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Python

Posted by Stefano Nebiolo
Stefano Nebiolo
1,991 Points

MergeSort python

Hi everybosy. I was doing some extra excercise trying to write down a code for the merge sort. It consist in a divide and conquer algorithm that split a list in two, until having singolar elements and then it sort them merging them together. I wrote a code, but the result I get is just slight different from the input list. I am not understanding where the problem is. Anyone able to help? P.S. don't mind the #comments, I was just plying around

def mergesort(data):

merge sorting of a list (divide and conquer)

res = []
if len(data) < 2:
    return data

mid = len(data)//2
#mid = int(len(data)/2)
fst = data[:mid]
snd = data[mid:]

mergesort(fst)
mergesort(snd)

fi = 0
si = 0
k = 0
while fi < len(fst) and si < len(snd):
    if fst[fi] < snd[si]:
        res.append(fst[fi])
        #data.append(fst[fi])
        fi += 1
    else:
        res.append(snd[si])
        #data.append(snd[si])
        si += 1
    k += 1

if fi<len(fst):
    res.extend(fst[fi:])
    #data.extend(fst[fi:])
elif si<len(snd):
    res.extend(snd[si:])
    #data.extend(snd[si:])
return res
#return data