Merge Sorting

Mahendra Kumar

arraysDSAlogic•••

Merge Sort is one of the most popular sorting algorithms that is based on the principle of the Divide and Conquer Algorithms.

A divide and conquer algorithm is a strategy for solving a large problem by

breaking the problem into smaller sub-problems
solving the sub-problems, and
Combine them to get the desired output.

def mergeSort(array):
    if len(array) > 1:
        #  r is the point where the array is divided into two subarrays
        r = len(array)//2
        L = array[:r]
        M = array[r:]
        # Sort the two halves
        mergeSort(L)
        mergeSort(M)
        i = j = k = 0
        # Until we reach either end of either L or M, pick larger among
        # elements L and M and place them in the correct position at A[p..r]
        while i < len(L) and j < len(M):
            if L[i] < M[j]:
                array[k] = L[i]
                i += 1
            else:
                array[k] = M[j]
                j += 1
            k += 1
        # When we run out of elements in either L or M,
        # pick up the remaining elements and put in A[p..r]
        while i < len(L):
            array[k] = L[i]
            i += 1
            k += 1
        while j < len(M):
            array[k] = M[j]
            j += 1
            k += 1
# Print the array
def printList(array):
    for i in range(len(array)):
        print(array[i], end=" ")
    print()
# Driver program
if __name__ == '__main__':
    array = [6, 5, 12, 10, 9, 1]
    mergeSort(array)
    print("Sorted array is: ")
    printList(array)