Re: [Boost-users] [BGL] graph copy after Kruskal's algorithm?

From: Douglas Gregor (doug.gregor_at_[hidden])
Date: 2006-03-09 10:56:28

On Mar 6, 2006, at 12:23 AM, Alejandro Aragón wrote:
> Doug,
>
> I tried to follow your directions but I coundn't find any concrete
> example of using the get(vertex_all,orig,v) function.  I did something
> else, but I think it is not working.  Could you give me further
> directions to code it your way?
>
> This is what I came up with:
>
> // minimum_spanning_graph
> Graph* graph::minimum_spanning_graph(std::vector<Edge>& spanning_tree)
> {
>      // create an empty graph
>      // the original graph has pointer gPtr
>      Graph* copy = new Graph();
>
>      // iterate over all vertices in the original graph
>      Vertex v_new;
>      for (tie(vi, vi_end) = vertices(*gPtr); vi != vi_end; ++vi){
> 	v_new = add_vertex(*copy);

I think you can change this line to:

   v_new = add_vertex(get(vertex_all, *gPtr, *vi), *copy);

> 	coordmap[v_new] = coordmap[*vi];
>      }
>
>      // iterate over all the edges in the list produced by algorithm
>      bool inserted;
>      Edge e_new;
>      for (std::vector < Edge >::iterator ei = spanning_tree.begin();
> 	 ei != spanning_tree.end(); ++ei) {
> 	tie(e_new,inserted) = add_edge(source(*ei,*gPtr),target 
> (*ei,*gPtr),*copy);

And then change this line to:

   tie(e_new, inserted) = add_edge(source(*ei, *gPtr), target(*ei,  
*gPtr), get(edge_all, *gPtr, *ei), *copy);

> 	weightmap[e_new] = weightmap[*ei];
> 	anglemap[e_new] = anglemap[*ei];
>      }
>
>      std::cout<<"Number of edges in original graph =
> "<<num_edges(*gPtr)<<std::endl;
>      std::cout<<"Number of edges in minimum spanning graph
> ="<<num_edges(*copy)<<std::endl;
>
>      return copy;

boost/graph/copy.hpp uses edge_all and vertex_all; you might be able  
to look there for more hints.

        Doug