Merge pull request #1409 from shellhub/dev

BubbleSort Recursion

DIRECTORY.md

@@ -202,6 +202,7 @@
   * [BitonicSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/BitonicSort.java)
   * [BogoSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/BogoSort.java)
   * [BubbleSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/BubbleSort.java)
+  * [BubbleSortRecursion](https://github.com/TheAlgorithms/Java/blob/master/Sorts/BubbleSortRecursion.java)
   * [BucketSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/BucketSort.java)
   * [CocktailShakerSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/CocktailShakerSort.java)
   * [CombSort](https://github.com/TheAlgorithms/Java/blob/master/Sorts/CombSort.java)

Sorts/BubbleSortRecursion.java

@@ -0,0 +1,55 @@
+package Sorts;
+
+import java.util.Random;
+
+/**
+ * BubbleSort algorithm implements using recursion
+ */
+public class BubbleSortRecursion implements SortAlgorithm {
+    public static void main(String[] args) {
+        Integer[] array = new Integer[10];
+
+        Random random = new Random();
+        /* generate 10 random numbers from -50 to 49 */
+        for (int i = 0; i < array.length; ++i) {
+            array[i] = random.nextInt(100) - 50;
+        }
+
+        BubbleSortRecursion bubbleSortRecursion = new BubbleSortRecursion();
+        bubbleSortRecursion.sort(array);
+
+        /* check array is sorted or not */
+        for (int i = 0; i < array.length - 1; ++i) {
+            assert (array[i].compareTo(array[i + 1]) <= 0);
+        }
+    }
+
+    /**
+     * @param unsorted - an array should be sorted
+     * @return sorted array
+     */
+    @Override
+    public <T extends Comparable<T>> T[] sort(T[] unsorted) {
+        bubbleSort(unsorted, unsorted.length);
+        return unsorted;
+    }
+
+    /**
+     * BubbleSort algorithm implements using recursion
+     *
+     * @param unsorted array contains elements
+     * @param len      length of given array
+     */
+    private static <T extends Comparable<T>> void bubbleSort(T[] unsorted, int len) {
+        boolean swapped = false; /* flag to check if array is sorted or not */
+        for (int i = 0; i < len - 1; ++i) {
+            if (SortUtils.greater(unsorted[i], unsorted[i + 1])) {
+                SortUtils.swap(unsorted, i, i + 1);
+                swapped = true;
+            }
+        }
+        if (swapped) {
+            bubbleSort(unsorted, len - 1);
+        }
+    }
+}