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- //=======================================================================
- // 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 <vector>
- #include <iostream>
- #include <fstream>
- #include <iomanip>
- #include <boost/graph/adjacency_list.hpp>
- #include <boost/graph/bellman_ford_shortest_paths.hpp>
- using namespace boost;
- template < typename Graph, typename ParentMap >
- struct edge_writer
- {
- edge_writer(const Graph & g, const ParentMap & p)
- : m_g(g), m_parent(p)
- {
- }
- template < typename Edge >
- void operator() (std::ostream & out, const Edge & e) const
- {
- out << "[label=\"" << get(edge_weight, m_g, e) << "\"";
- typename graph_traits < Graph >::vertex_descriptor
- u = source(e, m_g), v = target(e, m_g);
- if (m_parent[v] == u)
- out << ", color=\"black\"";
- else
- out << ", color=\"grey\"";
- out << "]";
- }
- const Graph & m_g;
- ParentMap m_parent;
- };
- template < typename Graph, typename Parent >
- edge_writer < Graph, Parent >
- make_edge_writer(const Graph & g, const Parent & p)
- {
- return edge_writer < Graph, Parent > (g, p);
- }
- struct EdgeProperties {
- int weight;
- };
- int
- main()
- {
- enum { u, v, x, y, z, N };
- char name[] = { 'u', 'v', 'x', 'y', 'z' };
- typedef std::pair < int, int >E;
- const int n_edges = 10;
- E edge_array[] = { E(u, y), E(u, x), E(u, v), E(v, u),
- E(x, y), E(x, v), E(y, v), E(y, z), E(z, u), E(z,x) };
- int weight[n_edges] = { -4, 8, 5, -2, 9, -3, 7, 2, 6, 7 };
- typedef adjacency_list < vecS, vecS, directedS,
- no_property, EdgeProperties> Graph;
- #if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
- // VC++ can't handle the iterator constructor
- Graph g(N);
- for (std::size_t j = 0; j < n_edges; ++j)
- add_edge(edge_array[j].first, edge_array[j].second, g);
- #else
- Graph g(edge_array, edge_array + n_edges, N);
- #endif
- graph_traits < Graph >::edge_iterator ei, ei_end;
- property_map<Graph, int EdgeProperties::*>::type
- weight_pmap = get(&EdgeProperties::weight, g);
- int i = 0;
- for (boost::tie(ei, ei_end) = edges(g); ei != ei_end; ++ei, ++i)
- weight_pmap[*ei] = weight[i];
- std::vector<int> distance(N, (std::numeric_limits < short >::max)());
- std::vector<std::size_t> parent(N);
- for (i = 0; i < N; ++i)
- parent[i] = i;
- distance[z] = 0;
- #if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
- bool r = bellman_ford_shortest_paths
- (g, int(N), weight_pmap, &parent[0], &distance[0],
- closed_plus<int>(), std::less<int>(), default_bellman_visitor());
- #else
- bool r = bellman_ford_shortest_paths
- (g, int (N), weight_map(weight_pmap).distance_map(&distance[0]).
- predecessor_map(&parent[0]));
- #endif
- if (r)
- for (i = 0; i < N; ++i)
- std::cout << name[i] << ": " << std::setw(3) << distance[i]
- << " " << name[parent[i]] << std::endl;
- else
- std::cout << "negative cycle" << std::endl;
- std::ofstream dot_file("figs/bellman-eg.dot");
- dot_file << "digraph D {\n"
- << " rankdir=LR\n"
- << " size=\"5,3\"\n"
- << " ratio=\"fill\"\n"
- << " edge[style=\"bold\"]\n" << " node[shape=\"circle\"]\n";
- {
- for (boost::tie(ei, ei_end) = edges(g); ei != ei_end; ++ei) {
- graph_traits < Graph >::edge_descriptor e = *ei;
- graph_traits < Graph >::vertex_descriptor
- u = source(e, g), v = target(e, g);
- // VC++ doesn't like the 3-argument get function, so here
- // we workaround by using 2-nested get()'s.
- dot_file << name[u] << " -> " << name[v]
- << "[label=\"" << get(get(&EdgeProperties::weight, g), e) << "\"";
- if (parent[v] == u)
- dot_file << ", color=\"black\"";
- else
- dot_file << ", color=\"grey\"";
- dot_file << "]";
- }
- }
- dot_file << "}";
- return EXIT_SUCCESS;
- }
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