RhodeCode

 *

 * This file is a part of LEMON, a generic C++ optimization library.

 *

 * Copyright (C) 2003-2009

 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, EGRES).

 *

 * Permission to use, modify and distribute this software is granted

 * provided that this copyright notice appears in all copies. For

 * precise terms see the accompanying LICENSE file.

 *

 * This software is provided "AS IS" with no warranty of any kind,

 * express or implied, and with no claim as to its suitability for any

 * purpose.

 *

 */

#ifndef LEMON_BFS_H

#define LEMON_BFS_H

///\ingroup search

///\file

///\brief BFS algorithm.

#include <lemon/list_graph.h>

#include <lemon/bits/path_dump.h>

#include <lemon/core.h>

#include <lemon/error.h>

#include <lemon/maps.h>

#include <lemon/path.h>

namespace lemon {

  ///Default traits class of Bfs class.

  ///Default traits class of Bfs class.

  ///\tparam GR Digraph type.

  template<class GR>

  struct BfsDefaultTraits

  {

    ///The type of the digraph the algorithm runs on.

    typedef GR Digraph;

    ///\brief The type of the map that stores the predecessor

    ///arcs of the shortest paths.

    ///

    ///The type of the map that stores the predecessor

    ///arcs of the shortest paths.

    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;

    ///Instantiates a \c PredMap.

    ///This function instantiates a \ref PredMap.

    ///\param g is the digraph, to which we would like to define the

    ///\ref PredMap.

    static PredMap *createPredMap(const Digraph &g)

    {

      return new PredMap(g);

    }

    ///The type of the map that indicates which nodes are processed.

    ///The type of the map that indicates which nodes are processed.

    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;

    ///Instantiates a \c ProcessedMap.

    ///This function instantiates a \ref ProcessedMap.

    ///\param g is the digraph, to which

    ///we would like to define the \ref ProcessedMap

#ifdef DOXYGEN

    static ProcessedMap *createProcessedMap(const Digraph &g)

#else

    static ProcessedMap *createProcessedMap(const Digraph &)

#endif

    {

      return new ProcessedMap();

    }

    ///The type of the map that indicates which nodes are reached.

    ///The type of the map that indicates which nodes are reached.

    typedef typename Digraph::template NodeMap<bool> ReachedMap;

    ///Instantiates a \c ReachedMap.

    ///This function instantiates a \ref ReachedMap.

    ///\param g is the digraph, to which

    ///we would like to define the \ref ReachedMap.

    static ReachedMap *createReachedMap(const Digraph &g)

    {

      return new ReachedMap(g);

    }

    ///The type of the map that stores the distances of the nodes.

    ///The type of the map that stores the distances of the nodes.

    typedef typename Digraph::template NodeMap<int> DistMap;

    ///Instantiates a \c DistMap.

    ///This function instantiates a \ref DistMap.

    ///\param g is the digraph, to which we would like to define the

    ///\ref DistMap.

    static DistMap *createDistMap(const Digraph &g)

    {

      return new DistMap(g);

    }

  };

  ///%BFS algorithm class.

  ///\ingroup search

  ///This class provides an efficient implementation of the %BFS algorithm.

  ///

  ///There is also a \ref bfs() "function-type interface" for the BFS

  ///algorithm, which is convenient in the simplier cases and it can be

  ///used easier.

  ///

  ///\tparam GR The type of the digraph the algorithm runs on.

  ///The default type is \ref ListDigraph.

