Real world pre/post-order tree traversal examples

Question

I understand pre-order, in-order, and post-order tree traversal algorithms just fine. (Reference). I understand a few uses: in-order for traversing binary search trees in order

Answer 1

Topological sorting is a post-order traversal of trees (or directed acyclic graphs).

The idea is that the nodes of the graph represent tasks and an edge from A to B indicates that A has to be performed before B. A topological sort will arrange these tasks in a sequence such that all the dependencies of a task appear earlier than the task itself. Any build system like UNIX make has to implement this algorithm.

The example that Dario mentioned — destroying all nodes of a tree with manual memory management — is an instance of this problem. After all, the task of destroying a node depends on the destruction of its children.