{模板}Gcd及ExGcd

Gcd求最大公约数

int Gcd(int a,int b){    if(b == 0) return a;    return Gcd(b, a % b);}

ExGcd求解ax+by=Gcd(a,b)

int ExGcd(int a,int b,int &x,int &y){    if(b==0)    {        x=1;        y=0;        return a;    }    int r=ExGcd(b,a%b,x,y);    int t=x;    x=y;    y=t-a/b*y;    return r;}