#ifdef DOXYGEN

  template <typename GR,

            typename TR>

#else

  template <typename GR=ListDigraph,

            typename TR=BfsDefaultTraits<GR> >

#endif

  class Bfs {

  public:

    ///The type of the digraph the algorithm runs on.

    typedef typename TR::Digraph Digraph;

    ///\brief The type of the map that stores the predecessor arcs of the

    ///shortest paths.

    typedef typename TR::PredMap PredMap;

    ///The type of the map that stores the distances of the nodes.

    typedef typename TR::DistMap DistMap;

    ///The type of the map that indicates which nodes are reached.

    typedef typename TR::ReachedMap ReachedMap;

    ///The type of the map that indicates which nodes are processed.

    typedef typename TR::ProcessedMap ProcessedMap;

    ///The type of the paths.

    typedef PredMapPath<Digraph, PredMap> Path;

    //Creates the maps if necessary.

    void create_maps()

    {

      if(!_pred) {

        local_pred = true;

        _pred = Traits::createPredMap(*G);

      }

      if(!_dist) {

        local_dist = true;

        _dist = Traits::createDistMap(*G);

      }

      if(!_reached) {

        local_reached = true;

        _reached = Traits::createReachedMap(*G);

      }

      if(!_processed) {

        local_processed = true;

        _processed = Traits::createProcessedMap(*G);

      }

    }

  protected:

    Bfs() {}

  public:

    typedef Bfs Create;

    ///\name Named Template Parameters

    ///@{

    template <class T>

    struct SetPredMapTraits : public Traits {

      typedef T PredMap;

      static PredMap *createPredMap(const Digraph &)

      {

        LEMON_ASSERT(false, "PredMap is not initialized");

        return 0; // ignore warnings

      }

    };

    ///\brief \ref named-templ-param "Named parameter" for setting

    ///\c PredMap type.

    ///

    ///\ref named-templ-param "Named parameter" for setting

    ///\c PredMap type.

    template <class T>

    struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > {

      typedef Bfs< Digraph, SetPredMapTraits<T> > Create;

    };

    template <class T>

    struct SetDistMapTraits : public Traits {

      typedef T DistMap;

      static DistMap *createDistMap(const Digraph &)

      {

        LEMON_ASSERT(false, "DistMap is not initialized");

        return 0; // ignore warnings

      }

    };

    ///\brief \ref named-templ-param "Named parameter" for setting

    ///\c DistMap type.

    ///

    ///\ref named-templ-param "Named parameter" for setting

    ///\c DistMap type.

    template <class T>

    struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > {

      typedef Bfs< Digraph, SetDistMapTraits<T> > Create;

    };

    template <class T>

    struct SetReachedMapTraits : public Traits {

      typedef T ReachedMap;

      static ReachedMap *createReachedMap(const Digraph &)

      {

        LEMON_ASSERT(false, "ReachedMap is not initialized");

        return 0; // ignore warnings

      }

    };

    ///\brief \ref named-templ-param "Named parameter" for setting

    ///\c ReachedMap type.

    ///

    ///\ref named-templ-param "Named parameter" for setting

    ///\c ReachedMap type.

    template <class T>

    struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > {

      typedef Bfs< Digraph, SetReachedMapTraits<T> > Create;

    };

    template <class T>

    struct SetProcessedMapTraits : public Traits {

      typedef T ProcessedMap;

      static ProcessedMap *createProcessedMap(const Digraph &)

      {

        LEMON_ASSERT(false, "ProcessedMap is not initialized");

        return 0; // ignore warnings

      }

    };

    ///\brief \ref named-templ-param "Named parameter" for setting

    ///\c ProcessedMap type.

    ///

    ///\ref named-templ-param "Named parameter" for setting

    ///\c ProcessedMap type.

    template <class T>

    struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > {

      typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create;

    };

    struct SetStandardProcessedMapTraits : public Traits {

      typedef typename Digraph::template NodeMap<bool> ProcessedMap;

      static ProcessedMap *createProcessedMap(const Digraph &g)

      {

        return new ProcessedMap(g);

        return 0; // ignore warnings

      }

    };

    ///\brief \ref named-templ-param "Named parameter" for setting

    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.

    ///

    ///\ref named-templ-param "Named parameter" for setting

    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.

    ///If you don't set it explicitly, it will be automatically allocated.

    struct SetStandardProcessedMap :

      public Bfs< Digraph, SetStandardProcessedMapTraits > {

      typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create;

    };

    ///@}

  public:

    ///Constructor.

    ///Constructor.

    ///\param g The digraph the algorithm runs on.

