Kalyan Chavali Kalyan Chavali - 1 year ago 123
Python Question

Quicksort with insertion sort Python not working

I've been trying to run the quicksort with a switch to insertion sort when the sub array size is less than 10. So it turns out, i'm not getting a sorted list.

Where am i going wrong?

import random
import time

m = 0

def quicksort(numList, first, last):
if first<last:
sizeArr = last - first + 1
if(sizeArr < m):
insert_sort(numList, first, last)
mid = partition(numList, first, last)
quicksort(numList, first, mid-1)
quicksort(numList, mid + 1, last)

def partition(numList, first, last):
piv = numList[last]
i = first-1
for j in range(first,last):
if numList[j] < piv:
i += 1
temp = numList[i]
numList[i] = numList[j]
numList[j] = temp

tempo = numList[i+1]
numList[i+1] = numList[last]
numList[last] = tempo

return i+1

def insert_sort(numList, first, last):
for x in range(first, last):
key = numList[x]
y = x-1
while y > -1 and numList[y]> key:
numList[y+1] = numList[y]
y = y-1
numList[y+1] = key

if __name__ == '__main__':
start = time.time()
numList = random.sample(range(5000), 100)
m = 10
quicksort(numList, 0, len(numList) - 1)
print numList
print "Time taken: " + str(time.time() - start)

input is some random array of sizes between 100 - 1000000. I'm using a random generator as you can see.

Please help me.

Answer Source

You have an off-by-one error in insert_sort function. Iterate over range(first, last+1) and it will sort correctly.

Recommended from our users: Dynamic Network Monitoring from WhatsUp Gold from IPSwitch. Free Download