折半查找

全部代码
 1 #include <stdio.h>
 2 #include <assert.h>
 3 
 4 int BinarySearch(int arr[], int len, int key)
 5 {
 6     int low;
 7     int high;
 8     int mid;
 9 
10     assert(arr!=NULL && len>0);
11 
12     low = 0;
13     high = len-1;
14 
15     while(low <= high)
16     {
17         mid = (low+high)/2;
18         if(key < arr[mid])
19         {
20             high = mid-1;
21         }
22         else if(key > arr[mid])
23         {
24             low = mid+1;
25         }
26         else
27         {
28             return mid;
29         }
30     }
31     
32     return -1;
33 }
34 
35 int main(void)
36 {
37     int arr[] = {1, 2, 3, 4, 5, 6, 7};
38     int len = sizeof(arr)/sizeof(arr[0]);
39     printf("%d
", BinarySearch(arr, len, 6));
40 
41     return 0;
42 }