最大公约数GCD
long gcd(long n, long d)
{
long n1 = abs(n);
long n2 = abs(d);
int gcd = 1;
for (int k = 1; k <= n1 && k <= n2; k++)
{
if (n1 % k == 0 && n2 % k == 0)
{
gcd = k;
}
}
return gcd;
}
原文：http://www.cnblogs.com/denggelin/p/7134521.html