quickSort.py

def quick_sort(a_list):
	quick_sort_helper(a_list, 0, len(a_list) - 1)

def quick_sort_helper(a_list, first, last):
	if first < last:
		split_point = partition(a_list, first, last)
		quick_sort_helper(a_list, first, split_point - 1)
		quick_sort_helper(a_list, split_point + 1, last)

def partition(a_list, first, last):

	pivot_value = a_list[first]
	left_mark = first + 1
	right_mark = last

	done = False

	while not done:

		while  left_mark <= right_mark and a_list[left_mark] <= pivot_value:

			left_mark = left_mark + 1

		while a_list[right_mark] >= pivot_value and right_mark >= left_mark:
			
			right_mark = right_mark - 1

		if right_mark < left_mark:
			done = True
		else:
			temp = a_list[left_mark]
			a_list[left_mark] = a_list[right_mark]
			a_list[right_mark] = temp

	temp = a_list[first]
	a_list[first] = a_list[right_mark]
	a_list[right_mark] = temp

	return right_mark

a_list = [1, 6, 3, 2]
quick_sort(a_list)
print a_list