COIN-OR::LEMON - Graph Library

source: lemon/lemon/bfs.h @ 833:e20173729589

Last change on this file since 833:e20173729589 was 833:e20173729589, checked in by Peter Kovacs <kpeter@…>, 10 years ago

Small doc fixes in several files (#331)

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RevLine 
[209]1/* -*- mode: C++; indent-tabs-mode: nil; -*-
[100]2 *
[209]3 * This file is a part of LEMON, a generic C++ optimization library.
[100]4 *
[463]5 * Copyright (C) 2003-2009
[100]6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19#ifndef LEMON_BFS_H
20#define LEMON_BFS_H
21
22///\ingroup search
23///\file
[244]24///\brief BFS algorithm.
[100]25
26#include <lemon/list_graph.h>
27#include <lemon/bits/path_dump.h>
[220]28#include <lemon/core.h>
[100]29#include <lemon/error.h>
30#include <lemon/maps.h>
[278]31#include <lemon/path.h>
[100]32
33namespace lemon {
34
35  ///Default traits class of Bfs class.
36
37  ///Default traits class of Bfs class.
[157]38  ///\tparam GR Digraph type.
[100]39  template<class GR>
40  struct BfsDefaultTraits
41  {
[244]42    ///The type of the digraph the algorithm runs on.
[100]43    typedef GR Digraph;
[244]44
45    ///\brief The type of the map that stores the predecessor
[100]46    ///arcs of the shortest paths.
[209]47    ///
[244]48    ///The type of the map that stores the predecessor
[100]49    ///arcs of the shortest paths.
[763]50    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[244]51    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
[525]52    ///Instantiates a \c PredMap.
[209]53
[525]54    ///This function instantiates a \ref PredMap.
[244]55    ///\param g is the digraph, to which we would like to define the
[525]56    ///\ref PredMap.
[244]57    static PredMap *createPredMap(const Digraph &g)
[100]58    {
[244]59      return new PredMap(g);
[100]60    }
[244]61
[100]62    ///The type of the map that indicates which nodes are processed.
[209]63
[100]64    ///The type of the map that indicates which nodes are processed.
[763]65    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[833]66    ///By default, it is a NullMap.
[100]67    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
[525]68    ///Instantiates a \c ProcessedMap.
[209]69
[525]70    ///This function instantiates a \ref ProcessedMap.
[100]71    ///\param g is the digraph, to which
[525]72    ///we would like to define the \ref ProcessedMap
[100]73#ifdef DOXYGEN
[244]74    static ProcessedMap *createProcessedMap(const Digraph &g)
[100]75#else
[244]76    static ProcessedMap *createProcessedMap(const Digraph &)
[100]77#endif
78    {
79      return new ProcessedMap();
80    }
[244]81
[100]82    ///The type of the map that indicates which nodes are reached.
[209]83
[421]84    ///The type of the map that indicates which nodes are reached.
[763]85    ///It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]86    typedef typename Digraph::template NodeMap<bool> ReachedMap;
[525]87    ///Instantiates a \c ReachedMap.
[209]88
[525]89    ///This function instantiates a \ref ReachedMap.
[244]90    ///\param g is the digraph, to which
[525]91    ///we would like to define the \ref ReachedMap.
[244]92    static ReachedMap *createReachedMap(const Digraph &g)
[100]93    {
[244]94      return new ReachedMap(g);
[100]95    }
[209]96
[244]97    ///The type of the map that stores the distances of the nodes.
98
99    ///The type of the map that stores the distances of the nodes.
[763]100    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[100]101    typedef typename Digraph::template NodeMap<int> DistMap;
[525]102    ///Instantiates a \c DistMap.
[209]103
[525]104    ///This function instantiates a \ref DistMap.
[244]105    ///\param g is the digraph, to which we would like to define the
[525]106    ///\ref DistMap.
[244]107    static DistMap *createDistMap(const Digraph &g)
[100]108    {
[244]109      return new DistMap(g);
[100]110    }
111  };
[209]112
[100]113  ///%BFS algorithm class.
[209]114
[100]115  ///\ingroup search
116  ///This class provides an efficient implementation of the %BFS algorithm.
117  ///
[278]118  ///There is also a \ref bfs() "function-type interface" for the BFS
[244]119  ///algorithm, which is convenient in the simplier cases and it can be
120  ///used easier.
121  ///
122  ///\tparam GR The type of the digraph the algorithm runs on.
[421]123  ///The default type is \ref ListDigraph.
[100]124#ifdef DOXYGEN
125  template <typename GR,
[209]126            typename TR>
[100]127#else
128  template <typename GR=ListDigraph,
[209]129            typename TR=BfsDefaultTraits<GR> >
[100]130#endif
131  class Bfs {
132  public:
133
[244]134    ///The type of the digraph the algorithm runs on.
[100]135    typedef typename TR::Digraph Digraph;
[209]136
[244]137    ///\brief The type of the map that stores the predecessor arcs of the
138    ///shortest paths.
[100]139    typedef typename TR::PredMap PredMap;
[244]140    ///The type of the map that stores the distances of the nodes.
141    typedef typename TR::DistMap DistMap;
142    ///The type of the map that indicates which nodes are reached.
[100]143    typedef typename TR::ReachedMap ReachedMap;
[244]144    ///The type of the map that indicates which nodes are processed.
[100]145    typedef typename TR::ProcessedMap ProcessedMap;
[244]146    ///The type of the paths.
147    typedef PredMapPath<Digraph, PredMap> Path;
148
[421]149    ///The \ref BfsDefaultTraits "traits class" of the algorithm.
[244]150    typedef TR Traits;
151
[100]152  private:
153
154    typedef typename Digraph::Node Node;
155    typedef typename Digraph::NodeIt NodeIt;
156    typedef typename Digraph::Arc Arc;
157    typedef typename Digraph::OutArcIt OutArcIt;
158
[244]159    //Pointer to the underlying digraph.
[100]160    const Digraph *G;
[244]161    //Pointer to the map of predecessor arcs.
[100]162    PredMap *_pred;
[244]163    //Indicates if _pred is locally allocated (true) or not.
[100]164    bool local_pred;
[244]165    //Pointer to the map of distances.
[100]166    DistMap *_dist;
[244]167    //Indicates if _dist is locally allocated (true) or not.
[100]168    bool local_dist;
[244]169    //Pointer to the map of reached status of the nodes.
[100]170    ReachedMap *_reached;
[244]171    //Indicates if _reached is locally allocated (true) or not.
[100]172    bool local_reached;
[244]173    //Pointer to the map of processed status of the nodes.
[100]174    ProcessedMap *_processed;
[244]175    //Indicates if _processed is locally allocated (true) or not.
[100]176    bool local_processed;
177
178    std::vector<typename Digraph::Node> _queue;
179    int _queue_head,_queue_tail,_queue_next_dist;
180    int _curr_dist;
181
[280]182    //Creates the maps if necessary.
[209]183    void create_maps()
[100]184    {
185      if(!_pred) {
[209]186        local_pred = true;
187        _pred = Traits::createPredMap(*G);
[100]188      }
189      if(!_dist) {
[209]190        local_dist = true;
191        _dist = Traits::createDistMap(*G);
[100]192      }
193      if(!_reached) {
[209]194        local_reached = true;
195        _reached = Traits::createReachedMap(*G);
[100]196      }
197      if(!_processed) {
[209]198        local_processed = true;
199        _processed = Traits::createProcessedMap(*G);
[100]200      }
201    }
202
203  protected:
[209]204
[100]205    Bfs() {}
[209]206
[100]207  public:
[209]208
[100]209    typedef Bfs Create;
210
[421]211    ///\name Named Template Parameters
[100]212
213    ///@{
214
215    template <class T>
[257]216    struct SetPredMapTraits : public Traits {
[100]217      typedef T PredMap;
[209]218      static PredMap *createPredMap(const Digraph &)
[100]219      {
[290]220        LEMON_ASSERT(false, "PredMap is not initialized");
221        return 0; // ignore warnings
[100]222      }
223    };
224    ///\brief \ref named-templ-param "Named parameter" for setting
[525]225    ///\c PredMap type.
