RhodeCode

	  _reached->set(m,true);

	  _pred->set(m,e);

	  _dist->set(m,_curr_dist);

          reach = reach || (target == m);

	}

      return n;

    }

    ///Processes the next node.

    ///Processes the next node. And checks that at least one of

    ///reached node has true value in the \c nm node map. If one node

    ///with true value is reachable from the processed node then the

    ///rnode parameter will be set to the first of such nodes.

    ///

    ///\param nm The node map of possible targets.

    ///\retval rnode The reached target node.

    ///\return The processed node.

    ///

    ///\warning The queue must not be empty!

    template<class NM>

    Node processNextNode(const NM& nm, Node& rnode)

    {

      if(_queue_tail==_queue_next_dist) {

	_curr_dist++;

	_queue_next_dist=_queue_head;

      }

      Node n=_queue[_queue_tail++];

      _processed->set(n,true);

      Node m;

      for(OutArcIt e(*G,n);e!=INVALID;++e)

	if(!(*_reached)[m=G->target(e)]) {

	  _queue[_queue_head++]=m;

	  _reached->set(m,true);

	  _pred->set(m,e);

	  _dist->set(m,_curr_dist);

	  if (nm[m] && rnode == INVALID) rnode = m;

	}

      return n;

    }

    ///Next node to be processed.

    ///Next node to be processed.

    ///

    ///\return The next node to be processed or INVALID if the queue is

    /// empty.

    Node nextNode()

    { 

      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;

    }

    ///\brief Returns \c false if there are nodes

    ///to be processed in the queue

    ///

    ///Returns \c false if there are nodes

    ///to be processed in the queue

    bool emptyQueue() { return _queue_tail==_queue_head; }

    ///Returns the number of the nodes to be processed.

    ///Returns the number of the nodes to be processed in the queue.

    int queueSize() { return _queue_head-_queue_tail; }

    ///Executes the algorithm.

    ///Executes the algorithm.

    ///

    ///\pre init() must be called and at least one node should be added

    ///with addSource() before using this function.

    ///

    ///This method runs the %BFS algorithm from the root node(s)

    ///in order to

    ///compute the

    ///shortest path to each node. The algorithm computes

    ///- The shortest path tree.

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

    void start()

    {

      while ( !emptyQueue() ) processNextNode();

    }

    ///Executes the algorithm until \c dest is reached.

    ///Executes the algorithm until \c dest is reached.

    ///

    ///\pre init() must be called and at least one node should be added

    ///with addSource() before using this function.

    ///

    ///This method runs the %BFS algorithm from the root node(s)

    ///in order to compute the shortest path to \c dest.

    ///The algorithm computes

    ///- The shortest path to \c  dest.

    ///- The distance of \c dest from the root(s).

    void start(Node dest)

    {

      bool reach = false;

      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);

    }

    ///Executes the algorithm until a condition is met.

    ///Executes the algorithm until a condition is met.

    ///

    ///\pre init() must be called and at least one node should be added

    ///with addSource() before using this function.

    ///

    ///\param nm must be a bool (or convertible) node map. The

    ///algorithm will stop when it reaches a node \c v with

    /// <tt>nm[v]</tt> true.

    ///

    ///\return The reached node \c v with <tt>nm[v]</tt> true or

    ///\c INVALID if no such node was found.

    template<class NM>

    Node start(const NM &nm)

    {

      Node rnode = INVALID;

      while ( !emptyQueue() && rnode == INVALID ) {

	processNextNode(nm, rnode);

      }

      return rnode;

    }

    ///Runs %BFS algorithm from node \c s.

    ///This method runs the %BFS algorithm from a root node \c s

    ///in order to

    ///compute the

    ///shortest path to each node. The algorithm computes

    ///- The shortest path tree.

    ///- The distance of each node from the root.

    ///

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

    ///\code

    ///  b.init();

    ///  b.addSource(s);

    ///  b.start();

    ///\endcode

    void run(Node s) {

      init();

      addSource(s);

      start();

    }

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

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

    ///

    ///\return The length of the shortest s---t path if there exists one,

    ///0 otherwise.

