用两个栈实现队列 -- Java和python实现

python实现

# -*- 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())
        if self.stack2 != []:
            return self.stack2.pop()
        else:
            return None

java实现

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(stack2.size()<=0){
            while(stack1.size()>0){
                int temp = stack1.pop();
                stack2.push(temp);
            }
        }
        return stack2.pop();
    }
}