COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/bfs.h @ 440:88ed40ad0d4f

Last change on this file since 440:88ed40ad0d4f was 440:88ed40ad0d4f, checked in by Alpar Juttner <alpar@…>, 11 years ago

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[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 *
[440]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.
50    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
[244]51    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
[301]52    ///Instantiates a PredMap.
[209]53
[405]54    ///This function instantiates a PredMap.
[244]55    ///\param g is the digraph, to which we would like to define the
[301]56    ///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.
65    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
66    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
[301]67    ///Instantiates a ProcessedMap.
[209]68
[301]69    ///This function instantiates a ProcessedMap.
[100]70    ///\param g is the digraph, to which
[301]71    ///we would like to define the ProcessedMap
[100]72#ifdef DOXYGEN
[244]73    static ProcessedMap *createProcessedMap(const Digraph &g)
[100]74#else
[244]75    static ProcessedMap *createProcessedMap(const Digraph &)
[100]76#endif
77    {
78      return new ProcessedMap();
79    }
[244]80
[100]81    ///The type of the map that indicates which nodes are reached.
[209]82
[405]83    ///The type of the map that indicates which nodes are reached.
84    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]85    typedef typename Digraph::template NodeMap<bool> ReachedMap;
[301]86    ///Instantiates a ReachedMap.
[209]87
[301]88    ///This function instantiates a ReachedMap.
[244]89    ///\param g is the digraph, to which
[301]90    ///we would like to define the ReachedMap.
[244]91    static ReachedMap *createReachedMap(const Digraph &g)
[100]92    {
[244]93      return new ReachedMap(g);
[100]94    }
[209]95
[244]96    ///The type of the map that stores the distances of the nodes.
97
98    ///The type of the map that stores the distances of the nodes.
[100]99    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
100    typedef typename Digraph::template NodeMap<int> DistMap;
[301]101    ///Instantiates a DistMap.
[209]102
[301]103    ///This function instantiates a DistMap.
[244]104    ///\param g is the digraph, to which we would like to define the
[301]105    ///DistMap.
[244]106    static DistMap *createDistMap(const Digraph &g)
[100]107    {
[244]108      return new DistMap(g);
[100]109    }
110  };
[209]111
[100]112  ///%BFS algorithm class.
[209]113
[100]114  ///\ingroup search
115  ///This class provides an efficient implementation of the %BFS algorithm.
116  ///
[278]117  ///There is also a \ref bfs() "function-type interface" for the BFS
[244]118  ///algorithm, which is convenient in the simplier cases and it can be
119  ///used easier.
120  ///
121  ///\tparam GR The type of the digraph the algorithm runs on.
[405]122  ///The default type is \ref ListDigraph.
[100]123#ifdef DOXYGEN
124  template <typename GR,
[209]125            typename TR>
[100]126#else
127  template <typename GR=ListDigraph,
[209]128            typename TR=BfsDefaultTraits<GR> >
[100]129#endif
130  class Bfs {
131  public:
132
[244]133    ///The type of the digraph the algorithm runs on.
[100]134    typedef typename TR::Digraph Digraph;
[209]135
[244]136    ///\brief The type of the map that stores the predecessor arcs of the
137    ///shortest paths.
[100]138    typedef typename TR::PredMap PredMap;
[244]139    ///The type of the map that stores the distances of the nodes.
140    typedef typename TR::DistMap DistMap;
141    ///The type of the map that indicates which nodes are reached.
[100]142    typedef typename TR::ReachedMap ReachedMap;
[244]143    ///The type of the map that indicates which nodes are processed.
[100]144    typedef typename TR::ProcessedMap ProcessedMap;
[244]145    ///The type of the paths.
146    typedef PredMapPath<Digraph, PredMap> Path;
147
[405]148    ///The \ref BfsDefaultTraits "traits class" of the algorithm.
[244]149    typedef TR Traits;
150
[100]151  private:
152
153    typedef typename Digraph::Node Node;
154    typedef typename Digraph::NodeIt NodeIt;
155    typedef typename Digraph::Arc Arc;
156    typedef typename Digraph::OutArcIt OutArcIt;
157
[244]158    //Pointer to the underlying digraph.
[100]159    const Digraph *G;
[244]160    //Pointer to the map of predecessor arcs.
[100]161    PredMap *_pred;
[244]162    //Indicates if _pred is locally allocated (true) or not.
[100]163    bool local_pred;
[244]164    //Pointer to the map of distances.
[100]165    DistMap *_dist;
[244]166    //Indicates if _dist is locally allocated (true) or not.
[100]167    bool local_dist;
[244]168    //Pointer to the map of reached status of the nodes.
[100]169    ReachedMap *_reached;
[244]170    //Indicates if _reached is locally allocated (true) or not.
[100]171    bool local_reached;
[244]172    //Pointer to the map of processed status of the nodes.
[100]173    ProcessedMap *_processed;
[244]174    //Indicates if _processed is locally allocated (true) or not.
[100]175    bool local_processed;
176
177    std::vector<typename Digraph::Node> _queue;
178    int _queue_head,_queue_tail,_queue_next_dist;
179    int _curr_dist;
180
[280]181    //Creates the maps if necessary.
[209]182    void create_maps()
[100]183    {
184      if(!_pred) {
[209]185        local_pred = true;
186        _pred = Traits::createPredMap(*G);
[100]187      }
188      if(!_dist) {
[209]189        local_dist = true;
190        _dist = Traits::createDistMap(*G);
[100]191      }
192      if(!_reached) {
[209]193        local_reached = true;
194        _reached = Traits::createReachedMap(*G);
[100]195      }
196      if(!_processed) {
[209]197        local_processed = true;
198        _processed = Traits::createProcessedMap(*G);
[100]199      }
200    }
201
202  protected:
[209]203
[100]204    Bfs() {}
[209]205
[100]206  public:
[209]207
[100]208    typedef Bfs Create;
209
[405]210    ///\name Named Template Parameters
[100]211
212    ///@{
213
214    template <class T>
[257]215    struct SetPredMapTraits : public Traits {
[100]216      typedef T PredMap;
[209]217      static PredMap *createPredMap(const Digraph &)
[100]218      {
[290]219        LEMON_ASSERT(false, "PredMap is not initialized");
220        return 0; // ignore warnings
[100]221      }
222    };
223    ///\brief \ref named-templ-param "Named parameter" for setting
[301]224    ///PredMap type.
[100]225    ///
[244]226    ///\ref named-templ-param "Named parameter" for setting
[301]227    ///PredMap type.
[405]228    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
[100]229    template <class T>
[257]230    struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > {
231      typedef Bfs< Digraph, SetPredMapTraits<T> > Create;
[100]232    };
[209]233
[100]234    template <class T>
[257]235    struct SetDistMapTraits : public Traits {
[100]236      typedef T DistMap;
[209]237      static DistMap *createDistMap(const Digraph &)
[100]238      {
[290]239        LEMON_ASSERT(false, "DistMap is not initialized");
240        return 0; // ignore warnings
[100]241      }
242    };
243    ///\brief \ref named-templ-param "Named parameter" for setting
[301]244    ///DistMap type.
[100]245    ///
[244]246    ///\ref named-templ-param "Named parameter" for setting
[301]247    ///DistMap type.
[405]248    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
[100]249    template <class T>
[257]250    struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > {
251      typedef Bfs< Digraph, SetDistMapTraits<T> > Create;
[100]252    };
[209]253
[100]254    template <class T>
[257]255    struct SetReachedMapTraits : public Traits {
[100]256      typedef T ReachedMap;
[209]257      static ReachedMap *createReachedMap(const Digraph &)
[100]258      {
[290]259        LEMON_ASSERT(false, "ReachedMap is not initialized");
260        return 0; // ignore warnings
[100]261      }
262    };
263    ///\brief \ref named-templ-param "Named parameter" for setting
[301]264    ///ReachedMap type.
