扩展欧几里德算法求逆元3

int gcd(int x3,int y3)
{
    int x1 = 1,x2 = 0,y1 = 0,y2 = 1;
    while(1)
    {
        if (y3==1) return y2;
        int q=x3/y3;
        int t1=x1-q*y1,t2=x2-q*y2,t3=x3-q*y3;
        x1 = y1,x2 = y2,x3 = y3;
        y1 = t1,y2 = t2,y3 = t3;
    }
}