Preorder

Preorder just visits the root first:

• the root, then
• left subtree, then
• right subtree

Postorder

Postorder just visits the root last:

• left subtree, then
• right subtree, then
• the root

(Draw some examples)

If the preorder listing is given, can you determine the original tree?

Example

Preorder: 40 50 80 60 90

Draw the tree?