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package Sorts;

import static Sorts.SortUtils.print;

/**

* This method implements the Generic Merge Sort

*

* @author Varun Upadhyay (https://github.com/varunu28)

* @author Podshivalov Nikita (https://github.com/nikitap492)

* @see SortAlgorithm

*/

class MergeSort implements SortAlgorithm {

/**

* This method implements the Generic Merge Sort

*

* @param unsorted the array which should be sorted

* @param <T> Comparable class

* @return sorted array

*/

@Override

public <T extends Comparable<T>> T[] sort(T[] unsorted) {

doSort(unsorted, 0, unsorted.length - 1);

return unsorted;

}

/**

* @param arr The array to be sorted

* @param left The first index of the array

* @param right The last index of the array

* Recursively sorts the array in increasing order

**/

private static <T extends Comparable<T>> void doSort(T[] arr, int left, int right) {

if (left < right) {

int mid = left + (right - left) / 2;

doSort(arr, left, mid);

doSort(arr, mid + 1, right);

merge(arr, left, mid, right);

}

}

/**

* This method implements the merge step of the merge sort

*

* @param arr The array to be sorted

* @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

**/

private static <T extends Comparable<T>> void merge(T[] arr, int left, int mid, int right) {

int length = right - left + 1;

T[] temp = (T[]) new Comparable[length];

int i = left;

int j = mid + 1;

int k = 0;

while (i <= mid && j <= right) {

if (arr[i].compareTo(arr[j]) <= 0) {

temp[k++] = arr[i++];

} else {

temp[k++] = arr[j++];

}

}

while (i <= mid) {

temp[k++] = arr[i++];

}

while (j <= right) {

temp[k++] = arr[j++];

}

System.arraycopy(temp, 0, arr, left, length);

}

// Driver program

public static void main(String[] args) {

// Integer Input

Integer[] arr = {4, 23, 6, 78, 1, 54, 231, 9, 12};

MergeSort mergeSort = new MergeSort();

mergeSort.sort(arr);

// Output => 1 4 6 9 12 23 54 78 231

print(arr);

// String Inpu

String[] stringArray = {"c", "a", "e", "b", "d"};

mergeSort.sort(stringArray);

//Output => a b c d e

print(stringArray);

}

}