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):

# 基准

pivot_value = a_list[first]

left_mark = first + 1

right_mark = last

done = False

while not done:

# left_mark找到小于基准的数

while (left_mark <= right_mark and

a_list[left_mark] <= pivot_value):

left_mark = left_mark + 1

# right_mark找到大于基准的数

while (right_mark >= left_mark and

a_list[right_mark] >= pivot_value):

right_mark = right_mark - 1

# 停止条件

if right_mark < left_mark:

done = True

else:

a_list[left_mark], a_list[right_mark] = a_list[right_mark], a_list[left_mark]

# 将基准移到中间去，自此列表分成了两部分

a_list[first], a_list[right_mark] = a_list[right_mark], a_list[first]

# 返回基准所在位置

return right_mark

if __name__ == '__main__':

a_list = [54, 26, 93, 17, 77, 31, 44, 55, 20]

quick_sort(a_list)

print(a_list)