java 代码

import java.io.*;
import java.util.*;
class Main{
    private final static int N = 100000+10;
    private static  int[] stack = new int[N];
    private static  int tt = -1;
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int m = in.nextInt();
        while(m-- >0){
            String operate = in.next();
            if("empty".equals(operate)){
                System.out.println(empty()+"");
            }else if("pop".equals(operate)){
                pop();
            }else if("push".equals(operate)){
                int x = in.nextInt();
                push(x);
            }else{
                System.out.println(query()+"");
            }
        }
    }
    private static  void push(int x){
        stack[++tt] = x;
    }
    private static int pop(){
        return stack[tt--];
    }
    private static String empty(){
        return tt==-1 ? "YES" : "NO";
    }
    private static  int query(){
        return stack[tt];
    }
}