剑指offer05-用两个栈实现队列

# -*- coding:utf-8 -*-
class Solution:
    def __init__(self):
        self.stack1=list()
        self.stack2=list()
    def push(self, node):
        # write code here
        self.stack1.append(node)
    def pop(self):
        # return xx
        if not self.stack2:
            for i in range(len(self.stack1)):
                self.stack2.append(self.stack1.pop(-1))
        return self.stack2.pop(-1)