[100]265    ///
[244]266    ///\ref named-templ-param "Named parameter" for setting
[301]267    ///ReachedMap type.
[405]268    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]269    template <class T>
[257]270    struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > {
271      typedef Bfs< Digraph, SetReachedMapTraits<T> > Create;
[100]272    };
[209]273
[100]274    template <class T>
[257]275    struct SetProcessedMapTraits : public Traits {
[100]276      typedef T ProcessedMap;
[209]277      static ProcessedMap *createProcessedMap(const Digraph &)
[100]278      {
[290]279        LEMON_ASSERT(false, "ProcessedMap is not initialized");
280        return 0; // ignore warnings
[100]281      }
282    };
283    ///\brief \ref named-templ-param "Named parameter" for setting
[301]284    ///ProcessedMap type.
[100]285    ///
[244]286    ///\ref named-templ-param "Named parameter" for setting
[301]287    ///ProcessedMap type.
[405]288    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
[100]289    template <class T>
[257]290    struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > {
291      typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create;
[100]292    };
[209]293
[257]294    struct SetStandardProcessedMapTraits : public Traits {
[100]295      typedef typename Digraph::template NodeMap<bool> ProcessedMap;
[244]296      static ProcessedMap *createProcessedMap(const Digraph &g)
[100]297      {
[244]298        return new ProcessedMap(g);
[290]299        return 0; // ignore warnings
[100]300      }
301    };
[244]302    ///\brief \ref named-templ-param "Named parameter" for setting
[301]303    ///ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
[100]304    ///
[244]305    ///\ref named-templ-param "Named parameter" for setting
[301]306    ///ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
[100]307    ///If you don't set it explicitly, it will be automatically allocated.
[257]308    struct SetStandardProcessedMap :
309      public Bfs< Digraph, SetStandardProcessedMapTraits > {
310      typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create;
[100]311    };
[209]312
[100]313    ///@}
314
[209]315  public:
316
[100]317    ///Constructor.
[209]318
[244]319    ///Constructor.
320    ///\param g The digraph the algorithm runs on.
321    Bfs(const Digraph &g) :
322      G(&g),
[100]323      _pred(NULL), local_pred(false),
324      _dist(NULL), local_dist(false),
325      _reached(NULL), local_reached(false),
326      _processed(NULL), local_processed(false)
327    { }
[209]328
[100]329    ///Destructor.
[209]330    ~Bfs()
[100]331    {
332      if(local_pred) delete _pred;
333      if(local_dist) delete _dist;
334      if(local_reached) delete _reached;
335      if(local_processed) delete _processed;
336    }
337
[244]338    ///Sets the map that stores the predecessor arcs.
[100]339
[244]340    ///Sets the map that stores the predecessor arcs.
[405]341    ///If you don't use this function before calling \ref run(Node) "run()"
342    ///or \ref init(), an instance will be allocated automatically.
343    ///The destructor deallocates this automatically allocated map,
344    ///of course.
[100]345    ///\return <tt> (*this) </tt>
[209]346    Bfs &predMap(PredMap &m)
[100]347    {
348      if(local_pred) {
[209]349        delete _pred;
350        local_pred=false;
[100]351      }
352      _pred = &m;
353      return *this;
354    }
355
[244]356    ///Sets the map that indicates which nodes are reached.
[100]357
[244]358    ///Sets the map that indicates which nodes are reached.
[405]359    ///If you don't use this function before calling \ref run(Node) "run()"
360    ///or \ref init(), an instance will be allocated automatically.
361    ///The destructor deallocates this automatically allocated map,
362    ///of course.
[100]363    ///\return <tt> (*this) </tt>
[209]364    Bfs &reachedMap(ReachedMap &m)
[100]365    {
366      if(local_reached) {
[209]367        delete _reached;
368        local_reached=false;
[100]369      }
370      _reached = &m;
371      return *this;
372    }
373
[244]374    ///Sets the map that indicates which nodes are processed.
[100]375
[244]376    ///Sets the map that indicates which nodes are processed.
[405]377    ///If you don't use this function before calling \ref run(Node) "run()"
378    ///or \ref init(), an instance will be allocated automatically.
379    ///The destructor deallocates this automatically allocated map,
380    ///of course.
[100]381    ///\return <tt> (*this) </tt>
[209]382    Bfs &processedMap(ProcessedMap &m)
[100]383    {
384      if(local_processed) {
[209]385        delete _processed;
386        local_processed=false;
[100]387      }
388      _processed = &m;
389      return *this;
390    }
391
[244]392    ///Sets the map that stores the distances of the nodes.
[100]393
[244]394    ///Sets the map that stores the distances of the nodes calculated by
395    ///the algorithm.
[405]396    ///If you don't use this function before calling \ref run(Node) "run()"
397    ///or \ref init(), an instance will be allocated automatically.
398    ///The destructor deallocates this automatically allocated map,
399    ///of course.
[100]400    ///\return <tt> (*this) </tt>
[209]401    Bfs &distMap(DistMap &m)
[100]402    {
403      if(local_dist) {
[209]404        delete _dist;
405        local_dist=false;
[100]406      }
407      _dist = &m;
408      return *this;
409    }
410
411  public:
[244]412
[405]413    ///\name Execution Control
414    ///The simplest way to execute the BFS algorithm is to use one of the
415    ///member functions called \ref run(Node) "run()".\n
416    ///If you need more control on the execution, first you have to call
417    ///\ref init(), then you can add several source nodes with
418    ///\ref addSource(). Finally the actual path computation can be
419    ///performed with one of the \ref start() functions.
[100]420
421    ///@{
422
[405]423    ///\brief Initializes the internal data structures.
424    ///
[244]425    ///Initializes the internal data structures.
[100]426    void init()
427    {
428      create_maps();
429      _queue.resize(countNodes(*G));
430      _queue_head=_queue_tail=0;
431      _curr_dist=1;
432      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
[209]433        _pred->set(u,INVALID);
434        _reached->set(u,false);
435        _processed->set(u,false);
[100]436      }
437    }
[209]438
[100]439    ///Adds a new source node.
440
441    ///Adds a new source node to the set of nodes to be processed.
442    ///
443    void addSource(Node s)
444    {
445      if(!(*_reached)[s])
[209]446        {
447          _reached->set(s,true);
448          _pred->set(s,INVALID);
449          _dist->set(s,0);
450          _queue[_queue_head++]=s;
451          _queue_next_dist=_queue_head;
452        }
[100]453    }
[209]454
[100]455    ///Processes the next node.
456
457    ///Processes the next node.
458    ///
459    ///\return The processed node.
460    ///
[244]461    ///\pre The queue must not be empty.
[100]462    Node processNextNode()
463    {
464      if(_queue_tail==_queue_next_dist) {
[209]465        _curr_dist++;
466        _queue_next_dist=_queue_head;
[100]467      }
468      Node n=_queue[_queue_tail++];
469      _processed->set(n,true);
470      Node m;
471      for(OutArcIt e(*G,n);e!=INVALID;++e)
[209]472        if(!(*_reached)[m=G->target(e)]) {
473          _queue[_queue_head++]=m;
474          _reached->set(m,true);
475          _pred->set(m,e);
476          _dist->set(m,_curr_dist);
477        }
[100]478      return n;
479    }
480
481    ///Processes the next node.
482
[244]483    ///Processes the next node and checks if the given target node
[100]484    ///is reached. If the target node is reachable from the processed
[244]485    ///node, then the \c reach parameter will be set to \c true.
[100]486    ///
487    ///\param target The target node.
