Not sure if you are looking for binary search. Looks like it is binary search though
Here is the function for binary search

int Multiwaysearch(keyList,start,end,searchKey)
{
    int k = 0;
   while( start <= end)
       {
               k = ( start + end)/2;
              if (searchKey = = keyList[k])
                  return k; // returns this position if  searchKey is found in keyList
              if (searchKey < keyList[k])
                   end = k -1;
              else
                  start = k+1;
        }
      return -1; // returns -1 indicating that no match was found
      return ( -k) // this might return the position the number would be found if the number is not in the  keyList.
}

 You don't have to use compare function here, but if you need to you could now modify anyway.
Hope this helps