tpl_test_acyclique.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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*/
 
 
# ifndef TPL_TEST_ACYCLIQUE_H
# define TPL_TEST_ACYCLIQUE_H
 
# include <tpl_graph_utils.H>
# include <ah-errors.H>
 
namespace Aleph
{
  template <class GT, class SA = Dft_Show_Arc<GT>>
  class Is_Graph_Acyclique
  {
    SA & sa;
 
    bool is_acyclique(typename GT::Node *curr)
    {
      if (IS_NODE_VISITED(curr, Test_Cycle))
        return false;
 
      NODE_BITS(curr).set_bit(Test_Cycle, true); // mark node
 
      for (Node_Arc_Iterator<GT, SA> i(curr, sa); i.has_curr(); i.next_ne())
        {
          typename GT::Arc *arc = i.get_current_arc_ne();
          if (IS_ARC_VISITED(arc, Test_Cycle))
            continue;
 
          ARC_BITS(arc).set_bit(Test_Cycle, true);
 
          if (not is_acyclique(i.get_tgt_node()))
            return false;
        }
 
      // all arcs traversed without finding a cycle ==>
      // the graph is acyclic through curr_node
      return true;
    }
 
    bool is_acyclique(GT & g, size_t num_arcs)
    {
      ah_domain_error_if(g.is_digraph())
        << "is_graph_acyclique() does not work for digraphs";
 
      if (num_arcs >= g.get_num_nodes())
        return false;
 
      g.reset_bit_arcs(Test_Cycle);
      g.reset_bit_nodes(Test_Cycle);
 
      for (typename GT::Node_Iterator it(g); it.has_curr(); it.next_ne())
        {
          typename GT::Node *curr = it.get_current_node_ne();
          if (IS_NODE_VISITED(curr, Test_Cycle))
            continue;
 
          if (not is_acyclique(curr))
            return false;
        }
 
      return true;
    }
 
  public:
    Is_Graph_Acyclique(SA && __sa = SA()) : sa(__sa)
    { /* empty */
    }
 
    Is_Graph_Acyclique(SA & __sa) : sa(__sa)
    { /* empty */
    }
 
    bool operator ()(GT & g, size_t num_arcs)
    {
      return is_acyclique(g, num_arcs);
    }
 
    bool operator ()(GT & g)
    {
      return is_acyclique(g, g.get_num_arcs());
    }
  };
 
  template <class GT, class SA = Dft_Show_Arc<GT>>
  class Has_Cycle
  {
    SA & sa;
 
  public:
    Has_Cycle(SA && __sa = SA()) : sa(__sa)
    { /* empty */
    }
 
    Has_Cycle(SA & __sa) : sa(__sa)
    { /* empty */
    }
 
    bool operator ()(GT & g) const
    {
      return not Is_Graph_Acyclique<GT, SA>(sa)(g);
    }
 
    bool operator ()(GT & g, size_t num_arcs) const
    {
      return not Is_Graph_Acyclique<GT, SA>(sa)(g, num_arcs);
    }
  };
} // end namespace Aleph
 
# endif //  TPL_TEST_ACYCLIQUE_H