implementation of extended euclidian theorem

1int gcd(int a, int b, int& x, int& y) {
2    if (b == 0) {
3        x = 1;
4        y = 0;
5        return a;
6    }
7    int x1, y1;
8    int d = gcd(b, a % b, x1, y1);
9    x = y1;
10    y = x1 - y1 * (a / b);
11    return d;
12}
13