    ///\note Apart from the return value, b.run(s) is

    ///just a shortcut of the following code.

    ///\code

    ///  b.init();

    ///  b.addSource(s);

    ///  b.start(t);

    ///\endcode

    int run(Node s,Node t) {

      init();

      addSource(s);

      start(t);

      return reached(t) ? _curr_dist : 0;

    }

    ///@}

    ///\name Query Functions

    ///The result of the %BFS algorithm can be obtained using these

    ///functions.\n

    ///Before the use of these functions,

    ///either run() or start() must be calleb.

    ///@{

    typedef PredMapPath<Digraph, PredMap> Path;

    ///Gives back the shortest path.

    ///Gives back the shortest path.

    ///\pre The \c t should be reachable from the source.

    Path path(Node t) 

    {

      return Path(*G, *_pred, t);

    }

    ///The distance of a node from the root(s).

    ///Returns the distance of a node from the root(s).

    ///\pre \ref run() must be called before using this function.

    ///\warning If node \c v in unreachable from the root(s) the return value

    ///of this function is undefined.

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

    ///Returns the 'previous arc' of the shortest path tree.

    ///For a node \c v it returns the 'previous arc'

    ///of the shortest path tree,

    ///i.e. it returns the last arc of a shortest path from the root(s) to \c

    ///v. It is \ref INVALID

    ///if \c v is unreachable from the root(s) or \c v is a root. The

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

    ///\ref predNode().

    ///\pre Either \ref run() or \ref start() must be called before using

    ///this function.

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

    ///Returns the 'previous node' of the shortest path tree.

    ///For a node \c v it returns the 'previous node'

    ///of the shortest path tree,

    ///i.e. it returns the last but one node from a shortest path from the

    ///root(a) to \c /v.

    ///It is INVALID if \c v is unreachable from the root(s) or

    ///if \c v itself a root.

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

    ///tree used in \ref predArc().

    ///\pre Either \ref run() or \ref start() must be called before

    ///using this function.

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

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

    ///Returns a reference to the NodeMap of distances.

    ///Returns a reference to the NodeMap of distances.

    ///\pre Either \ref run() or \ref init() must

    ///be called before using this function.

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

    ///Returns a reference to the shortest path tree map.

    ///Returns a reference to the NodeMap of the arcs of the

    ///shortest path tree.

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

    ///must be called before using this function.

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

    ///Checks if a node is reachable from the root.

    ///Returns \c true if \c v is reachable from the root.

    ///\warning The source nodes are indicated as unreached.

    ///\pre Either \ref run() or \ref start()

    ///must be called before using this function.

    ///

    bool reached(Node v) { 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 digraph type the algorithm runs on. 

    typedef GR Digraph;

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

    ///arcs of the shortest paths.

    /// 

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

    ///arcs of the shortest paths.

    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.

    ///

    typedef NullMap<typename Digraph::Node,typename GR::Arc> PredMap;

    ///Instantiates a PredMap.

    ///This function instantiates a \ref PredMap. 

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

    ///\todo The digraph alone may be insufficient to initialize

#ifdef DOXYGEN

    static PredMap *createPredMap(const GR &g) 

#else

    static PredMap *createPredMap(const GR &) 

#endif

    {

      return new PredMap();

    }

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

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

    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.

    ///\todo named parameter to set this type, function to read and write.

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

    ///Instantiates a 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 GR &g)

#else

    static ProcessedMap *createProcessedMap(const GR &)

#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.

    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.

    ///\todo named parameter to set this type, function to read and write.

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

    ///Instantiates a 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 GR &G)

    {

      return new ReachedMap(G);

    }

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

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

    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.

    ///

    typedef NullMap<typename Digraph::Node,int> DistMap;

    ///Instantiates a DistMap.

    ///This function instantiates a \ref DistMap. 

