Merge pull request #5345 from vaibs28/master

BAEL-2211 Merge Sort

algorithms/src/main/java/com/baeldung/algorithms/mergesort/MergeSort.java

@@ -0,0 +1,50 @@
+package com.baeldung.algorithms.mergesort;
+
+public class MergeSort {
+
+    public static void main(String[] args) {
+        int[] a = { 5, 1, 6, 2, 3, 4 };
+        mergeSort(a, a.length);
+        for (int i = 0; i < a.length; i++)
+            System.out.println(a[i]);
+    }
+
+    public static void mergeSort(int[] a, int n) {
+        if (n < 2)
+            return;
+        int mid = n / 2;
+        int[] l = new int[mid];
+        int[] r = new int[n - mid];
+
+        for (int i = 0; i < mid; i++) {
+            l[i] = a[i];
+        }
+        for (int i = mid; i < n; i++) {
+            r[i - mid] = a[i];
+        }
+        mergeSort(l, mid);
+        mergeSort(r, n - mid);
+
+        merge(a, l, r, mid, n - mid);
+    }
+
+    public static void merge(int[] a, int[] l, int[] r, int left, int right) {
+
+        int i = 0, j = 0, k = 0;
+
+        while (i < left && j < right) {
+
+            if (l[i] < r[j])
+                a[k++] = l[i++];
+            else
+                a[k++] = r[j++];
+
+        }
+
+        while (i < left)
+            a[k++] = l[i++];
+
+        while (j < right)
+            a[k++] = r[j++];
+    }
+}

algorithms/src/test/java/com/baeldung/algorithms/mergesort/MergeSortUnitTest.java

@@ -0,0 +1,17 @@
+package com.baeldung.algorithms.mergesort;
+
+import org.junit.Assert;
+
+import org.junit.Test;
+
+public class MergeSortUnitTest {
+
+    @Test
+    public void positiveTest() {
+        int[] actual = { 5, 1, 6, 2, 3, 4 };
+        int[] expected = { 1, 2, 3, 4, 5, 6 };
+        MergeSort.mergeSort(actual, actual.length);
+        Assert.assertArrayEquals(expected, actual);
+    }
+
+}