#include <iostream>
#include <assert.h>
using namespace std ;


// Use binary search to look for stuff in array A[start], .., A[end]
// inclusive. Returns the index i such that A[i] == stuff or
// returns -1 if not found.
//

int rec_bsearch(int A[], int start, int end, int stuff) ;

int bsearch(int A[], int start, int end, int stuff) {

   int middle ;

   while (start <= end) {

      // assert(start <= end) ;

      middle = ( start + end ) / 2 ;

      assert (start <= middle && middle <= end) ;
      
      if ( A[middle] == stuff) {

         return middle ;

      } else if ( A[middle] < stuff ) {

         start = middle + 1 ;

      } else {

         end = middle - 1 ;

      }

   }  // end of while ( ...  )

   return -1 ;

}

// Note: linear search is much slower than binary search.
//
int linear_search(int A[], int start, int end, int stuff) {

   for (int i=start ; i<=end ; i++) {
      if (A[i] == stuff) return i ;
   }

   return -1 ;
}


// Call recursive binary search, non-recursive binary search
// or linear search, depending. Still gets the job done.
//
int weird_search(int A[], int start, int end, int stuff) {

   if ( (start%2 == 0) && (end%2 == 0) ) {
      return bsearch(A,start,end,stuff) ;

   } else if ( (start%2 == 1) && (end%2 == 1) ) {
      return linear_search(A,start,end,stuff) ;

   } else {
      return rec_bsearch(A,start,end,stuff) ;

   }
}


//  This version calls weird_search().
//  It might end up recursively calling itself, or not.
//  It doesn't matter for correctness. 
// (It can affect the running time, though.)
// 
int rec_bsearch(int A[], int start, int end, int stuff) {

   int middle ;

   if (start > end) return -1 ;

   middle = ( start + end ) / 2  ;  


   if ( A[middle] == stuff ) return middle ;


   if ( A[middle] < stuff ) {

      return weird_search(A, middle + 1, end, stuff) ;

   } else {

      return weird_search(A, start, middle - 1, stuff) ;

   }

}



int main() {

   int A[15] = { 2, 5, 6, 9, 10, 12, 14, 17, 21, 32, 39, 41, 44, 45, 60 } ;

   int result ;

   result = rec_bsearch(A, 0, 14, 41) ;
   if (result == -1) {
      cout << "41 is not in array A[].\n" ;
   } else {
      cout << "41 is in A[" << result << "]\n" ;
   }

   result = rec_bsearch(A, 0, 14, 23) ;
   if (result == -1) {
      cout << "23 is not in array A[].\n" ;
   } else {
      cout << "23 is in A[" << result << "]\n" ;
   }

   cout << "\n\n" ;

   int plusOne ;

   for (int i=0 ; i < 15 ; i++) {

      result = rec_bsearch(A, 0, 14, A[i]) ;
      if (result == -1) {
	 cout << A[i] << " is not in array A[].\n" ;
      } else {
	 cout << A[i] << " is in A[" << result << "]\n" ;
      }

      plusOne = A[i] + 1 ;

      result = rec_bsearch(A, 0, 14, plusOne) ;
      if (result == -1) {
	 cout << plusOne << " is not in array A[].\n" ;
      } else {
	 cout << plusOne << " is in A[" << result << "]\n" ;
      }

   }

   return 0 ;

}