[100]226    ///
[244]227    ///\ref named-templ-param "Named parameter" for setting
[525]228    ///\c PredMap type.
[763]229    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[100]230    template <class T>
[257]231    struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > {
232      typedef Bfs< Digraph, SetPredMapTraits<T> > Create;
[100]233    };
[209]234
[100]235    template <class T>
[257]236    struct SetDistMapTraits : public Traits {
[100]237      typedef T DistMap;
[209]238      static DistMap *createDistMap(const Digraph &)
[100]239      {
[290]240        LEMON_ASSERT(false, "DistMap is not initialized");
241        return 0; // ignore warnings
[100]242      }
243    };
244    ///\brief \ref named-templ-param "Named parameter" for setting
[525]245    ///\c DistMap type.
[100]246    ///
[244]247    ///\ref named-templ-param "Named parameter" for setting
[525]248    ///\c DistMap type.
[763]249    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[100]250    template <class T>
[257]251    struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > {
252      typedef Bfs< Digraph, SetDistMapTraits<T> > Create;
[100]253    };
[209]254
[100]255    template <class T>
[257]256    struct SetReachedMapTraits : public Traits {
[100]257      typedef T ReachedMap;
[209]258      static ReachedMap *createReachedMap(const Digraph &)
[100]259      {
[290]260        LEMON_ASSERT(false, "ReachedMap is not initialized");
261        return 0; // ignore warnings
[100]262      }
263    };
264    ///\brief \ref named-templ-param "Named parameter" for setting
[525]265    ///\c ReachedMap type.
[100]266    ///
[244]267    ///\ref named-templ-param "Named parameter" for setting
[525]268    ///\c ReachedMap type.
[763]269    ///It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]270    template <class T>
[257]271    struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > {
272      typedef Bfs< Digraph, SetReachedMapTraits<T> > Create;
[100]273    };
[209]274
[100]275    template <class T>
[257]276    struct SetProcessedMapTraits : public Traits {
[100]277      typedef T ProcessedMap;
[209]278      static ProcessedMap *createProcessedMap(const Digraph &)
[100]279      {
[290]280        LEMON_ASSERT(false, "ProcessedMap is not initialized");
281        return 0; // ignore warnings
[100]282      }
283    };
284    ///\brief \ref named-templ-param "Named parameter" for setting
[525]285    ///\c ProcessedMap type.
[100]286    ///
[244]287    ///\ref named-templ-param "Named parameter" for setting
[525]288    ///\c ProcessedMap type.
[763]289    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[100]290    template <class T>
[257]291    struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > {
292      typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create;
[100]293    };
[209]294
[257]295    struct SetStandardProcessedMapTraits : public Traits {
[100]296      typedef typename Digraph::template NodeMap<bool> ProcessedMap;
[244]297      static ProcessedMap *createProcessedMap(const Digraph &g)
[100]298      {
[244]299        return new ProcessedMap(g);
[290]300        return 0; // ignore warnings
[100]301      }
302    };
[244]303    ///\brief \ref named-templ-param "Named parameter" for setting
[525]304    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
[100]305    ///
[244]306    ///\ref named-templ-param "Named parameter" for setting
[525]307    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
[100]308    ///If you don't set it explicitly, it will be automatically allocated.
[257]309    struct SetStandardProcessedMap :
310      public Bfs< Digraph, SetStandardProcessedMapTraits > {
311      typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create;
[100]312    };
[209]313
[100]314    ///@}
315
[209]316  public:
317
[100]318    ///Constructor.
[209]319
[244]320    ///Constructor.
321    ///\param g The digraph the algorithm runs on.
322    Bfs(const Digraph &g) :
323      G(&g),
[100]324      _pred(NULL), local_pred(false),
325      _dist(NULL), local_dist(false),
326      _reached(NULL), local_reached(false),
327      _processed(NULL), local_processed(false)
328    { }
[209]329
[100]330    ///Destructor.
[209]331    ~Bfs()
[100]332    {
333      if(local_pred) delete _pred;
334      if(local_dist) delete _dist;
335      if(local_reached) delete _reached;
336      if(local_processed) delete _processed;
337    }
338
[244]339    ///Sets the map that stores the predecessor arcs.
[100]340
[244]341    ///Sets the map that stores the predecessor arcs.
[421]342    ///If you don't use this function before calling \ref run(Node) "run()"
343    ///or \ref init(), an instance will be allocated automatically.
344    ///The destructor deallocates this automatically allocated map,
345    ///of course.
[100]346    ///\return <tt> (*this) </tt>
[209]347    Bfs &predMap(PredMap &m)
[100]348    {
349      if(local_pred) {
[209]350        delete _pred;
351        local_pred=false;
[100]352      }
353      _pred = &m;
354      return *this;
355    }
356
[244]357    ///Sets the map that indicates which nodes are reached.
[100]358
[244]359    ///Sets the map that indicates which nodes are reached.
[421]360    ///If you don't use this function before calling \ref run(Node) "run()"
361    ///or \ref init(), an instance will be allocated automatically.
362    ///The destructor deallocates this automatically allocated map,
363    ///of course.
[100]364    ///\return <tt> (*this) </tt>
[209]365    Bfs &reachedMap(ReachedMap &m)
[100]366    {
367      if(local_reached) {
[209]368        delete _reached;
369        local_reached=false;
[100]370      }
371      _reached = &m;
372      return *this;
373    }
374
[244]375    ///Sets the map that indicates which nodes are processed.
[100]376
[244]377    ///Sets the map that indicates which nodes are processed.
[421]378    ///If you don't use this function before calling \ref run(Node) "run()"
379    ///or \ref init(), an instance will be allocated automatically.
380    ///The destructor deallocates this automatically allocated map,
381    ///of course.
[100]382    ///\return <tt> (*this) </tt>
[209]383    Bfs &processedMap(ProcessedMap &m)
[100]384    {
385      if(local_processed) {
[209]386        delete _processed;
387        local_processed=false;
[100]388      }
389      _processed = &m;
390      return *this;
391    }
392
[244]393    ///Sets the map that stores the distances of the nodes.
[100]394
[244]395    ///Sets the map that stores the distances of the nodes calculated by
396    ///the algorithm.
[421]397    ///If you don't use this function before calling \ref run(Node) "run()"
398    ///or \ref init(), an instance will be allocated automatically.
399    ///The destructor deallocates this automatically allocated map,
400    ///of course.
[100]401    ///\return <tt> (*this) </tt>
[209]402    Bfs &distMap(DistMap &m)
[100]403    {
404      if(local_dist) {
[209]405        delete _dist;
406        local_dist=false;
[100]407      }
408      _dist = &m;
409      return *this;
410    }
411
412  public:
[244]413
[421]414    ///\name Execution Control
415    ///The simplest way to execute the BFS algorithm is to use one of the
416    ///member functions called \ref run(Node) "run()".\n
[760]417    ///If you need better control on the execution, you have to call
418    ///\ref init() first, then you can add several source nodes with
[421]419    ///\ref addSource(). Finally the actual path computation can be
420    ///performed with one of the \ref start() functions.
[100]421
422    ///@{
423
[421]424    ///\brief Initializes the internal data structures.
425    ///
[244]426    ///Initializes the internal data structures.
[100]427    void init()
428    {
429      create_maps();
430      _queue.resize(countNodes(*G));
431      _queue_head=_queue_tail=0;
432      _curr_dist=1;
433      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
[209]434        _pred->set(u,INVALID);
435        _reached->set(u,false);
436        _processed->set(u,false);
[100]437      }
438    }
[209]439
[100]440    ///Adds a new source node.
441
442    ///Adds a new source node to the set of nodes to be processed.