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

#ifdef DOXYGEN

    static DistMap *createDistMap(const GR &g)

#else

    static DistMap *createDistMap(const GR &)

#endif

    {

      return new DistMap();

    }

  };

  /// Default traits used by \ref BfsWizard

  /// To make it easier to use Bfs algorithm

  ///we have created a wizard class.

  /// This \ref BfsWizard class needs default traits,

  ///as well as the \ref Bfs class.

  /// The \ref BfsWizardBase is a class to be the default traits of the

  /// \ref BfsWizard class.

  template<class GR>

  class BfsWizardBase : public BfsWizardDefaultTraits<GR>

  {

    typedef BfsWizardDefaultTraits<GR> Base;

  protected:

    /// Type of the nodes in the digraph.

    typedef typename Base::Digraph::Node Node;

    /// Pointer to the underlying digraph.

    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 source node.

    Node _source;

    public:

    /// Constructor.

    /// This constructor does not require parameters, therefore it initiates

    /// all of the attributes to default values (0, INVALID).

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

			   _dist(0), _source(INVALID) {}

    /// Constructor.

    /// This constructor requires some parameters,

    /// listed in the parameters list.

    /// Others are initiated to 0.

    /// \param g is the initial value of  \ref _g

    /// \param s is the initial value of  \ref _source

    BfsWizardBase(const GR &g, Node s=INVALID) :

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

      _reached(0), _processed(0), _pred(0), _dist(0), _source(s) {}

  };

  /// A class to make the usage of Bfs algorithm easier

  /// This class is created to make it easier to use Bfs algorithm.

  /// It uses the functions and features of the plain \ref Bfs,

  /// but it is much simpler to use it.

  ///

  /// Simplicity means that the way to change the types defined

  /// in the traits class is based on functions that returns the new class

  /// and not on templatable built-in classes.

  /// When using the plain \ref Bfs

  /// the new class with the modified type comes from

  /// the original class by using the ::

  /// operator. In the case of \ref BfsWizard only

  /// a function have to be called and it will

  /// return the needed class.

  ///

  /// It does not have own \ref run method. When its \ref run method is called

  /// it initiates a plain \ref Bfs class, and calls the \ref Bfs::run

  /// method of it.

  template<class TR>

  class BfsWizard : public TR

  {

    typedef TR Base;

    ///The type of the underlying digraph.

    typedef typename TR::Digraph Digraph;

    //\e

    typedef typename Digraph::Node Node;

    //\e

    typedef typename Digraph::NodeIt NodeIt;

    //\e

    typedef typename Digraph::Arc Arc;

    //\e

    typedef typename Digraph::OutArcIt OutArcIt;

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

    ///the reached nodes

    typedef typename TR::ReachedMap ReachedMap;

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

    ///the processed nodes

    typedef typename TR::ProcessedMap ProcessedMap;

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

    ///arcs of the shortest paths.

    typedef typename TR::PredMap PredMap;

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

    typedef typename TR::DistMap DistMap;

  public:

    /// Constructor.

    BfsWizard() : TR() {}

    /// Constructor that requires parameters.

    /// Constructor that requires parameters.

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

    BfsWizard(const Digraph &g, Node s=INVALID) :

      TR(g,s) {}

    ///Copy constructor

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

    ~BfsWizard() {}

    ///Runs Bfs algorithm from a given node.

    ///Runs Bfs algorithm from a given node.

    ///The node can be given by the \ref source function.

    void run()

    {

      if(Base::_source==INVALID) throw UninitializedParameter();

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

      if(Base::_reached)

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

      if(Base::_processed) 

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

      if(Base::_pred) 

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

      if(Base::_dist) 

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

      alg.run(Base::_source);

    }

    ///Runs Bfs algorithm from the given node.

    ///Runs Bfs algorithm from the given node.

