题解 | #完全数计算#

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        System.out.println(getNum(n));

    }

    //获取完美数个数
    private static int getNum(int n) {
        if (n == 1) {
            return 0;
        }
        int count = 0;
        for (int i = 2; i <= n; i++) {
            if (test(i)) {
                // System.out.println(i);
                count++;
            }
        }
        return count;
    }

    //判断是否是完美数
    private static boolean test(int i) {
        int sum = 0;//累计真因子的和
        for (int j = 1; j < i; j++) {
            if (i % j == 0) {
                sum += j;
            }
        }
        return sum == i;
    }
}

解题思路:

1, 对所有候选数进行遍历, 累计完美数的个数即可