Add Merge sort in Java

src/main/java/sortalgorithms/MergeSort.java

@@ -0,0 +1,64 @@
+package com.jagjit.Hactoberfest;
+
+import java.util.Arrays;
+
+public class MergeSort {
+
+	private static void merge(int[] inputArray, int start, int mid, int end) {
+
+		int i = 0, first = start, last = mid + 1;
+	    int[] tmp = new int[end - start + 1];
+
+	    while (first <= mid && last <= end) {
+	      tmp[i++] = inputArray[first] < inputArray[last] ? inputArray[first++] : inputArray[last++];
+	    }
+	    while (first <= mid) {
+	      tmp[i++] = inputArray[first++];
+	    }
+	    while (last <= end) {
+	      tmp[i++] = inputArray[last++];
+	    }
+	    i = 0;
+	    while (start <= end) {
+	    	inputArray[start++] = tmp[i++];
+	    }
+
+	}
+
+	private static void mergesort(int[] inputArray, int start, int end) {
+
+		// split the array into two parts
+		if (start < end) {
+
+			int mid = (start + end) / 2;
+
+			mergesort(inputArray, start, mid);
+
+			mergesort(inputArray, mid + 1, end);
+
+			merge(inputArray, start, mid, end);
+
+		}
+	}
+
+	public static void mergesort(int[] inputArray) {
+		mergesort(inputArray, 0, inputArray.length - 1);
+	}
+
+	public static void main(String[] args) {
+
+		System.out.println("Unsorted Array");
+		int[] inputArray = { 2, 6, 3, 5, 1  };
+
+		System.out.println(Arrays.toString(inputArray));
+		// System.out.println(Arrays.toString(input));
+
+		// sorting array using MergeSort algorithm
+		mergesort(inputArray);
+
+		System.out.println("After sorting using Mergesort");
+		System.out.println(Arrays.toString(inputArray));
+
+	}
+
+}