    ///\param s is the given source.

    void run(Node s)

    {

      Base::_source=s;

      run();

    }

    template<class T>

    struct DefPredMapBase : public Base {

      typedef T PredMap;

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

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

    };

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

    ///function for setting PredMap

    ///

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

    ///function for setting PredMap

    ///

    template<class T>

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

    {

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

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

    }

    template<class T>

    struct DefReachedMapBase : public Base {

      typedef T ReachedMap;

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

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

    };

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

    ///function for setting ReachedMap

    ///

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

    ///function for setting ReachedMap

    ///

    template<class T>

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

    {

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

    }

    template<class T>

    struct DefProcessedMapBase : public Base {

      typedef T ProcessedMap;

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

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

    };

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

    ///function for setting ProcessedMap

    ///

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

    ///function for setting ProcessedMap

    ///

    template<class T>

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

    {

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

    }

    template<class T>

    struct DefDistMapBase : public Base {

      typedef T DistMap;

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

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

    };

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

    ///function for setting DistMap type

    ///

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

    ///function for setting DistMap type

    ///

    template<class T>

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

    {

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

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

    }

    /// Sets the source node, from which the Bfs algorithm runs.

    /// Sets the source node, from which the Bfs algorithm runs.

    /// \param s is the source node.

    BfsWizard<TR> &source(Node s) 

    {

      Base::_source=s;

      return *this;

    }

  };

  ///Function type interface for Bfs algorithm.

  /// \ingroup search

  ///Function type interface for Bfs algorithm.

  ///

  ///This function also has several

  ///\ref named-templ-func-param "named parameters",

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

  ///The following

  ///example shows how to use these parameters.

  ///\code

  ///  bfs(g,source).predMap(preds).run();

  ///\endcode

  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"

  ///to the end of the parameter list.

  ///\sa BfsWizard

  ///\sa Bfs

  template<class GR>

  BfsWizard<BfsWizardBase<GR> >

  bfs(const GR &g,typename GR::Node s=INVALID)

  {

    return BfsWizard<BfsWizardBase<GR> >(g,s);

  }

#ifdef DOXYGEN

  /// \brief Visitor class for bfs.

  ///  

  /// This class defines the interface of the BfsVisit events, and

  /// it could be the base of a real Visitor class.

  template <typename _Digraph>

  struct BfsVisitor {

    typedef _Digraph Digraph;

    typedef typename Digraph::Arc Arc;

    typedef typename Digraph::Node Node;

    /// \brief Called when the arc reach a node.

    /// 

    /// It is called when the bfs find an arc which target is not

    /// reached yet.

    void discover(const Arc& arc) {}

    /// \brief Called when the node reached first time.

    /// 

    /// It is Called when the node reached first time.

    void reach(const Node& node) {}

    /// \brief Called when the arc examined but target of the arc 

    /// already discovered.

    /// 

    /// It called when the arc examined but the target of the arc 

    /// already discovered.

    void examine(const Arc& arc) {}

    /// \brief Called for the source node of the bfs.

    /// 

    /// It is called for the source node of the bfs.

    void start(const Node& node) {}

    /// \brief Called when the node processed.

    /// 

    /// It is Called when the node processed.

    void process(const Node& node) {}

  };

#else

  template <typename _Digraph>

  struct BfsVisitor {

    typedef _Digraph Digraph;

    typedef typename Digraph::Arc Arc;

    typedef typename Digraph::Node Node;

    void discover(const Arc&) {}

    void reach(const Node&) {}

    void examine(const Arc&) {}

    void start(const Node&) {}

    void process(const Node&) {}

    template <typename _Visitor>

    struct Constraints {

      void constraints() {

	Arc arc;

	Node node;

	visitor.discover(arc);

	visitor.reach(node);

	visitor.examine(arc);

	visitor.start(node);

        visitor.process(node);

      }

      _Visitor& visitor;

    };

  };

#endif

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

  ///

  /// Default traits class of BfsVisit class.

  /// \tparam _Digraph Digraph type.

  template<class _Digraph>

  struct BfsVisitDefaultTraits {

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

    typedef _Digraph Digraph;

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

    /// 

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

    /// It must meet the \ref concepts::WriteMap "WriteMap" concept.

    /// \todo named parameter to set this type, function to read and write.

