#ifndef BinaryTreeNode_
#define BinaryTreeNode_

template <class T> class BinaryTree;

template <class T>
class BinaryTreeNode {
   friend void Visit(BinaryTreeNode<T> *);
   friend void InOrder(BinaryTreeNode<T> *);
   friend void PreOrder(BinaryTreeNode<T> *);
   friend void PostOrder(BinaryTreeNode<T> *);
   friend void LevelOrder(BinaryTreeNode<T> *);
   friend void main(void);
   public:
      BinaryTreeNode() {LeftChild = RightChild = 0;}
      BinaryTreeNode(const T& e)
            {data = e;
             LeftChild = RightChild = 0;}
      BinaryTreeNode(const T& e, BinaryTreeNode *l,
                     BinaryTreeNode *r)
            {data = e;
             LeftChild = l;
             RightChild = r;}
   private:
      T data;
      BinaryTreeNode<T> *LeftChild,   // left subtree
                        *RightChild;  // right subtree
};

#endif