    Bfs(const Digraph &g) :

      G(&g),

      _pred(NULL), local_pred(false),

      _dist(NULL), local_dist(false),

      _reached(NULL), local_reached(false),

      _processed(NULL), local_processed(false)

    { }

    ///Destructor.

    ~Bfs()

    {

      if(local_pred) delete _pred;

      if(local_dist) delete _dist;

      if(local_reached) delete _reached;

      if(local_processed) delete _processed;

    }

    ///  b.start(t);

    ///\endcode

    bool run(Node s,Node t) {

      init();

      addSource(s);

      start(t);

      return reached(t);

    }

    ///Runs the algorithm to visit all nodes in the digraph.

    ///This method runs the %BFS algorithm in order to

    ///compute the shortest path to each node.

    ///

    ///The algorithm computes

    ///- the shortest path tree (forest),

    ///- the distance of each node from the root(s).

    ///

    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.

    ///\code

    ///  b.init();

    ///  for (NodeIt n(gr); n != INVALID; ++n) {

    ///    if (!b.reached(n)) {

    ///      b.addSource(n);

    ///      b.start();

    ///    }

    ///  }

    ///\endcode

    void run() {

      init();

      for (NodeIt n(*G); n != INVALID; ++n) {

        if (!reached(n)) {

          addSource(n);

          start();

        }

      }

    }

    ///@}

    ///\name Query Functions

    ///The results of the BFS algorithm can be obtained using these

    ///functions.\n

    ///Either \ref run(Node) "run()" or \ref start() should be called

    ///before using them.

    ///@{

    ///

    ///\warning \c t should be reached from the root(s).

    ///

    ///\pre Either \ref run(Node) "run()" or \ref init()

    ///must be called before using this function.

    Path path(Node t) const { return Path(*G, *_pred, t); }

    ///

    ///\warning If node \c v is not reached from the root(s), then

    ///the return value of this function is undefined.

    ///

    ///\pre Either \ref run(Node) "run()" or \ref init()

    ///must be called before using this function.

    int dist(Node v) const { return (*_dist)[v]; }

    ///This function returns the 'previous arc' of the shortest path

    ///tree for the node \c v, i.e. it returns the last arc of a

    ///shortest path from a root to \c v. It is \c INVALID if \c v

    ///is not reached from the root(s) or if \c v is a root.

    ///

    ///The shortest path tree used here is equal to the shortest path

    ///

    ///\pre Either \ref run(Node) "run()" or \ref init()

    ///must be called before using this function.

    Arc predArc(Node v) const { return (*_pred)[v];}

    ///This function returns the 'previous node' of the shortest path

    ///tree for the node \c v, i.e. it returns the last but one node

    ///if \c v is not reached from the root(s) or if \c v is a root.

    ///

    ///The shortest path tree used here is equal to the shortest path

    ///

    ///\pre Either \ref run(Node) "run()" or \ref init()

    ///must be called before using this function.

    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:

                                  G->source((*_pred)[v]); }

    ///\brief Returns a const reference to the node map that stores the

    /// distances of the nodes.

    ///

    ///Returns a const reference to the node map that stores the distances

    ///of the nodes calculated by the algorithm.

    ///

    ///\pre Either \ref run(Node) "run()" or \ref init()

    ///must be called before using this function.

    const DistMap &distMap() const { return *_dist;}

    ///\brief Returns a const reference to the node map that stores the

    ///predecessor arcs.

    ///

    ///Returns a const reference to the node map that stores the predecessor

    ///

    ///\pre Either \ref run(Node) "run()" or \ref init()

    ///must be called before using this function.

    const PredMap &predMap() const { return *_pred;}

    ///Returns \c true if \c v is reached from the root(s).

    ///

    ///\pre Either \ref run(Node) "run()" or \ref init()

    ///must be called before using this function.

    bool reached(Node v) const { return (*_reached)[v]; }

    ///@}

  };

  ///Default traits class of bfs() function.

  ///Default traits class of bfs() function.

