如何解決歸並排序算法中的遞歸問題？

Question

在示例中，我想使用合並排序對 station 的屬性 f 進行排序。

class mergesort_algorithm():


 def Merge_Sort(self,stations):

     length = len(stations)
     middle = int(length/2-1)

     if length<=1:
         return stations
     else:
         list1 = self.Merge_Sort(stations[:middle])
         list2 = self.Merge_Sort(stations[middle:])

         return self.Merge(list1,list2)




 def Merge(self,list1,list2):
     list3 = []
     length1 = len(list1)
     length2 = len(list2)
     point1 = 0
     point2 = 0


     while point1<=length1-1 and point2<=length2-1:

         if list1[point1].f<list2[point2].f:
             list3.append(list1[point1])
             point1 += 1

         else:
             list3.append(list2[point2])
             point2 += 1

     if point1>length1:
         for i in range(list2):
             if i>=point2:
                 list3.append(list2[point2])

     if point2>length2:
         for i in range(list1):
             if i>=point1:
                 list3.append(list1[point1])

     for item in list3:
         print(item.name)
     print("-----")
     return list3

當我運行代碼對電台列表進行排序時，它會報告錯誤。

File "/home/surface/Final-Year-Project/FYP/Util/Mergesort_algorithm.py", line 16, in Merge_Sort
    list1 = self.Merge_Sort(stations[:middle])
  File "/home/surface/Final-Year-Project/FYP/Util/Mergesort_algorithm.py", line 17, in Merge_Sort
    list2 = self.Merge_Sort(stations[middle:])
  File "/home/surface/Final-Year-Project/FYP/Util/Mergesort_algorithm.py", line 17, in Merge_Sort
    list2 = self.Merge_Sort(stations[middle:])
  File "/home/surface/Final-Year-Project/FYP/Util/Mergesort_algorithm.py", line 17, in Merge_Sort
    list2 = self.Merge_Sort(stations[middle:])
  [Previous line repeated 989 more times]
  File "/home/surface/Final-Year-Project/FYP/Util/Mergesort_algorithm.py", line 16, in Merge_Sort
    list1 = self.Merge_Sort(stations[:middle])
  File "/home/surface/Final-Year-Project/FYP/Util/Mergesort_algorithm.py", line 11, in Merge_Sort
    middle = int(length/2-1)
RecursionError: maximum recursion depth exceeded while calling a Python object

我不知道如何解決它。 似乎有很多遞歸。 我發現一些解決方案使用： import sys和sys.setrecursionlimit(1000000)

Answer 1

假設len(stations)為 2。則middle為 0。因此stations[:middle]為空，但stations[middle:]的長度為 2，並且存在無限遞歸。