/Src/Dependencies/Boost/boost/graph/st_connected.hpp

 1// Copyright (C) 2006 The Trustees of Indiana University.
 2
 3// Use, modification and distribution is subject to the Boost Software
 4// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
 5// http://www.boost.org/LICENSE_1_0.txt)
 6
 7//  Authors: Douglas Gregor
 8//           Andrew Lumsdaine
 9#ifndef BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
10#define BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
11
12#include <boost/graph/graph_traits.hpp>
13#include <boost/graph/two_bit_color_map.hpp>
14#include <boost/graph/iteration_macros.hpp>
15#include <boost/pending/queue.hpp>
16
17namespace boost { namespace graph {
18
19template<typename Graph, typename ColorMap>
20bool 
21st_connected(const Graph& g, 
22             typename graph_traits<Graph>::vertex_descriptor s,
23             typename graph_traits<Graph>::vertex_descriptor t,
24             ColorMap color)
25{
26  typedef typename property_traits<ColorMap>::value_type Color;
27  typedef color_traits<Color> ColorTraits;
28  typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
29
30  // Set all vertices to white (unvisited)
31  BGL_FORALL_VERTICES_T(v, g, Graph)
32    put(color, v, ColorTraits::white());
33
34  // Vertices found from the source are grey
35  put(color, s, ColorTraits::gray());
36
37  // Vertices found from the target are greeen
38  put(color, t, ColorTraits::green());
39  queue<Vertex> Q;
40  Q.push(s);
41  Q.push(t);
42
43  while (!Q.empty()) {
44    Vertex u = Q.top(); Q.pop();
45    Color u_color = get(color, u);
46
47    BGL_FORALL_OUTEDGES_T(u, e, g, Graph) {
48      Vertex v = target(e, g);
49      Color v_color = get(color, v);
50      if (v_color == ColorTraits::white()) {
51        // We have not seen "v" before; mark it with the same color as u
52        Color u_color = get(color, u);
53        put(color, v, u_color);
54        
55        // Push it on the queue
56        Q.push(v);
57      } else if (v_color != ColorTraits::black() && u_color != v_color) {
58        // Colors have collided. We're done!
59        return true;
60      }
61    }
62    // u is done, so mark it black
63    put(color, u, ColorTraits::black());
64  }
65
66  return false;
67}
68
69template<typename Graph>
70inline bool 
71st_connected(const Graph& g, 
72             typename graph_traits<Graph>::vertex_descriptor s,
73             typename graph_traits<Graph>::vertex_descriptor t)
74{
75  return st_connected(g, s, t, 
76                      make_two_bit_color_map(num_vertices(g),
77                                             get(vertex_index, g)));
78}
79
80} } // end namespace boost::graph
81
82#endif // BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP