Add basic algorithm code about gcd

jbee37142 · jbee37142 · commit c0271a0861b2 · 2017-06-05T19:46:29.000+09:00
diff --git a/src/test/java/algorithm/basic/GcdAndGcm.java b/src/test/java/algorithm/basic/GcdAndGcm.java
@@ -0,0 +1,52 @@
+package algorithm.basic;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.junit.Assert.assertThat;
+
+public class GcdAndGcm {
+
+    /*
+        TASK
+        입력받은 두 수의 최대 공약수를 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);
+    }
+}
diff --git a/src/test/java/exercise/KnapsackProblem.java b/src/test/java/exercise/KnapsackProblem.java
@@ -0,0 +1,7 @@
+package exercise;
+
+/**
+ * Created by Jbee on 2017. 6. 5..
+ */
+public class KnapsackProblem {
+}
