5 用两个栈实现队列

题目描述

用两个栈来实现一个队列，完成队列的Push和Pop操作。 队列中的元素为int类型。

import java.util.Stack;
 
public class Solution {
    Stack<Integer> stack1 = new Stack<Integer>();
    Stack<Integer> stack2 = new Stack<Integer>();
     
    public void push(int node) {
        stack1.push(node);
    }
     
    public int pop() {
        if(stack1.empty()&& stack2.empty())
            throw new RuntimeException("Queue is empty!");
         
        if(stack2.empty()){
            while(!stack1.empty()){
                stack2.push(stack1.pop());
         }
        }
        return stack2.pop();
    }
}

20180303

# -*- 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 self.stack2==[]:
            while self.stack1!=[]:
                self.stack2.append(self.stack1.pop(-1))
        return self.stack2.pop(-1)