  ///\tparam GR Digraph type.

  template<class GR>

  struct BfsWizardDefaultTraits

  {

    ///The type of the digraph the algorithm runs on.

    typedef GR Digraph;

    ///\brief The type of the map that stores the predecessor

    ///arcs of the shortest paths.

    ///

    ///The type of the map that stores the predecessor

    ///arcs of the shortest paths.

    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;

    ///Instantiates a PredMap.

    ///This function instantiates a PredMap.

    ///\param g is the digraph, to which we would like to define the

    ///PredMap.

    static PredMap *createPredMap(const Digraph &g)

    {

      return new PredMap(g);

    }

    ///The type of the map that indicates which nodes are processed.

    ///The type of the map that indicates which nodes are processed.

    ///By default it is a NullMap.

    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;

    ///Instantiates a ProcessedMap.

    ///This function instantiates a ProcessedMap.

    ///\param g is the digraph, to which

    ///we would like to define the ProcessedMap.

#ifdef DOXYGEN

    static ProcessedMap *createProcessedMap(const Digraph &g)

#else

    static ProcessedMap *createProcessedMap(const Digraph &)

#endif

    {

      return new ProcessedMap();

    }

    ///The type of the map that indicates which nodes are reached.

    ///The type of the map that indicates which nodes are reached.

    typedef typename Digraph::template NodeMap<bool> ReachedMap;

    ///Instantiates a ReachedMap.

    ///This function instantiates a ReachedMap.

    ///\param g is the digraph, to which

    ///we would like to define the ReachedMap.

    static ReachedMap *createReachedMap(const Digraph &g)

    {

      return new ReachedMap(g);

    }

    ///The type of the map that stores the distances of the nodes.

    ///The type of the map that stores the distances of the nodes.

    typedef typename Digraph::template NodeMap<int> DistMap;

    ///Instantiates a DistMap.

    ///This function instantiates a DistMap.

    ///\param g is the digraph, to which we would like to define

    ///the DistMap

    static DistMap *createDistMap(const Digraph &g)

    {

      return new DistMap(g);

    }

    ///The type of the shortest paths.

    ///The type of the shortest paths.

    typedef lemon::Path<Digraph> Path;

  };

  /// Default traits class used by BfsWizard

  template<class GR>

  class BfsWizardBase : public BfsWizardDefaultTraits<GR>

  {

    typedef BfsWizardDefaultTraits<GR> Base;

  protected:

    //The type of the nodes in the digraph.

    typedef typename Base::Digraph::Node Node;

    //Pointer to the digraph the algorithm runs on.

    void *_g;

    //Pointer to the map of reached nodes.

    void *_reached;

    //Pointer to the map of processed nodes.

    void *_processed;

    //Pointer to the map of predecessors arcs.

    void *_pred;

    //Pointer to the map of distances.

    void *_dist;

    //Pointer to the shortest path to the target node.

    void *_path;

    //Pointer to the distance of the target node.

    int *_di;

    public:

    /// Constructor.

    /// all of the attributes to \c 0.

    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),

                      _dist(0), _path(0), _di(0) {}

    /// Constructor.

    /// This constructor requires one parameter,

    /// others are initiated to \c 0.

    /// \param g The digraph the algorithm runs on.

    BfsWizardBase(const GR &g) :

      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),

      _reached(0), _processed(0), _pred(0), _dist(0),  _path(0), _di(0) {}

  };

  /// Auxiliary class for the function-type interface of BFS algorithm.

  /// This auxiliary class is created to implement the

  /// \ref bfs() "function-type interface" of \ref Bfs algorithm.

  /// It does not have own \ref run(Node) "run()" method, it uses the

  /// functions and features of the plain \ref Bfs.

  ///

  /// This class should only be used through the \ref bfs() function,

  /// which makes it easier to use the algorithm.

  template<class TR>

  class BfsWizard : public TR

  {

    typedef TR Base;

    typedef typename TR::Digraph Digraph;

    typedef typename Digraph::Node Node;

    typedef typename Digraph::NodeIt NodeIt;

    typedef typename Digraph::Arc Arc;

    typedef typename Digraph::OutArcIt OutArcIt;

    typedef typename TR::PredMap PredMap;

    typedef typename TR::DistMap DistMap;

    typedef typename TR::ReachedMap ReachedMap;

    typedef typename TR::ProcessedMap ProcessedMap;

    typedef typename TR::Path Path;

  public:

    /// Constructor.

