graph-traverse.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
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
# ifndef GRAPH_TRAVERSE_H
# define GRAPH_TRAVERSE_H
 
# include <ah-graph-concepts.H>
 
# include <tuple>
# include <cassert>
# include <tpl_agraph.H>
# include <tpl_dynListStack.H>
# include <tpl_dynListQueue.H>
 
namespace // local constants to avoid collisions with aleph-graph.H
{
  constexpr unsigned char GT_Unprocessed = 0;
  constexpr unsigned char GT_Processing  = 1;
  constexpr unsigned char GT_Processed   = 2;
}
 
template <AlephGraph GT, class Itor,
          template <typename T> class Q = DynListStack,
          ArcFilter<GT> Show_Arc = Dft_Show_Arc<GT>>
class Graph_Traverse
{
  GT & g;
  Show_Arc sa;
 
  static bool seed_arc(typename GT::Arc *a, typename GT::Node *tgt) noexcept
  {
    if (tgt->state() != GT_Unprocessed)
      {
        a->set_state(GT_Processed);
        return false;
      }
    a->set_state(GT_Processing);
    tgt->set_state(GT_Processing);
    return true;
  }
 
public:
  Graph_Traverse(GT & __g, Show_Arc __sa = Show_Arc()) : g(__g), sa(__sa) {}
 
  template <class Node_Op>
  size_t operator ()(typename GT::Node *start, Node_Op & op)
  {
    assert(start != nullptr);
    g.reset_nodes();
    g.reset_arcs();
 
    size_t count = 1;
    start->set_state(GT_Processed);
    if (not op(start))
      return count;
 
    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() == GT_Processing);
        arc->set_state(GT_Processed);
 
        typename GT::Node *s = g.get_src_node(arc);
        typename GT::Node *t = g.get_tgt_node(arc);
        if (s->state() == GT_Processed and t->state() == GT_Processed)
          continue;
 
        typename GT::Node *curr = s->state() == GT_Processed ? t : s;
        assert(curr->state() == GT_Processing);
        ++count;
        curr->set_state(GT_Processed);
        if (not op(curr))
          return count;
 
        for (Itor it(curr, sa); it.has_curr(); it.next_ne())
          {
            typename GT::Arc *a = it.get_curr();
            if (a->state() != GT_Unprocessed)
              continue;
            typename GT::Node *tgt = g.get_connected_node(a, curr);
            if (seed_arc(a, tgt))
              q.put(a);
          }
      }
 
    return count;
  }
 
  template <class Node_Op>
  size_t operator ()(typename GT::Node *start, Node_Op && op = Node_Op())
  {
    return (*this)(start, op);
  }
 
  template <class Op>
  size_t exec(typename GT::Node *start, Op & op)
  {
    assert(start != nullptr);
    g.reset_nodes();
    g.reset_arcs();
 
    size_t count = 1;
    start->set_state(GT_Processed);
    if (not op(start, nullptr))
      return count;
 
    using Pair = std::tuple<typename GT::Node *, typename GT::Arc *>;
    Q<Pair> 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(std::make_tuple(start, a));
      }
 
    const size_t n = g.vsize();
    while (not q.is_empty() and count < n)
      {
        const Pair p = q.get();
        typename GT::Arc *arc = get<1>(p);
        assert(arc->state() == GT_Processing);
        assert(get<0>(p)->state() == GT_Processed);
        arc->set_state(GT_Processed);
 
        typename GT::Node *curr = g.get_connected_node(arc, get<0>(p));
        assert(curr->state() == GT_Processing);
        ++count;
        curr->set_state(GT_Processed);
        if (not op(curr, arc))
          return count;
 
        for (Itor it(curr, sa); it.has_curr(); it.next_ne())
          {
            typename GT::Arc *a = it.get_curr();
            if (a->state() != GT_Unprocessed)
              continue;
            typename GT::Node *tgt = g.get_connected_node(a, curr);
            if (seed_arc(a, tgt))
              q.put(std::make_tuple(curr, a));
          }
      }
 
    return count;
  }
 
  template <class Operation>
  size_t exec(typename GT::Node *start, Operation && op = Operation())
  {
    return exec(start, op);
  }
 
  template <class Node_Op, class Arc_Op>
  std::tuple<size_t, size_t> operator ()(typename GT::Node *start,
                                    Node_Op & node_op, Arc_Op & arc_op)
  {
    assert(start != nullptr);
    g.reset_nodes();
    g.reset_arcs();
    Q<typename GT::Arc *> q;
 
    size_t node_count = 1;
    size_t arc_count = 0;
 
    start->set_state(GT_Processed);
    if (not node_op(start))
      return std::make_tuple(1, 0);
 
    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);
        // Deliberately NOT the shared seed_arc() helper: this overload
        // reports "back edges" too (arcs into an already-Processing node
        // discovered via another arc), which is why it tests
        // `!= GT_Processed` instead of `== GT_Unprocessed` — a `Processing`
        // tgt still enqueues `a` and calls arc_op(a) here, unlike the
        // Unprocessed-only seed_arc() used by the other two overloads. See
        // DualOpVisitsNodesAndArcs. This still guards the self-loop case
        // (tgt == start is already Processed by this point).
        if (tgt->state() != GT_Processed)
          {
            a->set_state(GT_Processing);
            tgt->set_state(GT_Processing);
            q.put(a);
            ++arc_count;
            if (not arc_op(a))
              return std::make_tuple(node_count, arc_count);
          }
        else
          a->set_state(GT_Processed);
      }
 
    while (not q.is_empty())
      {
        typename GT::Arc *arc = q.get();
        assert(arc->state() == GT_Processing);
        arc->set_state(GT_Processed);
 
        typename GT::Node *s = g.get_src_node(arc);
        typename GT::Node *t = g.get_tgt_node(arc);
        if (s->state() == GT_Processed and t->state() == GT_Processed)
          continue;
 
        typename GT::Node *curr = s->state() == GT_Processed ? t : s;
        assert(curr->state() == GT_Processing);
        ++node_count;
        curr->set_state(GT_Processed);
        if (not node_op(curr))
          return std::make_tuple(node_count, arc_count);
 
        for (Itor it(curr, sa); it.has_curr(); it.next_ne())
          {
            typename GT::Arc *a = it.get_curr();
            if (a->state() != GT_Unprocessed)
              continue;
            typename GT::Node *tgt = g.get_connected_node(a, curr);
            if (tgt->state() != GT_Processed)
              {
                q.put(a);
                tgt->set_state(GT_Processing);
                a->set_state(GT_Processing);
                ++arc_count;
                if (not arc_op(a))
                  return std::make_tuple(node_count, arc_count);
              }
            else
              a->set_state(GT_Processed);
          }
      }
 
    return std::make_tuple(node_count, arc_count);
  }
 
  template <class Node_Op, class Arc_Op>
  std::tuple<size_t, size_t> operator ()(typename GT::Node *start,
                                    Node_Op && node_op = Node_Op(),
                                    Arc_Op && arc_op = Arc_Op())
  {
    return (*this)(start, node_op, arc_op);
  }
};
 
 
template <class GT, class Itor,
          class Show_Arc = Dft_Show_Arc<GT>>
using Graph_Traverse_DFS = Graph_Traverse<GT, Itor, DynListStack, Show_Arc>;
 
template <class GT, class Itor,
          class Show_Arc = Dft_Show_Arc<GT>>
using Graph_Traverse_BFS = Graph_Traverse<GT, Itor, DynListQueue, Show_Arc>;
 
 
# endif // GRAPH_TRAVERSE_H