COIN-OR::LEMON - Graph Library

source: lemon/lemon/bfs.h @ 835:c92296660262

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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 *
[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
[834]704    ///This method runs the %BFS algorithm in order to visit all nodes
705    ///in the digraph.
[244]706    ///
707    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
708    ///\code
709    ///  b.init();
710    ///  for (NodeIt n(gr); n != INVALID; ++n) {
711    ///    if (!b.reached(n)) {
712    ///      b.addSource(n);
713    ///      b.start();
714    ///    }
715    ///  }
716    ///\endcode
717    void run() {
718      init();
719      for (NodeIt n(*G); n != INVALID; ++n) {
720        if (!reached(n)) {
721          addSource(n);
722          start();
723        }
724      }
725    }
726
[100]727    ///@}
728
729    ///\name Query Functions
[421]730    ///The results of the BFS algorithm can be obtained using these
[100]731    ///functions.\n
[421]732    ///Either \ref run(Node) "run()" or \ref start() should be called
733    ///before using them.
[209]734
[100]735    ///@{
736
[763]737    ///The shortest path to the given node.
[100]738
[763]739    ///Returns the shortest path to the given node from the root(s).
[244]740    ///
[421]741    ///\warning \c t should be reached from the root(s).
[244]742    ///
[421]743    ///\pre Either \ref run(Node) "run()" or \ref init()
744    ///must be called before using this function.
[244]745    Path path(Node t) const { return Path(*G, *_pred, t); }
[100]746
[763]747    ///The distance of the given node from the root(s).
[100]748
[763]749    ///Returns the distance of the given node from the root(s).
[244]750    ///
[421]751    ///\warning If node \c v is not reached from the root(s), then
[244]752    ///the return value of this function is undefined.
753    ///
[421]754    ///\pre Either \ref run(Node) "run()" or \ref init()
755    ///must be called before using this function.
[100]756    int dist(Node v) const { return (*_dist)[v]; }
757
[763]758    ///\brief Returns the 'previous arc' of the shortest path tree for
759    ///the given node.
760    ///
[244]761    ///This function returns the 'previous arc' of the shortest path
762    ///tree for the node \c v, i.e. it returns the last arc of a
[421]763    ///shortest path from a root to \c v. It is \c INVALID if \c v
764    ///is not reached from the root(s) or if \c v is a root.
[244]765    ///
766    ///The shortest path tree used here is equal to the shortest path
[763]767    ///tree used in \ref predNode() and \ref predMap().
[244]768    ///
[421]769    ///\pre Either \ref run(Node) "run()" or \ref init()
770    ///must be called before using this function.
[100]771    Arc predArc(Node v) const { return (*_pred)[v];}
772
[763]773    ///\brief Returns the 'previous node' of the shortest path tree for
774    ///the given node.
775    ///
[244]776    ///This function returns the 'previous node' of the shortest path
777    ///tree for the node \c v, i.e. it returns the last but one node
[763]778    ///of a shortest path from a root to \c v. It is \c INVALID
[421]779    ///if \c v is not reached from the root(s) or if \c v is a root.
[244]780    ///
[100]781    ///The shortest path tree used here is equal to the shortest path
[763]782    ///tree used in \ref predArc() and \ref predMap().
[244]783    ///
[421]784    ///\pre Either \ref run(Node) "run()" or \ref init()
785    ///must be called before using this function.
[100]786    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
[209]787                                  G->source((*_pred)[v]); }
788
[244]789    ///\brief Returns a const reference to the node map that stores the
790    /// distances of the nodes.
791    ///
792    ///Returns a const reference to the node map that stores the distances
793    ///of the nodes calculated by the algorithm.
794    ///
[421]795    ///\pre Either \ref run(Node) "run()" or \ref init()
[244]796    ///must be called before using this function.
[100]797    const DistMap &distMap() const { return *_dist;}
[209]798
[244]799    ///\brief Returns a const reference to the node map that stores the
800    ///predecessor arcs.
801    ///
802    ///Returns a const reference to the node map that stores the predecessor
[763]803    ///arcs, which form the shortest path tree (forest).
[244]804    ///
[421]805    ///\pre Either \ref run(Node) "run()" or \ref init()
[100]806    ///must be called before using this function.
807    const PredMap &predMap() const { return *_pred;}
[209]808
[763]809    ///Checks if the given node is reached from the root(s).
[100]810
[421]811    ///Returns \c true if \c v is reached from the root(s).
812    ///
813    ///\pre Either \ref run(Node) "run()" or \ref init()
[100]814    ///must be called before using this function.
[244]815    bool reached(Node v) const { return (*_reached)[v]; }
[209]816
[100]817    ///@}
818  };
819
[244]820  ///Default traits class of bfs() function.
[100]821
[244]822  ///Default traits class of bfs() function.
[157]823  ///\tparam GR Digraph type.
