We define the Perfect Number is a positive integer that is equal to the sum of all its positive divisors except itself.
Now, given an integer n, write a function that returns true when it is a perfect number and false when it is not.Example:
Input: 28 Output: True Explanation: 28 = 1 + 2 + 4 + 7 + 14
Note: The input number n will not exceed 100,000,000. (1e8)
static public bool CheckPerfectNumber(int num) {if (num == 0 || num == 1) return false;int sum = 1;for (int i = 2; i < Math.Sqrt(num); i++) {if (num % i == 0) {sum += i + num / i;}}return sum == num;}
原文：http://www.cnblogs.com/xiejunzhao/p/664dcb858d73bad5eca8a74ae1665c83.html