[erlang-questions] graphs and trees

Thomas Lindgren thomasl_erlang@REDACTED
Thu Dec 20 10:23:35 CET 2007

--- mats cronqvist <mats.cronqvist@REDACTED>

>   so i've made a directad acyclic graph by calling
> various functions in
> the digraph module. i theory, the resulting graph
> should be a tree. is
> there some snazzy graph theory trick to show that
> the graph is indeed a
> tree?

Here is a straightforward algorithm, O(number of

Visit all nodes starting from the root, marking each
node when visited. If you visit an already seen node,
it's not a tree.

If some node remains unmarked after this traversal,
it's not a tree either. (It's not connected, or there
is no unique root, or ...)


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