[100]824  template<class GR>
825  struct BfsWizardDefaultTraits
826  {
[244]827    ///The type of the digraph the algorithm runs on.
[100]828    typedef GR Digraph;
[244]829
830    ///\brief The type of the map that stores the predecessor
[100]831    ///arcs of the shortest paths.
[209]832    ///
[244]833    ///The type of the map that stores the predecessor
[100]834    ///arcs of the shortest paths.
[763]835    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[278]836    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
[301]837    ///Instantiates a PredMap.
[209]838
[301]839    ///This function instantiates a PredMap.
[244]840    ///\param g is the digraph, to which we would like to define the
[301]841    ///PredMap.
[244]842    static PredMap *createPredMap(const Digraph &g)
[100]843    {
[278]844      return new PredMap(g);
[100]845    }
846
847    ///The type of the map that indicates which nodes are processed.
[209]848
[100]849    ///The type of the map that indicates which nodes are processed.
[763]850    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[833]851    ///By default, it is a NullMap.
[100]852    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
[301]853    ///Instantiates a ProcessedMap.
[209]854
[301]855    ///This function instantiates a ProcessedMap.
[100]856    ///\param g is the digraph, to which
[301]857    ///we would like to define the ProcessedMap.
[100]858#ifdef DOXYGEN
[244]859    static ProcessedMap *createProcessedMap(const Digraph &g)
[100]860#else
[244]861    static ProcessedMap *createProcessedMap(const Digraph &)
[100]862#endif
863    {
864      return new ProcessedMap();
865    }
[244]866
[100]867    ///The type of the map that indicates which nodes are reached.
[209]868
[100]869    ///The type of the map that indicates which nodes are reached.
[763]870    ///It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]871    typedef typename Digraph::template NodeMap<bool> ReachedMap;
[301]872    ///Instantiates a ReachedMap.
[209]873
[301]874    ///This function instantiates a ReachedMap.
[244]875    ///\param g is the digraph, to which
[301]876    ///we would like to define the ReachedMap.
[244]877    static ReachedMap *createReachedMap(const Digraph &g)
[100]878    {
[244]879      return new ReachedMap(g);
[100]880    }
[209]881
[244]882    ///The type of the map that stores the distances of the nodes.
883
884    ///The type of the map that stores the distances of the nodes.
[763]885    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
[278]886    typedef typename Digraph::template NodeMap<int> DistMap;
[301]887    ///Instantiates a DistMap.
[209]888
[301]889    ///This function instantiates a DistMap.
[210]890    ///\param g is the digraph, to which we would like to define
[301]891    ///the DistMap
[244]892    static DistMap *createDistMap(const Digraph &g)
[100]893    {
[278]894      return new DistMap(g);
[100]895    }
[278]896
897    ///The type of the shortest paths.
898
899    ///The type of the shortest paths.
[763]900    ///It must conform to the \ref concepts::Path "Path" concept.
[278]901    typedef lemon::Path<Digraph> Path;
[100]902  };
[209]903
[301]904  /// Default traits class used by BfsWizard
[100]905
[763]906  /// Default traits class used by BfsWizard.
907  /// \tparam GR The type of the digraph.
[100]908  template<class GR>
909  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
910  {
911
912    typedef BfsWizardDefaultTraits<GR> Base;
913  protected:
[244]914    //The type of the nodes in the digraph.
[100]915    typedef typename Base::Digraph::Node Node;
916
[244]917    //Pointer to the digraph the algorithm runs on.
[100]918    void *_g;
[244]919    //Pointer to the map of reached nodes.
[100]920    void *_reached;
[244]921    //Pointer to the map of processed nodes.
[100]922    void *_processed;
[244]923    //Pointer to the map of predecessors arcs.
[100]924    void *_pred;
[244]925    //Pointer to the map of distances.
[100]926    void *_dist;
[278]927    //Pointer to the shortest path to the target node.
928    void *_path;
929    //Pointer to the distance of the target node.
930    int *_di;
[209]931
[100]932    public:
933    /// Constructor.
[209]934
[763]935    /// This constructor does not require parameters, it initiates
[278]936    /// all of the attributes to \c 0.
[100]937    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
[278]938                      _dist(0), _path(0), _di(0) {}
[100]939
940    /// Constructor.
[209]941
[278]942    /// This constructor requires one parameter,
943    /// others are initiated to \c 0.
[244]944    /// \param g The digraph the algorithm runs on.
[278]945    BfsWizardBase(const GR &g) :
[209]946      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
[278]947      _reached(0), _processed(0), _pred(0), _dist(0),  _path(0), _di(0) {}
[100]948
949  };
[209]950
[278]951  /// Auxiliary class for the function-type interface of BFS algorithm.
[100]952
[278]953  /// This auxiliary class is created to implement the
954  /// \ref bfs() "function-type interface" of \ref Bfs algorithm.
