Question

Implement GenericMergeSort

public static<E extends Comparable<E>> void  MergeSort(E[] list) {

//implement the body

}

Answer 1

public static <E extends Comparable<E>> void mergeSort(E[] list) {

      if (list.length > 1) {

            // Merge sort the first half

            E[] firstHalf = (E[])(new Comparable[list.length / 2]);

            System.arraycopy(list, 0, firstHalf, 0, list.length / 2);

            mergeSort(firstHalf);

            // Merge sort the second half

            int secondHalfLength = list.length - list.length / 2;

            E[] secondHalf = (E[])(new Comparable[secondHalfLength]);

            System.arraycopy(list, list.length / 2, secondHalf, 0, secondHalfLength);

            mergeSort(secondHalf);

            // Merge firstHalf with secondHalf into list

            merge(firstHalf, secondHalf, list);

      }

}

public static <E extends Comparable<E>> void merge(E[] list1, E[] list2, E[] temp) {

      int current1 = 0; // Current index in list1

      int current2 = 0; // Current index in list2

      int current3 = 0; // Current index in temp

      while (current1 < list1.length && current2 < list2.length) {

            if (list1[current1].compareTo(list2[current2]) < 0)

                  temp[current3++] = list1[current1++];

            else

                  temp[current3++] = list2[current2++];

      }

      while (current1 < list1.length)

            temp[current3++] = list1[current1++];

      while (current2 < list2.length)

            temp[current3++] = list2[current2++];

}