Performing depth-first algorithm from a specific vertex

Question

I am trying to find a way to perform the depth-first algorithm from a specific vertex by using the boost graph library.

The depth-first algorithm provided by Boost library evaluates the graph beginning from the start vertex to the last vertex. But what if the graph has to be searched from a specific vertex?

Any suggestions?

score 3 · Answer 1 · answered Jul 18 '17 at 17:33

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BGL Provides two mechanisms for setting the starting vertex of depth_first_search. You can either use the overload operator which requires supplying a ColorMap, or you can directly set the property of your visitor:

boost::depth_first_search(myGraph, boost::visitor(myVisitor).root_vertex(myVertex));

answered Jul 18 '17 at 17:33

Carter12s

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This should be the answer in my opinion, as there is no documentation that I can find that describes on how to supply a colormap. – Sailanarmo May 11 '18 at 15:18

score 3 · Accepted Answer · answered Jan 07 '11 at 15:10

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Have a look at BGL's documentation.

There is an overload where you can provide the start vertex.

template <class Graph, class DFSVisitor, class ColorMap>
void depth_first_search(const Graph& g, DFSVisitor vis, ColorMap color, 
                        typename graph_traits<Graph>::vertex_descriptor start)

answered Jan 07 '11 at 15:10

Benoît

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Indeed the overload is present, but it is undocumented how to supply a colormap. – richelbilderbeek Mar 21 '17 at 12:16

Peter Newman · Answer 3 · 2020-04-07T21:07:01.220

boost::depth_first_search(myGraph, boost::visitor(myVisitor).root_vertex(myVertex));

This is simply an example of using the named parameter version of the call to depth_first_search(). See Named Parameters. I found that even if you do specify a vertex other than the root of the graph to start from, the algorithm will still visit all of the vertices in the graph. It will just start from the one you specify.

To visit only those vertices reachable from a specified vertex you need to use the depth_first_visit algorithm. This requires a color map to be specified. Here's a color map that worked for me.

    using Graph = boost::adjacency_list;
    using IndexMap = boost::property_map::const_type;
    IndexMap indexMap = boost::get(boost::vertex_index, m_graph);

    using ColorMap = boost::iterator_property_map;
    std::vector color_vec(num_vertices(m_graph));
    ColorMap colorMap(&color_vec.front(), indexMap);

Performing depth-first algorithm from a specific vertex

3 Answers3