minStack.py

#! /usr/bin/env python3
# -*- coding: utf-8 -*-

# Source: https://leetcode.com/problems/min-stack/
# Author: Miao Zhang
# Date:   2021-01-22

class MinStack:

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

    def push(self, x: int) -> None:
        minval = self.getMin()
        if minval is None or minval > x:
            minval = x
        self.stack.append([x, minval])
        
    def pop(self) -> None:
        if self.stack:
            self.stack.pop()

    def top(self) -> int:
        if self.stack:
            return self.stack[-1][0]
        else:
            return -1
        
    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()