hamiltonian.H

/* Aleph-w

     / \  | | ___ _ __ | |__      __      __
    / _ \ | |/ _ \ '_ \| '_ \ ____\ \ /\ / / Data structures & Algorithms
   / ___ \| |  __/ |_) | | | |_____\ V  V /  version 1.9b
  /_/   \_\_|\___| .__/|_| |_|      \_/\_/   https://github.com/lrleon/Aleph-w
                 |_|         

  This file is part of Aleph-w library

  Copyright (c) 2002-2018 Leandro Rabindranath Leon & Alejandro Mujica

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
# ifndef HAMILTONIAN_H
# define HAMILTONIAN_H

# include <tpl_graph.H>

namespace Aleph 
{

template <class GT, 
          class SN = Dft_Show_Node<GT>,
          class SA = Dft_Show_Arc<GT> >
class Test_Hamiltonian_Sufficiency
{
  SN & sn;
  SA & sa;

  bool test_graph(GT & g)
  {
    assert(not g.is_digraph());

    const size_t & n = g.get_num_nodes();

    for (Node_Iterator<GT, SN> i(g, sn); i.has_curr(); i.next_ne())
      {
        typename GT::Node * src = i.get_curr_ne();
        const size_t & nsrc = g.get_num_arcs(src);

        i.next_ne();

        for (Node_Iterator<GT, SN> j(i); j.has_curr(); j.next_ne())
          if (nsrc + g.get_num_arcs(j.get_curr_ne()) < n)
            return false;
      }

    return true;
  }

  bool test_digraph(GT & g)
  {
    assert(g.is_digraph());

    g.reset_counter_nodes();

      // una primera pasada sobre arcos para contar grados de entrada
    for (Arc_Iterator<GT, SA> it(g, sa); it.has_curr(); it.next_ne())
      NODE_COUNTER(it.get_tgt_node_ne())++;

    const size_t & n = g.get_num_nodes();

    for (Node_Iterator<GT, SN> i(g, sn); i.has_curr(); i.next_ne())
      {
        typename GT::Node * src = i.get_curr_ne();

        for (Node_Iterator<GT, SN> j(g, sn); j.has_curr(); j.next_ne())
          {
            typename GT::Node * tgt = j.get_curr_ne();

            if (src == tgt)
              continue;

            if (g.get_num_arcs(src) + NODE_COUNTER(tgt) >= n)
              continue;

                // buscar si hay arco src-->tgt
            bool terminate = true;
            for (Node_Arc_Iterator<GT, SA> it(src, sa); it.has_curr(); 
                 it.next_ne())
              if (src == it.get_tgt_node_ne())
                {
                  terminate = false;
                  break;
                }
            
            if (terminate)
              return false;
          }
      } 

    return true;
  }

public:

  Test_Hamiltonian_Sufficiency(SN && __sn = SN(), SA && __sa = SA()) 
    : sn(__sn), sa(__sa)
  {
    // empty 
  }

      // retorna true si el grafo o digrafo satisface la prueba de
      // suficiencia para ser hamiltoniano.
  bool operator () (GT & g)
  {
    if (g.is_digraph())
      return test_digraph(g);
    else
      return test_graph(g);
  }
};



} // end namespace Aleph

# endif // HAMILTONIAN_H