利用Python实现归并排序

Posted 2020-10-04

利用python进行归并排序，摘抄自http://blog.csdn.net/minxihou/article/details/51821052

“代码真的不是一气呵成的，而且也不是想当然写出来的。可能需要反复断点中断来查看是否有逻辑错误。在理解了问题的基础下我们需要先把大体的代码框架最好先写出来，
特别是主要的逻辑判断语句。但是不需要太care我循环体或者判断里面语句怎么实现，当你把这一步做到的时候能避免很多不必要的错误发生。”

 1 import random
 2 
 3 def ConfiationAlgorithm(str):
 4     if len(str) <= 1: #子序列
 5         return str
 6     mid = (len(str) // 2)
 7     left = ConfiationAlgorithm(str[:mid])#递归的切片操作
 8     right = ConfiationAlgorithm(str[mid:])
 9     result = []
10     #i,j = 0,0
11 
12     while len(left) > 0 and len(right) > 0:
13         if (left[0] <= right[0]):
14             #result.append(left[0])
15             result.append(left.pop(0))
16             #i+= 1
17         else:
18             #result.append(right[0])
19             result.append(right.pop(0))
20             #j+= 1
21 
22     if (len(left) > 0):
23         result.extend(ConfiationAlgorithm(left))
24     else:
25         result.extend(ConfiationAlgorithm(right))
26     return result
27 
28 if __name__ == ‘__main__‘:
29     a = [20,30,64,16,8,0,99,24,75,100,69]
30     print(ConfiationAlgorithm(a))
31     b = [random.randint(1,1000) for i in range(10)]
32     print(ConfiationAlgorithm(b))

另一种思路

 1 def merge(left, right):
 2     i, j = 0, 0
 3     result = []
 4     while i < len(left) and j < len(right):
 5         if left[i] <= right[j]:
 6             result.append(left[i])
 7             i += 1
 8         else:
 9             result.append(right[j])
10             j += 1
11     result += left[i:]
12     result += right[j:]
13     return result
14 
15 def merge_sort(lists):
16     # 归并排序
17     if len(lists) <= 1:
18         return lists
19     num = len(lists) / 2
20     left = merge_sort(lists[:num])
21     right = merge_sort(lists[num:])
22     return merge(left, right)