[421]955  /// It does not have own \ref run(Node) "run()" method, it uses the
956  /// functions and features of the plain \ref Bfs.
[100]957  ///
[278]958  /// This class should only be used through the \ref bfs() function,
959  /// which makes it easier to use the algorithm.
[100]960  template<class TR>
961  class BfsWizard : public TR
962  {
963    typedef TR Base;
964
965    typedef typename TR::Digraph Digraph;
[244]966
[100]967    typedef typename Digraph::Node Node;
968    typedef typename Digraph::NodeIt NodeIt;
969    typedef typename Digraph::Arc Arc;
970    typedef typename Digraph::OutArcIt OutArcIt;
[209]971
[100]972    typedef typename TR::PredMap PredMap;
973    typedef typename TR::DistMap DistMap;
[244]974    typedef typename TR::ReachedMap ReachedMap;
975    typedef typename TR::ProcessedMap ProcessedMap;
[278]976    typedef typename TR::Path Path;
[100]977
978  public:
[244]979
[100]980    /// Constructor.
981    BfsWizard() : TR() {}
982
983    /// Constructor that requires parameters.
984
985    /// Constructor that requires parameters.
986    /// These parameters will be the default values for the traits class.
[278]987    /// \param g The digraph the algorithm runs on.
988    BfsWizard(const Digraph &g) :
989      TR(g) {}
[100]990
991    ///Copy constructor
992    BfsWizard(const TR &b) : TR(b) {}
993
994    ~BfsWizard() {}
995
[278]996    ///Runs BFS algorithm from the given source node.
[209]997
[278]998    ///This method runs BFS algorithm from node \c s
999    ///in order to compute the shortest path to each node.
1000    void run(Node s)
1001    {
1002      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1003      if (Base::_pred)
1004        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1005      if (Base::_dist)
1006        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1007      if (Base::_reached)
1008        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1009      if (Base::_processed)
1010        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1011      if (s!=INVALID)
1012        alg.run(s);
1013      else
1014        alg.run();
1015    }
1016
1017    ///Finds the shortest path between \c s and \c t.
1018
1019    ///This method runs BFS algorithm from node \c s
1020    ///in order to compute the shortest path to node \c t
1021    ///(it stops searching when \c t is processed).
1022    ///
1023    ///\return \c true if \c t is reachable form \c s.
1024    bool run(Node s, Node t)
1025    {
1026      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1027      if (Base::_pred)
1028        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1029      if (Base::_dist)
1030        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1031      if (Base::_reached)
1032        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1033      if (Base::_processed)
1034        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1035      alg.run(s,t);
1036      if (Base::_path)
1037        *reinterpret_cast<Path*>(Base::_path) = alg.path(t);
1038      if (Base::_di)
1039        *Base::_di = alg.dist(t);
1040      return alg.reached(t);
1041    }
1042
1043    ///Runs BFS algorithm to visit all nodes in the digraph.
1044
[834]1045    ///This method runs BFS algorithm in order to visit all nodes
1046    ///in the digraph.
[100]1047    void run()
1048    {
[278]1049      run(INVALID);
[100]1050    }
[209]1051
[244]1052    template<class T>
[257]1053    struct SetPredMapBase : public Base {
[244]1054      typedef T PredMap;
1055      static PredMap *createPredMap(const Digraph &) { return 0; };
[257]1056      SetPredMapBase(const TR &b) : TR(b) {}
[244]1057    };
[763]1058
1059    ///\brief \ref named-templ-param "Named parameter" for setting
1060    ///the predecessor map.
[244]1061    ///
[763]1062    ///\ref named-templ-param "Named parameter" function for setting
1063    ///the map that stores the predecessor arcs of the nodes.
[244]1064    template<class T>
[257]1065    BfsWizard<SetPredMapBase<T> > predMap(const T &t)
[244]1066    {
1067      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1068      return BfsWizard<SetPredMapBase<T> >(*this);
[244]1069    }
1070
1071    template<class T>
[257]1072    struct SetReachedMapBase : public Base {
[244]1073      typedef T ReachedMap;
1074      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
[257]1075      SetReachedMapBase(const TR &b) : TR(b) {}
[244]1076    };
[763]1077
1078    ///\brief \ref named-templ-param "Named parameter" for setting
1079    ///the reached map.
[244]1080    ///
[763]1081    ///\ref named-templ-param "Named parameter" function for setting
1082    ///the map that indicates which nodes are reached.
[244]1083    template<class T>
[257]1084    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)
[244]1085    {
1086      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1087      return BfsWizard<SetReachedMapBase<T> >(*this);
[244]1088    }
1089
1090    template<class T>
[278]1091    struct SetDistMapBase : public Base {
1092      typedef T DistMap;
1093      static DistMap *createDistMap(const Digraph &) { return 0; };
1094      SetDistMapBase(const TR &b) : TR(b) {}
1095    };
[763]1096
1097    ///\brief \ref named-templ-param "Named parameter" for setting
1098    ///the distance map.
