507. Perfect Number -E

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)

A:

------------------------------------注意要排除 1 ，  except itself ---------

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