c++ leetcode刷题 #633 平方数之和

solution 1 : same as #167

bool judgeSequareSum(int c){
    for(int i=0, j=round(sqrt(c));i<=j; i++){
        for(; i<j;j--){
            if(i*i + j*j <= c) break;
        }
        if(i*i + j*j == c) return true;
    }
    return false;
}

solution 2: b = round(sqrt( c) - a) , 循环a 查找是否存在b

 bool judgeSquareSum(int c) {
    for(long long i= 0 ;i* i <= c; i++){
    
        long long f= round(sqrt(c- i*i));
        if(f*f == (c-i*i)) return true;
    }
    return false;
    }