tpl_components.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 TPL_COMPONENTS_H
# define TPL_COMPONENTS_H
 
# include <tpl_agraph.H>
# include <ah-errors.H>
 
namespace Aleph {
 
template <class GT, class SA = Dft_Show_Arc<GT>>
class Build_Subgraph
{
  SA sa;
  const GT * gptr = nullptr;
  size_t count = 0;
 
public:
 
  Build_Subgraph(SA arc_filter = SA())
    : sa(arc_filter) { /* empty */ }
 
  private:
 
  // Recursive DFS to build mapped subgraph
  void build_subgraph(GT & sg, typename GT::Node * g_src)
  {
    if (IS_NODE_VISITED(g_src, Build_Subtree))
      return;
 
    // Mark source node as visited
    NODE_BITS(g_src).set_bit(Build_Subtree, true);
    ++count;
 
    // Get or create mapped node in subgraph
    auto sg_src = mapped_node<GT>(g_src);
    if (sg_src == nullptr)
      {
        sg_src = sg.insert_node(g_src->get_info());
        GT::map_nodes(g_src, sg_src);
      }
 
    // Explore adjacent arcs
    for (Node_Arc_Iterator<GT, SA> i(g_src, sa); i.has_curr(); i.next_ne())
      {
        auto arc = i.get_current_arc_ne();
        if (IS_ARC_VISITED(arc, Build_Subtree))
          continue;
 
        // Mark arc as visited
        ARC_BITS(arc).set_bit(Build_Subtree, true);
 
        // Get or create mapped target node
        auto g_tgt = i.get_tgt_node();
        auto sg_tgt = mapped_node<GT>(g_tgt);
        if (sg_tgt == nullptr)
          {
            sg_tgt = sg.insert_node(g_tgt->get_info());
            GT::map_nodes(g_tgt, sg_tgt);
          }
 
        // Insert arc in subgraph and establish mapping
        auto sg_arc = sg.insert_arc(sg_src, sg_tgt, arc->get_info());
        GT::map_arcs(arc, sg_arc);
 
        // Recurse on target node
        build_subgraph(sg, g_tgt);
      }
  }
 
  // Recursive DFS to build list of reachable nodes
  template <template <class> class List>
  void build_subgraph(List<typename GT::Node*> & l, typename GT::Node * p)
  {
    if (IS_NODE_VISITED(p, Build_Subtree))
      return;
 
    // Mark node as visited and add to list
    NODE_BITS(p).set_bit(Build_Subtree, true);
    ++count;
    l.append(p);
 
    // Explore adjacent arcs
    for (Node_Arc_Iterator<GT, SA> it(p, sa);
         count < gptr->get_num_nodes() and it.has_curr(); it.next_ne())
      {
        auto arc = it.get_current_arc_ne();
        if (IS_ARC_VISITED(arc, Build_Subtree))
          continue;
 
        // Mark arc as visited and recurse
        ARC_BITS(arc).set_bit(Build_Subtree, true);
        build_subgraph(l, it.get_tgt_node());
      }
  }
 
public:
 
  void operator () (const GT & g, GT & sg, typename GT::Node * g_src)
  {
    ah_invalid_argument_if(g_src == nullptr)
      << "Build_Subgraph: source node cannot be null";
 
    gptr = &g;
    count = 0;
    build_subgraph(sg, g_src);
  }
 
  GT operator () (const GT & g, typename GT::Node * src)
  {
    ah_invalid_argument_if(src == nullptr)
      << "Build_Subgraph: source node cannot be null";
 
    GT sg;
    gptr = &g;
    count = 0;
    build_subgraph(sg, src);
    return sg;
  }
 
  void operator () (const GT & g, DynList<typename GT::Node*> & list,
                    typename GT::Node * src)
  {
    ah_invalid_argument_if(src == nullptr)
      << "Build_Subgraph: source node cannot be null";
 
    gptr = &g;
    count = 0;
    build_subgraph<DynList>(list, src);
  }
};
 
 
template <class GT, class SA = Dft_Show_Arc<GT>>
class Unconnected_Components
{
  SA sa;
 
public:
 
  Unconnected_Components(SA arc_filter = SA())
    : sa(arc_filter) { /* empty */ }
 
  template <template <class> class List>
  void compute_blocks(const GT & g, List<GT> & list)
  {
    g.reset_nodes();
    g.reset_arcs();
    size_t count = 0;  // Count of visited nodes
 
    for (typename GT::Node_Iterator it(g);
         count < g.get_num_nodes() and it.has_curr(); it.next_ne())
      {
        auto curr = it.get_current_node_ne();
        if (IS_NODE_VISITED(curr, Build_Subtree))
          continue;
 
        // Create new subgraph for this component
        GT & subgraph = list.append(GT());
 
        Build_Subgraph<GT, SA> build(sa);
        build(g, subgraph, curr);
 
        count += subgraph.get_num_nodes();
      }
  }
 
  template <template <class> class List>
  void compute_lists(const GT & g, List<List<typename GT::Node*>> & list)
  {
    g.reset_nodes();
    g.reset_arcs();
    size_t count = 0;  // Count of visited nodes
 
    for (typename GT::Node_Iterator i(g);
         count < g.get_num_nodes() and i.has_curr(); i.next_ne())
      {
        auto curr = i.get_current_node_ne();
        if (IS_NODE_VISITED(curr, Build_Subtree))
          continue;
 
        // Create new node list for this component
        auto & l = list.append(List<typename GT::Node*>());
 
        Build_Subgraph<GT, SA> build(sa);
        build(g, l, curr);
 
        count += l.size();
      }
  }
 
  void operator () (const GT & g, DynList<GT> & list)
  {
    compute_blocks<DynList>(g, list);
  }
 
  void operator () (const GT & g, DynList<DynList<typename GT::Node*>> & list)
  {
    compute_lists<DynList>(g, list);
  }
 
  size_t count_components(const GT & g)
  {
    DynList<DynList<typename GT::Node*>> components;
    compute_lists<DynList>(g, components);
    return components.size();
  }
 
  bool is_connected(const GT & g)
  {
    if (g.get_num_nodes() <= 1)
      return true;
    return count_components(g) == 1;
  }
};
 
 
} // end namespace Aleph
 
# endif //  TPL_COMPONENTS_H