c - 折半查找(二分法检索)

 #include <stdio.h>

 #define LEN 10

 /*
 折半查找(二分法检索).
 */

 int
 index_of(int *a, int k) {
     int l = ;
     int r = LEN -;
     int m;
     while(l <= r) {
         m = (r + l) >> ;    //右移(即除以2).
         if(k == a[m])
             return m;    //找到,则直接返回下标.
         else if(k > a[m])
             l = m + ;
         else
             r = m - ;
     }
     return -;    //结束循环后,仍未找到,则表示没有.
 }

 int
 main(void) {
             // 0  1, 2, 3, 4, 5, 6, 7, 8,  9
     int a[] = {, , , , , , , , , };
     int i = index_of(a, );
     printf("%d\n", i);
 }