HJ56 完全数计算

1. 题目

读题

HJ54 表达式求值

 

 

考查点

 

2. 解法

思路

 

代码逻辑

 

具体实现

public class HJ56 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        System.out.println(getPerfectNumCnt(n));

    }

    public static int getPerfectNumCnt(int n) {

        int cnt = 0;
        for (int i = 2; i <= n; i++) {
            if (isPerfectNum(i)) {
                cnt++;
            }
        }
        return cnt;

    }

    public static boolean isPerfectNum(int n) {
        int sum = 0;
        for (int i = 1; i * i <= n; i++) {
            if (n % i == 0) {
                sum += i;
                if (i * i < n && i != 1) {
                    sum += n / i;
                }

            }
        }
        return sum == n;
    }

}

 

3. 总结