[278]1099    ///
[763]1100    ///\ref named-templ-param "Named parameter" function for setting
1101    ///the map that stores the distances of the nodes calculated
1102    ///by the algorithm.
[278]1103    template<class T>
1104    BfsWizard<SetDistMapBase<T> > distMap(const T &t)
1105    {
1106      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1107      return BfsWizard<SetDistMapBase<T> >(*this);
1108    }
1109
1110    template<class T>
[257]1111    struct SetProcessedMapBase : public Base {
[244]1112      typedef T ProcessedMap;
1113      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
[257]1114      SetProcessedMapBase(const TR &b) : TR(b) {}
[244]1115    };
[763]1116
1117    ///\brief \ref named-func-param "Named parameter" for setting
1118    ///the processed map.
[244]1119    ///
[763]1120    ///\ref named-templ-param "Named parameter" function for setting
1121    ///the map that indicates which nodes are processed.
[244]1122    template<class T>
[257]1123    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)
[244]1124    {
1125      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
[257]1126      return BfsWizard<SetProcessedMapBase<T> >(*this);
[244]1127    }
1128
1129    template<class T>
[278]1130    struct SetPathBase : public Base {
1131      typedef T Path;
1132      SetPathBase(const TR &b) : TR(b) {}
[244]1133    };
[278]1134    ///\brief \ref named-func-param "Named parameter"
1135    ///for getting the shortest path to the target node.
[244]1136    ///
[278]1137    ///\ref named-func-param "Named parameter"
1138    ///for getting the shortest path to the target node.
[244]1139    template<class T>
[278]1140    BfsWizard<SetPathBase<T> > path(const T &t)
[244]1141    {
[278]1142      Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t));
1143      return BfsWizard<SetPathBase<T> >(*this);
1144    }
1145
1146    ///\brief \ref named-func-param "Named parameter"
1147    ///for getting the distance of the target node.
1148    ///
1149    ///\ref named-func-param "Named parameter"
1150    ///for getting the distance of the target node.
1151    BfsWizard dist(const int &d)
1152    {
1153      Base::_di=const_cast<int*>(&d);
1154      return *this;
[244]1155    }
1156
[100]1157  };
[209]1158
[278]1159  ///Function-type interface for BFS algorithm.
[100]1160
1161  /// \ingroup search
[278]1162  ///Function-type interface for BFS algorithm.
[100]1163  ///
[278]1164  ///This function also has several \ref named-func-param "named parameters",
[100]1165  ///they are declared as the members of class \ref BfsWizard.
[278]1166  ///The following examples show how to use these parameters.
[100]1167  ///\code
[278]1168  ///  // Compute shortest path from node s to each node
1169  ///  bfs(g).predMap(preds).distMap(dists).run(s);
1170  ///
1171  ///  // Compute shortest path from s to t
1172  ///  bool reached = bfs(g).path(p).dist(d).run(s,t);
[100]1173  ///\endcode
[421]1174  ///\warning Don't forget to put the \ref BfsWizard::run(Node) "run()"
[100]1175  ///to the end of the parameter list.
1176  ///\sa BfsWizard
1177  ///\sa Bfs
1178  template<class GR>
1179  BfsWizard<BfsWizardBase<GR> >
[278]1180  bfs(const GR &digraph)
[100]1181  {
[278]1182    return BfsWizard<BfsWizardBase<GR> >(digraph);
[100]1183  }
1184
1185#ifdef DOXYGEN
[244]1186  /// \brief Visitor class for BFS.
[209]1187  ///
[100]1188  /// This class defines the interface of the BfsVisit events, and
[244]1189  /// it could be the base of a real visitor class.
[525]1190  template <typename GR>
[100]1191  struct BfsVisitor {
[525]1192    typedef GR Digraph;
[100]1193    typedef typename Digraph::Arc Arc;
1194    typedef typename Digraph::Node Node;
[244]1195    /// \brief Called for the source node(s) of the BFS.
[209]1196    ///
[244]1197    /// This function is called for the source node(s) of the BFS.
1198    void start(const Node& node) {}
1199    /// \brief Called when a node is reached first time.
1200    ///
1201    /// This function is called when a node is reached first time.
1202    void reach(const Node& node) {}
1203    /// \brief Called when a node is processed.
1204    ///
1205    /// This function is called when a node is processed.
1206    void process(const Node& node) {}
1207    /// \brief Called when an arc reaches a new node.
1208    ///
1209    /// This function is called when the BFS finds an arc whose target node
1210    /// is not reached yet.
[100]1211    void discover(const Arc& arc) {}
[244]1212    /// \brief Called when an arc is examined but its target node is
[100]1213    /// already discovered.
