1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
|
//=======================================================================
// Copyright 2001 Jeremy G. Siek, Andrew Lumsdaine, Lie-Quan Lee,
//
// This file is part of the Boost Graph Library
//
// You should have received a copy of the License Agreement for the
// Boost Graph Library along with the software; see the file LICENSE.
// If not, contact Office of Research, Indiana University,
// Bloomington, IN 47405.
//
// Permission to modify the code and to distribute the code is
// granted, provided the text of this NOTICE is retained, a notice if
// the code was modified is included with the above COPYRIGHT NOTICE
// and with the COPYRIGHT NOTICE in the LICENSE file, and that the
// LICENSE file is distributed with the modified code.
//
// LICENSOR MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED.
// By way of example, but not limitation, Licensor MAKES NO
// REPRESENTATIONS OR WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY
// PARTICULAR PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE COMPONENTS
// OR DOCUMENTATION WILL NOT INFRINGE ANY PATENTS, COPYRIGHTS, TRADEMARKS
// OR OTHER RIGHTS.
//=======================================================================
#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);
}
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, property < edge_weight_t, int > > Graph;
#ifdef BOOST_MSVC
// 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, edge_weight_t>::type weight_pmap = get(edge_weight, g);
int i = 0;
for (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;
#ifdef BOOST_MSVC
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 (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(edge_weight, g), e) << "\"";
if (parent[v] == u)
dot_file << ", color=\"black\"";
else
dot_file << ", color=\"grey\"";
dot_file << "]";
}
}
dot_file << "}";
return EXIT_SUCCESS;
}
|
