gcd的各种写法

1.

ll gcd(ll a, ll b)
{
    while(b^=a^=b^=a%=b);
    return a;
}

2.

ll gcd(ll a, ll b)
{
    return b ? gcd(b, a % b) : a; //前面在判断b是否等于0
}
//

int gcd(int a, int b)
{
    return b == 0 ? a : gcd(b, a%b);
}

3.

int gcd(int x, int y)
{
    int r = x % y;
    while(r)
    {
        x = y;
        y = r;
        r = x % y;
    }
    return y;
}

4.未完待续……