[209]1214    ///
[244]1215    /// This function is called when an arc is examined but its target node is
[100]1216    /// already discovered.
1217    void examine(const Arc& arc) {}
1218  };
1219#else
[525]1220  template <typename GR>
[100]1221  struct BfsVisitor {
[525]1222    typedef GR Digraph;
[100]1223    typedef typename Digraph::Arc Arc;
1224    typedef typename Digraph::Node Node;
[244]1225    void start(const Node&) {}
1226    void reach(const Node&) {}
1227    void process(const Node&) {}
[100]1228    void discover(const Arc&) {}
1229    void examine(const Arc&) {}
1230
1231    template <typename _Visitor>
1232    struct Constraints {
1233      void constraints() {
[209]1234        Arc arc;
1235        Node node;
[244]1236        visitor.start(node);
1237        visitor.reach(node);
1238        visitor.process(node);
[209]1239        visitor.discover(arc);
1240        visitor.examine(arc);
[100]1241      }
1242      _Visitor& visitor;
1243    };
1244  };
1245#endif
1246
1247  /// \brief Default traits class of BfsVisit class.
1248  ///
1249  /// Default traits class of BfsVisit class.
[525]1250  /// \tparam GR The type of the digraph the algorithm runs on.
1251  template<class GR>
[100]1252  struct BfsVisitDefaultTraits {
1253
[244]1254    /// \brief The type of the digraph the algorithm runs on.
[525]1255    typedef GR Digraph;
[100]1256
1257    /// \brief The type of the map that indicates which nodes are reached.
[209]1258    ///
[100]1259    /// The type of the map that indicates which nodes are reached.
[763]1260    /// It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
[100]1261    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1262
[301]1263    /// \brief Instantiates a ReachedMap.
[100]1264    ///
[301]1265    /// This function instantiates a ReachedMap.
[100]1266    /// \param digraph is the digraph, to which
[301]1267    /// we would like to define the ReachedMap.
[100]1268    static ReachedMap *createReachedMap(const Digraph &digraph) {
1269      return new ReachedMap(digraph);
1270    }
1271
1272  };
1273
1274  /// \ingroup search
[209]1275  ///
[525]1276  /// \brief BFS algorithm class with visitor interface.
[209]1277  ///
[525]1278  /// This class provides an efficient implementation of the BFS algorithm
[100]1279  /// with visitor interface.
1280  ///
[525]1281  /// The BfsVisit class provides an alternative interface to the Bfs
[100]1282  /// class. It works with callback mechanism, the BfsVisit object calls
[244]1283  /// the member functions of the \c Visitor class on every BFS event.
[100]1284  ///
[252]1285  /// This interface of the BFS algorithm should be used in special cases
1286  /// when extra actions have to be performed in connection with certain
1287  /// events of the BFS algorithm. Otherwise consider to use Bfs or bfs()
1288  /// instead.
1289  ///
[525]1290  /// \tparam GR The type of the digraph the algorithm runs on.
1291  /// The default type is \ref ListDigraph.
1292  /// The value of GR is not used directly by \ref BfsVisit,
1293  /// it is only passed to \ref BfsVisitDefaultTraits.
1294  /// \tparam VS The Visitor type that is used by the algorithm.
1295  /// \ref BfsVisitor "BfsVisitor<GR>" is an empty visitor, which
[244]1296  /// does not observe the BFS events. If you want to observe the BFS
1297  /// events, you should implement your own visitor class.
[525]1298  /// \tparam TR Traits class to set various data types used by the
[100]1299  /// algorithm. The default traits class is
[525]1300  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<GR>".
[100]1301  /// See \ref BfsVisitDefaultTraits for the documentation of
[244]1302  /// a BFS visit traits class.
[100]1303#ifdef DOXYGEN
[525]1304  template <typename GR, typename VS, typename TR>
[100]1305#else
[525]1306  template <typename GR = ListDigraph,
1307            typename VS = BfsVisitor<GR>,
1308            typename TR = BfsVisitDefaultTraits<GR> >
[100]1309#endif
1310  class BfsVisit {
1311  public:
[209]1312
[244]1313    ///The traits class.
[525]1314    typedef TR Traits;
[100]1315
[244]1316    ///The type of the digraph the algorithm runs on.
[100]1317    typedef typename Traits::Digraph Digraph;
1318
[244]1319    ///The visitor type used by the algorithm.
[525]1320    typedef VS Visitor;
[100]1321
[244]1322    ///The type of the map that indicates which nodes are reached.
[100]1323    typedef typename Traits::ReachedMap ReachedMap;
1324
1325  private:
1326
1327    typedef typename Digraph::Node Node;
1328    typedef typename Digraph::NodeIt NodeIt;
1329    typedef typename Digraph::Arc Arc;
1330    typedef typename Digraph::OutArcIt OutArcIt;
1331
[244]1332    //Pointer to the underlying digraph.
