lc155.最小栈

class MinStack:

    def __init__(self):
        """
        initialize your data structure here.
        """
        self.A, self.B = [], []

    def push(self, x: int) -> None:
        self.A.append(x)
        if not self.B or x <= self.B[-1]:
            self.B.append(x)

    def pop(self) -> None:
        if self.A[-1] == self.B[-1]:
            self.B.pop()
        return self.A.pop()

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

    def getMin(self) -> int:
        return self.B[-1]


# Your MinStack object will be instantiated and called as such:
# obj = MinStack()
# obj.push(x)
# obj.pop()
# param_3 = obj.top()
# param_4 = obj.getMin()