[244]488    ///\retval reach Indicates if the target node is reached.
489    ///It should be initially \c false.
490    ///
[100]491    ///\return The processed node.
492    ///
[244]493    ///\pre The queue must not be empty.
[100]494    Node processNextNode(Node target, bool& reach)
495    {
496      if(_queue_tail==_queue_next_dist) {
[209]497        _curr_dist++;
498        _queue_next_dist=_queue_head;
[100]499      }
500      Node n=_queue[_queue_tail++];
501      _processed->set(n,true);
502      Node m;
503      for(OutArcIt e(*G,n);e!=INVALID;++e)
[209]504        if(!(*_reached)[m=G->target(e)]) {
505          _queue[_queue_head++]=m;
506          _reached->set(m,true);
507          _pred->set(m,e);
508          _dist->set(m,_curr_dist);
[100]509          reach = reach || (target == m);
[209]510        }
[100]511      return n;
512    }
513
514    ///Processes the next node.
515
[244]516    ///Processes the next node and checks if at least one of reached
517    ///nodes has \c true value in the \c nm node map. If one node
518    ///with \c true value is reachable from the processed node, then the
519    ///\c rnode parameter will be set to the first of such nodes.
[100]520    ///
[244]521    ///\param nm A \c bool (or convertible) node map that indicates the
522    ///possible targets.
[100]523    ///\retval rnode The reached target node.
[244]524    ///It should be initially \c INVALID.
525    ///
[100]526    ///\return The processed node.
527    ///
[244]528    ///\pre The queue must not be empty.
[100]529    template<class NM>
530    Node processNextNode(const NM& nm, Node& rnode)
531    {
532      if(_queue_tail==_queue_next_dist) {
[209]533        _curr_dist++;
534        _queue_next_dist=_queue_head;
[100]535      }
536      Node n=_queue[_queue_tail++];
537      _processed->set(n,true);
538      Node m;
539      for(OutArcIt e(*G,n);e!=INVALID;++e)
[209]540        if(!(*_reached)[m=G->target(e)]) {
541          _queue[_queue_head++]=m;
542          _reached->set(m,true);
543          _pred->set(m,e);
544          _dist->set(m,_curr_dist);
545          if (nm[m] && rnode == INVALID) rnode = m;
546        }
[100]547      return n;
548    }
[209]549
[244]550    ///The next node to be processed.
[100]551
[244]552    ///Returns the next node to be processed or \c INVALID if the queue
553    ///is empty.
554    Node nextNode() const
[209]555    {
[100]556      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
557    }
[209]558
[405]559    ///Returns \c false if there are nodes to be processed.
560
561    ///Returns \c false if there are nodes to be processed
562    ///in the queue.
[244]563    bool emptyQueue() const { return _queue_tail==_queue_head; }
564
[100]565    ///Returns the number of the nodes to be processed.
[209]566
[405]567    ///Returns the number of the nodes to be processed
568    ///in the queue.
[244]569    int queueSize() const { return _queue_head-_queue_tail; }
[209]570
[100]571    ///Executes the algorithm.
572
573    ///Executes the algorithm.
574    ///
[244]575    ///This method runs the %BFS algorithm from the root node(s)
576    ///in order to compute the shortest path to each node.
[100]577    ///
[244]578    ///The algorithm computes
579    ///- the shortest path tree (forest),
580    ///- the distance of each node from the root(s).
581    ///
582    ///\pre init() must be called and at least one root node should be
583    ///added with addSource() before using this function.
584    ///
585    ///\note <tt>b.start()</tt> is just a shortcut of the following code.
586    ///\code
587    ///  while ( !b.emptyQueue() ) {
588    ///    b.processNextNode();
589    ///  }
590    ///\endcode
[100]591    void start()
592    {
593      while ( !emptyQueue() ) processNextNode();
594    }
[209]595
[244]596    ///Executes the algorithm until the given target node is reached.
[100]597
[244]598    ///Executes the algorithm until the given target node is reached.
[100]599    ///
600    ///This method runs the %BFS algorithm from the root node(s)
[286]601    ///in order to compute the shortest path to \c t.
[244]602    ///
[100]603    ///The algorithm computes
[286]604    ///- the shortest path to \c t,
605    ///- the distance of \c t from the root(s).
[244]606    ///
607    ///\pre init() must be called and at least one root node should be
608    ///added with addSource() before using this function.
609    ///
610    ///\note <tt>b.start(t)</tt> is just a shortcut of the following code.
611    ///\code
612    ///  bool reach = false;
613    ///  while ( !b.emptyQueue() && !reach ) {
614    ///    b.processNextNode(t, reach);
615    ///  }
616    ///\endcode
[286]617    void start(Node t)
[100]618    {
619      bool reach = false;
[286]620      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
[100]621    }
[209]622
[100]623    ///Executes the algorithm until a condition is met.
624
625    ///Executes the algorithm until a condition is met.
626    ///
[244]627    ///This method runs the %BFS algorithm from the root node(s) in
628    ///order to compute the shortest path to a node \c v with
629    /// <tt>nm[v]</tt> true, if such a node can be found.
[100]630    ///
[244]631    ///\param nm A \c bool (or convertible) node map. The algorithm
632    ///will stop when it reaches a node \c v with <tt>nm[v]</tt> true.
[100]633    ///
634    ///\return The reached node \c v with <tt>nm[v]</tt> true or
635    ///\c INVALID if no such node was found.
[244]636    ///
637    ///\pre init() must be called and at least one root node should be
638    ///added with addSource() before using this function.
639    ///
640    ///\note <tt>b.start(nm)</tt> is just a shortcut of the following code.
641    ///\code
642    ///  Node rnode = INVALID;
643    ///  while ( !b.emptyQueue() && rnode == INVALID ) {
644    ///    b.processNextNode(nm, rnode);
645    ///  }
646    ///  return rnode;
647    ///\endcode
648    template<class NodeBoolMap>
649    Node start(const NodeBoolMap &nm)
[100]650    {
651      Node rnode = INVALID;
652      while ( !emptyQueue() && rnode == INVALID ) {
[209]653        processNextNode(nm, rnode);
[100]654      }
655      return rnode;
656    }
[209]657
[286]658    ///Runs the algorithm from the given source node.
[209]659
[244]660    ///This method runs the %BFS algorithm from node \c s
661    ///in order to compute the shortest path to each node.
[100]662    ///
[244]663    ///The algorithm computes
664    ///- the shortest path tree,
665    ///- the distance of each node from the root.
666    ///
667    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
[100]668    ///\code
669    ///  b.init();
670    ///  b.addSource(s);
671    ///  b.start();
672    ///\endcode
673    void run(Node s) {
674      init();
675      addSource(s);
676      start();
677    }
[209]678
[100]679    ///Finds the shortest path between \c s and \c t.
[209]680
[244]681    ///This method runs the %BFS algorithm from node \c s
[286]682    ///in order to compute the shortest path to node \c t
683    ///(it stops searching when \c t is processed).
[100]684    ///
[286]685    ///\return \c true if \c t is reachable form \c s.
[244]686    ///
687    ///\note Apart from the return value, <tt>b.run(s,t)</tt> is just a
688    ///shortcut of the following code.
[100]689    ///\code
690    ///  b.init();
691    ///  b.addSource(s);
692    ///  b.start(t);
693    ///\endcode
[286]694    bool run(Node s,Node t) {
[100]695      init();
696      addSource(s);
697      start(t);
[286]698      return reached(t);
[100]699    }
[209]700
[244]701    ///Runs the algorithm to visit all nodes in the digraph.
702
703    ///This method runs the %BFS algorithm in order to
704    ///compute the shortest path to each node.
705    ///
706    ///The algorithm computes
707    ///- the shortest path tree (forest),
708    ///- the distance of each node from the root(s).
