用两个栈实现队列详解（附Java、Python源码）——《剑指Offer》

import java.util.Stack;

public class JzOffer5 {
    Stack<Integer> in = new Stack<Integer>();
    Stack<Integer> out = new Stack<Integer>();

    public void push(int node){
        in.push(node);
    }

    public int pop(){
        if (out.isEmpty()) {
            while (!in.isEmpty()) {
                out.push(in.pop());
            }
        }
        return out.pop();
    }
}

# -*- 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()