Calculate the GCD (greatest common denominator) of two integers using the Euclidean algorithm. Recursive or iterative functions.

gcd.c

//Helper fn
int pgcdr(int a, int b)
{
	if (a) return pgcdr(b % a, a);
	else return b;
}

//Recursive gcd fn
int gcdr(int a, int b)
{
	if (!a) return 0;
	if (a < 0) a = -a;
	return pgcdr((b<0?-b:b) % a, a);
}

//Non-recursive gcd fn
int gcd(int a, int b)
{
	if (a < 0) a = -a;
	if (b < 0) b = -b;
	int al = a;
	while (a)
	{
		al = a;
		a = b % a;
		b = al;
	}
	return al;
}