C--二分搜索

 //二分搜索
   //时间复杂度小 log2 n
 int search(int key, int a[], int len)
 {
     int ret = -;
     int left = ;
     int right = len-;
     int mid;
     while(left<right)
     {
         mid = (right + left)/;
         if(a[mid] == key)
         {
             ret = mid;
             break;
         }else if(a[mid] >key){
             right  = mid-;
         }else{
             left = mid-;
         }
     }
     return ret;
 }
 int main()
 {
     int a[] = {,,,,};
     int r = search(, a, sizeof(a)/sizeof(a[]));
     printf("%d",r);
     return ;
 }