Python – Quick Sort
In the tutorial, we will implement Quick Sort Algorithm in Python.
We will write a function named quick_sort() which takes list as argument and sorts this list using Quick Sort algorithm. Also, by default, this quick_sort() function sorts the list in ascending order. To get the descending order, all you have to do is just reverse the list.
Python Program
def quick_sort(alist, start, end):
#Sorts the list from indexes start to end - 1 inclusive
if end - start > 1:
p = partition(alist, start, end)
quick_sort(alist, start, p)
quick_sort(alist, p + 1, end)
def partition(alist, start, end):
pivot = alist[start]
i = start + 1
j = end - 1
while True:
while (i <= j and alist[i] <= pivot):
i = i + 1
while (i <= j and alist[j] >= pivot):
j = j - 1
if i <= j:
alist[i], alist[j] = alist[j], alist[i]
else:
alist[start], alist[j] = alist[j], alist[start]
return j
# Input list
alist = [1, 74, 96, 5, 42, 63]
print('Input List\n', alist)
# Sort list
quick_sort(alist, 0, len(alist))
print('Sorted List\n', alist)Output
Input List
[1, 74, 96, 5, 42, 63]
Sorted List
[1, 5, 42, 63, 74, 96]Conclusion
In this tutorial of Python Examples, we learned how to implement Quick Sort algorithm in Python.