443    ///
444    void addSource(Node s)
445    {
446      if(!(*_reached)[s])
[209]447        {
448          _reached->set(s,true);
449          _pred->set(s,INVALID);
450          _dist->set(s,0);
451          _queue[_queue_head++]=s;
452          _queue_next_dist=_queue_head;
453        }
[100]454    }
[209]455
[100]456    ///Processes the next node.
457
458    ///Processes the next node.
459    ///
460    ///\return The processed node.
461    ///
[244]462    ///\pre The queue must not be empty.
[100]463    Node processNextNode()
464    {
465      if(_queue_tail==_queue_next_dist) {
[209]466        _curr_dist++;
467        _queue_next_dist=_queue_head;
[100]468      }
469      Node n=_queue[_queue_tail++];
470      _processed->set(n,true);
471      Node m;
472      for(OutArcIt e(*G,n);e!=INVALID;++e)
[209]473        if(!(*_reached)[m=G->target(e)]) {
474          _queue[_queue_head++]=m;
475          _reached->set(m,true);
476          _pred->set(m,e);
477          _dist->set(m,_curr_dist);
478        }
[100]479      return n;
480    }
481
482    ///Processes the next node.
483
[244]484    ///Processes the next node and checks if the given target node
[100]485    ///is reached. If the target node is reachable from the processed
[244]486    ///node, then the \c reach parameter will be set to \c true.
[100]487    ///
488    ///\param target The target node.
[244]489    ///\retval reach Indicates if the target node is reached.
490    ///It should be initially \c false.
491    ///
[100]492    ///\return The processed node.
493    ///
[244]494    ///\pre The queue must not be empty.
[100]495    Node processNextNode(Node target, bool& reach)
496    {
497      if(_queue_tail==_queue_next_dist) {
[209]498        _curr_dist++;
499        _queue_next_dist=_queue_head;
[100]500      }
501      Node n=_queue[_queue_tail++];
502      _processed->set(n,true);
503      Node m;
504      for(OutArcIt e(*G,n);e!=INVALID;++e)
[209]505        if(!(*_reached)[m=G->target(e)]) {
506          _queue[_queue_head++]=m;
507          _reached->set(m,true);
508          _pred->set(m,e);
509          _dist->set(m,_curr_dist);
[100]510          reach = reach || (target == m);
[209]511        }
[100]512      return n;
513    }
514
515    ///Processes the next node.
516
[244]517    ///Processes the next node and checks if at least one of reached
518    ///nodes has \c true value in the \c nm node map. If one node
519    ///with \c true value is reachable from the processed node, then the
520    ///\c rnode parameter will be set to the first of such nodes.
[100]521    ///
[244]522    ///\param nm A \c bool (or convertible) node map that indicates the
523    ///possible targets.
[100]524    ///\retval rnode The reached target node.
[244]525    ///It should be initially \c INVALID.
526    ///
[100]527    ///\return The processed node.
528    ///
[244]529    ///\pre The queue must not be empty.
[100]530    template<class NM>
531    Node processNextNode(const NM& nm, Node& rnode)
532    {
533      if(_queue_tail==_queue_next_dist) {
[209]534        _curr_dist++;
535        _queue_next_dist=_queue_head;
[100]536      }
537      Node n=_queue[_queue_tail++];
538      _processed->set(n,true);
539      Node m;
540      for(OutArcIt e(*G,n);e!=INVALID;++e)
[209]541        if(!(*_reached)[m=G->target(e)]) {
542          _queue[_queue_head++]=m;
543          _reached->set(m,true);
544          _pred->set(m,e);
545          _dist->set(m,_curr_dist);
546          if (nm[m] && rnode == INVALID) rnode = m;
547        }
[100]548      return n;
549    }
[209]550
[244]551    ///The next node to be processed.
[100]552
[244]553    ///Returns the next node to be processed or \c INVALID if the queue
554    ///is empty.
555    Node nextNode() const
[209]556    {
[100]557      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
558    }
[209]559
[421]560    ///Returns \c false if there are nodes to be processed.
561
562    ///Returns \c false if there are nodes to be processed
563    ///in the queue.
[244]564    bool emptyQueue() const { return _queue_tail==_queue_head; }
565
[100]566    ///Returns the number of the nodes to be processed.
[209]567
[421]568    ///Returns the number of the nodes to be processed
569    ///in the queue.
[244]570    int queueSize() const { return _queue_head-_queue_tail; }
[209]571
[100]572    ///Executes the algorithm.
573
574    ///Executes the algorithm.
575    ///
[244]576    ///This method runs the %BFS algorithm from the root node(s)
577    ///in order to compute the shortest path to each node.
[100]578    ///
[244]579    ///The algorithm computes
580    ///- the shortest path tree (forest),
581    ///- the distance of each node from the root(s).
582    ///
583    ///\pre init() must be called and at least one root node should be
584    ///added with addSource() before using this function.
585    ///
586    ///\note <tt>b.start()</tt> is just a shortcut of the following code.
587    ///\code
588    ///  while ( !b.emptyQueue() ) {
589    ///    b.processNextNode();
590    ///  }
591    ///\endcode
[100]592    void start()
593    {
594      while ( !emptyQueue() ) processNextNode();
595    }
[209]596
[244]597    ///Executes the algorithm until the given target node is reached.
[100]598
[244]599    ///Executes the algorithm until the given target node is reached.
[100]600    ///
601    ///This method runs the %BFS algorithm from the root node(s)
[286]602    ///in order to compute the shortest path to \c t.
[244]603    ///
[100]604    ///The algorithm computes
[286]605    ///- the shortest path to \c t,
606    ///- the distance of \c t from the root(s).
[244]607    ///
608    ///\pre init() must be called and at least one root node should be
609    ///added with addSource() before using this function.
610    ///
611    ///\note <tt>b.start(t)</tt> is just a shortcut of the following code.
612    ///\code
613    ///  bool reach = false;
614    ///  while ( !b.emptyQueue() && !reach ) {
615    ///    b.processNextNode(t, reach);
616    ///  }
617    ///\endcode
[286]618    void start(Node t)
[100]619    {
620      bool reach = false;
[286]621      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
[100]622    }
[209]623
[100]624    ///Executes the algorithm until a condition is met.
625
626    ///Executes the algorithm until a condition is met.
627    ///
[244]628    ///This method runs the %BFS algorithm from the root node(s) in
629    ///order to compute the shortest path to a node \c v with
630    /// <tt>nm[v]</tt> true, if such a node can be found.
[100]631    ///
[244]632    ///\param nm A \c bool (or convertible) node map. The algorithm
633    ///will stop when it reaches a node \c v with <tt>nm[v]</tt> true.
[100]634    ///
635    ///\return The reached node \c v with <tt>nm[v]</tt> true or
636    ///\c INVALID if no such node was found.
[244]637    ///
638    ///\pre init() must be called and at least one root node should be
639    ///added with addSource() before using this function.
640    ///
641    ///\note <tt>b.start(nm)</tt> is just a shortcut of the following code.
642    ///\code
643    ///  Node rnode = INVALID;
644    ///  while ( !b.emptyQueue() && rnode == INVALID ) {
645    ///    b.processNextNode(nm, rnode);
646    ///  }
647    ///  return rnode;
648    ///\endcode
649    template<class NodeBoolMap>
650    Node start(const NodeBoolMap &nm)
[100]651    {
652      Node rnode = INVALID;
653      while ( !emptyQueue() && rnode == INVALID ) {
[209]654        processNextNode(nm, rnode);
[100]655      }
656      return rnode;
657    }
[209]658
[286]659    ///Runs the algorithm from the given source node.
[209]660
[244]661    ///This method runs the %BFS algorithm from node \c s
662    ///in order to compute the shortest path to each node.
[100]663    ///
[244]664    ///The algorithm computes
665    ///- the shortest path tree,
666    ///- the distance of each node from the root.
