ØUse an explicit List class as well as a Node class or structure
Ø pval() then is a List, rather than a pointer
to Node
Øprint_preorder() or other routines that traverse the tree would need
some way to efficiently step through the nodes in the list.
–I.e., don’t actually destroy the list
using Pop()
–You could let the List() give you it’s
first node, or you could define a list iterator type as described in the textbook.