[100]1333    const Digraph *_digraph;
[244]1334    //Pointer to the visitor object.
[100]1335    Visitor *_visitor;
[244]1336    //Pointer to the map of reached status of the nodes.
[100]1337    ReachedMap *_reached;
[244]1338    //Indicates if _reached is locally allocated (true) or not.
[100]1339    bool local_reached;
1340
1341    std::vector<typename Digraph::Node> _list;
1342    int _list_front, _list_back;
1343
[280]1344    //Creates the maps if necessary.
[100]1345    void create_maps() {
1346      if(!_reached) {
[209]1347        local_reached = true;
1348        _reached = Traits::createReachedMap(*_digraph);
[100]1349      }
1350    }
1351
1352  protected:
1353
1354    BfsVisit() {}
[209]1355
[100]1356  public:
1357
1358    typedef BfsVisit Create;
1359
[421]1360    /// \name Named Template Parameters
[100]1361
1362    ///@{
1363    template <class T>
[257]1364    struct SetReachedMapTraits : public Traits {
[100]1365      typedef T ReachedMap;
1366      static ReachedMap *createReachedMap(const Digraph &digraph) {
[290]1367        LEMON_ASSERT(false, "ReachedMap is not initialized");
1368        return 0; // ignore warnings
[100]1369      }
1370    };
[209]1371    /// \brief \ref named-templ-param "Named parameter" for setting
[244]1372    /// ReachedMap type.
[100]1373    ///
[244]1374    /// \ref named-templ-param "Named parameter" for setting ReachedMap type.
[100]1375    template <class T>
[257]1376    struct SetReachedMap : public BfsVisit< Digraph, Visitor,
1377                                            SetReachedMapTraits<T> > {
1378      typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create;
[100]1379    };
1380    ///@}
1381
[209]1382  public:
1383
[100]1384    /// \brief Constructor.
1385    ///
1386    /// Constructor.
1387    ///
[244]1388    /// \param digraph The digraph the algorithm runs on.
1389    /// \param visitor The visitor object of the algorithm.
[209]1390    BfsVisit(const Digraph& digraph, Visitor& visitor)
[100]1391      : _digraph(&digraph), _visitor(&visitor),
[209]1392        _reached(0), local_reached(false) {}
1393
[100]1394    /// \brief Destructor.
1395    ~BfsVisit() {
1396      if(local_reached) delete _reached;
1397    }
1398
[244]1399    /// \brief Sets the map that indicates which nodes are reached.
[100]1400    ///
[244]1401    /// Sets the map that indicates which nodes are reached.
[421]1402    /// If you don't use this function before calling \ref run(Node) "run()"
1403    /// or \ref init(), an instance will be allocated automatically.
1404    /// The destructor deallocates this automatically allocated map,
1405    /// of course.
[100]1406    /// \return <tt> (*this) </tt>
1407    BfsVisit &reachedMap(ReachedMap &m) {
1408      if(local_reached) {
[209]1409        delete _reached;
1410        local_reached = false;
[100]1411      }
1412      _reached = &m;
1413      return *this;
1414    }
1415
1416  public:
[244]1417
[421]1418    /// \name Execution Control
1419    /// The simplest way to execute the BFS algorithm is to use one of the
1420    /// member functions called \ref run(Node) "run()".\n
[760]1421    /// If you need better control on the execution, you have to call
1422    /// \ref init() first, then you can add several source nodes with
[421]1423    /// \ref addSource(). Finally the actual path computation can be
1424    /// performed with one of the \ref start() functions.
[100]1425
1426    /// @{
[244]1427
[100]1428    /// \brief Initializes the internal data structures.
1429    ///
1430    /// Initializes the internal data structures.
1431    void init() {
1432      create_maps();
1433      _list.resize(countNodes(*_digraph));
1434      _list_front = _list_back = -1;
1435      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
[209]1436        _reached->set(u, false);
[100]1437      }
1438    }
[209]1439
[100]1440    /// \brief Adds a new source node.
1441    ///
1442    /// Adds a new source node to the set of nodes to be processed.
1443    void addSource(Node s) {
1444      if(!(*_reached)[s]) {
[209]1445          _reached->set(s,true);
1446          _visitor->start(s);
1447          _visitor->reach(s);
[100]1448          _list[++_list_back] = s;
[209]1449        }
[100]1450    }
[209]1451
[100]1452    /// \brief Processes the next node.
1453    ///
1454    /// Processes the next node.
1455    ///
1456    /// \return The processed node.
1457    ///
[244]1458    /// \pre The queue must not be empty.
