模拟队列

输入样例：

10
push 6
empty
query
pop
empty
push 3
push 4
pop
query
push 6

输出样例：

NO
6
YES
4

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int m = sc.nextInt();
        int[] q = new int[100010];
        int hh = 0; //头
        int tt = -1;//尾
        while (m-- > 0){
            String s = sc.next();
            if (s.equals("push")){
                int x = sc.nextInt();
                q[++tt] = x;
            } else if (s.equals("pop")){
                hh++;
            } else if (s.equals("empty")){
                if (hh<=tt) System.out.println("NO");
                else System.out.println("YES");
            } else
                System.out.println(q[hh]);
        }
    }
}