quicksort.py

#!/usr/bin/python
def quickSort(alist):
    quickSortHelper(alist,0,len(alist)-1)

def quickSortHelper(alist,first,last):
    if first<last:
        splitpoint = partition(alist,first,last)
        quickSortHelper(alist,first,splitpoint-1)
        quickSortHelper(alist,splitpoint+1,last)
def partition(alist,first,last):
    pivotvalue = alist[first]

    leftmark = first+1
    rightmark = last
    
    done = False

    while not done:
        while leftmark <= rightmark and alist[leftmark] <= pivotvalue:
                leftmark = leftmark + 1
        
        while leftmark <= rightmark and alist[rightmark] >= pivotvalue:
                rightmark = rightmark - 1
        
        if rightmark < leftmark:
            done = True
        else:
            temp = alist[leftmark]
            alist[leftmark] = alist[rightmark]
            alist[rightmark] = temp

    temp = alist [first]
    alist[first] = alist[rightmark]
    alist[rightmark] = temp

    return rightmark


alist = [54,26,93,17,77,31,44,55,20]
quickSort(alist)
print(alist)