[209]1459    Node processNextNode() {
[100]1460      Node n = _list[++_list_front];
1461      _visitor->process(n);
1462      Arc e;
1463      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1464        Node m = _digraph->target(e);
1465        if (!(*_reached)[m]) {
1466          _visitor->discover(e);
1467          _visitor->reach(m);
1468          _reached->set(m, true);
1469          _list[++_list_back] = m;
1470        } else {
1471          _visitor->examine(e);
1472        }
1473      }
1474      return n;
1475    }
1476
1477    /// \brief Processes the next node.
1478    ///
[244]1479    /// Processes the next node and checks if the given target node
[100]1480    /// is reached. If the target node is reachable from the processed
[244]1481    /// node, then the \c reach parameter will be set to \c true.
[100]1482    ///
1483    /// \param target The target node.
[244]1484    /// \retval reach Indicates if the target node is reached.
1485    /// It should be initially \c false.
1486    ///
[100]1487    /// \return The processed node.
1488    ///
[244]1489    /// \pre The queue must not be empty.
[100]1490    Node processNextNode(Node target, bool& reach) {
1491      Node n = _list[++_list_front];
1492      _visitor->process(n);
1493      Arc e;
1494      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1495        Node m = _digraph->target(e);
1496        if (!(*_reached)[m]) {
1497          _visitor->discover(e);
1498          _visitor->reach(m);
1499          _reached->set(m, true);
1500          _list[++_list_back] = m;
1501          reach = reach || (target == m);
1502        } else {
1503          _visitor->examine(e);
1504        }
1505      }
1506      return n;
1507    }
1508
1509    /// \brief Processes the next node.
1510    ///
[244]1511    /// Processes the next node and checks if at least one of reached
1512    /// nodes has \c true value in the \c nm node map. If one node
1513    /// with \c true value is reachable from the processed node, then the
1514    /// \c rnode parameter will be set to the first of such nodes.
[100]1515    ///
[244]1516    /// \param nm A \c bool (or convertible) node map that indicates the
1517    /// possible targets.
[100]1518    /// \retval rnode The reached target node.
[244]1519    /// It should be initially \c INVALID.
1520    ///
[100]1521    /// \return The processed node.
1522    ///
[244]1523    /// \pre The queue must not be empty.
[100]1524    template <typename NM>
1525    Node processNextNode(const NM& nm, Node& rnode) {
1526      Node n = _list[++_list_front];
1527      _visitor->process(n);
1528      Arc e;
1529      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1530        Node m = _digraph->target(e);
1531        if (!(*_reached)[m]) {
1532          _visitor->discover(e);
1533          _visitor->reach(m);
1534          _reached->set(m, true);
1535          _list[++_list_back] = m;
1536          if (nm[m] && rnode == INVALID) rnode = m;
1537        } else {
1538          _visitor->examine(e);
1539        }
1540      }
1541      return n;
1542    }
1543
[244]1544    /// \brief The next node to be processed.
[100]1545    ///
[244]1546    /// Returns the next node to be processed or \c INVALID if the queue
1547    /// is empty.
1548    Node nextNode() const {
[100]1549      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1550    }
1551
1552    /// \brief Returns \c false if there are nodes
[244]1553    /// to be processed.
[100]1554    ///
1555    /// Returns \c false if there are nodes
[244]1556    /// to be processed in the queue.
1557    bool emptyQueue() const { return _list_front == _list_back; }
[100]1558
1559    /// \brief Returns the number of the nodes to be processed.
1560    ///
1561    /// Returns the number of the nodes to be processed in the queue.
[244]1562    int queueSize() const { return _list_back - _list_front; }
[209]1563
[100]1564    /// \brief Executes the algorithm.
1565    ///
1566    /// Executes the algorithm.
1567    ///
[244]1568    /// This method runs the %BFS algorithm from the root node(s)
1569    /// in order to compute the shortest path to each node.
1570    ///
1571    /// The algorithm computes
1572    /// - the shortest path tree (forest),
1573    /// - the distance of each node from the root(s).
1574    ///
1575    /// \pre init() must be called and at least one root node should be added
[100]1576    /// with addSource() before using this function.
[244]1577    ///
1578    /// \note <tt>b.start()</tt> is just a shortcut of the following code.
1579    /// \code
1580    ///   while ( !b.emptyQueue() ) {
1581    ///     b.processNextNode();
1582    ///   }
1583    /// \endcode
[100]1584    void start() {
1585      while ( !emptyQueue() ) processNextNode();
1586    }
[209]1587
[244]1588    /// \brief Executes the algorithm until the given target node is reached.
[100]1589    ///
[244]1590    /// Executes the algorithm until the given target node is reached.
[100]1591    ///
[244]1592    /// This method runs the %BFS algorithm from the root node(s)
[286]1593    /// in order to compute the shortest path to \c t.
[244]1594    ///
1595    /// The algorithm computes
[286]1596    /// - the shortest path to \c t,
1597    /// - the distance of \c t from the root(s).
[244]1598    ///
1599    /// \pre init() must be called and at least one root node should be
1600    /// added with addSource() before using this function.