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

    /// \brief Instantiates a ReachedMap.

    ///

    /// This function instantiates a \ref ReachedMap. 

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

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

    static ReachedMap *createReachedMap(const Digraph &digraph) {

      return new ReachedMap(digraph);

    }

  };

  /// \ingroup search

  ///  

  /// \brief %BFS Visit algorithm class.

  ///  

  /// 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

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

  ///

  /// \tparam _Digraph The digraph type the algorithm runs on. The default value is

  /// \ref ListDigraph. The value of _Digraph is not used directly by Bfs, it

  /// is only passed to \ref BfsDefaultTraits.

  /// \tparam _Visitor The Visitor object for the algorithm. The 

  /// \ref BfsVisitor "BfsVisitor<_Digraph>" 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 _Traits Traits class to set various data types used by the 

  /// algorithm. The default traits class is

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

  /// See \ref BfsVisitDefaultTraits for the documentation of

  /// a Bfs visit traits class.

#ifdef DOXYGEN

  template <typename _Digraph, typename _Visitor, typename _Traits>

#else

  template <typename _Digraph = ListDigraph,

	    typename _Visitor = BfsVisitor<_Digraph>,

	    typename _Traits = BfsDefaultTraits<_Digraph> >

#endif

  class BfsVisit {

  public:

    /// \brief \ref Exception for uninitialized parameters.

    ///

    /// This error represents problems in the initialization

    /// of the parameters of the algorithms.

    class UninitializedParameter : public lemon::UninitializedParameter {

    public:

      virtual const char* what() const throw() 

      {

	return "lemon::BfsVisit::UninitializedParameter";

      }

    };

    typedef _Traits Traits;

    typedef typename Traits::Digraph Digraph;

    typedef _Visitor Visitor;

    ///The type of the map indicating which nodes are reached.

    typedef typename Traits::ReachedMap ReachedMap;

  private:

    typedef typename Digraph::Node Node;

    typedef typename Digraph::NodeIt NodeIt;

    typedef typename Digraph::Arc Arc;

    typedef typename Digraph::OutArcIt OutArcIt;

    /// Pointer to the underlying digraph.

    const Digraph *_digraph;

    /// Pointer to the visitor object.

    Visitor *_visitor;

    ///Pointer to the map of reached status of the nodes.

    ReachedMap *_reached;

    ///Indicates if \ref _reached is locally allocated (\c true) or not.

    bool local_reached;

    std::vector<typename Digraph::Node> _list;

    int _list_front, _list_back;

    /// \brief Creates the maps if necessary.

    ///

    /// Creates the maps if necessary.

    void create_maps() {

      if(!_reached) {

	local_reached = true;

	_reached = Traits::createReachedMap(*_digraph);

      }

    }

  protected:

    BfsVisit() {}

  public:

    typedef BfsVisit Create;

    /// \name Named template parameters

    ///@{

    template <class T>

    struct DefReachedMapTraits : public Traits {

      typedef T ReachedMap;

      static ReachedMap *createReachedMap(const Digraph &digraph) {

	throw UninitializedParameter();

      }

    };

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

    /// ReachedMap type

    ///

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

    template <class T>

    struct DefReachedMap : public BfsVisit< Digraph, Visitor,

					    DefReachedMapTraits<T> > {

      typedef BfsVisit< Digraph, Visitor, DefReachedMapTraits<T> > Create;

    };

    ///@}

  public:      

    /// \brief Constructor.

    ///

    /// Constructor.

    ///

    /// \param digraph the digraph the algorithm will run on.

    /// \param visitor The visitor of the algorithm.

    ///

    BfsVisit(const Digraph& digraph, Visitor& visitor) 

      : _digraph(&digraph), _visitor(&visitor),

	_reached(0), local_reached(false) {}

    /// \brief Destructor.

    ///

    /// Destructor.

    ~BfsVisit() {

      if(local_reached) delete _reached;

    }

    /// \brief Sets the map indicating if a node is reached.

    ///

    /// Sets the map indicating if a node is reached.

