二分查找算法

 1 #include <stdio.h>
 2 
 3 int binarySearch(int *array, int length, int num);
 4 int main(int argc, const char * argv[]) {
 5     
 6     int array[] = {1, 2, 3, 4, 5};
 7     
 8     int length = sizeof (array) / sizeof(int);
 9     
10     int a = binarySearch(array, length, 4);
11     
12     printf("%d\n",a);
13     
14     return 0;
15 }
16 
17 int binarySearch(int *array, int length, int num)
18 {
19     int low = 0;
20     int high = length - 1;
21     while (low <= high)
22     {
23         int middle = (low + high) / 2;
24         
25         if (array[middle] == num)
26         {
27             return middle;
28         }
29         else if(array[middle] > num)
30             high = middle - 1;
31         else
32             low = middle + 1;
33     }
34     return 0;
35 }