剑指offer包含min函数的栈python

# -*- coding:utf-8 -*-
class Solution:
    def __init__(self):
        self.stack1 = []
        self.stack2 = []
        self.cur = -1
    def push(self, node):
        # write code here
        if self.cur == -1:#第一个
            self.stack1.append(node)
            self.stack2.append(node)
            self.cur+=1
        else:
            self.stack1.append(node)
            if self.stack2[-1] <= node:
                self.stack2.append(self.stack2[-1])
            else:
                self.stack2.append(node)
            self.cur+=1
        
    def pop(self):
        # write code here
        self.cur -= 1
        self.stack2.pop()
        return self.stack1.pop()
        
    def top(self):
        # write code here
        return self.stack1[-1]
    def min(self):
        # write code here
        return self.stack2[-1]