COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/bfs.h @ 220:a5d8c039f218

Last change on this file since 220:a5d8c039f218 was 220:a5d8c039f218, checked in by Balazs Dezso <deba@…>, 11 years ago

Reorganize header files (Ticket #97)

In addition on some places the DefaultMap?<G, K, V> is replaced with
ItemSetTraits?<G, K>::template Map<V>::Type, to decrease the dependencies
of different tools. It is obviously better solution.

File size: 48.2 KB
Line 
1/* -*- mode: C++; indent-tabs-mode: nil; -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library.
4 *
5 * Copyright (C) 2003-2008
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
24///\brief Bfs algorithm.
25
26#include <lemon/list_graph.h>
27#include <lemon/bits/path_dump.h>
28#include <lemon/core.h>
29#include <lemon/error.h>
30#include <lemon/maps.h>
31
32namespace lemon {
33
34
35
36  ///Default traits class of Bfs class.
37
38  ///Default traits class of Bfs class.
39  ///\tparam GR Digraph type.
40  template<class GR>
41  struct BfsDefaultTraits
42  {
43    ///The digraph type the algorithm runs on.
44    typedef GR Digraph;
45    ///\brief The type of the map that stores the last
46    ///arcs of the shortest paths.
47    ///
48    ///The type of the map that stores the last
49    ///arcs of the shortest paths.
50    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
51    ///
52    typedef typename Digraph::template NodeMap<typename GR::Arc> PredMap;
53    ///Instantiates a PredMap.
54
55    ///This function instantiates a \ref PredMap.
56    ///\param G is the digraph, to which we would like to define the PredMap.
57    ///\todo The digraph alone may be insufficient to initialize
58    static PredMap *createPredMap(const GR &G)
59    {
60      return new PredMap(G);
61    }
62    ///The type of the map that indicates which nodes are processed.
63
64    ///The type of the map that indicates which nodes are processed.
65    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
66    ///\todo named parameter to set this type, function to read and write.
67    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
68    ///Instantiates a ProcessedMap.
69
70    ///This function instantiates a \ref ProcessedMap.
71    ///\param g is the digraph, to which
72    ///we would like to define the \ref ProcessedMap
73#ifdef DOXYGEN
74    static ProcessedMap *createProcessedMap(const GR &g)
75#else
76    static ProcessedMap *createProcessedMap(const GR &)
77#endif
78    {
79      return new ProcessedMap();
80    }
81    ///The type of the map that indicates which nodes are reached.
82
83    ///The type of the map that indicates which nodes are reached.
84    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
85    ///\todo named parameter to set this type, function to read and write.
86    typedef typename Digraph::template NodeMap<bool> ReachedMap;
87    ///Instantiates a ReachedMap.
88
89    ///This function instantiates a \ref ReachedMap.
90    ///\param G is the digraph, to which
91    ///we would like to define the \ref ReachedMap.
92    static ReachedMap *createReachedMap(const GR &G)
93    {
94      return new ReachedMap(G);
95    }
96    ///The type of the map that stores the dists of the nodes.
97
98    ///The type of the map that stores the dists of the nodes.
99    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
100    ///
101    typedef typename Digraph::template NodeMap<int> DistMap;
102    ///Instantiates a DistMap.
103
104    ///This function instantiates a \ref DistMap.
105    ///\param G is the digraph, to which we would like to define
106    ///the \ref DistMap
107    static DistMap *createDistMap(const GR &G)
108    {
109      return new DistMap(G);
110    }
111  };
112
113  ///%BFS algorithm class.
114
115  ///\ingroup search
116  ///This class provides an efficient implementation of the %BFS algorithm.
117  ///
118  ///\tparam GR The digraph type the algorithm runs on. The default value is
119  ///\ref ListDigraph. The value of GR is not used directly by Bfs, it
120  ///is only passed to \ref BfsDefaultTraits.
121  ///\tparam TR Traits class to set various data types used by the algorithm.
