归并排序
1 def merge(li, low,mid, high):
2 i = low
3 j = mid+1
4 ltmp = []
5 while i<=mid and j <=high:
6 if li[i]<li[j]:
7 ltmp.append(li[i])
8 i += 1
9 else:
10 ltmp.append(li[j])
11 j += 1
12 while i<=mid:
13 ltmp.append(li[i])
14 i += 1
15 while j<=high:
16 ltmp.append(li[j])
17 j += 1
18 li[low:high+1]=ltmp
19 # li = [1,5,7,8,9,2,5,7,10]
20 # merge(li,0,len(li)//2,len(li)-1)
21 # 本算法时间复杂度为O(n*logn)
22 def merge_sort(li,low,high):
23 if low<high:
24 mid = (low+high)//2
25 merge_sort(li,low,mid)
26 merge_sort(li,mid+1,high)
27 merge(li,low,mid,high)
28
29
30 import time
31 def timer(func):
32 def inner(*args,**kwargs):
33 start = time.time()
34 ret = func(*args,**kwargs)
35 end = time.time()
36 print(end-start)
37 return ret
38 return inner
39 @timer
40 def outer(li,low,high):
41 merge_sort(li,low,high)
42 # import random
43 # li = list(range(1000))
44 # random.shuffle(li)
45 # print(li)
46 # outer(li,0,len(li)-1) # 1000个数据费时0.004s
47 # print(li)
48
49 # li = list(range(10000))
50 # random.shuffle(li)
51 # print(li)
52 # outer(li,0,len(li)-1) # 10000个数据费时0.05s
53 # print(li)
