/**
 * This class includes a silmple method to compute the greatest common divisor of
 * two possitive integers using Euclid's algorithm.
 * Time complexity is O(log n), being n the greatest number
 */

/**
 * @author adrian
 *
 */
public class Gcd {

    // computes the greatest common divisor of two possitive integers using Euclid's algorithm
    public int gcd(int a, int b) {
        if (a < 0 || b < 0) {
            throw new java.lang.IllegalArgumentException("Numbers must be non-negative");
        }
        if (b == 0) {
            return a;
        }
        return gcd(b, a%b);
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        Gcd solver = new Gcd();

        // set input numbers
        int a = 30;
        int b = 12;
        if (a == 0 || b == 0) {
            throw new java.lang.IllegalArgumentException("Numbers must be non-zero integers");
        }
        System.out.println("Greatest common divisor for " + a + " and " + b
                + " is: " + solver.gcd(a, b));

    }

}