667    ///
668    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
[100]669    ///\code
670    ///  b.init();
671    ///  b.addSource(s);
672    ///  b.start();
673    ///\endcode
674    void run(Node s) {
675      init();
676      addSource(s);
677      start();
678    }
[209]679
[100]680    ///Finds the shortest path between \c s and \c t.
[209]681
[244]682    ///This method runs the %BFS algorithm from node \c s
[286]683    ///in order to compute the shortest path to node \c t
684    ///(it stops searching when \c t is processed).
[100]685    ///
[286]686    ///\return \c true if \c t is reachable form \c s.
[244]687    ///
688    ///\note Apart from the return value, <tt>b.run(s,t)</tt> is just a
689    ///shortcut of the following code.
[100]690    ///\code
691    ///  b.init();
692    ///  b.addSource(s);
693    ///  b.start(t);
694    ///\endcode
[286]695    bool run(Node s,Node t) {
[100]696      init();
697      addSource(s);
698      start(t);
[286]699      return reached(t);
[100]700    }
[209]701
[244]702    ///Runs the algorithm to visit all nodes in the digraph.
703
704    ///This method runs the %BFS algorithm in order to
705    ///compute the shortest path to each node.
706    ///
707    ///The algorithm computes
708    ///- the shortest path tree (forest),
709    ///- the distance of each node from the root(s).
710    ///
711    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
712    ///\code
713    ///  b.init();
714    ///  for (NodeIt n(gr); n != INVALID; ++n) {
715    ///    if (!b.reached(n)) {
716    ///      b.addSource(n);
717    ///      b.start();
718    ///    }
719    ///  }
720    ///\endcode
721    void run() {
722      init();
723      for (NodeIt n(*G); n != INVALID; ++n) {
724        if (!reached(n)) {
725          addSource(n);
726          start();
727        }
728      }
729    }
730
[100]731    ///@}
732
733    ///\name Query Functions
[421]734    ///The results of the BFS algorithm can be obtained using these
[100]735    ///functions.\n
[421]736    ///Either \ref run(Node) "run()" or \ref start() should be called
737    ///before using them.
[209]738
[100]739    ///@{
740
[763]741    ///The shortest path to the given node.
[100]742
[763]743    ///Returns the shortest path to the given node from the root(s).
[244]744    ///
[421]745    ///\warning \c t should be reached from the root(s).
[244]746    ///
[421]747    ///\pre Either \ref run(Node) "run()" or \ref init()
748    ///must be called before using this function.
[244]749    Path path(Node t) const { return Path(*G, *_pred, t); }
[100]750
[763]751    ///The distance of the given node from the root(s).
[100]752
[763]753    ///Returns the distance of the given node from the root(s).
[244]754    ///
[421]755    ///\warning If node \c v is not reached from the root(s), then
[244]756    ///the return value of this function is undefined.
757    ///
[421]758    ///\pre Either \ref run(Node) "run()" or \ref init()
759    ///must be called before using this function.
[100]760    int dist(Node v) const { return (*_dist)[v]; }
761
[763]762    ///\brief Returns the 'previous arc' of the shortest path tree for
763    ///the given node.
764    ///
[244]765    ///This function returns the 'previous arc' of the shortest path
766    ///tree for the node \c v, i.e. it returns the last arc of a
[421]767    ///shortest path from a root to \c v. It is \c INVALID if \c v
768    ///is not reached from the root(s) or if \c v is a root.
[244]769    ///
770    ///The shortest path tree used here is equal to the shortest path
[763]771    ///tree used in \ref predNode() and \ref predMap().
[244]772    ///
[421]773    ///\pre Either \ref run(Node) "run()" or \ref init()
774    ///must be called before using this function.
[100]775    Arc predArc(Node v) const { return (*_pred)[v];}
776
[763]777    ///\brief Returns the 'previous node' of the shortest path tree for
778    ///the given node.
779    ///
[244]780    ///This function returns the 'previous node' of the shortest path
781    ///tree for the node \c v, i.e. it returns the last but one node
[763]782    ///of a shortest path from a root to \c v. It is \c INVALID
[421]783    ///if \c v is not reached from the root(s) or if \c v is a root.
[244]784    ///
[100]785    ///The shortest path tree used here is equal to the shortest path
[763]786    ///tree used in \ref predArc() and \ref predMap().
[244]787    ///
[421]788    ///\pre Either \ref run(Node) "run()" or \ref init()
789    ///must be called before using this function.
[100]790    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
[209]791                                  G->source((*_pred)[v]); }
792
[244]793    ///\brief Returns a const reference to the node map that stores the
794    /// distances of the nodes.
795    ///
796    ///Returns a const reference to the node map that stores the distances
797    ///of the nodes calculated by the algorithm.
798    ///
[421]799    ///\pre Either \ref run(Node) "run()" or \ref init()
[244]800    ///must be called before using this function.
[100]801    const DistMap &distMap() const { return *_dist;}
[209]802
[244]803    ///\brief Returns a const reference to the node map that stores the
804    ///predecessor arcs.
805    ///
806    ///Returns a const reference to the node map that stores the predecessor
[763]807    ///arcs, which form the shortest path tree (forest).
[244]808    ///
[421]809    ///\pre Either \ref run(Node) "run()" or \ref init()
[100]810    ///must be called before using this function.
811    const PredMap &predMap() const { return *_pred;}
[209]812
[763]813    ///Checks if the given node is reached from the root(s).
[100]814
[421]815    ///Returns \c true if \c v is reached from the root(s).
816    ///
817    ///\pre Either \ref run(Node) "run()" or \ref init()
[100]818    ///must be called before using this function.
[244]819    bool reached(Node v) const { return (*_reached)[v]; }
[209]820
[100]821    ///@}
822  };
823
[244]824  ///Default traits class of bfs() function.
[100]825
[244]826  ///Default traits class of bfs() function.
[157]827  ///\tparam GR Digraph type.
[100]828  template<class GR>
829  struct BfsWizardDefaultTraits
830  {
[244]831    ///The type of the digraph the algorithm runs on.
[100]832    typedef GR Digraph;
[244]833
834    ///\brief The type of the map that stores the predecessor
[100]835    ///arcs of the shortest paths.
[209]836    ///
[244]837    ///The type of the map that stores the predecessor
[100]838    ///arcs of the shortest paths.
[763]839    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[278]840    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
[301]841    ///Instantiates a PredMap.
[209]842
[301]843    ///This function instantiates a PredMap.
[244]844    ///\param g is the digraph, to which we would like to define the
[301]845    ///PredMap.
[244]846    static PredMap *createPredMap(const Digraph &g)
[100]847    {
[278]848      return new PredMap(g);
[100]849    }
850
851    ///The type of the map that indicates which nodes are processed.
[209]852
[100]853    ///The type of the map that indicates which nodes are processed.
[763]854    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[833]855    ///By default, it is a NullMap.
[100]856    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
[301]857    ///Instantiates a ProcessedMap.
[209]858
[301]859    ///This function instantiates a ProcessedMap.
[100]860    ///\param g is the digraph, to which
[301]861    ///we would like to define the ProcessedMap.
[100]862#ifdef DOXYGEN
[244]863    static ProcessedMap *createProcessedMap(const Digraph &g)
[100]864#else
[244]865    static ProcessedMap *createProcessedMap(const Digraph &)
[100]866#endif
867    {
868      return new ProcessedMap();
869    }
[244]870
[100]871    ///The type of the map that indicates which nodes are reached.
[209]872
[100]873    ///The type of the map that indicates which nodes are reached.
[763]874    ///It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]875    typedef typename Digraph::template NodeMap<bool> ReachedMap;
[301]876    ///Instantiates a ReachedMap.
[209]877
[301]878    ///This function instantiates a ReachedMap.
[244]879    ///\param g is the digraph, to which
[301]880    ///we would like to define the ReachedMap.