122  ///The default traits class is
123  ///\ref BfsDefaultTraits "BfsDefaultTraits<GR>".
124  ///See \ref BfsDefaultTraits for the documentation of
125  ///a Bfs traits class.
126
127#ifdef DOXYGEN
128  template <typename GR,
129            typename TR>
130#else
131  template <typename GR=ListDigraph,
132            typename TR=BfsDefaultTraits<GR> >
133#endif
134  class Bfs {
135  public:
136    /**
137     * \brief \ref Exception for uninitialized parameters.
138     *
139     * This error represents problems in the initialization
140     * of the parameters of the algorithms.
141     */
142    class UninitializedParameter : public lemon::UninitializedParameter {
143    public:
144      virtual const char* what() const throw() {
145        return "lemon::Bfs::UninitializedParameter";
146      }
147    };
148
149    typedef TR Traits;
150    ///The type of the underlying digraph.
151    typedef typename TR::Digraph Digraph;
152
153    ///\brief The type of the map that stores the last
154    ///arcs of the shortest paths.
155    typedef typename TR::PredMap PredMap;
156    ///The type of the map indicating which nodes are reached.
157    typedef typename TR::ReachedMap ReachedMap;
158    ///The type of the map indicating which nodes are processed.
159    typedef typename TR::ProcessedMap ProcessedMap;
160    ///The type of the map that stores the dists of the nodes.
161    typedef typename TR::DistMap DistMap;
162  private:
163
164    typedef typename Digraph::Node Node;
165    typedef typename Digraph::NodeIt NodeIt;
166    typedef typename Digraph::Arc Arc;
167    typedef typename Digraph::OutArcIt OutArcIt;
168
169    /// Pointer to the underlying digraph.
170    const Digraph *G;
171    ///Pointer to the map of predecessors arcs.
172    PredMap *_pred;
173    ///Indicates if \ref _pred is locally allocated (\c true) or not.
174    bool local_pred;
175    ///Pointer to the map of distances.
176    DistMap *_dist;
177    ///Indicates if \ref _dist is locally allocated (\c true) or not.
178    bool local_dist;
179    ///Pointer to the map of reached status of the nodes.
180    ReachedMap *_reached;
181    ///Indicates if \ref _reached is locally allocated (\c true) or not.
182    bool local_reached;
183    ///Pointer to the map of processed status of the nodes.
184    ProcessedMap *_processed;
185    ///Indicates if \ref _processed is locally allocated (\c true) or not.
186    bool local_processed;
187
188    std::vector<typename Digraph::Node> _queue;
189    int _queue_head,_queue_tail,_queue_next_dist;
190    int _curr_dist;
191
192    ///Creates the maps if necessary.
193
194    ///\todo Better memory allocation (instead of new).
195    void create_maps()
196    {
197      if(!_pred) {
198        local_pred = true;
199        _pred = Traits::createPredMap(*G);
200      }
201      if(!_dist) {
202        local_dist = true;
203        _dist = Traits::createDistMap(*G);
204      }
205      if(!_reached) {
206        local_reached = true;
207        _reached = Traits::createReachedMap(*G);
208      }
209      if(!_processed) {
210        local_processed = true;
211        _processed = Traits::createProcessedMap(*G);
212      }
213    }
214
215  protected:
216
217    Bfs() {}
218
219  public:
220
221    typedef Bfs Create;
222
223    ///\name Named template parameters
224
225    ///@{
226
227    template <class T>
228    struct DefPredMapTraits : public Traits {
229      typedef T PredMap;
230      static PredMap *createPredMap(const Digraph &)
231      {
232        throw UninitializedParameter();
233      }
234    };
235    ///\brief \ref named-templ-param "Named parameter" for setting
236    ///PredMap type
237    ///
238    ///\ref named-templ-param "Named parameter" for setting PredMap type
