0155-min-stack.py

# time complexity: O(1)
# space complexity: O(n)
class MinStack:

    def __init__(self):
        self.minStack = []
        self.stack = []

    def push(self, val: int) -> None:
        self.stack.append(val)
        if not self.minStack or val <= self.minStack[-1]:
            self.minStack.append(val)

    def pop(self) -> None:
        if self.minStack[-1] == self.stack[-1]:
            self.minStack.pop()
        self.stack.pop()

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

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


# Your MinStack object will be instantiated and called as such:
obj = MinStack()
obj.push(-2)
obj.push(0)
obj.push(-3)
print(obj.getMin())
obj.pop()
print(obj.top())
print(obj.getMin())