[244]881    static ReachedMap *createReachedMap(const Digraph &g)
[100]882    {
[244]883      return new ReachedMap(g);
[100]884    }
[209]885
[244]886    ///The type of the map that stores the distances of the nodes.
887
888    ///The type of the map that stores the distances of the nodes.
[763]889    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[278]890    typedef typename Digraph::template NodeMap<int> DistMap;
[301]891    ///Instantiates a DistMap.
[209]892
[301]893    ///This function instantiates a DistMap.
[210]894    ///\param g is the digraph, to which we would like to define
[301]895    ///the DistMap
[244]896    static DistMap *createDistMap(const Digraph &g)
[100]897    {
[278]898      return new DistMap(g);
[100]899    }
[278]900
901    ///The type of the shortest paths.
902
903    ///The type of the shortest paths.
[763]904    ///It must conform to the \ref concepts::Path "Path" concept.
[278]905    typedef lemon::Path<Digraph> Path;
[100]906  };
[209]907
[301]908  /// Default traits class used by BfsWizard
[100]909
[763]910  /// Default traits class used by BfsWizard.
911  /// \tparam GR The type of the digraph.
[100]912  template<class GR>
913  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
914  {
915
916    typedef BfsWizardDefaultTraits<GR> Base;
917  protected:
[244]918    //The type of the nodes in the digraph.
[100]919    typedef typename Base::Digraph::Node Node;
920
[244]921    //Pointer to the digraph the algorithm runs on.
[100]922    void *_g;
[244]923    //Pointer to the map of reached nodes.
[100]924    void *_reached;
[244]925    //Pointer to the map of processed nodes.
[100]926    void *_processed;
[244]927    //Pointer to the map of predecessors arcs.
[100]928    void *_pred;
[244]929    //Pointer to the map of distances.
[100]930    void *_dist;
[278]931    //Pointer to the shortest path to the target node.
932    void *_path;
933    //Pointer to the distance of the target node.
934    int *_di;
[209]935
[100]936    public:
937    /// Constructor.
[209]938
[763]939    /// This constructor does not require parameters, it initiates
[278]940    /// all of the attributes to \c 0.
[100]941    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
[278]942                      _dist(0), _path(0), _di(0) {}
[100]943
944    /// Constructor.
[209]945
[278]946    /// This constructor requires one parameter,
947    /// others are initiated to \c 0.
[244]948    /// \param g The digraph the algorithm runs on.
[278]949    BfsWizardBase(const GR &g) :
[209]950      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
[278]951      _reached(0), _processed(0), _pred(0), _dist(0),  _path(0), _di(0) {}
[100]952
953  };
[209]954
[278]955  /// Auxiliary class for the function-type interface of BFS algorithm.
[100]956
[278]957  /// This auxiliary class is created to implement the
958  /// \ref bfs() "function-type interface" of \ref Bfs algorithm.
[421]959  /// It does not have own \ref run(Node) "run()" method, it uses the
960  /// functions and features of the plain \ref Bfs.
[100]961  ///
[278]962  /// This class should only be used through the \ref bfs() function,
963  /// which makes it easier to use the algorithm.
[100]964  template<class TR>
965  class BfsWizard : public TR
966  {
967    typedef TR Base;
968
969    typedef typename TR::Digraph Digraph;
[244]970
[100]971    typedef typename Digraph::Node Node;
972    typedef typename Digraph::NodeIt NodeIt;
973    typedef typename Digraph::Arc Arc;
974    typedef typename Digraph::OutArcIt OutArcIt;
[209]975
[100]976    typedef typename TR::PredMap PredMap;
977    typedef typename TR::DistMap DistMap;
[244]978    typedef typename TR::ReachedMap ReachedMap;
979    typedef typename TR::ProcessedMap ProcessedMap;
[278]980    typedef typename TR::Path Path;
[100]981
982  public:
[244]983
[100]984    /// Constructor.
985    BfsWizard() : TR() {}
986
987    /// Constructor that requires parameters.
988
989    /// Constructor that requires parameters.
990    /// These parameters will be the default values for the traits class.
[278]991    /// \param g The digraph the algorithm runs on.
992    BfsWizard(const Digraph &g) :
993      TR(g) {}
[100]994
995    ///Copy constructor
996    BfsWizard(const TR &b) : TR(b) {}
997
998    ~BfsWizard() {}
999
[278]1000    ///Runs BFS algorithm from the given source node.
[209]1001
[278]1002    ///This method runs BFS algorithm from node \c s
1003    ///in order to compute the shortest path to each node.
1004    void run(Node s)
1005    {
1006      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1007      if (Base::_pred)
1008        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1009      if (Base::_dist)
1010        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1011      if (Base::_reached)
1012        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1013      if (Base::_processed)
1014        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1015      if (s!=INVALID)
1016        alg.run(s);
1017      else
1018        alg.run();
1019    }
1020
1021    ///Finds the shortest path between \c s and \c t.
1022
1023    ///This method runs BFS algorithm from node \c s
1024    ///in order to compute the shortest path to node \c t
1025    ///(it stops searching when \c t is processed).
1026    ///
1027    ///\return \c true if \c t is reachable form \c s.
1028    bool run(Node s, Node t)
1029    {
1030      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1031      if (Base::_pred)
1032        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1033      if (Base::_dist)
1034        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1035      if (Base::_reached)
1036        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1037      if (Base::_processed)
1038        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1039      alg.run(s,t);
1040      if (Base::_path)
1041        *reinterpret_cast<Path*>(Base::_path) = alg.path(t);
1042      if (Base::_di)
1043        *Base::_di = alg.dist(t);
1044      return alg.reached(t);
1045    }
1046
1047    ///Runs BFS algorithm to visit all nodes in the digraph.
1048
1049    ///This method runs BFS algorithm in order to compute
1050    ///the shortest path to each node.
[100]1051    void run()
1052    {
[278]1053      run(INVALID);
[100]1054    }
[209]1055
[244]1056    template<class T>
[257]1057    struct SetPredMapBase : public Base {
[244]1058      typedef T PredMap;
1059      static PredMap *createPredMap(const Digraph &) { return 0; };
[257]1060      SetPredMapBase(const TR &b) : TR(b) {}
[244]1061    };
[763]1062
1063    ///\brief \ref named-templ-param "Named parameter" for setting
1064    ///the predecessor map.
[244]1065    ///
[763]1066    ///\ref named-templ-param "Named parameter" function for setting
1067    ///the map that stores the predecessor arcs of the nodes.
[244]1068    template<class T>
[257]1069    BfsWizard<SetPredMapBase<T> > predMap(const T &t)
[244]1070    {
1071      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1072      return BfsWizard<SetPredMapBase<T> >(*this);
[244]1073    }
1074
1075    template<class T>
[257]1076    struct SetReachedMapBase : public Base {
[244]1077      typedef T ReachedMap;
1078      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
[257]1079      SetReachedMapBase(const TR &b) : TR(b) {}
[244]1080    };
[763]1081
1082    ///\brief \ref named-templ-param "Named parameter" for setting
1083    ///the reached map.
[244]1084    ///
[763]1085    ///\ref named-templ-param "Named parameter" function for setting
1086    ///the map that indicates which nodes are reached.
[244]1087    template<class T>
[257]1088    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)
[244]1089    {
1090      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1091      return BfsWizard<SetReachedMapBase<T> >(*this);
[244]1092    }
1093
1094    template<class T>
[278]1095    struct SetDistMapBase : public Base {
1096      typedef T DistMap;
1097      static DistMap *createDistMap(const Digraph &) { return 0; };
1098      SetDistMapBase(const TR &b) : TR(b) {}
1099    };
[763]1100
1101    ///\brief \ref named-templ-param "Named parameter" for setting
1102    ///the distance map.
[278]1103    ///
[763]1104    ///\ref named-templ-param "Named parameter" function for setting
1105    ///the map that stores the distances of the nodes calculated
1106    ///by the algorithm.
