Very nice presentation! In A* if you use a heuristic to select an edge (using a priority queue, i.e., your #3) it gives a best-first search. But it is is possi

Very nice presentation! In A* if you use a heuristic to select an edge (using a priority queue, i.e., your #3) it gives a best-first search. But it is is possible to just use a stack/queue an forget about the heuristic, then you get a nice generic way of tree (graph) traversal. Regarding your use of white/black/grey lists: in a tree (which is acylic), you would only need a list of nodes to visit, however, in a general graph you need to keep a list of nodes that you have already seen/visited so as not to get into a cycle when the graph is cyclic. In tracing garbage collection algorithms this is often used because the live program data generated by the mutator is cyclic, or at least potentially can be. Thanks for mentioning this, though I know my way around gc stuff, too, I would have never come up with this link here! Probably it is a good advice to anybody interested to spend some time reading into garbage collection algorithms, they contain many interesting algorithms on graphs, such as the Deutsch-Schorr-Waite algorithm for tree traversing without requiring an additional stack. The definitive book on garbage collection is 1996's Jones and Lins: http://www.amazon.com/Garbage-Collection-Algorithms-Automatic-Management/dp/0471941484 http://www.amazon.com/Garbage-Collection-Algorithms-Automati...