Question

In the Lemon C++ Graph Library, given a node in an undirected graph say, how does one find other nodes that are edge connected?

Answer 1

I’ll have a go at this even though I’m rusty with C++ and haven’t used Lemon before:

for (ListDigraph::OutArcIt arcIt(graph, node); arcIt != INVALID; ++arcIt) {

    Arc arc(*arcIt); // Lemon iterators are supposed to be convertible to items
                     // without operator*, so arc(a) might work too.

    Node oppositeNode( g.oppositeNode(node, arc) );

    // Do something with the opposite node.
    ...
}

I used this:
LEMON — an Open Source C++ Graph Template Library

… and this:
LEMON: Graph Class Reference

… and I’ve done a reasonable amount of work with graph theory over the years.

I hope it helps.