[278]1107    template<class T>
1108    BfsWizard<SetDistMapBase<T> > distMap(const T &t)
1109    {
1110      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1111      return BfsWizard<SetDistMapBase<T> >(*this);
1112    }
1113
1114    template<class T>
[257]1115    struct SetProcessedMapBase : public Base {
[244]1116      typedef T ProcessedMap;
1117      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
[257]1118      SetProcessedMapBase(const TR &b) : TR(b) {}
[244]1119    };
[763]1120
1121    ///\brief \ref named-func-param "Named parameter" for setting
1122    ///the processed map.
[244]1123    ///
[763]1124    ///\ref named-templ-param "Named parameter" function for setting
1125    ///the map that indicates which nodes are processed.
[244]1126    template<class T>
[257]1127    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)
[244]1128    {
1129      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1130      return BfsWizard<SetProcessedMapBase<T> >(*this);
[244]1131    }
1132
1133    template<class T>
[278]1134    struct SetPathBase : public Base {
1135      typedef T Path;
1136      SetPathBase(const TR &b) : TR(b) {}
[244]1137    };
[278]1138    ///\brief \ref named-func-param "Named parameter"
1139    ///for getting the shortest path to the target node.
[244]1140    ///
[278]1141    ///\ref named-func-param "Named parameter"
1142    ///for getting the shortest path to the target node.
[244]1143    template<class T>
[278]1144    BfsWizard<SetPathBase<T> > path(const T &t)
[244]1145    {
[278]1146      Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t));
1147      return BfsWizard<SetPathBase<T> >(*this);
1148    }
1149
1150    ///\brief \ref named-func-param "Named parameter"
1151    ///for getting the distance of the target node.
1152    ///
1153    ///\ref named-func-param "Named parameter"
1154    ///for getting the distance of the target node.
1155    BfsWizard dist(const int &d)
1156    {
1157      Base::_di=const_cast<int*>(&d);
1158      return *this;
[244]1159    }
1160
[100]1161  };
[209]1162
[278]1163  ///Function-type interface for BFS algorithm.
[100]1164
1165  /// \ingroup search
[278]1166  ///Function-type interface for BFS algorithm.
[100]1167  ///
[278]1168  ///This function also has several \ref named-func-param "named parameters",
[100]1169  ///they are declared as the members of class \ref BfsWizard.
[278]1170  ///The following examples show how to use these parameters.
[100]1171  ///\code
[278]1172  ///  // Compute shortest path from node s to each node
1173  ///  bfs(g).predMap(preds).distMap(dists).run(s);
1174  ///
1175  ///  // Compute shortest path from s to t
1176  ///  bool reached = bfs(g).path(p).dist(d).run(s,t);
[100]1177  ///\endcode
[421]1178  ///\warning Don't forget to put the \ref BfsWizard::run(Node) "run()"
[100]1179  ///to the end of the parameter list.
1180  ///\sa BfsWizard
1181  ///\sa Bfs
1182  template<class GR>
1183  BfsWizard<BfsWizardBase<GR> >
[278]1184  bfs(const GR &digraph)
[100]1185  {
[278]1186    return BfsWizard<BfsWizardBase<GR> >(digraph);
[100]1187  }
1188
1189#ifdef DOXYGEN
[244]1190  /// \brief Visitor class for BFS.
[209]1191  ///
[100]1192  /// This class defines the interface of the BfsVisit events, and
[244]1193  /// it could be the base of a real visitor class.
[525]1194  template <typename GR>
[100]1195  struct BfsVisitor {
[525]1196    typedef GR Digraph;
[100]1197    typedef typename Digraph::Arc Arc;
1198    typedef typename Digraph::Node Node;
[244]1199    /// \brief Called for the source node(s) of the BFS.
[209]1200    ///
[244]1201    /// This function is called for the source node(s) of the BFS.
1202    void start(const Node& node) {}
1203    /// \brief Called when a node is reached first time.
1204    ///
1205    /// This function is called when a node is reached first time.
1206    void reach(const Node& node) {}
1207    /// \brief Called when a node is processed.
1208    ///
1209    /// This function is called when a node is processed.
1210    void process(const Node& node) {}
1211    /// \brief Called when an arc reaches a new node.
1212    ///
1213    /// This function is called when the BFS finds an arc whose target node
1214    /// is not reached yet.
[100]1215    void discover(const Arc& arc) {}
[244]1216    /// \brief Called when an arc is examined but its target node is
[100]1217    /// already discovered.
[209]1218    ///
[244]1219    /// This function is called when an arc is examined but its target node is
[100]1220    /// already discovered.
1221    void examine(const Arc& arc) {}
1222  };
1223#else
[525]1224  template <typename GR>
[100]1225  struct BfsVisitor {
[525]1226    typedef GR Digraph;
[100]1227    typedef typename Digraph::Arc Arc;
1228    typedef typename Digraph::Node Node;
[244]1229    void start(const Node&) {}
1230    void reach(const Node&) {}
1231    void process(const Node&) {}
[100]1232    void discover(const Arc&) {}
1233    void examine(const Arc&) {}
1234
1235    template <typename _Visitor>
1236    struct Constraints {
1237      void constraints() {
[209]1238        Arc arc;
1239        Node node;
[244]1240        visitor.start(node);
1241        visitor.reach(node);
1242        visitor.process(node);
[209]1243        visitor.discover(arc);
1244        visitor.examine(arc);
[100]1245      }
1246      _Visitor& visitor;
1247    };
1248  };
1249#endif
1250
1251  /// \brief Default traits class of BfsVisit class.
1252  ///
1253  /// Default traits class of BfsVisit class.
[525]1254  /// \tparam GR The type of the digraph the algorithm runs on.
1255  template<class GR>
[100]1256  struct BfsVisitDefaultTraits {
1257
[244]1258    /// \brief The type of the digraph the algorithm runs on.
[525]1259    typedef GR Digraph;
[100]1260
1261    /// \brief The type of the map that indicates which nodes are reached.
[209]1262    ///
[100]1263    /// The type of the map that indicates which nodes are reached.
[763]1264    /// It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]1265    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1266
[301]1267    /// \brief Instantiates a ReachedMap.
[100]1268    ///
[301]1269    /// This function instantiates a ReachedMap.
[100]1270    /// \param digraph is the digraph, to which
[301]1271    /// we would like to define the ReachedMap.
[100]1272    static ReachedMap *createReachedMap(const Digraph &digraph) {
1273      return new ReachedMap(digraph);
1274    }
1275
1276  };
1277
1278  /// \ingroup search
[209]1279  ///
[525]1280  /// \brief BFS algorithm class with visitor interface.
[209]1281  ///
[525]1282  /// This class provides an efficient implementation of the BFS algorithm
[100]1283  /// with visitor interface.
1284  ///
[525]1285  /// The BfsVisit class provides an alternative interface to the Bfs
[100]1286  /// class. It works with callback mechanism, the BfsVisit object calls
[244]1287  /// the member functions of the \c Visitor class on every BFS event.
[100]1288  ///
[252]1289  /// This interface of the BFS algorithm should be used in special cases
1290  /// when extra actions have to be performed in connection with certain
1291  /// events of the BFS algorithm. Otherwise consider to use Bfs or bfs()
1292  /// instead.
1293  ///
[525]1294  /// \tparam GR The type of the digraph the algorithm runs on.
1295  /// The default type is \ref ListDigraph.
1296  /// The value of GR is not used directly by \ref BfsVisit,
1297  /// it is only passed to \ref BfsVisitDefaultTraits.
1298  /// \tparam VS The Visitor type that is used by the algorithm.
1299  /// \ref BfsVisitor "BfsVisitor<GR>" is an empty visitor, which
[244]1300  /// does not observe the BFS events. If you want to observe the BFS
1301  /// events, you should implement your own visitor class.
[525]1302  /// \tparam TR Traits class to set various data types used by the
[100]1303  /// algorithm. The default traits class is
[525]1304  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<GR>".
