Can a tree node be both a root node and a leaf node?

Question

Can a tree node be both a root node and leaf node? If so, why?

I understand that the root node is at Level 0 of the tree. I also understand that a leaf node is a tree node that has no children. So if a tree has a root node A and nothing else, would that root node A also be considered a leaf node?

Is it possible for a tree node to be both a root node and leaf node?

Answer 1

From this Wikipedia link on Tree Data Structures, section Terminologies used in Trees:

Root – The top node in a tree.

Leaf – A node with no children.

So by definition, if a Tree structure only consists of a single Node, that single Node will in fact be both a Root and a Leaf. Read the link for further detail.

Now, whether your professor considers this to be correct is a whole 'nother story.

Answer 2

If a tree node can have both a root node and leaf node, why?

You answered your own question:

I understand that the root node is at Level 0 of the tree. I also understand that a leaf node is a tree node that has no children.

Here's a diagram for better understanding:

  root
   |
tree node
   |
leaf node

So if a tree node had a root node of A and nothing else, would that be considered a leaf node also?

Refer to your definition directly above. Diagram for better understanding:

A - root node
    |
 tree node   <-- tree node & leaf node
    |
  (null)

It is possible and how is it possible for a tree node to be both a root node and leaf node?

If you consider the root node to be a tree node, then a root node with no children will be both a tree node and leaf node.

Answer 3

If a tree node can have both a root node and leaf node, why

If a node is somewhere in between the root and a leaf, it has both a root node and a leaf under it.

how is it possible for a tree node to be both a root node and leaf node?

If the tree only consists of one node, that node is both the root and a leaf.