template <class Comparable>
void BST<Comparable>::
remove  (const Comparable & x, BinaryNode<Comparable> * & t)
{
   if (t == NULL)
      return;

   if (x < t->element)
      remove (t->left);

   else if (x > t->element)
      remove (t->right);

   else if (t->left != NULL && t->right != NULL)
   {
      t->element = findMin (t->right)->element;
      remove (t->element, t->right);
   }
   else
   {
      BinaryNode<Comparable> *oldNode = t;
      t = t->left != NULL ? t->left : t->right;
      delete oldNode;
   }
}