20.包含min函数的栈（python）

 1 # -*- coding:utf-8 -*-
 2 class Solution:
 3     def __init__(self):
 4         self.stack1=[]
 5         self.stack2=[]
 6     def push(self, node):
 7         # write code here
 8         self.stack1.append(node)
 9         if len(self.stack2)==0 or self.stack2[-1]>node:
10             self.stack2.append(node)
11         else:
12             self.stack2.append(self.stack2[-1])
13     def pop(self):
14         if len(self.stack1)>0:
15             self.stack2.pop()
16             return self.stack1.pop()
17         # write code here
18     def top(self):
19         # write code here
20         if len(self.stack1)>0:
21             return self.stack1[-1]
22     def min(self):
23         # write code here
24         if len(self.stack2)>0:
25             return self.stack2[-1]