Printing the names of vertices in topological order with the Boost Graph Library

Question

I am trying to use the Boost Graph Library. I want to print out a topological sort for my graph. However the output I want on my graph is the actual names of the vertex, not the number positions. For example, on the following example:

typedef boost::adjacency_list<vecS, vecS, directedS,
                              property<vertex_name_t, std::string>,
                              property<edge_weight_t, int> > Graph;

typedef boost::graph_traits<Graph>::vertex_descriptor Vertex;
typedef std::vector< Vertex > container;
Graph g;
BOOST_CHECK(read_graphviz(in, g, dp, "id"));
container c;
topological_sort(g, std::back_inserter(c));

std::cout << "A topological ordering: ";
for ( container::reverse_iterator ii=c.rbegin(); ii!=c.rend(); ++ii)
    std::cout <<*ii<<" ";                                               
std:: cout <<std::endl;

I get the following output:

A topological ordering: 45 40 41 34 35 33 43 30 31 36 32 26 27 25 23 24 19 46 47 18 48 17 20 21 49 50 16 51 15 44 14 22 42 13 37 38 9 11 28 29 12 7 39 6 8 5 10 3 4 0 2 1 

Those values are the positions of the ordered vertices, but I would rather have the name of each vertex. Does anyone know how to do this?

Answer 1

I've always felt it easier to work with custom Node/Edge classes when using BGL:

struct Node {
    int x;
    int y;
    std::string name;
};

struct Edge {
    int weight;
};

//boost:: qualifiers removed for brevity
typedef adjacency_list<vecS, vecS, directedS, Node, Edge> Graph;

...
{
    Graph g;
    Graph::vertex_descriptor v = ...;

    g[v].x = 1;
    std::cout << g[v].name << std::endl;
}

But yes, as *ii is a vertex descriptor, you should be able to use it in the way @Tom Sirgedas mentioned. (Who posted his answer while I was writing mine)

Answer 2

Hmm, this generic programming confuses me :) Try this code. It should compile, at least!

std::cout << get(vertex_name, g, *ii) << " ";