Added rotate array function

Author: viktor-podzigun

Diff for: README.md

@@ -14,4 +14,5 @@ sbt test
 ### Overview
 
 * Arrays
-  * [ReverseArray](src/main/java/algorithms/array/ReverseArray.java) => [test](src/test/scala/algorithms/array/ReverseArraySpec.scala)
+  * [reverse](src/main/java/algorithms/array/ReverseArray.java) => [test](src/test/scala/algorithms/array/ReverseArraySpec.scala)
+  * [rotate](src/main/java/algorithms/array/RotateArray.java) => [test](src/test/scala/algorithms/array/RotateArraySpec.scala)

Diff for: src/main/java/algorithms/array/ArrayUtil.java

@@ -0,0 +1,18 @@
+package algorithms.array;
+
+public class ArrayUtil {
+
+    public static void print(int[] arr) {
+        StringBuilder sb = new StringBuilder("[");
+        for (int i = 0; i < arr.length; i++) {
+            if (i > 0) {
+                sb.append(", ");
+            }
+            
+            sb.append(arr[i]);
+        }
+
+        sb.append("]");
+        System.out.println(sb.toString());
+    }
+}

Diff for: src/main/java/algorithms/array/ReverseArray.java

@@ -12,23 +12,9 @@ public static int[] reverse(int[] arr, int offset, int length) {
             arr[i] = arr[j];
             arr[j] = tmp;
 
-            //printArray(arr);
+            //ArrayUtil.print(arr);
         }
 
         return arr;
     }
-    
-     static void printArray(int[] arr) {
-        StringBuilder sb = new StringBuilder("[");
-        for (int i = 0; i < arr.length; i++) {
-            if (i > 0) {
-                sb.append(", ");
-            }
-            
-            sb.append(arr[i]);
-        }
-
-        sb.append("]");
-        System.out.println(sb.toString());
-    }
 }

Diff for: src/main/java/algorithms/array/RotateArray.java

@@ -0,0 +1,21 @@
+package algorithms.array;
+
+public class RotateArray {
+    
+    public static int[] rotate(int[] arr, int n) {
+        if (arr.length > 0) {
+            int d = n % arr.length;
+
+            ReverseArray.reverse(arr, 0, d);
+            //ArrayUtil.print(arr);
+            
+            ReverseArray.reverse(arr, d, arr.length - d);
+            //ArrayUtil.print(arr);
+            
+            ReverseArray.reverse(arr);
+            //ArrayUtil.print(arr);
+        }
+        
+        return arr;
+    }
+}

Diff for: src/test/scala/algorithms/array/ReverseArraySpec.scala

@@ -7,21 +7,21 @@ class ReverseArraySpec extends FlatSpec with Matchers {
 
   it should "reverse the whole array" in {
     //when & then
-    reverse(Array.empty[Int]).toList shouldBe Nil
-    reverse(Array(1)).toList shouldBe List(1)
-    reverse(Array(1, 2)).toList shouldBe List(2, 1)
-    reverse(Array(1, 2, 3, 4, 5)).toList shouldBe List(5, 4, 3, 2, 1)
+    reverse(Array[Int]()) shouldBe Nil
+    reverse(Array(1)) shouldBe List(1)
+    reverse(Array(1, 2)) shouldBe List(2, 1)
+    reverse(Array(1, 2, 3, 4, 5)) shouldBe List(5, 4, 3, 2, 1)
   }
 