709    ///
710    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
711    ///\code
712    ///  b.init();
713    ///  for (NodeIt n(gr); n != INVALID; ++n) {
714    ///    if (!b.reached(n)) {
715    ///      b.addSource(n);
716    ///      b.start();
717    ///    }
718    ///  }
719    ///\endcode
720    void run() {
721      init();
722      for (NodeIt n(*G); n != INVALID; ++n) {
723        if (!reached(n)) {
724          addSource(n);
725          start();
726        }
727      }
728    }
729
[100]730    ///@}
731
732    ///\name Query Functions
[405]733    ///The results of the BFS algorithm can be obtained using these
[100]734    ///functions.\n
[405]735    ///Either \ref run(Node) "run()" or \ref start() should be called
736    ///before using them.
[209]737
[100]738    ///@{
739
[244]740    ///The shortest path to a node.
[100]741
[244]742    ///Returns the shortest path to a node.
743    ///
[405]744    ///\warning \c t should be reached from the root(s).
[244]745    ///
[405]746    ///\pre Either \ref run(Node) "run()" or \ref init()
747    ///must be called before using this function.
[244]748    Path path(Node t) const { return Path(*G, *_pred, t); }
[100]749
750    ///The distance of a node from the root(s).
751
752    ///Returns the distance of a node from the root(s).
[244]753    ///
[405]754    ///\warning If node \c v is not reached from the root(s), then
[244]755    ///the return value of this function is undefined.
756    ///
[405]757    ///\pre Either \ref run(Node) "run()" or \ref init()
758    ///must be called before using this function.
[100]759    int dist(Node v) const { return (*_dist)[v]; }
760
[244]761    ///Returns the 'previous arc' of the shortest path tree for a node.
[100]762
[244]763    ///This function returns the 'previous arc' of the shortest path
764    ///tree for the node \c v, i.e. it returns the last arc of a
[405]765    ///shortest path from a root to \c v. It is \c INVALID if \c v
766    ///is not reached from the root(s) or if \c v is a root.
[244]767    ///
768    ///The shortest path tree used here is equal to the shortest path
769    ///tree used in \ref predNode().
770    ///
[405]771    ///\pre Either \ref run(Node) "run()" or \ref init()
772    ///must be called before using this function.
[100]773    Arc predArc(Node v) const { return (*_pred)[v];}
774
[244]775    ///Returns the 'previous node' of the shortest path tree for a node.
[100]776
[244]777    ///This function returns the 'previous node' of the shortest path
778    ///tree for the node \c v, i.e. it returns the last but one node
[405]779    ///from a shortest path from a root to \c v. It is \c INVALID
780    ///if \c v is not reached from the root(s) or if \c v is a root.
[244]781    ///
[100]782    ///The shortest path tree used here is equal to the shortest path
783    ///tree used in \ref predArc().
[244]784    ///
[405]785    ///\pre Either \ref run(Node) "run()" or \ref init()
786    ///must be called before using this function.
[100]787    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
[209]788                                  G->source((*_pred)[v]); }
789
[244]790    ///\brief Returns a const reference to the node map that stores the
791    /// distances of the nodes.
792    ///
793    ///Returns a const reference to the node map that stores the distances
794    ///of the nodes calculated by the algorithm.
795    ///
[405]796    ///\pre Either \ref run(Node) "run()" or \ref init()
[244]797    ///must be called before using this function.
[100]798    const DistMap &distMap() const { return *_dist;}
[209]799
[244]800    ///\brief Returns a const reference to the node map that stores the
801    ///predecessor arcs.
802    ///
803    ///Returns a const reference to the node map that stores the predecessor
804    ///arcs, which form the shortest path tree.
805    ///
[405]806    ///\pre Either \ref run(Node) "run()" or \ref init()
[100]807    ///must be called before using this function.
808    const PredMap &predMap() const { return *_pred;}
[209]809
[405]810    ///Checks if a node is reached from the root(s).
[100]811
[405]812    ///Returns \c true if \c v is reached from the root(s).
813    ///
814    ///\pre Either \ref run(Node) "run()" or \ref init()
[100]815    ///must be called before using this function.
[244]816    bool reached(Node v) const { return (*_reached)[v]; }
[209]817
[100]818    ///@}
819  };
820
[244]821  ///Default traits class of bfs() function.
[100]822
[244]823  ///Default traits class of bfs() function.
[157]824  ///\tparam GR Digraph type.
[100]825  template<class GR>
826  struct BfsWizardDefaultTraits
827  {
[244]828    ///The type of the digraph the algorithm runs on.
[100]829    typedef GR Digraph;
[244]830
831    ///\brief The type of the map that stores the predecessor
[100]832    ///arcs of the shortest paths.
[209]833    ///
[244]834    ///The type of the map that stores the predecessor
[100]835    ///arcs of the shortest paths.
836    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
[278]837    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
[301]838    ///Instantiates a PredMap.
[209]839
[301]840    ///This function instantiates a PredMap.
[244]841    ///\param g is the digraph, to which we would like to define the
[301]842    ///PredMap.
[244]843    static PredMap *createPredMap(const Digraph &g)
[100]844    {
[278]845      return new PredMap(g);
[100]846    }
847
848    ///The type of the map that indicates which nodes are processed.
[209]849
[100]850    ///The type of the map that indicates which nodes are processed.
851    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
[278]852    ///By default it is a NullMap.
[100]853    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
[301]854    ///Instantiates a ProcessedMap.
[209]855
[301]856    ///This function instantiates a ProcessedMap.
[100]857    ///\param g is the digraph, to which
[301]858    ///we would like to define the ProcessedMap.
[100]859#ifdef DOXYGEN
[244]860    static ProcessedMap *createProcessedMap(const Digraph &g)
[100]861#else
[244]862    static ProcessedMap *createProcessedMap(const Digraph &)
[100]863#endif
864    {
865      return new ProcessedMap();
866    }
[244]867
[100]868    ///The type of the map that indicates which nodes are reached.
[209]869
[100]870    ///The type of the map that indicates which nodes are reached.
[244]871    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]872    typedef typename Digraph::template NodeMap<bool> ReachedMap;
[301]873    ///Instantiates a ReachedMap.
[209]874
[301]875    ///This function instantiates a ReachedMap.
[244]876    ///\param g is the digraph, to which
[301]877    ///we would like to define the ReachedMap.
[244]878    static ReachedMap *createReachedMap(const Digraph &g)
[100]879    {
[244]880      return new ReachedMap(g);
[100]881    }
[209]882
[244]883    ///The type of the map that stores the distances of the nodes.
884
885    ///The type of the map that stores the distances of the nodes.
[100]886    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
[278]887    typedef typename Digraph::template NodeMap<int> DistMap;
[301]888    ///Instantiates a DistMap.
[209]889
[301]890    ///This function instantiates a DistMap.
[210]891    ///\param g is the digraph, to which we would like to define
[301]892    ///the DistMap
[244]893    static DistMap *createDistMap(const Digraph &g)
[100]894    {
[278]895      return new DistMap(g);
[100]896    }
[278]897
898    ///The type of the shortest paths.
899
900    ///The type of the shortest paths.
901    ///It must meet the \ref concepts::Path "Path" concept.
902    typedef lemon::Path<Digraph> Path;
[100]903  };
[209]904
[301]905  /// Default traits class used by BfsWizard
[100]906
907  /// To make it easier to use Bfs algorithm
[244]908  /// we have created a wizard class.
[100]909  /// This \ref BfsWizard class needs default traits,
[244]910  /// as well as the \ref Bfs class.
[100]911  /// The \ref BfsWizardBase is a class to be the default traits of the
912  /// \ref BfsWizard class.
