Question

如果我想通过以下QuickSort算法进行排序，则会收到“ RecursionError：在比较中超出最大递归深度”失败，或者如果我将递归限制设置得更高，则Python在通过BubbleSort使用（Process进行排序后，将停止工作以退出代码-1073741571（0xC00000FD）完成。有谁知道我该如何解决这个问题

设置更高的递归限制

import time
import random
from sys import setrecursionlimit
#setrecursionlimit(1000000)

#------------------------------Sortieralgorithmen-----------------------------------------------
#-----------------------------------------------------------------------------------------------

def bubbleSort(array):

    length = len(array)

    for sorted in range(length):

        for j in range(0, length-sorted-1):
            if array[j] > array[j+1] :
                array[j], array[j+1] = array[j+1], array[j]



def help(array, low, high):
    pivot = array[low]
    fromhigh = high
    fromlow = low
    while True:
        while(array[fromhigh]>pivot):
            fromhigh = fromhigh-1
        while(array[fromlow]<pivot):
            fromlow = fromlow+1
        if(fromlow<fromhigh):
            array[fromlow], array[fromhigh] = array[fromhigh], array[fromlow]
        else:
            return fromhigh


def quickSort(array, low, high):
   if (low<high):
       pivot = help(array, low, high)
       quickSort(array, low, pivot)
       quickSort(array, pivot + 1, high)




#--------------------------------Zeitmessung-----------------------------------------------------
#------------------------------------------------------------------------------------------------

numb_elements = 6000

sortedarray = []
for i in range (0,numb_elements):
    sortedarray.append(i)

notsortedarray = random.sample(range(0,numb_elements),numb_elements)

copy1 = sortedarray.copy()
before = time.time()
bubbleSort(copy1)
after = time.time()
total = after-before
print("Bubblesort sortiertes Array:\t\t" + str(total))

copy2 = notsortedarray.copy()
before = time.time()
bubbleSort(copy2)
after = time.time()
total = after-before
print("Bubblesort nicht sortiertes Array:\t" + str(total))

copy3 = sortedarray.copy()
before = time.time()
quickSort(copy3, 0, len(copy3)-1)
after = time.time()
total = after-before
print("QuickSort sortiertes Array:\t\t\t" + str(total))

copy4 = notsortedarray.copy()
before = time.time()
quickSort(copy4, 0, len(copy4)-1)
after = time.time()
total = after-before
print("QuickSort nicht sortiertes Array:\t" + str(total)+"\t (Worst Case)")

Answer 1

一些介绍性跟踪显示了该问题：

indent = ""

def quickSort(array, low, high):
   global indent
   # print(indent, "quickSort ENTER", low, high)
   indent += "  "
   if (low<high):
       pivot = help(array, low, high)
       print(low, high, pivot)
       quickSort(array, low, pivot)
       quickSort(array, pivot + 1, high)

   indent = indent[2:]

看到堆栈问题后，我插入了包含数据透视表的打印语句。输出是

0 5999 0
1 5999 1
2 5999 2
3 5999 3
4 5999 4
5 5999 5
6 5999 6
...
994 5999 994
995 5999 995
996 5999 996
Traceback (most recent call last):
  File "so.py", line 79, in <module>
    quickSort(copy3, 0, len(copy3)-1)
  File "so.py", line 46, in quickSort
    quickSort(array, pivot + 1, high)
  File "so.py", line 46, in quickSort
    quickSort(array, pivot + 1, high)
  File "so.py", line 46, in quickSort
    quickSort(array, pivot + 1, high)
  [Previous line repeated 994 more times]
  File "so.py", line 43, in quickSort
    pivot = help(array, low, high)
  File "so.py", line 28, in help
    while(array[fromhigh]>pivot):
RecursionError: maximum recursion depth exceeded in comparison

您的问题是您的枢纽逻辑总是返回低元素，这会将您的算法更改为 O（N ^ 2），当N为大于允许的堆栈深度。

可以从那里拿走吗？请参阅这个可爱的debug博客以获取帮助。
即使是琐碎的print也会给您很多线索。

QuickSort不适用于超过2000个元素。为什么？

1 个答案: