注意这里遍历要用long long ，用int会溢出。

class Solution {
public:
    bool judgeSquareSum(int c) {
        bool flag = false;
        int tmp;
        for(long long i = 0; i * i <= c; i++){
            if(i * i == c){
                flag = true;
                break;
            }else{
                tmp = c - i * i;
                int j = sqrt(tmp);
                if(i * i + j * j == c){
                    flag = true;
                    break;
                }
            }
        }
        return flag;
    }
};