[100]1305  /// See \ref BfsVisitDefaultTraits for the documentation of
[244]1306  /// a BFS visit traits class.
[100]1307#ifdef DOXYGEN
[525]1308  template <typename GR, typename VS, typename TR>
[100]1309#else
[525]1310  template <typename GR = ListDigraph,
1311            typename VS = BfsVisitor<GR>,
1312            typename TR = BfsVisitDefaultTraits<GR> >
[100]1313#endif
1314  class BfsVisit {
1315  public:
[209]1316
[244]1317    ///The traits class.
[525]1318    typedef TR Traits;
[100]1319
[244]1320    ///The type of the digraph the algorithm runs on.
[100]1321    typedef typename Traits::Digraph Digraph;
1322
[244]1323    ///The visitor type used by the algorithm.
[525]1324    typedef VS Visitor;
[100]1325
[244]1326    ///The type of the map that indicates which nodes are reached.
[100]1327    typedef typename Traits::ReachedMap ReachedMap;
1328
1329  private:
1330
1331    typedef typename Digraph::Node Node;
1332    typedef typename Digraph::NodeIt NodeIt;
1333    typedef typename Digraph::Arc Arc;
1334    typedef typename Digraph::OutArcIt OutArcIt;
1335
[244]1336    //Pointer to the underlying digraph.
[100]1337    const Digraph *_digraph;
[244]1338    //Pointer to the visitor object.
[100]1339    Visitor *_visitor;
[244]1340    //Pointer to the map of reached status of the nodes.
[100]1341    ReachedMap *_reached;
[244]1342    //Indicates if _reached is locally allocated (true) or not.
[100]1343    bool local_reached;
1344
1345    std::vector<typename Digraph::Node> _list;
1346    int _list_front, _list_back;
1347
[280]1348    //Creates the maps if necessary.
[100]1349    void create_maps() {
1350      if(!_reached) {
[209]1351        local_reached = true;
1352        _reached = Traits::createReachedMap(*_digraph);
[100]1353      }
1354    }
1355
1356  protected:
1357
1358    BfsVisit() {}
[209]1359
[100]1360  public:
1361
1362    typedef BfsVisit Create;
1363
[421]1364    /// \name Named Template Parameters
[100]1365
1366    ///@{
1367    template <class T>
[257]1368    struct SetReachedMapTraits : public Traits {
[100]1369      typedef T ReachedMap;
1370      static ReachedMap *createReachedMap(const Digraph &digraph) {
[290]1371        LEMON_ASSERT(false, "ReachedMap is not initialized");
1372        return 0; // ignore warnings
[100]1373      }
1374    };
[209]1375    /// \brief \ref named-templ-param "Named parameter" for setting
[244]1376    /// ReachedMap type.
[100]1377    ///
[244]1378    /// \ref named-templ-param "Named parameter" for setting ReachedMap type.
[100]1379    template <class T>
[257]1380    struct SetReachedMap : public BfsVisit< Digraph, Visitor,
1381                                            SetReachedMapTraits<T> > {
1382      typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create;
[100]1383    };
1384    ///@}
1385
[209]1386  public:
1387
[100]1388    /// \brief Constructor.
1389    ///
1390    /// Constructor.
1391    ///
[244]1392    /// \param digraph The digraph the algorithm runs on.
1393    /// \param visitor The visitor object of the algorithm.
[209]1394    BfsVisit(const Digraph& digraph, Visitor& visitor)
[100]1395      : _digraph(&digraph), _visitor(&visitor),
[209]1396        _reached(0), local_reached(false) {}
1397
[100]1398    /// \brief Destructor.
1399    ~BfsVisit() {
1400      if(local_reached) delete _reached;
1401    }
1402
[244]1403    /// \brief Sets the map that indicates which nodes are reached.
[100]1404    ///
[244]1405    /// Sets the map that indicates which nodes are reached.
[421]1406    /// If you don't use this function before calling \ref run(Node) "run()"
1407    /// or \ref init(), an instance will be allocated automatically.
1408    /// The destructor deallocates this automatically allocated map,
1409    /// of course.
[100]1410    /// \return <tt> (*this) </tt>
1411    BfsVisit &reachedMap(ReachedMap &m) {
1412      if(local_reached) {
[209]1413        delete _reached;
1414        local_reached = false;
[100]1415      }
1416      _reached = &m;
1417      return *this;
1418    }
1419
1420  public:
[244]1421
[421]1422    /// \name Execution Control
1423    /// The simplest way to execute the BFS algorithm is to use one of the
1424    /// member functions called \ref run(Node) "run()".\n
[760]1425    /// If you need better control on the execution, you have to call
1426    /// \ref init() first, then you can add several source nodes with
[421]1427    /// \ref addSource(). Finally the actual path computation can be
1428    /// performed with one of the \ref start() functions.
[100]1429
1430    /// @{
[244]1431
[100]1432    /// \brief Initializes the internal data structures.
1433    ///
1434    /// Initializes the internal data structures.
1435    void init() {
1436      create_maps();
1437      _list.resize(countNodes(*_digraph));
1438      _list_front = _list_back = -1;
1439      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
[209]1440        _reached->set(u, false);
[100]1441      }
1442    }
[209]1443
[100]1444    /// \brief Adds a new source node.
1445    ///
1446    /// Adds a new source node to the set of nodes to be processed.
1447    void addSource(Node s) {
1448      if(!(*_reached)[s]) {
[209]1449          _reached->set(s,true);
1450          _visitor->start(s);
1451          _visitor->reach(s);
[100]1452          _list[++_list_back] = s;
[209]1453        }
[100]1454    }
[209]1455
[100]1456    /// \brief Processes the next node.
1457    ///
1458    /// Processes the next node.
1459    ///
1460    /// \return The processed node.
1461    ///
[244]1462    /// \pre The queue must not be empty.
[209]1463    Node processNextNode() {
[100]1464      Node n = _list[++_list_front];
1465      _visitor->process(n);
1466      Arc e;
1467      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1468        Node m = _digraph->target(e);
1469        if (!(*_reached)[m]) {
1470          _visitor->discover(e);
1471          _visitor->reach(m);
1472          _reached->set(m, true);
1473          _list[++_list_back] = m;
1474        } else {
1475          _visitor->examine(e);
1476        }
1477      }
1478      return n;
1479    }
1480
1481    /// \brief Processes the next node.
1482    ///
[244]1483    /// Processes the next node and checks if the given target node
[100]1484    /// is reached. If the target node is reachable from the processed
[244]1485    /// node, then the \c reach parameter will be set to \c true.
[100]1486    ///
1487    /// \param target The target node.
[244]1488    /// \retval reach Indicates if the target node is reached.
1489    /// It should be initially \c false.
1490    ///
[100]1491    /// \return The processed node.
1492    ///
[244]1493    /// \pre The queue must not be empty.
[100]1494    Node processNextNode(Node target, bool& reach) {
1495      Node n = _list[++_list_front];
1496      _visitor->process(n);
1497      Arc e;
1498      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1499        Node m = _digraph->target(e);
1500        if (!(*_reached)[m]) {
1501          _visitor->discover(e);
1502          _visitor->reach(m);
1503          _reached->set(m, true);
1504          _list[++_list_back] = m;
1505          reach = reach || (target == m);
1506        } else {
1507          _visitor->examine(e);
1508        }
1509      }
1510      return n;
1511    }
1512
1513    /// \brief Processes the next node.
1514    ///
[244]1515    /// Processes the next node and checks if at least one of reached
1516    /// nodes has \c true value in the \c nm node map. If one node
1517    /// with \c true value is reachable from the processed node, then the
1518    /// \c rnode parameter will be set to the first of such nodes.
[100]1519    ///
[244]1520    /// \param nm A \c bool (or convertible) node map that indicates the
1521    /// possible targets.
[100]1522    /// \retval rnode The reached target node.
[244]1523    /// It should be initially \c INVALID.
