| //======================================================================= |
| // 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; |
| } |