Re: [Boost-users] How to find ancestor nodes in a graph, thanks

From: Douglas Gregor (doug.gregor_at_[hidden])
Date: 2006-07-05 08:56:22

On Jul 4, 2006, at 7:49 PM, sean yang wrote:
> My question is: (1) is there an easy (some API, sorry I am not  
> familar with the library) way to reverse edge direction?

Yes, the "reverse_graph" adaptor reverses the edge direction.

> (2) is there an easy way to add a 'printf()' during BFS?

You can write your own BFS visitor, which has an "examine_vertex"  
method that printf()'s the current vertex as it is processed.

The whole thing will look something like this:

   struct print_visitor : boost::bfs_visitor<> {
     template<typename Graph, typename Vertex>
    void examine_vertex(Vertex u, const Graph& g) {
      printf(...);
    }
   };

   breadth_first_search(boost::make_reverse_graph(travel), target_2,  
boost::visitor(print_visitor()));

        Doug