Hi all, I need to get the list of all reachable vertices from a given vertex in a graph. I'm currently using the BFS algorithm to achieve that, which seems to fit well to my need. To understand its behavior, I simplified the http://www.boost.org/doc/libs/1_38_0/libs/graph/example/bfs.cpp example source code to this : typedef boost::adjacency_list< boost::vecS, boost::vecS, boost::directedS > Graph; Graph G(1); boost::add_edge(0, 1, G); boost::add_edge(1, 2, G); boost::add_edge(2, 5, G); boost::add_edge(3, 2, G); boost::add_edge(4, 3, G); boost::add_edge(5, 3, G); typedef Graph::vertex_descriptor Vertex; std::vector<int> distances; distances.reserve(6); std::fill_n(&distances[0], 6, 0); // The source vertex Vertex s = *(boost::vertices(G).first); boost::breadth_first_search(G, s, boost::visitor(boost::make_bfs_visitor(boost::record_distances(&distances[0], boost::on_tree_edge())))); boost::print_graph(G); for (int i = 0; i < 6; i++) { std::cout << "Node " << i << " : "; if (distances[i] != 0) std::cout << "reachable, distance " << distances[i] << std::endl; else std::cout << "not reachable" << std::endl; } However, I encounter the following issue : in this example, vertices are numbered from 0 to 5. However, in my project, this is not the case, vertices could be numbered 5, 38, 42, 384... Using a vector in that case might not work as expected, a map would probably be better. I'm not quite familiar with BGL so far, maybe should I deal with a specific property map? Or using a visitor to record a vertex distance upon graph discovery? I'm a little bit lost, any help will be greatly appreciated! Thank you very much, -- Florian PONROY Thales Land & Joint France Tel. : +33(0)1 41 304 363 Fax : +33(0)1 41 303 560 Email : florian.ponroy@fr.thalesgroup.com