python 快速排序 qsort

def qsort(arr, start, end):
    if start > end: return
    def partition(arr, start, end):
        pivot = arr[start]
        i = start+1
        while i <= end:
            if pivot < arr[i]:
                arr[i], arr[end] = arr[end], arr[i]
                end -= 1
            else:
                i += 1
        if end > start:
            arr[start], arr[end] = arr[end], arr[start]
        return end
    mid = partition(arr, start, end)
    qsort(arr, start, mid-1)
    qsort(arr, mid+1, end)

arr = []
qsort(arr,0, -1)
print arr

from random import randint
for k in range(1, 100):
    arr = [randint(0,100) for i in range(k)]
    arr2 = (list(arr))
    qsort(arr, 0, len(arr)-1)
    arr2.sort()
    for j in range(0, len(arr)):
        assert arr[j] == arr2[j]