C47 Answer

/* Puzzle C47 -- check that an array has at least one
|                element -N for each element N
|
|  Return the count of the number of elements missing a match,
|  zero or more. If one the value zero is in the array, it must
|  be matched with a second zero.
|
|  Note that an array might have more than one -N for a particular N.
*/
int posNegMatch( int arr[], int size )
{
  int j, k ;
  int target, found;
  int missingCount = 0;
  
  /* each element j should have a match */
  for ( j=0; j<size; j++ )
  {
    target = -arr[j];
    found = 0;
 
    /* the match can be anywhere in the array, except at j */
    /* (this is so a zero will not match itself */
    for ( k=0; k<size && !found; k++ )
    {
      if ( k != j && arr[k] == target ) found = 1;  
    }
    
    /* if no match was found increment the count */
    if ( !found ) missingCount++ ;
  }
  
  return missingCount ;
}