Editing Tree traversal (section)

====Arbitrary trees====
To traverse arbitrary trees (not necessarily binary trees) with depth-first search, perform the following operations at each node:
# If the current node is empty then return.
# Visit the current node for pre-order traversal.
# For each ''i'' from 1 to the current node's number of subtrees − 1, or from the latter to the former for reverse traversal, do:
## Recursively traverse the current node's ''i''-th subtree.
## Visit the current node for in-order traversal.
# Recursively traverse the current node's last subtree.
# Visit the current node for post-order traversal.

Depending on the problem at hand, pre-order, post-order, and especially one of the number of subtrees − 1 in-order operations may be optional. Also, in practice more than one of pre-order, post-order, and in-order operations may be required. For example, when inserting into a ternary tree, a pre-order operation is performed by comparing items. A post-order operation may be needed afterwards to re-balance the tree.