几种求gcd的方法

int gcd1(int a, int b){
    return b > 0 ? gcd1(b, a % b) : a;
}

int gcd2(int a, int b){
    while(b ^= a ^= b ^= a %= b);
    return a;
}

int gcd3(int a, int b){
    int r;
    while(b > 0){
        r = a % b;
        a = b;
        b = r;
    }
    return a;
}

 简单测试发现3最快1最慢