思路：（转）

代码：

# -*- coding:utf-8 -*-
class Solution:
stack1 = []
stack2 = []

def push(self, node):
self.stack1.append(node)

def pop(self):
if len(self.stack2) > 0:
return self.stack2.pop()
else:
while len(self.stack1) > 0:
self.stack2.append(self.stack1.pop())
return self.pop()