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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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