/* Programmed by Kurt Normark, April 2003 */

#include <stdio.h>

int look_up_from_to(int v, int a[], int from, int to);

/* Search for v in the sorted array a which holds n elements. 
   Return index of v, of -1 if v is not found */
int look_up(int v, int a[], int n){
  return look_up_from_to(v, a, 0, n-1);
}

int look_up_from_to(int v, int a[], int from, int to){
  int mid = (from+to)/2;
  int result;

  if (from > to) 
    result = -1;
  else if (v == a[mid])
    result = mid;
  else if (v < a[mid])
    result = look_up_from_to(v, a, from, mid-1);
  else 
    result = look_up_from_to(v, a, mid+1, to);  

  return result;
}

int main(void) {
  int tab[] = {-33, -15, -7, 3, 7, 9, 10, 17, 24, 33};
  int tab_size = sizeof(tab)/sizeof(int);
  int search_el, result_index, i;

  printf("The table: ");
  for(i=0; i < tab_size; i++) printf("%5i", tab[i]);
  printf("\n\n");

  do{
    printf("Search for which integer element (for exit: 0): "); 
    scanf("%i", &search_el);
    if (search_el != 0){
      result_index = look_up(search_el, tab, tab_size);
      printf("Search result: %i\n", result_index);
    }
  }
  while (search_el != 0);


  return 0;
}