LeetCode : Perfect Number

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

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