    BfsWizard() : TR() {}

    /// Constructor that requires parameters.

    /// Constructor that requires parameters.

    /// These parameters will be the default values for the traits class.

    /// \param g The digraph the algorithm runs on.

    BfsWizard(const Digraph &g) :

      TR(g) {}

    ///Copy constructor

    BfsWizard(const TR &b) : TR(b) {}

    ~BfsWizard() {}

    ///Runs BFS algorithm from the given source node.

    ///This method runs BFS algorithm from node \c s

    ///in order to compute the shortest path to each node.

    void run(Node s)

    {

      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));

      if (Base::_pred)

        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));

      if (Base::_dist)

        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));

      if (Base::_reached)

        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));

      if (Base::_processed)

        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));

      if (s!=INVALID)

        alg.run(s);

      else

        alg.run();

    }

    ///Finds the shortest path between \c s and \c t.

    ///This method runs BFS algorithm from node \c s

    ///in order to compute the shortest path to node \c t

    ///(it stops searching when \c t is processed).

    ///

    ///\return \c true if \c t is reachable form \c s.

    bool run(Node s, Node t)

    {

      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));

      if (Base::_pred)

        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));

      if (Base::_dist)

        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));

      if (Base::_reached)

        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));

      if (Base::_processed)

        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));

      alg.run(s,t);

      if (Base::_path)

        *reinterpret_cast<Path*>(Base::_path) = alg.path(t);

      if (Base::_di)

        *Base::_di = alg.dist(t);

      return alg.reached(t);

    }

    ///Runs BFS algorithm to visit all nodes in the digraph.

    ///This method runs BFS algorithm in order to compute

    ///the shortest path to each node.

    void run()

    {

      run(INVALID);

    }

    template<class T>

    struct SetPredMapBase : public Base {

      typedef T PredMap;

      static PredMap *createPredMap(const Digraph &) { return 0; };

      SetPredMapBase(const TR &b) : TR(b) {}

    };

    ///

    template<class T>

    BfsWizard<SetPredMapBase<T> > predMap(const T &t)

    {

      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));

      return BfsWizard<SetPredMapBase<T> >(*this);

    }

    template<class T>

    struct SetReachedMapBase : public Base {

      typedef T ReachedMap;

      static ReachedMap *createReachedMap(const Digraph &) { return 0; };

      SetReachedMapBase(const TR &b) : TR(b) {}

    };

    ///

    template<class T>

    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)

    {

      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));

      return BfsWizard<SetReachedMapBase<T> >(*this);

    }

    template<class T>

    struct SetDistMapBase : public Base {

      typedef T DistMap;

      static DistMap *createDistMap(const Digraph &) { return 0; };

      SetDistMapBase(const TR &b) : TR(b) {}

    };

    ///

    template<class T>

    BfsWizard<SetDistMapBase<T> > distMap(const T &t)

    {

      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));

      return BfsWizard<SetDistMapBase<T> >(*this);

    }

    template<class T>

    struct SetProcessedMapBase : public Base {

      typedef T ProcessedMap;

      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };

      SetProcessedMapBase(const TR &b) : TR(b) {}

    };

    ///

    template<class T>

    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)

    {

      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));

      return BfsWizard<SetProcessedMapBase<T> >(*this);

    }

    template<class T>

    struct SetPathBase : public Base {

      typedef T Path;

      SetPathBase(const TR &b) : TR(b) {}

    };

    ///\brief \ref named-func-param "Named parameter"

    ///for getting the shortest path to the target node.

    ///

    ///\ref named-func-param "Named parameter"

    ///for getting the shortest path to the target node.

    template<class T>

    BfsWizard<SetPathBase<T> > path(const T &t)

    {

      Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t));

      return BfsWizard<SetPathBase<T> >(*this);

    }

    ///\brief \ref named-func-param "Named parameter"

    ///for getting the distance of the target node.

