135 lines
4.3 KiB
C++
135 lines
4.3 KiB
C++
//=======================================================================
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// Copyright 2001 Jeremy G. Siek, Andrew Lumsdaine, Lie-Quan Lee,
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//=======================================================================
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#include <boost/config.hpp>
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#include <vector>
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#include <iostream>
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#include <fstream>
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#include <iomanip>
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#include <boost/graph/adjacency_list.hpp>
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#include <boost/graph/bellman_ford_shortest_paths.hpp>
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using namespace boost;
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template < typename Graph, typename ParentMap > struct edge_writer
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{
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edge_writer(const Graph& g, const ParentMap& p) : m_g(g), m_parent(p) {}
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template < typename Edge >
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void operator()(std::ostream& out, const Edge& e) const
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{
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out << "[label=\"" << get(edge_weight, m_g, e) << "\"";
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typename graph_traits< Graph >::vertex_descriptor u = source(e, m_g),
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v = target(e, m_g);
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if (m_parent[v] == u)
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out << ", color=\"black\"";
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else
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out << ", color=\"grey\"";
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out << "]";
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}
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const Graph& m_g;
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ParentMap m_parent;
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};
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template < typename Graph, typename Parent >
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edge_writer< Graph, Parent > make_edge_writer(const Graph& g, const Parent& p)
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{
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return edge_writer< Graph, Parent >(g, p);
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}
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struct EdgeProperties
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{
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int weight;
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};
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int main()
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{
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enum
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{
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u,
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v,
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x,
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y,
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z,
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N
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};
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char name[] = { 'u', 'v', 'x', 'y', 'z' };
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typedef std::pair< int, int > E;
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const int n_edges = 10;
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E edge_array[] = { E(u, y), E(u, x), E(u, v), E(v, u), E(x, y), E(x, v),
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E(y, v), E(y, z), E(z, u), E(z, x) };
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int weight[n_edges] = { -4, 8, 5, -2, 9, -3, 7, 2, 6, 7 };
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typedef adjacency_list< vecS, vecS, directedS, no_property, EdgeProperties >
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Graph;
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#if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
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// VC++ can't handle the iterator constructor
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Graph g(N);
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for (std::size_t j = 0; j < n_edges; ++j)
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add_edge(edge_array[j].first, edge_array[j].second, g);
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#else
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Graph g(edge_array, edge_array + n_edges, N);
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#endif
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graph_traits< Graph >::edge_iterator ei, ei_end;
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property_map< Graph, int EdgeProperties::* >::type weight_pmap
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= get(&EdgeProperties::weight, g);
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int i = 0;
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for (boost::tie(ei, ei_end) = edges(g); ei != ei_end; ++ei, ++i)
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weight_pmap[*ei] = weight[i];
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std::vector< int > distance(N, (std::numeric_limits< short >::max)());
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std::vector< std::size_t > parent(N);
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for (i = 0; i < N; ++i)
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parent[i] = i;
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distance[z] = 0;
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#if defined(BOOST_MSVC) && BOOST_MSVC <= 1300
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bool r = bellman_ford_shortest_paths(g, int(N), weight_pmap, &parent[0],
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&distance[0], closed_plus< int >(), std::less< int >(),
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default_bellman_visitor());
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#else
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bool r = bellman_ford_shortest_paths(g, int(N),
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weight_map(weight_pmap)
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.distance_map(&distance[0])
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.predecessor_map(&parent[0]));
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#endif
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if (r)
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for (i = 0; i < N; ++i)
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std::cout << name[i] << ": " << std::setw(3) << distance[i] << " "
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<< name[parent[i]] << std::endl;
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else
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std::cout << "negative cycle" << std::endl;
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std::ofstream dot_file("figs/bellman-eg.dot");
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dot_file << "digraph D {\n"
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<< " rankdir=LR\n"
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<< " size=\"5,3\"\n"
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<< " ratio=\"fill\"\n"
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<< " edge[style=\"bold\"]\n"
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<< " node[shape=\"circle\"]\n";
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{
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for (boost::tie(ei, ei_end) = edges(g); ei != ei_end; ++ei)
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{
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graph_traits< Graph >::edge_descriptor e = *ei;
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graph_traits< Graph >::vertex_descriptor u = source(e, g),
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v = target(e, g);
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// VC++ doesn't like the 3-argument get function, so here
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// we workaround by using 2-nested get()'s.
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dot_file << name[u] << " -> " << name[v] << "[label=\""
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<< get(get(&EdgeProperties::weight, g), e) << "\"";
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if (parent[v] == u)
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dot_file << ", color=\"black\"";
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else
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dot_file << ", color=\"grey\"";
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dot_file << "]";
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}
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}
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dot_file << "}";
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return EXIT_SUCCESS;
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}
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