c++二分法

如上图，二分法查找，查找的过程是先确定待查找数的范围区间，然后逐步缩小查找范围，直到找到或找不到为止。

c++代码的实现

 1 #include<iostream>
 2 using namespace std;
 3 const int len=10;
 4 int find_array(int a[],int len,int key);
 5 int full_array(int a[],int len);
 6 int main()
 7 {
 8     int i_array[len];
 9     full_array(i_array,len);
10     cout<<"input the element you want to find"<<endl;
11     int key,num;
12     cin>>key;
13     num=find_array(i_array,len,key);
14     if(num!=-1)
15     {
16         cout<<"successful find"<<i_array[num]<<endl;
17     }
18     else
19     {
20         cout<<"not the element"<<endl;
21     }
22 
23     return 0;
24 }
25 
26 int full_array(int *a,int len)
27 {
28     cout<<"please input "<<len<<" element init the array"<<endl;
29     int i=0;
30     while(i!=len)
31     {
32         cin>>a[i];
33         i++;
34     }
35     return 0;
36 }
37 
38 int find_array(int a[],int len,int key)
39 {
40     int low=0,high=len-1,middle;
41     while(low<high)
42     {
43         middle=(low+high)/2;
44 
45         if(key==a[middle])
46         {
47             return middle ;
48         }
49         else if(key>a[middle])
50         {
51             low=middle+1;
52         }
53         else
54         {
55             low=middle-1;
56         }
57         
58     }
59     return -1;
60 }

ok。