# LeetCode - 0633. Sum of Square Numbers
### 題目網址：https://leetcode.com/problems/sum-of-square-numbers/
###### tags: `LeetCode` `Medium` `數學` `數論`

/*
    -LeetCode format-
    Problem: 633. Sum of Square Numbers
    Difficulty: Medium
    
    by Inversionpeter
*/



class Solution {
public:
    bool judgeSquareSum(int c) {
        for (int i = 2; i <= sqrt(c); ++i)
            if (!(c % i)) {
                int counts = 0;
                while (!(c % i)) {
                    ++counts;
                    c /= i;
                }
                if ((i & 3) == 3 && (counts & 1))
                    return false;
            }
        return (c & 3) != 3;
    }
};