Re: [Boost-users] boost/graph - induced subgraph

Hi Matthew, If you post a small but complete C++ program I'll take a closer look. Cheers, Jeremy On Mar 23, 2004, at 7:15 AM, Matthew Galati wrote:

Is it possible to find the minimum spanning tree of an induced subgraph?

vector< graph_traits<Graph>::vertex_descriptor > vd; typedef subgraph< Graph > SubGraph; SubGraph & inducedG = subG.create_subgraph(vd.begin(), vd.end());

Here is the example I am looking at:

induced verts: 1 2 3 4 5 7

Original Graph: 0 <--> 1 2 5 7 1 <--> 0 3 5 7 2 <--> 0 3 4 5 3 <--> 2 1 4 5 4 <--> 2 3 5 6 5 <--> 0 1 2 3 4 6 7 6 <--> 4 5 7 7 <--> 0 1 5 6

Induced Graph: 1 <--> 3 5 7 2 <--> 3 4 5 3 <--> 2 1 4 5 4 <--> 2 3 5 5 <--> 1 2 3 4 7 7 <--> 1 5

So, the "create_subgraph" seems to be working fine. But, when I run kruskals with:

vector::edge_descriptor> spanning_tree; kruskal_minimum_spanning_tree(inducedG, back_inserter(spanning_tree));

for (vei = spanning_tree.begin(); vei != spanning_tree.end(); ++vei) { pair ij = incident(*vei, inducedG); int edge_index = e_index[*vei]; cout << "e_index: " << edge_index << " : " << ij.first << " " << ij.second << endl;

I get a spanning tree of just 4 edges (while the subgraph has 6 vertices). Also, how does the edge_index of the subgraph correspond to the original graph? For example, edge (4,1) is not in the original graph, but it shows up in my spanning tree.

Spanning Tree: e_index: 3 : 2 0 e_index: 7 : 4 0 e_index: 4 : 3 1 e_index: 8 : 4 1

Thanks, Matthew

-- Matthew Galati ISE Lehigh University IBM Service Parts Solutions 610.758.4042 (Office) 610.882.0779 (Home) magh@lehigh.edu, magal11@us.ibm.com http://sagan.ie.lehigh.edu/mgalati/

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