129 lines
3.9 KiB
C++
129 lines
3.9 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 >
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struct edge_writer
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{
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edge_writer(const Graph & g, const ParentMap & p)
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: m_g(g), m_parent(p)
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{
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}
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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
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u = source(e, m_g), 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 >
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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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int weight;
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};
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int
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main()
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{
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enum { u, v, x, y, z, N };
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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),
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E(x, y), E(x, v), 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,
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no_property, EdgeProperties> 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
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weight_pmap = 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
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(g, int(N), weight_pmap, &parent[0], &distance[0],
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closed_plus<int>(), std::less<int>(), default_bellman_visitor());
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#else
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bool r = bellman_ford_shortest_paths
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(g, int (N), weight_map(weight_pmap).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" << " 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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graph_traits < Graph >::edge_descriptor e = *ei;
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graph_traits < Graph >::vertex_descriptor
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u = source(e, g), 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]
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<< "[label=\"" << 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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