155.最小栈.py

#
# @lc app=leetcode.cn id=155 lang=python3
#
# [155] 最小栈
#

# @lc code=start
class MinStack:

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


    def push(self, x: int) -> None:
        if not self.stack:self.stack.append((x,x)) 
        else:
            self.stack.append((x,min(x,self.stack[-1][1])))


    def pop(self) -> None:
        if self.stack: self.stack.pop()
        

    def top(self) -> int:
        if self.stack: return self.stack[-1][0]
        else: return None

    def getMin(self) -> int:
        if self.stack: return self.stack[-1][1]
        else: return None


# 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()
# @lc code=end