为了通过练习学习python,我试图用python实现并测试出快速排序算法。用负数排序Python列表
实现本身并不困难,那种然而,结果是有点令人费解:
当我一个列表排序,
[ '35', '-1', '-2',' -7' , '-8', '3', '-4', '20', '-6', '53']
结果给我
[ '-1', '-2','-3','-4','-6','-7','-8','20','35','53']
因此, st被排序,但负整数按相反的顺序排序。
我怀疑这可能是一个问题,因为我正在整理从文件中读入的整数列表,而int的类型实际上不是int,而是其他的东西(可能是字符串)。可能会解决这个问题吗?
这里是快速排序实现
#quicksort -> the conquer part of the algorithm
def quicksort(input_list, start_index, end_index):
if start_index < end_index:
#partition the list of integers.
pivot = partition(input_list, start_index, end_index)
#recursive call on both sides of the pivot, that is excluding the pivot itself
quicksort(input_list, start_index, pivot-1)
quicksort(input_list, pivot+1, end_index)
return input_list
#divide part of the algorithm
def partition(input_list, start_index, end_index):
#declare variables required for sorting
pivot = input_list[start_index]
left = start_index + 1
right = end_index
sorted = False
while not sorted:
#break condition so that left index is crossed with right index
#or if the value of left crosses the pivot value
while left <= right and input_list[left] <= pivot:
#increment left index
left = left + 1
#break the loop when right and left indexes cross
#or if the right value crosses the pivot value
while right >= left and input_list[right] >= pivot:
right = right-1
if right < left:
sorted = True
else:
#swap places for left value and the right value cause they are not in order
temp = input_list[left]
input_list[left] = input_list[right]
input_list[right] = temp
#swap the value at start index with what's now at the right half. Then return right for the new pivot
temp = input_list[start_index]
input_list[start_index] = input_list[right]
input_list[right] = temp
return right
任何帮助表示赞赏代码。谢谢大家的时间和帮助。
谢谢!我将int映射到列表并且一切正常。所以这不是代码中的错误,而是类型错误,我正在排序和它的行为。谢谢ShadowRanger。我学到了很多! –