913  template<class GR>
914  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
915  {
916
917    typedef BfsWizardDefaultTraits<GR> Base;
918  protected:
[244]919    //The type of the nodes in the digraph.
[100]920    typedef typename Base::Digraph::Node Node;
921
[244]922    //Pointer to the digraph the algorithm runs on.
[100]923    void *_g;
[244]924    //Pointer to the map of reached nodes.
[100]925    void *_reached;
[244]926    //Pointer to the map of processed nodes.
[100]927    void *_processed;
[244]928    //Pointer to the map of predecessors arcs.
[100]929    void *_pred;
[244]930    //Pointer to the map of distances.
[100]931    void *_dist;
[278]932    //Pointer to the shortest path to the target node.
933    void *_path;
934    //Pointer to the distance of the target node.
935    int *_di;
[209]936
[100]937    public:
938    /// Constructor.
[209]939
[100]940    /// This constructor does not require parameters, therefore it initiates
[278]941    /// all of the attributes to \c 0.
[100]942    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
[278]943                      _dist(0), _path(0), _di(0) {}
[100]944
945    /// Constructor.
[209]946
[278]947    /// This constructor requires one parameter,
948    /// others are initiated to \c 0.
[244]949    /// \param g The digraph the algorithm runs on.
[278]950    BfsWizardBase(const GR &g) :
[209]951      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
[278]952      _reached(0), _processed(0), _pred(0), _dist(0),  _path(0), _di(0) {}
[100]953
954  };
[209]955
[278]956  /// Auxiliary class for the function-type interface of BFS algorithm.
[100]957
[278]958  /// This auxiliary class is created to implement the
959  /// \ref bfs() "function-type interface" of \ref Bfs algorithm.
[405]960  /// It does not have own \ref run(Node) "run()" method, it uses the
961  /// functions and features of the plain \ref Bfs.
[100]962  ///
[278]963  /// This class should only be used through the \ref bfs() function,
964  /// which makes it easier to use the algorithm.
[100]965  template<class TR>
966  class BfsWizard : public TR
967  {
968    typedef TR Base;
969
[244]970    ///The type of the digraph the algorithm runs on.
[100]971    typedef typename TR::Digraph Digraph;
[244]972
[100]973    typedef typename Digraph::Node Node;
974    typedef typename Digraph::NodeIt NodeIt;
975    typedef typename Digraph::Arc Arc;
976    typedef typename Digraph::OutArcIt OutArcIt;
[209]977
[244]978    ///\brief The type of the map that stores the predecessor
[100]979    ///arcs of the shortest paths.
980    typedef typename TR::PredMap PredMap;
[244]981    ///\brief The type of the map that stores the distances of the nodes.
[100]982    typedef typename TR::DistMap DistMap;
[244]983    ///\brief The type of the map that indicates which nodes are reached.
984    typedef typename TR::ReachedMap ReachedMap;
985    ///\brief The type of the map that indicates which nodes are processed.
986    typedef typename TR::ProcessedMap ProcessedMap;
[278]987    ///The type of the shortest paths
988    typedef typename TR::Path Path;
[100]989
990  public:
[244]991
[100]992    /// Constructor.
993    BfsWizard() : TR() {}
994
995    /// Constructor that requires parameters.
996
997    /// Constructor that requires parameters.
998    /// These parameters will be the default values for the traits class.
[278]999    /// \param g The digraph the algorithm runs on.
1000    BfsWizard(const Digraph &g) :
1001      TR(g) {}
[100]1002
1003    ///Copy constructor
1004    BfsWizard(const TR &b) : TR(b) {}
1005
1006    ~BfsWizard() {}
1007
[278]1008    ///Runs BFS algorithm from the given source node.
[209]1009
[278]1010    ///This method runs BFS algorithm from node \c s
1011    ///in order to compute the shortest path to each node.
1012    void run(Node s)
1013    {
1014      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1015      if (Base::_pred)
1016        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1017      if (Base::_dist)
1018        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1019      if (Base::_reached)
1020        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1021      if (Base::_processed)
1022        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1023      if (s!=INVALID)
1024        alg.run(s);
1025      else
1026        alg.run();
1027    }
1028
1029    ///Finds the shortest path between \c s and \c t.
1030
1031    ///This method runs BFS algorithm from node \c s
1032    ///in order to compute the shortest path to node \c t
1033    ///(it stops searching when \c t is processed).
1034    ///
1035    ///\return \c true if \c t is reachable form \c s.
1036    bool run(Node s, Node t)
1037    {
1038      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1039      if (Base::_pred)
1040        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1041      if (Base::_dist)
1042        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1043      if (Base::_reached)
1044        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1045      if (Base::_processed)
1046        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1047      alg.run(s,t);
1048      if (Base::_path)
1049        *reinterpret_cast<Path*>(Base::_path) = alg.path(t);
1050      if (Base::_di)
1051        *Base::_di = alg.dist(t);
1052      return alg.reached(t);
1053    }
1054
1055    ///Runs BFS algorithm to visit all nodes in the digraph.
1056
1057    ///This method runs BFS algorithm in order to compute
1058    ///the shortest path to each node.
[100]1059    void run()
1060    {
[278]1061      run(INVALID);
[100]1062    }
[209]1063
[244]1064    template<class T>
[257]1065    struct SetPredMapBase : public Base {
[244]1066      typedef T PredMap;
1067      static PredMap *createPredMap(const Digraph &) { return 0; };
[257]1068      SetPredMapBase(const TR &b) : TR(b) {}
[244]1069    };
[278]1070    ///\brief \ref named-func-param "Named parameter"
[301]1071    ///for setting PredMap object.
[244]1072    ///
[278]1073    ///\ref named-func-param "Named parameter"
[301]1074    ///for setting PredMap object.
[244]1075    template<class T>
[257]1076    BfsWizard<SetPredMapBase<T> > predMap(const T &t)
[244]1077    {
1078      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1079      return BfsWizard<SetPredMapBase<T> >(*this);
[244]1080    }
1081
1082    template<class T>
[257]1083    struct SetReachedMapBase : public Base {
[244]1084      typedef T ReachedMap;
1085      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
[257]1086      SetReachedMapBase(const TR &b) : TR(b) {}
[244]1087    };
[278]1088    ///\brief \ref named-func-param "Named parameter"
[301]1089    ///for setting ReachedMap object.
[244]1090    ///
[278]1091    /// \ref named-func-param "Named parameter"
[301]1092    ///for setting ReachedMap object.
[244]1093    template<class T>
[257]1094    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)
[244]1095    {
1096      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1097      return BfsWizard<SetReachedMapBase<T> >(*this);
[244]1098    }
1099
1100    template<class T>
[278]1101    struct SetDistMapBase : public Base {
1102      typedef T DistMap;
1103      static DistMap *createDistMap(const Digraph &) { return 0; };
1104      SetDistMapBase(const TR &b) : TR(b) {}
1105    };
1106    ///\brief \ref named-func-param "Named parameter"
[301]1107    ///for setting DistMap object.
[278]1108    ///
1109    /// \ref named-func-param "Named parameter"
[301]1110    ///for setting DistMap object.
[278]1111    template<class T>
1112    BfsWizard<SetDistMapBase<T> > distMap(const T &t)
1113    {
1114      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1115      return BfsWizard<SetDistMapBase<T> >(*this);
1116    }
1117
1118    template<class T>
[257]1119    struct SetProcessedMapBase : public Base {
[244]1120      typedef T ProcessedMap;
1121      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
[257]1122      SetProcessedMapBase(const TR &b) : TR(b) {}
[244]1123    };
[278]1124    ///\brief \ref named-func-param "Named parameter"
[301]1125    ///for setting ProcessedMap object.