1601    ///
1602    /// \note <tt>b.start(t)</tt> is just a shortcut of the following code.
1603    /// \code
1604    ///   bool reach = false;
1605    ///   while ( !b.emptyQueue() && !reach ) {
1606    ///     b.processNextNode(t, reach);
1607    ///   }
1608    /// \endcode
[286]1609    void start(Node t) {
[100]1610      bool reach = false;
[286]1611      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
[100]1612    }
[209]1613
[100]1614    /// \brief Executes the algorithm until a condition is met.
1615    ///
1616    /// Executes the algorithm until a condition is met.
1617    ///
[244]1618    /// This method runs the %BFS algorithm from the root node(s) in
1619    /// order to compute the shortest path to a node \c v with
1620    /// <tt>nm[v]</tt> true, if such a node can be found.
[100]1621    ///
[244]1622    /// \param nm must be a bool (or convertible) node map. The
1623    /// algorithm will stop when it reaches a node \c v with
[100]1624    /// <tt>nm[v]</tt> true.
1625    ///
[244]1626    /// \return The reached node \c v with <tt>nm[v]</tt> true or
1627    /// \c INVALID if no such node was found.
1628    ///
1629    /// \pre init() must be called and at least one root node should be
1630    /// added with addSource() before using this function.
1631    ///
1632    /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code.
1633    /// \code
1634    ///   Node rnode = INVALID;
1635    ///   while ( !b.emptyQueue() && rnode == INVALID ) {
1636    ///     b.processNextNode(nm, rnode);
1637    ///   }
1638    ///   return rnode;
1639    /// \endcode
[100]1640    template <typename NM>
1641    Node start(const NM &nm) {
1642      Node rnode = INVALID;
1643      while ( !emptyQueue() && rnode == INVALID ) {
[209]1644        processNextNode(nm, rnode);
[100]1645      }
1646      return rnode;
1647    }
1648
[286]1649    /// \brief Runs the algorithm from the given source node.
[100]1650    ///
[244]1651    /// This method runs the %BFS algorithm from node \c s
1652    /// in order to compute the shortest path to each node.
1653    ///
1654    /// The algorithm computes
1655    /// - the shortest path tree,
1656    /// - the distance of each node from the root.
1657    ///
1658    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
[100]1659    ///\code
1660    ///   b.init();
1661    ///   b.addSource(s);
1662    ///   b.start();
1663    ///\endcode
1664    void run(Node s) {
1665      init();
1666      addSource(s);
1667      start();
1668    }
1669
[286]1670    /// \brief Finds the shortest path between \c s and \c t.
1671    ///
1672    /// This method runs the %BFS algorithm from node \c s
1673    /// in order to compute the shortest path to node \c t
1674    /// (it stops searching when \c t is processed).
1675    ///
1676    /// \return \c true if \c t is reachable form \c s.
1677    ///
1678    /// \note Apart from the return value, <tt>b.run(s,t)</tt> is just a
1679    /// shortcut of the following code.
1680    ///\code
1681    ///   b.init();
1682    ///   b.addSource(s);
1683    ///   b.start(t);
1684    ///\endcode
1685    bool run(Node s,Node t) {
1686      init();
1687      addSource(s);
1688      start(t);
1689      return reached(t);
1690    }
1691
[244]1692    /// \brief Runs the algorithm to visit all nodes in the digraph.
[209]1693    ///
[834]1694    /// This method runs the %BFS algorithm in order to visit all nodes
1695    /// in the digraph.
[244]1696    ///
1697    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
[100]1698    ///\code
1699    ///  b.init();
[244]1700    ///  for (NodeIt n(gr); n != INVALID; ++n) {
1701    ///    if (!b.reached(n)) {
1702    ///      b.addSource(n);
[100]1703    ///      b.start();
1704    ///    }
1705    ///  }
1706    ///\endcode
1707    void run() {
1708      init();
1709      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1710        if (!reached(it)) {
1711          addSource(it);
1712          start();
1713        }
1714      }
1715    }
[244]1716
[100]1717    ///@}
1718
1719    /// \name Query Functions
[421]1720    /// The results of the BFS algorithm can be obtained using these
[100]1721    /// functions.\n
[421]1722    /// Either \ref run(Node) "run()" or \ref start() should be called
1723    /// before using them.
1724
[100]1725    ///@{
1726
[763]1727    /// \brief Checks if the given node is reached from the root(s).
[100]1728    ///
[421]1729    /// Returns \c true if \c v is reached from the root(s).
1730    ///
1731    /// \pre Either \ref run(Node) "run()" or \ref init()
[100]1732    /// must be called before using this function.
[437]1733    bool reached(Node v) const { return (*_reached)[v]; }
[244]1734
[100]1735    ///@}
[244]1736
[100]1737  };
1738
1739} //END OF NAMESPACE LEMON
1740
1741#endif
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