Updated MergeSort.java

Updated MergeSort into its generic form
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Varun Upadhyay 2017-08-25 11:43:44 -07:00 committed by GitHub
parent e9b1e2542b
commit 146a08cabf

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@ -1,109 +1,100 @@
import java.util.Scanner;
/**
* This class implements MergeSort
* @author Unknown
*
* @author Varun Upadhyay (https://github.com/varunu28)
*
*/
public class MergeSort {
/** Array for mergeSort*/
private int[] array;
/** Temp Merge Array*/
private int[] tempMergArr;
/** Length of the array*/
private int length;
class MergeSort {
/**
* Sorts inputArr with merge sort algorithm
*
* @param inputArr Array to be sorted
*/
public final void sort(int inputArr[]) {
this.array = inputArr;
this.length = inputArr.length;
this.tempMergArr = new int[this.length];
this.mergeSort(0, this.length - 1);
* This method implements the Generic Merge Sort
*
* @param arr The array to be sorted
* @param temp The copy of the actual array
* @param left The first index of the array
* @param right The last index of the array
* Recursively sorts the array in increasing order
**/
public static <T extends Comparable<T>> void MS(T[] arr, T[] temp, int left, int right) {
if (left < right) {
int mid = left + (right - left) / 2;
MS(arr, temp, left, mid);
MS(arr, temp,mid + 1, right);
merge(arr, temp, left, mid, right);
}
}
/**
* Partitions Array into recursively smaller pieces
* This method implements the merge step of the merge sort
*
* @param lowerIndex lower bound to include in the first partition
* @param higherIndex upper bound to include in the third partition
*/
private void mergeSort(int lowerIndex, int higherIndex) {
if (lowerIndex < higherIndex) {
int middle = lowerIndex + (higherIndex - lowerIndex) / 2;
// Below step sorts the left side of the array
this.mergeSort(lowerIndex, middle);
// Below step sorts the right side of the array
this.mergeSort(middle + 1, higherIndex);
// Now merge both sides
this.mergeParts(lowerIndex, middle, higherIndex);
}
}
* @param arr The array to be sorted
* @param temp The copy of the actual array
* @param left The first index of the array
* @param mid The middle index of the array
* @param right The last index of the array
* merges two parts of an array in increasing order
**/
/**
* Merges partitions
*
* @param lowerIndex The lower index
* @param middle The middle index
* @param higherIndex The higher index
*/
private void mergeParts(int lowerIndex, int middle, int higherIndex) {
for (int i = lowerIndex; i <= higherIndex; i++) {
this.tempMergArr[i] = this.array[i];
public static <T extends Comparable<T>> void merge(T[] arr, T[] temp, int left, int mid, int right) {
for (int i=left;i<=right;i++) {
temp[i] = arr[i];
}
int i = lowerIndex;
int j = middle + 1;
int k = lowerIndex;
while (i <= middle && j <= higherIndex) {
if (this.tempMergArr[i] <= this.tempMergArr[j]) {
this.array[k] = this.tempMergArr[i];
int i= left;
int j = mid + 1;
int k = left;
while (i<=mid && j<=right) {
if (temp[i].compareTo(temp[j]) <= 0) {
arr[k] = temp[i];
i++;
} else {
this.array[k] = this.tempMergArr[j];
}
else {
arr[k] = temp[j];
j++;
}
k++;
}
while (i <= middle) {
this.array[k] = this.tempMergArr[i];
k++;
while (i <= mid) {
arr[k] = temp[i];
i++;
k++;
}
}
/**
* Gets input to sort
*
* @return unsorted array of integers to sort
*/
public static int[] getInput() {
final int numElements = 6;
int[] unsorted = new int[numElements];
Scanner input = new Scanner(System.in);
System.out.println("Enter any 6 Numbers for Unsorted Array : ");
for (int i = 0; i < numElements; i++) {
unsorted[i] = input.nextInt();
}
input.close();
return unsorted;
}
// Driver program
public static void main(String[] args) {
/**
* Main Method
*
* @param args Command line arguments
*/
public static void main(String args[]) {
int[] inputArr = getInput();
MergeSort mergeSort = new MergeSort();
mergeSort.sort(inputArr);
for (int i : inputArr) {
System.out.print(i);
System.out.print(" ");
// Integer Input
int[] arr = {4,23,6,78,1,54,231,9,12};
Integer[] array = new Integer[arr.length];
for (int i=0;i<array.length;i++) {
array[i] = arr[i];
}
// Copy of actual array
Integer[] temp = new Integer[arr.length];
MS(array, temp, 0, arr.length-1);
// Output => 1 4 6 9 12 23 54 78 231
for (int i=0;i<arr.length;i++) {
System.out.print(array[i] + " ");
}
System.out.println();
// String Input
String[] array1 = {"c", "a", "e", "b","d"};
String[] temp1 = new String[array1.length];
MS(array1, temp1, 0, array1.length-1);
//Output => a b c d e
for(int i=0; i<array1.length; i++)
{
System.out.print(array1[i]+"\t");
}
}
}