Question

Since black red tree is a binary search tree I have decided to use inheritance for implementation. Here is how in short node inheritance looks in my code:

struct BST_node
{
   // public interface here

   int key;
   BST_node* left;
   BST_node* right;
   BST_node* parent;
};

struct BRT_node : BST_node
{
   // public interface here

   NodeColour colour;
};

Problem I have encountered with this is pointers in derived class are type of the base class. Therefore I cannot use them in context of derived class without explicit casting. Maybe hiding members and using virtual accesor methods could do the trick, but that would destroy this simple syntax:

node->left = node->parent;

Is there a better way of doing this?

Answer 1

What’s wrong with putting all the data members in BRT_node?

struct BRT_node
{
    int key;
    BRT_node* next;
    BRT_node* prev;
    BRT_node* parent;
    NodeColour colour;
};

This way, you get to keep the “nice syntax” of node->left = node->parent;.

The problem with using inheritance here is because the red-black tree algorithms require BRT_nodes, not BST_nodes. So inheritance in this case isn’t appropriate.