算法基础 顺序查找 二分查找

 1 #顺序查找即在给定范围内逐个遍历，查找需要的数据直到找到或者退出,适合任何类型的查找对象。复杂度为O(n)下面一列表为例，展示顺序查找算法
 2 list1 = [i for i in range(100)] #使用列表生成式，生成一个0~99的步长为1列表。
 3 find_num = int(input("inpute you want find num"))
 4 for i in range(len(list1)):
 5     if  find_num == list1[i]:
 6         print("num index is %d"%i)
 7         break
 8 print("the  num not in list")
 9 
10 #二分查找。二分查找适合查找对象已完成排序，复杂度为O(log n)还是以list1作为查找对象,假设列表按照升序排列
11 def Find_Num(num, list1):
12     low = 0
13     top = len(list1) - 1
14     if len(list1) == 0:
15         print("list is null")
16         exit()
17     while low <= top:
18         task = int((low + top)/2)
19         guess = list1[task]
20         if num == list1[task]:
21             print("the num1 index is %d"%task)
22             break
23         if num > list1[task]:
24             low = task + 1
25         elif num < list1[task]:
26             top = task - 1
27     else:
28         print("num not in list1")
29 Find_Num(20, list1)