    ///

    ///\ref named-func-param "Named parameter"

    ///for getting the distance of the target node.

    BfsWizard dist(const int &d)

    {

      Base::_di=const_cast<int*>(&d);

      return *this;

    }

  };

  ///Function-type interface for BFS algorithm.

  /// \ingroup search

  ///Function-type interface for BFS algorithm.

  ///

  ///This function also has several \ref named-func-param "named parameters",

  ///they are declared as the members of class \ref BfsWizard.

  ///The following examples show how to use these parameters.

  ///\code

  ///  // Compute shortest path from node s to each node

  ///  bfs(g).predMap(preds).distMap(dists).run(s);

    /// \brief Called when an arc is examined but its target node is

    /// already discovered.

    ///

    /// This function is called when an arc is examined but its target node is

    /// already discovered.

    void examine(const Arc& arc) {}

  };

#else

  template <typename GR>

  struct BfsVisitor {

    typedef GR Digraph;

    typedef typename Digraph::Arc Arc;

    typedef typename Digraph::Node Node;

    void start(const Node&) {}

    void reach(const Node&) {}

    void process(const Node&) {}

    void discover(const Arc&) {}

    void examine(const Arc&) {}

    template <typename _Visitor>

    struct Constraints {

      void constraints() {

        Arc arc;

        Node node;

        visitor.start(node);

        visitor.reach(node);

        visitor.process(node);

        visitor.discover(arc);

        visitor.examine(arc);

      }

      _Visitor& visitor;

    };

  };

#endif

  /// \brief Default traits class of BfsVisit class.

  ///

  /// Default traits class of BfsVisit class.

  /// \tparam GR The type of the digraph the algorithm runs on.

  template<class GR>

  struct BfsVisitDefaultTraits {

    /// \brief The type of the digraph the algorithm runs on.

    typedef GR Digraph;

    /// \brief The type of the map that indicates which nodes are reached.

    ///

    /// The type of the map that indicates which nodes are reached.

    typedef typename Digraph::template NodeMap<bool> ReachedMap;

    /// \brief Instantiates a ReachedMap.

    ///

    /// This function instantiates a ReachedMap.

    /// \param digraph is the digraph, to which

    /// we would like to define the ReachedMap.

    static ReachedMap *createReachedMap(const Digraph &digraph) {

      return new ReachedMap(digraph);

    }

  };

  /// \ingroup search

  ///

  /// \brief BFS algorithm class with visitor interface.

  ///

  /// This class provides an efficient implementation of the BFS algorithm

  /// with visitor interface.

  ///

  /// The BfsVisit class provides an alternative interface to the Bfs

  /// class. It works with callback mechanism, the BfsVisit object calls

  /// the member functions of the \c Visitor class on every BFS event.

  ///

  /// This interface of the BFS algorithm should be used in special cases

  /// when extra actions have to be performed in connection with certain

  /// events of the BFS algorithm. Otherwise consider to use Bfs or bfs()

  /// instead.

  ///

  /// \tparam GR The type of the digraph the algorithm runs on.

  /// The default type is \ref ListDigraph.

  /// The value of GR is not used directly by \ref BfsVisit,

  /// it is only passed to \ref BfsVisitDefaultTraits.

  /// \tparam VS The Visitor type that is used by the algorithm.

  /// \ref BfsVisitor "BfsVisitor<GR>" is an empty visitor, which

  /// does not observe the BFS events. If you want to observe the BFS

  /// events, you should implement your own visitor class.

  /// \tparam TR Traits class to set various data types used by the

  /// algorithm. The default traits class is

  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<GR>".

  /// See \ref BfsVisitDefaultTraits for the documentation of

  /// a BFS visit traits class.

