题解 | #自守数#

采用取模的方式判断：

举例：假如输入为9376

1、对10取模，获得6：

2、对100取模，获得76；

3、对1000取模，获得376；

import java.util.Scanner;

/**
 * 【自守数】
 *
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int nextInt = sc.nextInt();

        int count = 2;
        for (int i = 2; i <= nextInt; i++) {
            if (isSelfNumber(i)) {
                count++;
            }
        }
        System.out.println(count);
    }
  
	/**
 	 * 判断是否为自守数
 	 *
 	 */
    public static boolean isSelfNumber(int num) {
        int multi = num * num;
        if (num < 10) {
            return multi % 10 == num;
        } else if (num < 100) {
            return multi % 100 == num;
        } else if (num < 1000) {
            return multi % 1000 == num;
        } else {
            return multi % 10000 == num;
        }
    }
}