1//
2//=======================================================================
3// Copyright 1997-2001 University of Notre Dame.
4// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
5//
6// Distributed under the Boost Software License, Version 1.0. (See
7// accompanying file LICENSE_1_0.txt or copy at
8// http://www.boost.org/LICENSE_1_0.txt)
9//=======================================================================
10//
11#ifndef BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
12#define BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
13
14#include <boost/config.hpp>
15#include <boost/graph/depth_first_search.hpp>
16#include <boost/graph/properties.hpp>
17#include <boost/graph/graph_concepts.hpp>
18#include <boost/graph/overloading.hpp>
19#include <boost/static_assert.hpp>
20#include <boost/concept/assert.hpp>
21
22namespace boost {
23
24 namespace detail {
25
26 // This visitor is used both in the connected_components algorithm
27 // and in the kosaraju strong components algorithm during the
28 // second DFS traversal.
29 template <class ComponentsMap>
30 class components_recorder : public dfs_visitor<>
31 {
32 typedef typename property_traits<ComponentsMap>::value_type comp_type;
33 public:
34 components_recorder(ComponentsMap c,
35 comp_type& c_count)
36 : m_component(c), m_count(c_count) {}
37
38 template <class Vertex, class Graph>
39 void start_vertex(Vertex, Graph&) {
40 if (m_count == (std::numeric_limits<comp_type>::max)())
41 m_count = 0; // start counting components at zero
42 else
43 ++m_count;
44 }
45 template <class Vertex, class Graph>
46 void discover_vertex(Vertex u, Graph&) {
47 put(m_component, u, m_count);
48 }
49 protected:
50 ComponentsMap m_component;
51 comp_type& m_count;
52 };
53
54 } // namespace detail
55
56 // This function computes the connected components of an undirected
57 // graph using a single application of depth first search.
58
59 template <class Graph, class ComponentMap, class P, class T, class R>
60 inline typename property_traits<ComponentMap>::value_type
61 connected_components(const Graph& g, ComponentMap c,
62 const bgl_named_params<P, T, R>& params
63 BOOST_GRAPH_ENABLE_IF_MODELS_PARM(Graph, vertex_list_graph_tag))
64 {
65 if (num_vertices(g) == 0) return 0;
66
67 typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
68 BOOST_CONCEPT_ASSERT(( WritablePropertyMapConcept<ComponentMap, Vertex> ));
69 typedef typename boost::graph_traits<Graph>::directed_category directed;
70 BOOST_STATIC_ASSERT((boost::is_same<directed, undirected_tag>::value));
71
72 typedef typename property_traits<ComponentMap>::value_type comp_type;
73 // c_count initialized to "nil" (with nil represented by (max)())
74 comp_type c_count((std::numeric_limits<comp_type>::max)());
75 detail::components_recorder<ComponentMap> vis(c, c_count);
76 depth_first_search(g, params.visitor(vis));
77 return c_count + 1;
78 }
79
80 template <class Graph, class ComponentMap>
81 inline typename property_traits<ComponentMap>::value_type
82 connected_components(const Graph& g, ComponentMap c
83 BOOST_GRAPH_ENABLE_IF_MODELS_PARM(Graph, vertex_list_graph_tag))
84 {
85 if (num_vertices(g) == 0) return 0;
86
87 typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
88 BOOST_CONCEPT_ASSERT(( WritablePropertyMapConcept<ComponentMap, Vertex> ));
89 // typedef typename boost::graph_traits<Graph>::directed_category directed;
90 // BOOST_STATIC_ASSERT((boost::is_same<directed, undirected_tag>::value));
91
92 typedef typename property_traits<ComponentMap>::value_type comp_type;
93 // c_count initialized to "nil" (with nil represented by (max)())
94 comp_type c_count((std::numeric_limits<comp_type>::max)());
95 detail::components_recorder<ComponentMap> vis(c, c_count);
96 depth_first_search(g, visitor(vis));
97 return c_count + 1;
98 }
99
100
101} // namespace boost
102
103#ifdef BOOST_GRAPH_USE_MPI
104# include <boost/graph/distributed/connected_components.hpp>
105#endif
106
107#endif // BOOST_GRAPH_CONNECTED_COMPONENTS_HPP
108

source code of boost/boost/graph/connected_components.hpp