507. Perfect Number（LeetCode）

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)

class Solution {
public:
    bool checkPerfectNumber(int num) {
       int sum = 0;
        if(num==0)
            return false;
        for (int i = 1; i*i < num; i++)
        {
            if (num%i == 0)
            {
                sum += i;
                sum += num / i;
            }
        }
        if (sum== num*2)
            return true;
        else
            return false;
    }
};