/**
 * Delete all copies of str from the node list np.
 */
struct node *
np_delete_all (struct node *np, char *str)
{
  // You can't delete from the empty list
  if (np == NULL)
    return NULL;

  // Remove all copies of str from the rest of the list
  struct node *newcdr = np_delete_all (cdr (np), str);

  // Is str at the front of the list?  If so, delete the first element
  // and return the modified cdr.
  if (strcmp (car (np), str) == 0)
    {
      free (np);
      return newcdr;
    }
  // Otherwise, just update the cdr
  else
    {
      set_cdr (np, newcdr);
      return np;
    }
} // np_delete_all

/**
 * Find the last node in a non-null list.
 */
struct node *
np_last_node (struct node *np)
{
  while (np->next != NULL)
   np = np->next;
  return np;
} // np_last_node

int
list_delete_all (struct list *lst, char *str)
{
  // Delete the elements
  lst->head = np_delete_all (lst->head, str);

  // Update the tail
  if (lst->head == NULL)
    lst->tail = NULL;
  else
    lst->tail = np_last_node (lst->head);

  // Update the length
  lst->length = np_length (lst->head);

  // And we're done
  return 1;
} // list_delete_all