tpl_test_path.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
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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  SOFTWARE.
*/
 
 
# ifndef TEST_PATH_H
# define TEST_PATH_H
 
# include <ah-graph-concepts.H>
 
# include <tpl_graph.H>
 
namespace Aleph {
 
 
      template <AlephGraph GT, ArcFilter<GT> SA = Dft_Show_Arc<GT> > 
class Test_For_Path
{
  SA sa;
  typename GT::Node * tgt = nullptr;
 
  bool test_path(typename GT::Node * curr)  
  {
    if (curr == tgt) 
      return true; // tgt was reached
 
    if (IS_NODE_VISITED(curr, Find_Path)) // was curr_node visited?
      return false; // yes, do not explore
 
    NODE_BITS(curr).set_bit(Find_Path, true); // paint curr_node
 
    // recursively search through curr's arcs 
    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, Find_Path)) 
          continue; 
 
        ARC_BITS(arc).set_bit(Find_Path, true); // paint arc
        if (test_path(i.get_tgt_node())) 
          return true;
      }
 
    // all of curr_node's adjacent arcs were explored without
    // finding end_node ==> there is no path through curr_node
    return false;
  }
 
  bool test_path(const GT & g, typename GT::Node * src, typename GT::Node * dest)
  {      // if the graph is connected ==> a path exists
    if (not g.is_digraph() and g.get_num_arcs() >= g.get_num_nodes()) 
      return true;
 
    g.reset_bit_nodes(Find_Path); 
    g.reset_bit_arcs(Find_Path);
 
    tgt = dest;
 
        // recursively search through src's adjacent arcs
    for (Node_Arc_Iterator<GT, SA> i(src, sa); i.has_curr(); i.next_ne())
      {
        typename GT::Arc * arc = i.get_current_arc_ne();
        ARC_BITS(arc).set_bit(Find_Path, true); // mark arc
        if (test_path(i.get_tgt_node())) 
          return true; 
      }
 
    // all of start_node's arcs have been explored without
    // finding a path to end_node ==> no path exists
    return false;
  }
 
public:
 
  Test_For_Path(SA __sa = SA()) : sa(__sa) { /* empty */ }
 
  bool operator () (const GT& g, typename GT::Node * start_node, 
        typename GT::Node * end_node) 
  {
    return test_path(g, start_node, end_node);
  }
};
 
 
 
} // end namespace Aleph
 
# endif // TEST_PAT_H