[244]1126    ///
[278]1127    /// \ref named-func-param "Named parameter"
[301]1128    ///for setting ProcessedMap object.
[244]1129    template<class T>
[257]1130    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)
[244]1131    {
1132      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1133      return BfsWizard<SetProcessedMapBase<T> >(*this);
[244]1134    }
1135
1136    template<class T>
[278]1137    struct SetPathBase : public Base {
1138      typedef T Path;
1139      SetPathBase(const TR &b) : TR(b) {}
[244]1140    };
[278]1141    ///\brief \ref named-func-param "Named parameter"
1142    ///for getting the shortest path to the target node.
[244]1143    ///
[278]1144    ///\ref named-func-param "Named parameter"
1145    ///for getting the shortest path to the target node.
[244]1146    template<class T>
[278]1147    BfsWizard<SetPathBase<T> > path(const T &t)
[244]1148    {
[278]1149      Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t));
1150      return BfsWizard<SetPathBase<T> >(*this);
1151    }
1152
1153    ///\brief \ref named-func-param "Named parameter"
1154    ///for getting the distance of the target node.
1155    ///
1156    ///\ref named-func-param "Named parameter"
1157    ///for getting the distance of the target node.
1158    BfsWizard dist(const int &d)
1159    {
1160      Base::_di=const_cast<int*>(&d);
1161      return *this;
[244]1162    }
1163
[100]1164  };
[209]1165
[278]1166  ///Function-type interface for BFS algorithm.
[100]1167
1168  /// \ingroup search
[278]1169  ///Function-type interface for BFS algorithm.
[100]1170  ///
[278]1171  ///This function also has several \ref named-func-param "named parameters",
[100]1172  ///they are declared as the members of class \ref BfsWizard.
[278]1173  ///The following examples show how to use these parameters.
[100]1174  ///\code
[278]1175  ///  // Compute shortest path from node s to each node
1176  ///  bfs(g).predMap(preds).distMap(dists).run(s);
1177  ///
1178  ///  // Compute shortest path from s to t
1179  ///  bool reached = bfs(g).path(p).dist(d).run(s,t);
[100]1180  ///\endcode
[405]1181  ///\warning Don't forget to put the \ref BfsWizard::run(Node) "run()"
[100]1182  ///to the end of the parameter list.
1183  ///\sa BfsWizard
1184  ///\sa Bfs
1185  template<class GR>
1186  BfsWizard<BfsWizardBase<GR> >
[278]1187  bfs(const GR &digraph)
[100]1188  {
[278]1189    return BfsWizard<BfsWizardBase<GR> >(digraph);
[100]1190  }
1191
1192#ifdef DOXYGEN
[244]1193  /// \brief Visitor class for BFS.
[209]1194  ///
[100]1195  /// This class defines the interface of the BfsVisit events, and
[244]1196  /// it could be the base of a real visitor class.
[100]1197  template <typename _Digraph>
1198  struct BfsVisitor {
1199    typedef _Digraph Digraph;
1200    typedef typename Digraph::Arc Arc;
1201    typedef typename Digraph::Node Node;
[244]1202    /// \brief Called for the source node(s) of the BFS.
[209]1203    ///
[244]1204    /// This function is called for the source node(s) of the BFS.
1205    void start(const Node& node) {}
1206    /// \brief Called when a node is reached first time.
1207    ///
1208    /// This function is called when a node is reached first time.
1209    void reach(const Node& node) {}
1210    /// \brief Called when a node is processed.
1211    ///
1212    /// This function is called when a node is processed.
1213    void process(const Node& node) {}
1214    /// \brief Called when an arc reaches a new node.
1215    ///
1216    /// This function is called when the BFS finds an arc whose target node
1217    /// is not reached yet.
[100]1218    void discover(const Arc& arc) {}
[244]1219    /// \brief Called when an arc is examined but its target node is
[100]1220    /// already discovered.
[209]1221    ///
[244]1222    /// This function is called when an arc is examined but its target node is
[100]1223    /// already discovered.
1224    void examine(const Arc& arc) {}
1225  };
1226#else
1227  template <typename _Digraph>
1228  struct BfsVisitor {
1229    typedef _Digraph Digraph;
1230    typedef typename Digraph::Arc Arc;
1231    typedef typename Digraph::Node Node;
[244]1232    void start(const Node&) {}
1233    void reach(const Node&) {}
1234    void process(const Node&) {}
[100]1235    void discover(const Arc&) {}
1236    void examine(const Arc&) {}
1237
1238    template <typename _Visitor>
1239    struct Constraints {
1240      void constraints() {
[209]1241        Arc arc;
1242        Node node;
[244]1243        visitor.start(node);
1244        visitor.reach(node);
1245        visitor.process(node);
[209]1246        visitor.discover(arc);
1247        visitor.examine(arc);
[100]1248      }
1249      _Visitor& visitor;
1250    };
1251  };
1252#endif
1253
1254  /// \brief Default traits class of BfsVisit class.
1255  ///
1256  /// Default traits class of BfsVisit class.
[244]1257  /// \tparam _Digraph The type of the digraph the algorithm runs on.
[100]1258  template<class _Digraph>
1259  struct BfsVisitDefaultTraits {
1260
[244]1261    /// \brief The type of the digraph the algorithm runs on.
[100]1262    typedef _Digraph Digraph;
1263
1264    /// \brief The type of the map that indicates which nodes are reached.
[209]1265    ///
[100]1266    /// The type of the map that indicates which nodes are reached.
[244]1267    /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]1268    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1269
[301]1270    /// \brief Instantiates a ReachedMap.
[100]1271    ///
[301]1272    /// This function instantiates a ReachedMap.
[100]1273    /// \param digraph is the digraph, to which
[301]1274    /// we would like to define the ReachedMap.
[100]1275    static ReachedMap *createReachedMap(const Digraph &digraph) {
1276      return new ReachedMap(digraph);
1277    }
1278
1279  };
1280
1281  /// \ingroup search
[209]1282  ///
[244]1283  /// \brief %BFS algorithm class with visitor interface.
[209]1284  ///
[100]1285  /// This class provides an efficient implementation of the %BFS algorithm
1286  /// with visitor interface.
1287  ///
1288  /// The %BfsVisit class provides an alternative interface to the Bfs
1289  /// class. It works with callback mechanism, the BfsVisit object calls
[244]1290  /// the member functions of the \c Visitor class on every BFS event.
[100]1291  ///
[252]1292  /// This interface of the BFS algorithm should be used in special cases
1293  /// when extra actions have to be performed in connection with certain
1294  /// events of the BFS algorithm. Otherwise consider to use Bfs or bfs()
1295  /// instead.
1296  ///
[244]1297  /// \tparam _Digraph The type of the digraph the algorithm runs on.
[210]1298  /// The default value is
[244]1299  /// \ref ListDigraph. The value of _Digraph is not used directly by
1300  /// \ref BfsVisit, it is only passed to \ref BfsVisitDefaultTraits.
1301  /// \tparam _Visitor The Visitor type that is used by the algorithm.
1302  /// \ref BfsVisitor "BfsVisitor<_Digraph>" is an empty visitor, which
1303  /// does not observe the BFS events. If you want to observe the BFS
1304  /// events, you should implement your own visitor class.
[209]1305  /// \tparam _Traits Traits class to set various data types used by the
[100]1306  /// algorithm. The default traits class is
1307  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<_Digraph>".
1308  /// See \ref BfsVisitDefaultTraits for the documentation of
[244]1309  /// a BFS visit traits class.
[100]1310#ifdef DOXYGEN
1311  template <typename _Digraph, typename _Visitor, typename _Traits>
1312#else
1313  template <typename _Digraph = ListDigraph,
[209]1314            typename _Visitor = BfsVisitor<_Digraph>,
[288]1315            typename _Traits = BfsVisitDefaultTraits<_Digraph> >
[100]1316#endif
1317  class BfsVisit {
1318  public:
[209]1319
[244]1320    ///The traits class.