    /// If you don't use this function before calling \ref run(),

    /// it will allocate one. The destuctor deallocates this

    /// automatically allocated map, of course.

    /// \return <tt> (*this) </tt>

    BfsVisit &reachedMap(ReachedMap &m) {

      if(local_reached) {

	delete _reached;

	local_reached = false;

      }

      _reached = &m;

      return *this;

    }

  public:

    /// \name Execution control

    /// The simplest way to execute the algorithm is to use

    /// one of the member functions called \c run(...).

    /// \n

    /// If you need more control on the execution,

    /// first you must call \ref init(), then you can adda source node

    /// with \ref addSource().

    /// Finally \ref start() will perform the actual path

    /// computation.

    /// @{

    /// \brief Initializes the internal data structures.

    ///

    /// Initializes the internal data structures.

    ///

    void init() {

      create_maps();

      _list.resize(countNodes(*_digraph));

      _list_front = _list_back = -1;

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

	_reached->set(u, false);

      }

    }

    /// \brief Adds a new source node.

    ///

    /// Adds a new source node to the set of nodes to be processed.

    void addSource(Node s) {

      if(!(*_reached)[s]) {

	  _reached->set(s,true);

	  _visitor->start(s);

	  _visitor->reach(s);

          _list[++_list_back] = s;

	}

    }

    /// \brief Processes the next node.

    ///

    /// Processes the next node.

    ///

    /// \return The processed node.

    ///

    /// \pre The queue must not be empty!

    Node processNextNode() { 

      Node n = _list[++_list_front];

      _visitor->process(n);

      Arc e;

      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {

        Node m = _digraph->target(e);

        if (!(*_reached)[m]) {

          _visitor->discover(e);

          _visitor->reach(m);

          _reached->set(m, true);

          _list[++_list_back] = m;

        } else {

          _visitor->examine(e);

        }

      }

      return n;

    }

    /// \brief Processes the next node.

    ///

    /// Processes the next node. And checks that the given target node

    /// is reached. If the target node is reachable from the processed

    /// node then the reached parameter will be set true. The reached

    /// parameter should be initially false.

    ///

    /// \param target The target node.

    /// \retval reach Indicates that the target node is reached.

    /// \return The processed node.

    ///

    /// \warning The queue must not be empty!

    Node processNextNode(Node target, bool& reach) {

      Node n = _list[++_list_front];

      _visitor->process(n);

      Arc e;

      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {

        Node m = _digraph->target(e);

        if (!(*_reached)[m]) {

          _visitor->discover(e);

          _visitor->reach(m);

          _reached->set(m, true);

          _list[++_list_back] = m;

          reach = reach || (target == m);

        } else {

          _visitor->examine(e);

        }

      }

      return n;

    }

    /// \brief Processes the next node.

    ///

    /// Processes the next node. And checks that at least one of

    /// reached node has true value in the \c nm node map. If one node

    /// with true value is reachable from the processed node then the

    /// rnode parameter will be set to the first of such nodes.

    ///

    /// \param nm The node map of possible targets.

    /// \retval rnode The reached target node.

    /// \return The processed node.

    ///

    /// \warning The queue must not be empty!

    template <typename NM>

    Node processNextNode(const NM& nm, Node& rnode) {

      Node n = _list[++_list_front];

      _visitor->process(n);

      Arc e;

      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {

        Node m = _digraph->target(e);

        if (!(*_reached)[m]) {

          _visitor->discover(e);

          _visitor->reach(m);

          _reached->set(m, true);

          _list[++_list_back] = m;

          if (nm[m] && rnode == INVALID) rnode = m;

        } else {

          _visitor->examine(e);

        }

      }

      return n;

    }

    /// \brief Next node to be processed.

    ///

    /// Next node to be processed.

    ///

    /// \return The next node to be processed or INVALID if the stack is

    /// empty.

    Node nextNode() { 

      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;

    }

    /// \brief Returns \c false if there are nodes

    /// to be processed in the queue

    ///

    /// Returns \c false if there are nodes

    /// to be processed in the queue

    bool emptyQueue() { return _list_front == _list_back; }

    /// \brief Returns the number of the nodes to be processed.

