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- // Copyright (C) 2006 The Trustees of Indiana University.
- // Use, modification and distribution is subject to 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)
- // Authors: Douglas Gregor
- // Andrew Lumsdaine
- #ifndef BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
- #define BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
- #include <boost/graph/graph_traits.hpp>
- #include <boost/graph/two_bit_color_map.hpp>
- #include <boost/graph/iteration_macros.hpp>
- #include <boost/pending/queue.hpp>
- namespace boost { namespace graph {
- template<typename Graph, typename ColorMap>
- bool
- st_connected(const Graph& g,
- typename graph_traits<Graph>::vertex_descriptor s,
- typename graph_traits<Graph>::vertex_descriptor t,
- ColorMap color)
- {
- typedef typename property_traits<ColorMap>::value_type Color;
- typedef color_traits<Color> ColorTraits;
- typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
- // Set all vertices to white (unvisited)
- BGL_FORALL_VERTICES_T(v, g, Graph)
- put(color, v, ColorTraits::white());
- // Vertices found from the source are grey
- put(color, s, ColorTraits::gray());
- // Vertices found from the target are greeen
- put(color, t, ColorTraits::green());
- queue<Vertex> Q;
- Q.push(s);
- Q.push(t);
- while (!Q.empty()) {
- Vertex u = Q.top(); Q.pop();
- Color u_color = get(color, u);
- BGL_FORALL_OUTEDGES_T(u, e, g, Graph) {
- Vertex v = target(e, g);
- Color v_color = get(color, v);
- if (v_color == ColorTraits::white()) {
- // We have not seen "v" before; mark it with the same color as u
- Color u_color = get(color, u);
- put(color, v, u_color);
-
- // Push it on the queue
- Q.push(v);
- } else if (v_color != ColorTraits::black() && u_color != v_color) {
- // Colors have collided. We're done!
- return true;
- }
- }
- // u is done, so mark it black
- put(color, u, ColorTraits::black());
- }
- return false;
- }
- template<typename Graph>
- inline bool
- st_connected(const Graph& g,
- typename graph_traits<Graph>::vertex_descriptor s,
- typename graph_traits<Graph>::vertex_descriptor t)
- {
- return st_connected(g, s, t,
- make_two_bit_color_map(num_vertices(g),
- get(vertex_index, g)));
- }
- } } // end namespace boost::graph
- #endif // BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
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