12. To write a python program merge sort.

 def merge_sort(arr):

    if len(arr) > 1:

        mid = len(arr) // 2

        left_half = arr[:mid]

        right_half = arr[mid:]

        merge_sort(left_half)

        merge_sort(right_half)

        i = j = k = 0

        while i < len(left_half) and j < len(right_half):

            if left_half[i] < right_half[j]:

                arr[k] = left_half[i]

                i += 1

            else:

                arr[k] = right_half[j]

                j += 1

            k += 1

        while i < len(left_half):

            arr[k] = left_half[i]

            i += 1

            k += 1

        while j < len(right_half):

            arr[k] = right_half[j]

            j += 1

            k += 1

# Example usage:

arr = [64, 25, 12, 22, 11]

merge_sort(arr)

print("Sorted array:", arr)