    ///

    /// Returns the number of the nodes to be processed in the queue.

    int queueSize() { return _list_back - _list_front; }

    /// \brief Executes the algorithm.

    ///

    /// Executes the algorithm.

    ///

    /// \pre init() must be called and at least one node should be added

    /// with addSource() before using this function.

    void start() {

      while ( !emptyQueue() ) processNextNode();

    }

    /// \brief Executes the algorithm until \c dest is reached.

    ///

    /// Executes the algorithm until \c dest is reached.

    ///

    /// \pre init() must be called and at least one node should be added

    /// with addSource() before using this function.

    void start(Node dest) {

      bool reach = false;

      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);

    }

    /// \brief Executes the algorithm until a condition is met.

    ///

    /// Executes the algorithm until a condition is met.

    ///

    /// \pre init() must be called and at least one node should be added

    /// with addSource() before using this function.

    ///

    ///\param nm must be a bool (or convertible) node map. The

    ///algorithm will stop when it reaches a node \c v with

    /// <tt>nm[v]</tt> true.

    ///

    ///\return The reached node \c v with <tt>nm[v]</tt> true or

    ///\c INVALID if no such node was found.

    template <typename NM>

    Node start(const NM &nm) {

      Node rnode = INVALID;

      while ( !emptyQueue() && rnode == INVALID ) {

	processNextNode(nm, rnode);

      }

      return rnode;

    }

    /// \brief Runs %BFSVisit algorithm from node \c s.

    ///

    /// This method runs the %BFS algorithm from a root node \c s.

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

    ///\code

    ///   b.init();

    ///   b.addSource(s);

    ///   b.start();

    ///\endcode

    void run(Node s) {

      init();

      addSource(s);

      start();

    }

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

    ///    

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

    /// compute the %BFS path to each node. The algorithm computes

    /// - The %BFS tree.

    /// - The distance of each node from the root in the %BFS tree.

    ///

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

    ///\code

      while(_stack_head>=0 && _stack[_stack_head]==INVALID) {

	_processed->set(m,true);

	--_stack_head;

	if(_stack_head>=0) {

	  m=G->source(_stack[_stack_head]);

	  ++_stack[_stack_head];

	}

      }

      return e;

    }

    ///Next arc to be processed.

    ///Next arc to be processed.

    ///

    ///\return The next arc to be processed or INVALID if the stack is

    /// empty.

    OutArcIt nextArc()

    { 

      return _stack_head>=0?_stack[_stack_head]:INVALID;

    }

    ///\brief Returns \c false if there are nodes

    ///to be processed in the queue

    ///

    ///Returns \c false if there are nodes

    ///to be processed in the queue

    bool emptyQueue() { return _stack_head<0; }

    ///Returns the number of the nodes to be processed.

    ///Returns the number of the nodes to be processed in the queue.

    int queueSize() { return _stack_head+1; }

    ///Executes the algorithm.

    ///Executes the algorithm.

    ///

    ///\pre init() must be called and at least one node should be added

    ///with addSource() before using this function.

    ///

    ///This method runs the %DFS algorithm from the root node(s)

    ///in order to

    ///compute the

    ///%DFS path to each node. The algorithm computes

    ///- The %DFS tree.

    ///- The distance of each node from the root(s) in the %DFS tree.

    ///

    void start()

    {

      while ( !emptyQueue() ) processNextArc();

    }

    ///Executes the algorithm until \c dest is reached.

    ///Executes the algorithm until \c dest is reached.

    ///

    ///\pre init() must be called and at least one node should be added

    ///with addSource() before using this function.

    ///

    ///This method runs the %DFS algorithm from the root node(s)

    ///in order to

    ///compute the

    ///%DFS path to \c dest. The algorithm computes

    ///- The %DFS path to \c  dest.

    ///- The distance of \c dest from the root(s) in the %DFS tree.