Krishnakanth Jc - 1 year ago 58

Python Question

Sorting is not happening correctly. Can some one help on sorting with this approach. Also please let me know where I am going wrong. I am new to Python so I am doing this myself. I am using the usual approach as we do in C or other languages.

`base =[5,4,3,2,1]`

def splitarray (low, high):

if low < high:

mid = (high+low)/2

splitarray (low, mid)

splitarray (mid+1,high)

merge(low,mid,high)

else:

return

def merge(low,mid,high):

print("merge " +str(low) + " - " +str(mid)+" - "+ str(high))

result = [0]*len(base)

k = 0

i=low

j=mid+1

l=0

while i <= mid and j <= high:

if (base[i] < base[j]):

result[k]= base[i]

k+=1

i += 1

if (base[i] > base[j]) :

result[k]= base[j]

j += 1

k += 1

while i <= mid:

result[k]= base[i]

k += 1

i += 1

while j <= high:

result[k]= base[j]

#count = count + mid - i

j += 1

k += 1

print result

l = low

k= 0

while l <= high:

base[l] = result[l]

l += 1

print base

splitarray(0,len(base)-1)

Answer Source

The issue with your current (updated) code appears to be with the last loop:

```
l = low
k= 0
while l <= high:
base[l] = result[l]
l += 1
```

Here you're copying the values from the `results`

list to the `base`

list. However, the results are all at the start of `results`

, not at the same coordinates you want them to go in `base`

. You seem to have *almost* got it right since you're setting `k`

to zero, but you don't end up using `k`

in the loop.

Try:

```
l = low
k= 0
while l <= high:
base[l] = result[k] # read the result from index k, not l
l += 1
k += 1 # increment k as well
```

This should work as intended. Note that while this will do the sorting correctly, this isn't a very elegant way of sorting in Python. To start with, you can only sort the one global variable `base`

, not any list (it would be much nicer to pass the list as a parameter). However, since this looks like something you've written mostly for the learning experience, I'll leave further improvements up to you.