二分查找 

 1 # 为了返回找到列表的下标，故而携带两个参数
 2 def binary_search(num, my_list, left, right):
 3     if left == right:
 4         return left if my_list[left] == num else f'没找到{num}'
 5     mid = (right+left) // 2
 6     mid_num = my_list[mid]
 7     if num == mid_num:
 8         return mid
 9     elif num > mid_num:
10         return binary_search(num, my_list, mid+1, right)
11     else:
12         return binary_search(num, my_list, left, mid-1)
13 
14 
15 # 二分查找的循环实现
16 def while_binary_search(num, lis):
17     left = 0
18     right = len(lis) - 1
19     while True:
20         if left == right:
21             return left if lis[left] == num else f'没找到{num}'
22         mid = (left+right) // 2
23         mid_num = lis[mid]
24         if mid_num == num:
25             return mid
26         elif mid_num > num:
27             right = mid - 1
28         else:
29             left = mid + 1
30 
31 
32 if __name__ == '__main__':
33     my_list = [0, 1, 5, 7, 10, 11, 15, 18, 19]
34     # print(binary_search(10, my_list, 0, len(my_list)-1))
35     print(while_binary_search(15, my_list))

 

posted @ 2021-12-06 10:42  Avery_rainys  阅读(23)  评论(0)    收藏  举报