Greatest Common Divisor

gcd.c

/*
 * Source : https://www.math.wustl.edu/~victor/mfmm/compaa/gcd.c
 */
#include <stdio.h>

/* Standard C Function: Greatest Common Divisor */
int gcd(int a, int b)
{
	int c;
	while (a != 0) {
		c = a; a = b % a;  b = c;
	}
	return b;
}

/* Recursive Standard C Function: Greatest Common Divisor */
int gcdr(int a, int b)
{
	if (a == 0) return b;
	return gcdr(b%a, a);
}

/* Recursive one line implementation
int gcd(int a,int b) {
	return a == 0 ? b : gcd(b % a, a);
}

int gcd(int a, int b)
{
	return b ? gcd(b, a%b) : a;
}
*/


int main(void)
{
	int a, b, c;
	a = 299792458;
	b = 6447287;
	c = 256964964;

	printf("a=%d, b=%d, c=%d\n", a, b, c);

	printf("gcd(a,b)=gcd(%d,%d)=%d\n", a, b, gcd(a, b));
	printf("gcd(a,b)=gcdr(%d,%d)=%d\n", a, b, gcdr(a, b));

	printf("gcd(a,c)=gcd(%d,%d)=%d\n", a, c, gcd(a, c));
	printf("gcd(a,c)=gcdr(%d,%d)=%d\n", a, c, gcdr(a, c));

	printf("gcd(c,b)=gcd(%d,%d)=%d\n", c, b, gcd(c, b));
	printf("gcd(c,b)=gcdr(%d,%d)=%d\n", c, b, gcdr(c, b));

	printf("gcd(a,b,c)=gcd(%d,gcd(%d,%d))=%d\n", a, b, c, gcd(a, gcd(b, c)));
	printf("gcd(a,b,c)=gcdr(%d,gcdr(%d,%d))=%d\n", a, b, c, gcdr(a, gcdr(b, c)));

	return 0;
}