83 lines
2.5 KiB
C++
83 lines
2.5 KiB
C++
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// Copyright (C) 2006 The Trustees of Indiana University.
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// Use, modification and distribution is subject to the Boost Software
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// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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// Authors: Douglas Gregor
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// Andrew Lumsdaine
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#ifndef BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
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#define BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
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#include <boost/graph/graph_traits.hpp>
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#include <boost/graph/two_bit_color_map.hpp>
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#include <boost/graph/iteration_macros.hpp>
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#include <boost/pending/queue.hpp>
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namespace boost { namespace graph {
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template<typename Graph, typename ColorMap>
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bool
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st_connected(const Graph& g,
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typename graph_traits<Graph>::vertex_descriptor s,
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typename graph_traits<Graph>::vertex_descriptor t,
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ColorMap color)
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{
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typedef typename property_traits<ColorMap>::value_type Color;
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typedef color_traits<Color> ColorTraits;
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typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
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// Set all vertices to white (unvisited)
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BGL_FORALL_VERTICES_T(v, g, Graph)
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put(color, v, ColorTraits::white());
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// Vertices found from the source are grey
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put(color, s, ColorTraits::gray());
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// Vertices found from the target are greeen
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put(color, t, ColorTraits::green());
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queue<Vertex> Q;
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Q.push(s);
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Q.push(t);
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while (!Q.empty()) {
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Vertex u = Q.top(); Q.pop();
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Color u_color = get(color, u);
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BGL_FORALL_OUTEDGES_T(u, e, g, Graph) {
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Vertex v = target(e, g);
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Color v_color = get(color, v);
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if (v_color == ColorTraits::white()) {
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// We have not seen "v" before; mark it with the same color as u
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Color u_color = get(color, u);
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put(color, v, u_color);
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// Push it on the queue
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Q.push(v);
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} else if (v_color != ColorTraits::black() && u_color != v_color) {
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// Colors have collided. We're done!
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return true;
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}
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}
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// u is done, so mark it black
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put(color, u, ColorTraits::black());
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}
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return false;
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}
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template<typename Graph>
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inline bool
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st_connected(const Graph& g,
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typename graph_traits<Graph>::vertex_descriptor s,
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typename graph_traits<Graph>::vertex_descriptor t)
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{
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return st_connected(g, s, t,
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make_two_bit_color_map(num_vertices(g),
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get(vertex_index, g)));
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}
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} } // end namespace boost::graph
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#endif // BOOST_GRAPH_DISTRIBUTED_ST_CONNECTED_HPP
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