   it should "reverse part of the array" in {
     //when & then
-    reverse(Array(1, 2, 3, 4, 5, 6, 7), 0, 0).toList shouldBe List(1, 2, 3, 4, 5, 6, 7)
-    reverse(Array(1, 2, 3, 4, 5, 6, 7), 0, 1).toList shouldBe List(1, 2, 3, 4, 5, 6, 7)
-    reverse(Array(1, 2, 3, 4, 5, 6, 7), 0, 2).toList shouldBe List(2, 1, 3, 4, 5, 6, 7)
-    reverse(Array(1, 2, 3, 4, 5, 6, 7), 0, 3).toList shouldBe List(3, 2, 1, 4, 5, 6, 7)
-    reverse(Array(1, 2, 3, 4, 5, 6, 7), 1, 2).toList shouldBe List(1, 3, 2, 4, 5, 6, 7)
-    reverse(Array(1, 2, 3, 4, 5, 6, 7), 1, 4).toList shouldBe List(1, 5, 4, 3, 2, 6, 7)
-    reverse(Array(1, 2, 3, 4, 5, 6, 7), 5, 2).toList shouldBe List(1, 2, 3, 4, 5, 7, 6)
-    reverse(Array(1, 2, 3, 4, 5, 6, 7), 6, 0).toList shouldBe List(1, 2, 3, 4, 5, 6, 7)
+    reverse(Array(1, 2, 3, 4, 5, 6, 7), 0, 0) shouldBe List(1, 2, 3, 4, 5, 6, 7)
+    reverse(Array(1, 2, 3, 4, 5, 6, 7), 0, 1) shouldBe List(1, 2, 3, 4, 5, 6, 7)
+    reverse(Array(1, 2, 3, 4, 5, 6, 7), 0, 2) shouldBe List(2, 1, 3, 4, 5, 6, 7)
+    reverse(Array(1, 2, 3, 4, 5, 6, 7), 0, 3) shouldBe List(3, 2, 1, 4, 5, 6, 7)
+    reverse(Array(1, 2, 3, 4, 5, 6, 7), 1, 2) shouldBe List(1, 3, 2, 4, 5, 6, 7)
+    reverse(Array(1, 2, 3, 4, 5, 6, 7), 1, 4) shouldBe List(1, 5, 4, 3, 2, 6, 7)
+    reverse(Array(1, 2, 3, 4, 5, 6, 7), 5, 2) shouldBe List(1, 2, 3, 4, 5, 7, 6)
+    reverse(Array(1, 2, 3, 4, 5, 6, 7), 6, 0) shouldBe List(1, 2, 3, 4, 5, 6, 7)
   }
 }

Diff for: src/test/scala/algorithms/array/RotateArraySpec.scala

@@ -0,0 +1,25 @@
+package algorithms.array
+
+import RotateArray._
+import org.scalatest.{FlatSpec, Matchers}
+
+class RotateArraySpec extends FlatSpec with Matchers {
+
+  it should "rotate array elements" in {
+    //when & then
+    rotate(Array[Int](), 1) shouldBe Nil
+    rotate(Array(1), 1) shouldBe List(1)
+    rotate(Array(1, 2), 0) shouldBe List(1, 2)
+    rotate(Array(1, 2), 1) shouldBe List(2, 1)
+    rotate(Array(1, 2), 2) shouldBe List(1, 2)
+    rotate(Array(1, 2), 3) shouldBe List(2, 1)
+    rotate(Array(1, 2), 4) shouldBe List(1, 2)
+    rotate(Array(1, 2, 3, 4, 5), 0) shouldBe List(1, 2, 3, 4, 5)
+    rotate(Array(1, 2, 3, 4, 5), 1) shouldBe List(2, 3, 4, 5, 1)
+    rotate(Array(1, 2, 3, 4, 5), 2) shouldBe List(3, 4, 5, 1, 2)
+    rotate(Array(1, 2, 3, 4, 5), 3) shouldBe List(4, 5, 1, 2, 3)
+    rotate(Array(1, 2, 3, 4, 5), 4) shouldBe List(5, 1, 2, 3, 4)
+    rotate(Array(1, 2, 3, 4, 5), 5) shouldBe List(1, 2, 3, 4, 5)
+    rotate(Array(1, 2, 3, 4, 5), 6) shouldBe List(2, 3, 4, 5, 1)
+  }
+}