239    ///
240    template <class T>
241    struct DefPredMap : public Bfs< Digraph, DefPredMapTraits<T> > {
242      typedef Bfs< Digraph, DefPredMapTraits<T> > Create;
243    };
244
245    template <class T>
246    struct DefDistMapTraits : public Traits {
247      typedef T DistMap;
248      static DistMap *createDistMap(const Digraph &)
249      {
250        throw UninitializedParameter();
251      }
252    };
253    ///\brief \ref named-templ-param "Named parameter" for setting
254    ///DistMap type
255    ///
256    ///\ref named-templ-param "Named parameter" for setting DistMap type
257    ///
258    template <class T>
259    struct DefDistMap : public Bfs< Digraph, DefDistMapTraits<T> > {
260      typedef Bfs< Digraph, DefDistMapTraits<T> > Create;
261    };
262
263    template <class T>
264    struct DefReachedMapTraits : public Traits {
265      typedef T ReachedMap;
266      static ReachedMap *createReachedMap(const Digraph &)
267      {
268        throw UninitializedParameter();
269      }
270    };
271    ///\brief \ref named-templ-param "Named parameter" for setting
272    ///ReachedMap type
273    ///
274    ///\ref named-templ-param "Named parameter" for setting ReachedMap type
275    ///
276    template <class T>
277    struct DefReachedMap : public Bfs< Digraph, DefReachedMapTraits<T> > {
278      typedef Bfs< Digraph, DefReachedMapTraits<T> > Create;
279    };
280
281    template <class T>
282    struct DefProcessedMapTraits : public Traits {
283      typedef T ProcessedMap;
284      static ProcessedMap *createProcessedMap(const Digraph &)
285      {
286        throw UninitializedParameter();
287      }
288    };
289    ///\brief \ref named-templ-param "Named parameter" for setting
290    ///ProcessedMap type
291    ///
292    ///\ref named-templ-param "Named parameter" for setting ProcessedMap type
293    ///
294    template <class T>
295    struct DefProcessedMap : public Bfs< Digraph, DefProcessedMapTraits<T> > {
296      typedef Bfs< Digraph, DefProcessedMapTraits<T> > Create;
297    };
298
299    struct DefDigraphProcessedMapTraits : public Traits {
300      typedef typename Digraph::template NodeMap<bool> ProcessedMap;
301      static ProcessedMap *createProcessedMap(const Digraph &G)
302      {
303        return new ProcessedMap(G);
304      }
305    };
306    ///\brief \ref named-templ-param "Named parameter"
307    ///for setting the ProcessedMap type to be Digraph::NodeMap<bool>.
308    ///
309    ///\ref named-templ-param "Named parameter"
310    ///for setting the ProcessedMap type to be Digraph::NodeMap<bool>.
311    ///If you don't set it explicitly, it will be automatically allocated.
312    template <class T>
313    struct DefProcessedMapToBeDefaultMap :
314      public Bfs< Digraph, DefDigraphProcessedMapTraits> {
315      typedef Bfs< Digraph, DefDigraphProcessedMapTraits> Create;
316    };
317
318    ///@}
319
320  public:
321
322    ///Constructor.
323
324    ///\param _G the digraph the algorithm will run on.
325    ///
326    Bfs(const Digraph& _G) :
327      G(&_G),
328      _pred(NULL), local_pred(false),
329      _dist(NULL), local_dist(false),
330      _reached(NULL), local_reached(false),
331      _processed(NULL), local_processed(false)
332    { }
333
334    ///Destructor.
335    ~Bfs()
336    {
337      if(local_pred) delete _pred;
338      if(local_dist) delete _dist;
339      if(local_reached) delete _reached;
340      if(local_processed) delete _processed;
341    }
342
343    ///Sets the map storing the predecessor arcs.
344
345    ///Sets the map storing the predecessor arcs.
346    ///If you don't use this function before calling \ref run(),
347    ///it will allocate one. The destructor deallocates this
348    ///automatically allocated map, of course.
