Greated Common Divisor

int GCD(int a, int b){    int temp;    if(a < b)    {        temp = a;        a = b;        b = temp;    }    if(a % b == 0)        return b;    return GCD(b, a % b);}

Least Common Multiple

//最小公倍数等于两数之积除以最大公约数    int LCM(int a,int b){   return (a * b) / GCD(a, b); }