题解 | #两个队列实现栈#

import java.util.*;


public class Solution {
    Queue<Integer> queue1 = new LinkedList();
    Queue<Integer> queue2 = new LinkedList();

    public void push(int x){
        while(!queue1.isEmpty()){
            queue2.add(queue1.poll());
        }
        queue1.add(x);
        while(!queue2.isEmpty()){
            queue1.add(queue2.poll());
        }
    }

    public int pop(){
        return queue1.poll();
    }

    public int top(){
        return queue1.peek();
    }

    public boolean empty(){
        return queue1.isEmpty();
    }
}