.listout.pop()
        else:
            while self.listin:
                element = self.listin.pop()
                self.listout.append(element)
            return self.listout.pop()

    def peek(self) -> int:
        element = self.pop()
        self.listout.append(element)
        return element

    def empty(self) -> bool:
        if not self.listin and not self.listout:
            return True
        else:
            return False


# 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()

225用队列实现栈

class MyStack:

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

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

    def pop(self) -> int:
        if not self.myque:
            return None
        for i in range(len(self.myque) - 1):
            self.myque.append(self.myque.popleft())
        return self.myque.popleft()

    def top(self) -> int:
        if not self.myque:
            return None
        element = self.pop()
        self.myque.append(element)
        return element

    def empty(self) -> bool:
        return not self.myque

# 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()