Data Structures and Algorithms
with Object-Oriented Design Patterns in C++ 
The BinaryTree class has three member variables--key, left, and right. All three of them are pointers. The first is a pointer to an Object instance, and the latter two are pointers to BinaryTree instances. All three pointers are zero if the node represents the empty tree. Otherwise, the tree must have a root and two subtrees. Consequently, all three pointers are non-zero in a non-empty node.
Copyright © 1997 by Bruno R. Preiss, P.Eng. All rights reserved.