Data Structures
Doubly Linked list...
     private:   (each node has a node * prev)
       node * head;
       node * tail;  //???helpful?
Again, there is nothing in an ordered list
that will benefit from each node having a
pointer to the previous node.
UNLESS, there were operations to
backup or go forward from the “current”
position. In this case a doubly linked list
would be ideal