题解 | #完全数计算#

//代码

#include<iostream>
#include<set>
using namespace std;
int sum (set<int>& num) {
    int result = 0;
    for (auto j : num)
        result = j + result;
    return result;
}//set求和


bool perfect(int num) {
    if (num == 1)
        return false;
    set<int> yinzi;
    yinzi.insert(1);
    for (int i = 2; i * i < num; i++) {
        if (num % i == 0) {
            yinzi.insert(i);
            yinzi.insert(num / i);
        }
    }
    if (sum(yinzi) == num)
        return true;
    return false;
}//判断是否为完全数

int main() {
    int n;
    cin >> n;
    int count;

    for (int i = 1; i <= n; i++) {
        if (perfect(i))
            count++;

    }
    cout << count << endl;
    return 0;

}