GcdAndGcm.java

package algorithm.basicMath;

import org.junit.Test;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;

public class GcdAndGcm {

 /*
 TASK
 입력받은 두 수의 최대 공약수, 최소 공배수를 구한다.
 */

 @Test
 public void test() {
 assertThat(gcdByIteration(-1, 0), is(-1));
 assertThat(gcdByIteration(0, 0), is(0));
 assertThat(gcdByIteration(6, 8), is(2));
 assertThat(gcdByIteration(3, 3), is(3));

 assertThat(gcdByRecursion(-1, 0), is(-1));
 assertThat(gcdByRecursion(0, 0), is(0));
 assertThat(gcdByRecursion(6, 8), is(2));
 assertThat(gcdByRecursion(3, 3), is(3));

 assertThat(gcm(6, 8), is(24));
 }

 public int gcdByIteration(int a, int b) {
 if (a < 0 || b < 0) return -1;
 int mod;
 while (b != 0) {
 mod = a % b;
 a = b;
 b = mod;
 }
 return a;
 }

 public int gcdByRecursion(int a, int b) {
 if (a < 0 || b < 0) return -1;
 if (b == 0) {
 return a;
 }
 return gcdByRecursion(b, a % b);
 }

 public int gcm(int a, int b) {
 return a * b / gcdByRecursion(a, b);
 }
}