source: downloads/boost_1_34_1/libs/graph/example/kruskal-telephone.cpp @ 29

//=======================================================================
// Copyright 2001 Jeremy G. Siek, Andrew Lumsdaine, Lie-Quan Lee, 
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//=======================================================================
#include <boost/config.hpp>
#include <iostream>
#include <fstream>
#include <boost/lexical_cast.hpp>
#include <boost/graph/graphviz.hpp>
#include <boost/graph/kruskal_min_spanning_tree.hpp>

int
main()
{
  using namespace boost;
  GraphvizGraph g_dot;
  read_graphviz("figs/telephone-network.dot", g_dot);

  typedef adjacency_list < vecS, vecS, undirectedS, no_property,
    property < edge_weight_t, int > > Graph;
  Graph g(num_vertices(g_dot));
  property_map < GraphvizGraph, edge_attribute_t >::type
    edge_attr_map = get(edge_attribute, g_dot);
  graph_traits < GraphvizGraph >::edge_iterator ei, ei_end;
  for (tie(ei, ei_end) = edges(g_dot); ei != ei_end; ++ei) {
    int weight = lexical_cast < int >(edge_attr_map[*ei]["label"]);
    property < edge_weight_t, int >edge_property(weight);
    add_edge(source(*ei, g_dot), target(*ei, g_dot), edge_property, g);
  }

  std::vector < graph_traits < Graph >::edge_descriptor > mst;
  typedef std::vector < graph_traits < Graph >::edge_descriptor >::size_type size_type;
  kruskal_minimum_spanning_tree(g, std::back_inserter(mst));

  property_map < Graph, edge_weight_t >::type weight = get(edge_weight, g);
  int total_weight = 0;
  for (size_type e = 0; e < mst.size(); ++e)
    total_weight += get(weight, mst[e]);
  std::cout << "total weight: " << total_weight << std::endl;

  typedef graph_traits < Graph >::vertex_descriptor Vertex;
  for (size_type i = 0; i < mst.size(); ++i) {
    Vertex u = source(mst[i], g), v = target(mst[i], g);
    edge_attr_map[edge(u, v, g_dot).first]["color"] = "black";
  }
  std::ofstream out("figs/telephone-mst-kruskal.dot");
  graph_property < GraphvizGraph, graph_edge_attribute_t >::type &
    graph_edge_attr_map = get_property(g_dot, graph_edge_attribute);
  graph_edge_attr_map["color"] = "gray";
  graph_edge_attr_map["style"] = "bold";
  write_graphviz(out, g_dot);

  return EXIT_SUCCESS;
}