1.1. Easy¶

225. Implement Stack using Queues¶

class MyStack:

    def __init__(self):
        self.queue = collections.deque([])

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

    def pop(self) -> int:
        return self.queue.pop()

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

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

232. Implement Queue using Stacks¶

232. Implement Queue using Stacks

class MyQueue:

    def __init__(self):
        self.inStack, self.outStack = [], []

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

    def pop(self) -> int:
        self.move()
        return self.outStack.pop()

    def peek(self) -> int:
        self.move()
        return self.outStack[-1]

    def empty(self) -> bool:
        return not self.inStack and not self.outStack

    def move(self):
        if not self.outStack:
            while self.inStack:
                self.outStack.append(self.inStack.pop())