implementation of Merge Sort algorithm using array.

Author: abhinay5993

src/main/java/com/udemy/dsapart1/sortings/MergeSortingUsingDivideAndConquer.java

@@ -0,0 +1,85 @@
+package com.udemy.dsapart1.sortings;
+import java.util.Arrays;
+import java.util.Scanner;
+
+public class MergeSortingUsingDivideAndConquer {
+	
+	public static void main(String[] args) {
+	Scanner scInp=new Scanner(System.in);
+	System.out.print("\nEnter the size of Array : ");
+	int sizeOfArr = scInp.nextInt();
+	double[] inputArr = new double[sizeOfArr];
+	System.out.println("\nEnter the Array elements : ");
+	pushElementsIntoArray(inputArr);
+	System.out.println("\nInput Array : " + Arrays.toString(inputArr));
+	performMergeSort(inputArr);
+	System.out.println("\nRequired Merge Sorted array : "+Arrays.toString(inputArr));
+	}
+
+	
+	/**
+	 * Method to perform the Merge Sort algorithm using divide & Conquer approach.
+	 * 
+	 * @param inputArr2 
+	 * Time complexity - n*log n.
+	 * 
+	 */
+	private static void performMergeSort(double[] inputArr2) {
+		if (inputArr2.length < 2) {
+			return;
+		}
+		int midIndex = (inputArr2.length / 2);
+		double leftSubArray[] = new double[midIndex];
+		double rightSubArray[] = new double[inputArr2.length - midIndex];
+		// fill the elements to left sub-array
+		for (int i = 0; i < midIndex; i++) {
+			 leftSubArray[i] = inputArr2[i];
+		}
+		// fill the elements to right sub-array
+		for (int i = midIndex; i < inputArr2.length; i++) {
+			rightSubArray[i-midIndex] = inputArr2[i];
+		}
+		//recursive call on sorted left-sub array & right sub-array.
+		performMergeSort(leftSubArray);
+		performMergeSort(rightSubArray);
+		//Pass sorted sub-arrays
+		doSubArrayMergeOperation(leftSubArray,rightSubArray,inputArr2);
+	}
+
+	
+	/**
+	 * 
+	 * This method will perform merge operation on input sorted sub-array
+	 * @param leftSubArray
+	 * @param rightSubArray
+	 * @param inputArr2
+	 * 
+	 */
+	private static void doSubArrayMergeOperation(double[] leftSubArray, double[] rightSubArray, double[] inputArr2) {
+		int i = 0, j = 0, k = 0;
+		while (i < leftSubArray.length && j < rightSubArray.length) {
+			if (leftSubArray[i] <= rightSubArray[j]) {
+				inputArr2[k++] = leftSubArray[i++];
+			}
+			else {
+				inputArr2[k++] = rightSubArray[j++];
+			}
+		}
+		while (i < leftSubArray.length) {
+		inputArr2[k++] = leftSubArray[i++];
+		}
+		while (j < rightSubArray.length) {
+		inputArr2[k++] = rightSubArray[j++];
+		}
+	}
+
+
+	public static void pushElementsIntoArray(double inputArr[]) {
+		Scanner scInp1Obj = new Scanner(System.in);
+		for (int i = 0; i < inputArr.length; i++) {
+			System.out.print("\nEnter the element No " + (i + 1) + " : ");
+			inputArr[i] = scInp1Obj.nextDouble();
+		}
+	}
+	
+}