思路：注意下溢的時候退出就行

import java.util.LinkedList;import java.util.Queue;import java.util.Scanner;public class Main {		public static void main(String[] args) {		Scanner in = new Scanner(System.in);		int n = in.nextInt();		Queue que = new LinkedList();		for(int i=0; i<n; i++) {			int num = in.nextInt();			if(num == 1) {				int m = in.nextInt();				//進隊				que.offer(m);			} else if(num == 2) {				if(que.isEmpty()) {					System.out.PRintln("no");					return;				}				else					//出隊并刪除					System.out.println(que.poll());			} else if(num == 3) {				System.out.println(que.size());			}		}	}	}