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;
}
};