## traversal

(data) 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 EA 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.

Last updated: 2001-10-01

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