#ifdef DOXYGEN

  template <typename GR, typename VS, typename TR>

#else

  template <typename GR = ListDigraph,

            typename VS = BfsVisitor<GR>,

            typename TR = BfsVisitDefaultTraits<GR> >

    ///   b.start(t);

    ///\endcode

    bool run(Node s,Node t) {

      init();

      addSource(s);

      start(t);

      return reached(t);

    }

    /// \brief Runs the algorithm to visit all nodes in the digraph.

    ///

    /// This method runs the %BFS algorithm in order to

    /// compute the shortest path to each node.

    ///

    /// The algorithm computes

    /// - the shortest path tree (forest),

    /// - the distance of each node from the root(s).

    ///

    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.

    ///\code

    ///  b.init();

    ///  for (NodeIt n(gr); n != INVALID; ++n) {

    ///    if (!b.reached(n)) {

    ///      b.addSource(n);

    ///      b.start();

    ///    }

    ///  }

    ///\endcode

    void run() {

      init();

      for (NodeIt it(*_digraph); it != INVALID; ++it) {

        if (!reached(it)) {

          addSource(it);

          start();

        }

      }

    }

    ///@}

    /// \name Query Functions

    /// The results of the BFS algorithm can be obtained using these

    /// functions.\n

    /// Either \ref run(Node) "run()" or \ref start() should be called

    /// before using them.

    ///@{

    ///

    /// Returns \c true if \c v is reached from the root(s).

    ///

    /// \pre Either \ref run(Node) "run()" or \ref init()

    /// must be called before using this function.

    bool reached(Node v) const { return (*_reached)[v]; }

    ///@}

  };

} //END OF NAMESPACE LEMON

#endif

 *

 * This file is a part of LEMON, a generic C++ optimization library.

 *

 * Copyright (C) 2003-2009

 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, EGRES).

 *

 * Permission to use, modify and distribute this software is granted

 * provided that this copyright notice appears in all copies. For

 * precise terms see the accompanying LICENSE file.

 *

 * This software is provided "AS IS" with no warranty of any kind,

 * express or implied, and with no claim as to its suitability for any

 * purpose.

 *

 */

#ifndef LEMON_DFS_H

#define LEMON_DFS_H

///\ingroup search

///\file

///\brief DFS algorithm.

#include <lemon/list_graph.h>

#include <lemon/bits/path_dump.h>

#include <lemon/core.h>

#include <lemon/error.h>

#include <lemon/maps.h>

#include <lemon/path.h>

namespace lemon {

  ///Default traits class of Dfs class.

  ///Default traits class of Dfs class.

  ///\tparam GR Digraph type.

  template<class GR>

  struct DfsDefaultTraits

  {

    ///The type of the digraph the algorithm runs on.

    typedef GR Digraph;

    ///\brief The type of the map that stores the predecessor

    ///arcs of the %DFS paths.

    ///

    ///The type of the map that stores the predecessor

    ///arcs of the %DFS paths.

    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;

    ///Instantiates a \c PredMap.

    ///This function instantiates a \ref PredMap.

    ///\param g is the digraph, to which we would like to define the

    ///\ref PredMap.

    static PredMap *createPredMap(const Digraph &g)

    {

      return new PredMap(g);

    }

    ///The type of the map that indicates which nodes are processed.

    ///The type of the map that indicates which nodes are processed.

    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;

    ///Instantiates a \c ProcessedMap.

    ///This function instantiates a \ref ProcessedMap.

    ///\param g is the digraph, to which

    ///we would like to define the \ref ProcessedMap.

#ifdef DOXYGEN

    static ProcessedMap *createProcessedMap(const Digraph &g)

#else

    static ProcessedMap *createProcessedMap(const Digraph &)

#endif

    {

      return new ProcessedMap();

    }

    ///The type of the map that indicates which nodes are reached.

    ///The type of the map that indicates which nodes are reached.

    typedef typename Digraph::template NodeMap<bool> ReachedMap;

    ///Instantiates a \c ReachedMap.

    ///This function instantiates a \ref ReachedMap.

    ///\param g is the digraph, to which

    ///we would like to define the \ref ReachedMap.

    static ReachedMap *createReachedMap(const Digraph &g)

    {

      return new ReachedMap(g);