////   This file contains the C++ code from Program 10.7 of//   "Data Structures and Algorithms//    with Object-Oriented Design Patterns in C++"//   by Bruno R. Preiss.////   Copyright (c) 1998 by Bruno R. Preiss, P.Eng.  All rights reserved.////   http://www.pads.uwaterloo.ca/Bruno.Preiss/books/opus4/programs/pgm10_07.cpp//class AVLTree : public BST{protected:    int height;    int BalanceFactor () const;    void AdjustHeight ();    void LLRotation ();    void LRRotation ();    void RRRotation ();    void RLRotation ();    void AttachKey (Object&);    Object& DetachKey ();    void Balance ();public:    AVLTree ();    int Height () const;    AVLTree& Left () const;    AVLTree& Right () const;};