graph-traverse-generators.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  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 peen rson 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 GRAPH_TRAVERSE_GENERATORS_H
#define GRAPH_TRAVERSE_GENERATORS_H
 
# include <ah-graph-concepts.H>
 
#include <cassert>
 
#include <ah-errors.H>
#include <ah-generator.H>
#include <graph-traverse.H>
 
namespace Aleph
{
 
namespace graph_traverse_generator_detail
{
enum class Traverse_State : unsigned char
{
  Unprocessed = 0,
  Processing = 1,
  Processed = 2
};
} // namespace graph_traverse_generator_detail
 
template <AlephGraph GT, class Itor,
          template <typename T> class Q = DynListStack,
          ArcFilter<GT> Show_Arc = Dft_Show_Arc<GT>>
class Graph_Traverse_Generator
{
  using State = graph_traverse_generator_detail::Traverse_State;
 
  GT &g_;
  Show_Arc sa_;
 
  static unsigned char raw(State s) noexcept { return static_cast<unsigned char>(s); }
 
  static bool seed_arc(typename GT::Arc *a, typename GT::Node *tgt) noexcept
  {
    if (tgt->state() != raw(State::Unprocessed))
      {
        a->set_state(raw(State::Processed));
        return false;
      }
    a->set_state(raw(State::Processing));
    tgt->set_state(raw(State::Processing));
    return true;
  }
 
public:
  Graph_Traverse_Generator(GT &__g, Show_Arc __sa = Show_Arc()) : g_(__g), sa_(__sa) {}
 
  Aleph::Generator<typename GT::Node *> traverse(typename GT::Node *start) &
  {
    ah_invalid_argument_if(start == nullptr)
      << "Graph_Traverse_Generator::traverse(): null start node";
    g_.reset_nodes();
    g_.reset_arcs();
 
    size_t count = 1;
    start->set_state(raw(State::Processed));
    co_yield start;
 
    Q<typename GT::Arc *> q;
    for (Itor it(start, sa_); it.has_curr(); it.next_ne())
      {
        typename GT::Arc *a = it.get_curr();
        typename GT::Node *tgt = g_.get_connected_node(a, start);
        if (seed_arc(a, tgt))
          q.put(a);
      }
 
    const size_t n = g_.vsize();
    while (not q.is_empty() and count < n)
      {
        typename GT::Arc *arc = q.get();
        assert(arc->state() == raw(State::Processing));
        arc->set_state(raw(State::Processed));
 
        typename GT::Node *s = g_.get_src_node(arc);
        typename GT::Node *t = g_.get_tgt_node(arc);
        if (s->state() == raw(State::Processed) and t->state() == raw(State::Processed))
          continue;
 
        typename GT::Node *curr = s->state() == raw(State::Processed) ? t : s;
        assert(curr->state() == raw(State::Processing));
        ++count;
        curr->set_state(raw(State::Processed));
        co_yield curr;
 
        for (Itor it(curr, sa_); it.has_curr(); it.next_ne())
          {
            typename GT::Arc *a = it.get_curr();
            if (a->state() != raw(State::Unprocessed))
              continue;
            typename GT::Node *tgt = g_.get_connected_node(a, curr);
            if (seed_arc(a, tgt))
              q.put(a);
          }
      }
  }
};
 
template <class GT, class Itor, class Show_Arc = Dft_Show_Arc<GT>>
using Graph_Traverse_DFS_Generator =
  Graph_Traverse_Generator<GT, Itor, DynListStack, Show_Arc>;
 
template <class GT, class Itor, class Show_Arc = Dft_Show_Arc<GT>>
using Graph_Traverse_BFS_Generator =
  Graph_Traverse_Generator<GT, Itor, DynListQueue, Show_Arc>;
 
} // end namespace Aleph
 
#endif // GRAPH_TRAVERSE_GENERATORS_H