Question

what is Merge Sort? Python Program for Merge Sort.

Answer 1

Merge Sort is a Divide and Conqure algorithm. It divides input array in two halves, calls itself for the two halves and then merges the two sorted halves. The merge() function is used for merging two halves. 

Auxiliary Space  :   O(n)

Time complexity :  θ(nlog(n))

Python program for implementation of Merge Sort:

def mergeSort(arr):

    if len(arr) >1:

        mid = len(arr)//2 

        L = arr[:mid]

        R = arr[mid:]

         mergeSort(L)

        mergeSort(R)

         i = j = k = 0

         # Copy data to temp arrays L[] and R[]

        while i < len(L) and j < len(R):

            if L[i] < R[j]:

                arr[k] = L[i]

                i+=1

            else:

                arr[k] = R[j]

                j+=1

            k+=1

        while i < len(L):

            arr[k] = L[i]

            i+=1

            k+=1

         

        while j < len(R):

            arr[k] = R[j]

            j+=1

            k+=1        

a=[12,11,8,5,3,20]

mergeSort(a)

print(a)