633.cpp

class Solution {
public:
    bool judgeSquareSum(int c) {
        int half = (c >> 1), sb, b;
        for(int a = 0; a * a <= half; a++) {
            sb = c - a * a;
            b = sqrt(sb);
            if (b * b == sb) return true;
        }
        return false;
    }
};