1524    ///
[100]1525    /// \return The processed node.
1526    ///
[244]1527    /// \pre The queue must not be empty.
[100]1528    template <typename NM>
1529    Node processNextNode(const NM& nm, Node& rnode) {
1530      Node n = _list[++_list_front];
1531      _visitor->process(n);
1532      Arc e;
1533      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1534        Node m = _digraph->target(e);
1535        if (!(*_reached)[m]) {
1536          _visitor->discover(e);
1537          _visitor->reach(m);
1538          _reached->set(m, true);
1539          _list[++_list_back] = m;
1540          if (nm[m] && rnode == INVALID) rnode = m;
1541        } else {
1542          _visitor->examine(e);
1543        }
1544      }
1545      return n;
1546    }
1547
[244]1548    /// \brief The next node to be processed.
[100]1549    ///
[244]1550    /// Returns the next node to be processed or \c INVALID if the queue
1551    /// is empty.
1552    Node nextNode() const {
[100]1553      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1554    }
1555
1556    /// \brief Returns \c false if there are nodes
[244]1557    /// to be processed.
[100]1558    ///
1559    /// Returns \c false if there are nodes
[244]1560    /// to be processed in the queue.
1561    bool emptyQueue() const { return _list_front == _list_back; }
[100]1562
1563    /// \brief Returns the number of the nodes to be processed.
1564    ///
1565    /// Returns the number of the nodes to be processed in the queue.
[244]1566    int queueSize() const { return _list_back - _list_front; }
[209]1567
[100]1568    /// \brief Executes the algorithm.
1569    ///
1570    /// Executes the algorithm.
1571    ///
[244]1572    /// This method runs the %BFS algorithm from the root node(s)
1573    /// in order to compute the shortest path to each node.
1574    ///
1575    /// The algorithm computes
1576    /// - the shortest path tree (forest),
1577    /// - the distance of each node from the root(s).
1578    ///
1579    /// \pre init() must be called and at least one root node should be added
[100]1580    /// with addSource() before using this function.
[244]1581    ///
1582    /// \note <tt>b.start()</tt> is just a shortcut of the following code.
1583    /// \code
1584    ///   while ( !b.emptyQueue() ) {
1585    ///     b.processNextNode();
1586    ///   }
1587    /// \endcode
[100]1588    void start() {
1589      while ( !emptyQueue() ) processNextNode();
1590    }
[209]1591
[244]1592    /// \brief Executes the algorithm until the given target node is reached.
[100]1593    ///
[244]1594    /// Executes the algorithm until the given target node is reached.
[100]1595    ///
[244]1596    /// This method runs the %BFS algorithm from the root node(s)
[286]1597    /// in order to compute the shortest path to \c t.
[244]1598    ///
1599    /// The algorithm computes
[286]1600    /// - the shortest path to \c t,
1601    /// - the distance of \c t from the root(s).
[244]1602    ///
1603    /// \pre init() must be called and at least one root node should be
1604    /// added with addSource() before using this function.
1605    ///
1606    /// \note <tt>b.start(t)</tt> is just a shortcut of the following code.
1607    /// \code
1608    ///   bool reach = false;
1609    ///   while ( !b.emptyQueue() && !reach ) {
1610    ///     b.processNextNode(t, reach);
1611    ///   }
1612    /// \endcode
[286]1613    void start(Node t) {
[100]1614      bool reach = false;
[286]1615      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
[100]1616    }
[209]1617
[100]1618    /// \brief Executes the algorithm until a condition is met.
1619    ///
1620    /// Executes the algorithm until a condition is met.
1621    ///
[244]1622    /// This method runs the %BFS algorithm from the root node(s) in
1623    /// order to compute the shortest path to a node \c v with
1624    /// <tt>nm[v]</tt> true, if such a node can be found.
[100]1625    ///
[244]1626    /// \param nm must be a bool (or convertible) node map. The
1627    /// algorithm will stop when it reaches a node \c v with
[100]1628    /// <tt>nm[v]</tt> true.
1629    ///
[244]1630    /// \return The reached node \c v with <tt>nm[v]</tt> true or
1631    /// \c INVALID if no such node was found.
1632    ///
1633    /// \pre init() must be called and at least one root node should be
1634    /// added with addSource() before using this function.
1635    ///
1636    /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code.
1637    /// \code
1638    ///   Node rnode = INVALID;
1639    ///   while ( !b.emptyQueue() && rnode == INVALID ) {
1640    ///     b.processNextNode(nm, rnode);
1641    ///   }
1642    ///   return rnode;
1643    /// \endcode
[100]1644    template <typename NM>
1645    Node start(const NM &nm) {
1646      Node rnode = INVALID;
1647      while ( !emptyQueue() && rnode == INVALID ) {
[209]1648        processNextNode(nm, rnode);
[100]1649      }
1650      return rnode;
1651    }
1652
[286]1653    /// \brief Runs the algorithm from the given source node.
[100]1654    ///
[244]1655    /// This method runs the %BFS algorithm from node \c s
1656    /// in order to compute the shortest path to each node.
1657    ///
1658    /// The algorithm computes
1659    /// - the shortest path tree,
1660    /// - the distance of each node from the root.
1661    ///
1662    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
[100]1663    ///\code
1664    ///   b.init();
1665    ///   b.addSource(s);
1666    ///   b.start();
1667    ///\endcode
1668    void run(Node s) {
1669      init();
1670      addSource(s);
1671      start();
1672    }
1673
[286]1674    /// \brief Finds the shortest path between \c s and \c t.
1675    ///
1676    /// This method runs the %BFS algorithm from node \c s
1677    /// in order to compute the shortest path to node \c t
1678    /// (it stops searching when \c t is processed).
1679    ///
1680    /// \return \c true if \c t is reachable form \c s.
1681    ///
1682    /// \note Apart from the return value, <tt>b.run(s,t)</tt> is just a
1683    /// shortcut of the following code.
1684    ///\code
1685    ///   b.init();
1686    ///   b.addSource(s);
1687    ///   b.start(t);
1688    ///\endcode
1689    bool run(Node s,Node t) {
1690      init();
1691      addSource(s);
1692      start(t);
1693      return reached(t);
1694    }
1695
[244]1696    /// \brief Runs the algorithm to visit all nodes in the digraph.
[209]1697    ///
[100]1698    /// This method runs the %BFS algorithm in order to
[244]1699    /// compute the shortest path to each node.
[100]1700    ///
[244]1701    /// The algorithm computes
1702    /// - the shortest path tree (forest),
1703    /// - the distance of each node from the root(s).
1704    ///
1705    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
[100]1706    ///\code
1707    ///  b.init();
[244]1708    ///  for (NodeIt n(gr); n != INVALID; ++n) {
1709    ///    if (!b.reached(n)) {
1710    ///      b.addSource(n);
[100]1711    ///      b.start();
1712    ///    }
1713    ///  }
1714    ///\endcode
1715    void run() {
1716      init();
1717      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1718        if (!reached(it)) {
1719          addSource(it);
1720          start();
1721        }
1722      }
1723    }
[244]1724
[100]1725    ///@}
1726
1727    /// \name Query Functions
[421]1728    /// The results of the BFS algorithm can be obtained using these
[100]1729    /// functions.\n
[421]1730    /// Either \ref run(Node) "run()" or \ref start() should be called
1731    /// before using them.
1732
[100]1733    ///@{
1734
[763]1735    /// \brief Checks if the given node is reached from the root(s).
[100]1736    ///
[421]1737    /// Returns \c true if \c v is reached from the root(s).
1738    ///
1739    /// \pre Either \ref run(Node) "run()" or \ref init()
[100]1740    /// must be called before using this function.
[437]1741    bool reached(Node v) const { return (*_reached)[v]; }
[244]1742
[100]1743    ///@}
[244]1744
[100]1745  };
1746
1747} //END OF NAMESPACE LEMON
1748
1749#endif
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