boost/graph/topological_sort.hpp

   1 //
   2 //=======================================================================
   3 // Copyright 1997, 1998, 1999, 2000 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_TOPOLOGICAL_SORT_HPP
  12 #define BOOST_GRAPH_TOPOLOGICAL_SORT_HPP
  13
  14 #include <boost/config.hpp>
  15 #include <boost/property_map/property_map.hpp>
  16 #include <boost/graph/depth_first_search.hpp>
  17 #include <boost/graph/visitors.hpp>
  18 #include <boost/graph/exception.hpp>
  19
  20 namespace boost {
  21
  22
  23   // Topological sort visitor
  24   //
  25   // This visitor merely writes the linear ordering into an
  26   // OutputIterator. The OutputIterator could be something like an
  27   // ostream_iterator, or it could be a back/front_insert_iterator.
  28   // Note that if it is a back_insert_iterator, the recorded order is
  29   // the reverse topological order. On the other hand, if it is a
  30   // front_insert_iterator, the recorded order is the topological
  31   // order.
  32   //
  33   template <typename OutputIterator>
  34   struct topo_sort_visitor : public dfs_visitor<>
  35   {
  36     topo_sort_visitor(OutputIterator _iter)
  37       : m_iter(_iter) { }
  38
  39     template <typename Edge, typename Graph>
  40     void back_edge(const Edge&, Graph&) { throw not_a_dag(); }
  41
  42     template <typename Vertex, typename Graph>
  43     void finish_vertex(const Vertex& u, Graph&) { *m_iter++ = u; }
  44
  45     OutputIterator m_iter;
  46   };
  47
  48
  49   // Topological Sort
  50   //
  51   // The topological sort algorithm creates a linear ordering
  52   // of the vertices such that if edge (u,v) appears in the graph,
  53   // then u comes before v in the ordering. The graph must
  54   // be a directed acyclic graph (DAG). The implementation
  55   // consists mainly of a call to depth-first search.
  56   //
  57
  58   template <typename VertexListGraph, typename OutputIterator,
  59     typename P, typename T, typename R>
  60   void topological_sort(VertexListGraph& g, OutputIterator result,
  61                         const bgl_named_params<P, T, R>& params)
  62   {
  63     typedef topo_sort_visitor<OutputIterator> TopoVisitor;
  64     depth_first_search(g, params.visitor(TopoVisitor(result)));
  65   }
  66
  67   template <typename VertexListGraph, typename OutputIterator>
  68   void topological_sort(VertexListGraph& g, OutputIterator result)
  69   {
  70     topological_sort(g, result,
  71                      bgl_named_params<int, buffer_param_t>(0)); // bogus
  72   }
  73
  74 } // namespace boost
  75
  76 #endif /*BOOST_GRAPH_TOPOLOGICAL_SORT_H*/