题解 | 完全数计算

/*#牛客春招刷题训练营# https://www.nowcoder.com/discuss/726480854079250432*/
#include <iostream>//----------本来只是想先暴力再打表的结果暴力过了，实际上自测用5e5会超时
using namespace std;

int main() {
  int n, i = 5, ans = 0;
  cin >> n;
  if (n > 1000){
    i = 1001;
    ans = 3;
  }
  for (; i <= n; i++){
    int temp = 0;
    for (int j = 1; j < i; j++){
      if (i % j == 0)
        temp += j;
    }
    if (temp == i)
      ans++;
  }
  cout << ans;
}