题解 | 判断质数

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
		long num = in.nextLong();
		//计数器
		int count = 0;
	  
		if (num == 1) {
			System.out.println("No");
			count --;
		} else if (num == 2) {
			System.out.println("Yes");
			count --;
		} else {
			for (int i = 2; i <= Math.sqrt(num); i++) {
				if (num % i == 0) {
					count ++;
				} 
			}
		}
		
		if (count == 0) {
			System.out.println("Yes");
		} else if (count > 0){
			System.out.println("No");
		}
		









    }
}