class Solution {
public:
    bool judgeSquareSum(int c) {
        bool res = false;
        for (long long i = 0, j = sqrt(c); i <= j; i ++ )
        {
            while (i * i + j * j > c) j -- ;
            if (i * i + j * j == c)
            {
                res = true;
                return res;
            }
        }
        return res;
    }
};