//binary search

#include<stdio.h>
 
main()
{
   int i, first, last, middle, n, search, array[100];
 
   printf("enter array size: ");
   scanf("%d",&n);
 
   printf("enter %d integers", n);
 
   for ( i = 0 ; i < n ; i++ )
      scanf("%d",&array[i]);
 
   printf("enter value to find\n");
   scanf("%d",&search);
 
   first = 0;
   last = n - 1;
   middle = (first+last)/2;
 
   while( first <= last )
   {
      if ( array[middle] < search )
         first = middle + 1;    
      else if ( array[middle] == search ) 
      {
         printf("%d found at position %d.\n", search, middle+1);
         break;
      }
      else
         last = middle - 1;
 
      middle = (first + last)/2;
   }
   if ( first > last )
      printf("Not found!");
 
   return 0;   
}