题解 | #完全数计算#

规规矩矩用set不香吗

import java.util.HashSet;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int count = 0;
        for (int i = 1; i <= n; i++) {
            if (perfectNumber(i)) {
                count++;
            }
        }
        System.out.println(count);
    }

    private static boolean perfectNumber(int n) {
        //查找n的所有因子，存在set中
        int sum = 0;
        HashSet<Integer> set = new HashSet<>();
        for (int i = 1; i < n; i++) {
            if (n % i == 0) {
                set.add(i);
                sum += i;
            }
        }
        return sum == n;
    }

}