Processing nodes in a
graph one at a time, usually
in some specified order. Traversal of a tree is
recursively
defined to mean visiting the
root node and traversing its
children. Visiting a node usually involves transforming it in
some way or collecting data from it.
In "pre-order traversal", a node is visited __before__ its
children. In "post-order" traversal, a node is visited
__after__ its children. The more rarely used "in-order"
traversal is generally applicable only to binary trees, and is
where you visit first a node's left child, then the node
itself, and then its right child.
For the binary tree:
T
/ I S
/ D E
A pre-order traversal visits the nodes in the order T I D E S.
A post-order traversal visits them in the order D E I S T. An
in-order traversal visits them in the order D I E T S.