[100]1321    typedef _Traits Traits;
1322
[244]1323    ///The type of the digraph the algorithm runs on.
[100]1324    typedef typename Traits::Digraph Digraph;
1325
[244]1326    ///The visitor type used by the algorithm.
[100]1327    typedef _Visitor Visitor;
1328
[244]1329    ///The type of the map that indicates which nodes are reached.
[100]1330    typedef typename Traits::ReachedMap ReachedMap;
1331
1332  private:
1333
1334    typedef typename Digraph::Node Node;
1335    typedef typename Digraph::NodeIt NodeIt;
1336    typedef typename Digraph::Arc Arc;
1337    typedef typename Digraph::OutArcIt OutArcIt;
1338
[244]1339    //Pointer to the underlying digraph.
[100]1340    const Digraph *_digraph;
[244]1341    //Pointer to the visitor object.
[100]1342    Visitor *_visitor;
[244]1343    //Pointer to the map of reached status of the nodes.
[100]1344    ReachedMap *_reached;
[244]1345    //Indicates if _reached is locally allocated (true) or not.
[100]1346    bool local_reached;
1347
1348    std::vector<typename Digraph::Node> _list;
1349    int _list_front, _list_back;
1350
[280]1351    //Creates the maps if necessary.
[100]1352    void create_maps() {
1353      if(!_reached) {
[209]1354        local_reached = true;
1355        _reached = Traits::createReachedMap(*_digraph);
[100]1356      }
1357    }
1358
1359  protected:
1360
1361    BfsVisit() {}
[209]1362
[100]1363  public:
1364
1365    typedef BfsVisit Create;
1366
[405]1367    /// \name Named Template Parameters
[100]1368
1369    ///@{
1370    template <class T>
[257]1371    struct SetReachedMapTraits : public Traits {
[100]1372      typedef T ReachedMap;
1373      static ReachedMap *createReachedMap(const Digraph &digraph) {
[290]1374        LEMON_ASSERT(false, "ReachedMap is not initialized");
1375        return 0; // ignore warnings
[100]1376      }
1377    };
[209]1378    /// \brief \ref named-templ-param "Named parameter" for setting
[244]1379    /// ReachedMap type.
[100]1380    ///
[244]1381    /// \ref named-templ-param "Named parameter" for setting ReachedMap type.
[100]1382    template <class T>
[257]1383    struct SetReachedMap : public BfsVisit< Digraph, Visitor,
1384                                            SetReachedMapTraits<T> > {
1385      typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create;
[100]1386    };
1387    ///@}
1388
[209]1389  public:
1390
[100]1391    /// \brief Constructor.
1392    ///
1393    /// Constructor.
1394    ///
[244]1395    /// \param digraph The digraph the algorithm runs on.
1396    /// \param visitor The visitor object of the algorithm.
[209]1397    BfsVisit(const Digraph& digraph, Visitor& visitor)
[100]1398      : _digraph(&digraph), _visitor(&visitor),
[209]1399        _reached(0), local_reached(false) {}
1400
[100]1401    /// \brief Destructor.
1402    ~BfsVisit() {
1403      if(local_reached) delete _reached;
1404    }
1405
[244]1406    /// \brief Sets the map that indicates which nodes are reached.
[100]1407    ///
[244]1408    /// Sets the map that indicates which nodes are reached.
[405]1409    /// If you don't use this function before calling \ref run(Node) "run()"
1410    /// or \ref init(), an instance will be allocated automatically.
1411    /// The destructor deallocates this automatically allocated map,
1412    /// of course.
[100]1413    /// \return <tt> (*this) </tt>
1414    BfsVisit &reachedMap(ReachedMap &m) {
1415      if(local_reached) {
[209]1416        delete _reached;
1417        local_reached = false;
[100]1418      }
1419      _reached = &m;
1420      return *this;
1421    }
1422
1423  public:
[244]1424
[405]1425    /// \name Execution Control
1426    /// The simplest way to execute the BFS algorithm is to use one of the
1427    /// member functions called \ref run(Node) "run()".\n
1428    /// If you need more control on the execution, first you have to call
1429    /// \ref init(), then you can add several source nodes with
1430    /// \ref addSource(). Finally the actual path computation can be
1431    /// performed with one of the \ref start() functions.
[100]1432
1433    /// @{
[244]1434
[100]1435    /// \brief Initializes the internal data structures.
1436    ///
1437    /// Initializes the internal data structures.
1438    void init() {
1439      create_maps();
1440      _list.resize(countNodes(*_digraph));
1441      _list_front = _list_back = -1;
1442      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
[209]1443        _reached->set(u, false);
[100]1444      }
1445    }
[209]1446
[100]1447    /// \brief Adds a new source node.
1448    ///
1449    /// Adds a new source node to the set of nodes to be processed.
1450    void addSource(Node s) {
1451      if(!(*_reached)[s]) {
[209]1452          _reached->set(s,true);
1453          _visitor->start(s);
1454          _visitor->reach(s);
[100]1455          _list[++_list_back] = s;
[209]1456        }
[100]1457    }
[209]1458
[100]1459    /// \brief Processes the next node.
1460    ///
1461    /// Processes the next node.
1462    ///
1463    /// \return The processed node.
1464    ///
[244]1465    /// \pre The queue must not be empty.
[209]1466    Node processNextNode() {
[100]1467      Node n = _list[++_list_front];
1468      _visitor->process(n);
1469      Arc e;
1470      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1471        Node m = _digraph->target(e);
1472        if (!(*_reached)[m]) {
1473          _visitor->discover(e);
1474          _visitor->reach(m);
1475          _reached->set(m, true);
1476          _list[++_list_back] = m;
1477        } else {
1478          _visitor->examine(e);
1479        }
1480      }
1481      return n;
1482    }
1483
1484    /// \brief Processes the next node.
1485    ///
[244]1486    /// Processes the next node and checks if the given target node
[100]1487    /// is reached. If the target node is reachable from the processed
[244]1488    /// node, then the \c reach parameter will be set to \c true.
[100]1489    ///
1490    /// \param target The target node.
[244]1491    /// \retval reach Indicates if the target node is reached.
1492    /// It should be initially \c false.
1493    ///
[100]1494    /// \return The processed node.
1495    ///
[244]1496    /// \pre The queue must not be empty.
[100]1497    Node processNextNode(Node target, bool& reach) {
1498      Node n = _list[++_list_front];
1499      _visitor->process(n);
1500      Arc e;
1501      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1502        Node m = _digraph->target(e);
1503        if (!(*_reached)[m]) {
1504          _visitor->discover(e);
1505          _visitor->reach(m);
1506          _reached->set(m, true);
1507          _list[++_list_back] = m;
1508          reach = reach || (target == m);
1509        } else {
1510          _visitor->examine(e);
1511        }
1512      }
1513      return n;
1514    }
1515
1516    /// \brief Processes the next node.
1517    ///
[244]1518    /// Processes the next node and checks if at least one of reached
1519    /// nodes has \c true value in the \c nm node map. If one node
1520    /// with \c true value is reachable from the processed node, then the
1521    /// \c rnode parameter will be set to the first of such nodes.
[100]1522    ///
[244]1523    /// \param nm A \c bool (or convertible) node map that indicates the
1524    /// possible targets.
[100]1525    /// \retval rnode The reached target node.
[244]1526    /// It should be initially \c INVALID.
1527    ///
[100]1528    /// \return The processed node.
1529    ///
[244]1530    /// \pre The queue must not be empty.
