-- coding:utf-8 --

class Solution: def init(self): self.stack1 = [] self.stack2 = [] def push(self, node): # write code here self.stack1.append(node) def pop(self): # return xx if (len(self.stack2) == 0): while (len(self.stack1) != 0): self.stack2.append(self.stack1.pop()) return self.stack2.pop()