[100]1531    template <typename NM>
1532    Node processNextNode(const NM& nm, Node& rnode) {
1533      Node n = _list[++_list_front];
1534      _visitor->process(n);
1535      Arc e;
1536      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1537        Node m = _digraph->target(e);
1538        if (!(*_reached)[m]) {
1539          _visitor->discover(e);
1540          _visitor->reach(m);
1541          _reached->set(m, true);
1542          _list[++_list_back] = m;
1543          if (nm[m] && rnode == INVALID) rnode = m;
1544        } else {
1545          _visitor->examine(e);
1546        }
1547      }
1548      return n;
1549    }
1550
[244]1551    /// \brief The next node to be processed.
[100]1552    ///
[244]1553    /// Returns the next node to be processed or \c INVALID if the queue
1554    /// is empty.
1555    Node nextNode() const {
[100]1556      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1557    }
1558
1559    /// \brief Returns \c false if there are nodes
[244]1560    /// to be processed.
[100]1561    ///
1562    /// Returns \c false if there are nodes
[244]1563    /// to be processed in the queue.
1564    bool emptyQueue() const { return _list_front == _list_back; }
[100]1565
1566    /// \brief Returns the number of the nodes to be processed.
1567    ///
1568    /// Returns the number of the nodes to be processed in the queue.
[244]1569    int queueSize() const { return _list_back - _list_front; }
[209]1570
[100]1571    /// \brief Executes the algorithm.
1572    ///
1573    /// Executes the algorithm.
1574    ///
[244]1575    /// This method runs the %BFS algorithm from the root node(s)
1576    /// in order to compute the shortest path to each node.
1577    ///
1578    /// The algorithm computes
1579    /// - the shortest path tree (forest),
1580    /// - the distance of each node from the root(s).
1581    ///
1582    /// \pre init() must be called and at least one root node should be added
[100]1583    /// with addSource() before using this function.
[244]1584    ///
1585    /// \note <tt>b.start()</tt> is just a shortcut of the following code.
1586    /// \code
1587    ///   while ( !b.emptyQueue() ) {
1588    ///     b.processNextNode();
1589    ///   }
1590    /// \endcode
[100]1591    void start() {
1592      while ( !emptyQueue() ) processNextNode();
1593    }
[209]1594
[244]1595    /// \brief Executes the algorithm until the given target node is reached.
[100]1596    ///
[244]1597    /// Executes the algorithm until the given target node is reached.
[100]1598    ///
[244]1599    /// This method runs the %BFS algorithm from the root node(s)
[286]1600    /// in order to compute the shortest path to \c t.
[244]1601    ///
1602    /// The algorithm computes
[286]1603    /// - the shortest path to \c t,
1604    /// - the distance of \c t from the root(s).
[244]1605    ///
1606    /// \pre init() must be called and at least one root node should be
1607    /// added with addSource() before using this function.
1608    ///
1609    /// \note <tt>b.start(t)</tt> is just a shortcut of the following code.
1610    /// \code
1611    ///   bool reach = false;
1612    ///   while ( !b.emptyQueue() && !reach ) {
1613    ///     b.processNextNode(t, reach);
1614    ///   }
1615    /// \endcode
[286]1616    void start(Node t) {
[100]1617      bool reach = false;
[286]1618      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
[100]1619    }
[209]1620
[100]1621    /// \brief Executes the algorithm until a condition is met.
1622    ///
1623    /// Executes the algorithm until a condition is met.
1624    ///
[244]1625    /// This method runs the %BFS algorithm from the root node(s) in
1626    /// order to compute the shortest path to a node \c v with
1627    /// <tt>nm[v]</tt> true, if such a node can be found.
[100]1628    ///
[244]1629    /// \param nm must be a bool (or convertible) node map. The
1630    /// algorithm will stop when it reaches a node \c v with
[100]1631    /// <tt>nm[v]</tt> true.
1632    ///
[244]1633    /// \return The reached node \c v with <tt>nm[v]</tt> true or
1634    /// \c INVALID if no such node was found.
1635    ///
1636    /// \pre init() must be called and at least one root node should be
1637    /// added with addSource() before using this function.
1638    ///
1639    /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code.
1640    /// \code
1641    ///   Node rnode = INVALID;
1642    ///   while ( !b.emptyQueue() && rnode == INVALID ) {
1643    ///     b.processNextNode(nm, rnode);
1644    ///   }
1645    ///   return rnode;
1646    /// \endcode
[100]1647    template <typename NM>
1648    Node start(const NM &nm) {
1649      Node rnode = INVALID;
1650      while ( !emptyQueue() && rnode == INVALID ) {
[209]1651        processNextNode(nm, rnode);
[100]1652      }
1653      return rnode;
1654    }
1655
[286]1656    /// \brief Runs the algorithm from the given source node.
[100]1657    ///
[244]1658    /// This method runs the %BFS algorithm from node \c s
1659    /// in order to compute the shortest path to each node.
1660    ///
1661    /// The algorithm computes
1662    /// - the shortest path tree,
1663    /// - the distance of each node from the root.
1664    ///
1665    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
[100]1666    ///\code
1667    ///   b.init();
1668    ///   b.addSource(s);
1669    ///   b.start();
1670    ///\endcode
1671    void run(Node s) {
1672      init();
1673      addSource(s);
1674      start();
1675    }
1676
[286]1677    /// \brief Finds the shortest path between \c s and \c t.
1678    ///
1679    /// This method runs the %BFS algorithm from node \c s
1680    /// in order to compute the shortest path to node \c t
1681    /// (it stops searching when \c t is processed).
1682    ///
1683    /// \return \c true if \c t is reachable form \c s.
1684    ///
1685    /// \note Apart from the return value, <tt>b.run(s,t)</tt> is just a
1686    /// shortcut of the following code.
1687    ///\code
1688    ///   b.init();
1689    ///   b.addSource(s);
1690    ///   b.start(t);
1691    ///\endcode
1692    bool run(Node s,Node t) {
1693      init();
1694      addSource(s);
1695      start(t);
1696      return reached(t);
1697    }
1698
[244]1699    /// \brief Runs the algorithm to visit all nodes in the digraph.
[209]1700    ///
[100]1701    /// This method runs the %BFS algorithm in order to
[244]1702    /// compute the shortest path to each node.
[100]1703    ///
[244]1704    /// The algorithm computes
1705    /// - the shortest path tree (forest),
1706    /// - the distance of each node from the root(s).
1707    ///
1708    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
[100]1709    ///\code
1710    ///  b.init();
[244]1711    ///  for (NodeIt n(gr); n != INVALID; ++n) {
1712    ///    if (!b.reached(n)) {
1713    ///      b.addSource(n);
[100]1714    ///      b.start();
1715    ///    }
1716    ///  }
1717    ///\endcode
1718    void run() {
1719      init();
1720      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1721        if (!reached(it)) {
1722          addSource(it);
1723          start();
1724        }
1725      }
1726    }
[244]1727
[100]1728    ///@}
1729
1730    /// \name Query Functions
[405]1731    /// The results of the BFS algorithm can be obtained using these
[100]1732    /// functions.\n
[405]1733    /// Either \ref run(Node) "run()" or \ref start() should be called
1734    /// before using them.
1735
[100]1736    ///@{
1737
[405]1738    /// \brief Checks if a node is reached from the root(s).
[100]1739    ///
[405]1740    /// Returns \c true if \c v is reached from the root(s).
1741    ///
1742    /// \pre Either \ref run(Node) "run()" or \ref init()
[100]1743    /// must be called before using this function.
[420]1744    bool reached(Node v) const { return (*_reached)[v]; }
[244]1745
[100]1746    ///@}
[244]1747
[100]1748  };
1749
1750} //END OF NAMESPACE LEMON
1751
1752#endif
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