349    ///\return <tt> (*this) </tt>
350    Bfs &predMap(PredMap &m)
351    {
352      if(local_pred) {
353        delete _pred;
354        local_pred=false;
355      }
356      _pred = &m;
357      return *this;
358    }
359
360    ///Sets the map indicating the reached nodes.
361
362    ///Sets the map indicating the reached nodes.
363    ///If you don't use this function before calling \ref run(),
364    ///it will allocate one. The destructor deallocates this
365    ///automatically allocated map, of course.
366    ///\return <tt> (*this) </tt>
367    Bfs &reachedMap(ReachedMap &m)
368    {
369      if(local_reached) {
370        delete _reached;
371        local_reached=false;
372      }
373      _reached = &m;
374      return *this;
375    }
376
377    ///Sets the map indicating the processed nodes.
378
379    ///Sets the map indicating the processed nodes.
380    ///If you don't use this function before calling \ref run(),
381    ///it will allocate one. The destructor deallocates this
382    ///automatically allocated map, of course.
383    ///\return <tt> (*this) </tt>
384    Bfs &processedMap(ProcessedMap &m)
385    {
386      if(local_processed) {
387        delete _processed;
388        local_processed=false;
389      }
390      _processed = &m;
391      return *this;
392    }
393
394    ///Sets the map storing the distances calculated by the algorithm.
395
396    ///Sets the map storing the distances calculated by the algorithm.
397    ///If you don't use this function before calling \ref run(),
398    ///it will allocate one. The destructor deallocates this
399    ///automatically allocated map, of course.
400    ///\return <tt> (*this) </tt>
401    Bfs &distMap(DistMap &m)
402    {
403      if(local_dist) {
404        delete _dist;
405        local_dist=false;
406      }
407      _dist = &m;
408      return *this;
409    }
410
411  public:
412    ///\name Execution control
413    ///The simplest way to execute the algorithm is to use
414    ///one of the member functions called \c run(...).
415    ///\n
416    ///If you need more control on the execution,
417    ///first you must call \ref init(), then you can add several source nodes
418    ///with \ref addSource().
419    ///Finally \ref start() will perform the actual path
420    ///computation.
421
422    ///@{
423
424    ///\brief Initializes the internal data structures.
425    ///
426    ///Initializes the internal data structures.
427    ///
428    void init()
429    {
430      create_maps();
431      _queue.resize(countNodes(*G));
432      _queue_head=_queue_tail=0;
433      _curr_dist=1;
434      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
435        _pred->set(u,INVALID);
436        _reached->set(u,false);
437        _processed->set(u,false);
438      }
439    }
440
441    ///Adds a new source node.
442
443    ///Adds a new source node to the set of nodes to be processed.
444    ///
445    void addSource(Node s)
446    {
447      if(!(*_reached)[s])
448        {
449          _reached->set(s,true);
450          _pred->set(s,INVALID);
451          _dist->set(s,0);
452          _queue[_queue_head++]=s;
453          _queue_next_dist=_queue_head;
454        }
455    }
456
457    ///Processes the next node.
458
459    ///Processes the next node.
460    ///
461    ///\return The processed node.
462    ///
463    ///\warning The queue must not be empty!
464    Node processNextNode()
465    {
466      if(_queue_tail==_queue_next_dist) {
467        _curr_dist++;
468        _queue_next_dist=_queue_head;
469      }
470      Node n=_queue[_queue_tail++];
471      _processed->set(n,true);
472      Node m;
473      for(OutArcIt e(*G,n);e!=INVALID;++e)
474        if(!(*_reached)[m=G->target(e)]) {
475          _queue[_queue_head++]=m;
476          _reached->set(m,true);
477          _pred->set(m,e);
478          _dist->set(m,_curr_dist);
479        }
480      return n;
481    }
482
483    ///Processes the next node.
484
485    ///Processes the next node. And checks that the given target node
486    ///is reached. If the target node is reachable from the processed
487    ///node then the reached parameter will be set true. The reached
488    ///parameter should be initially false.
489    ///
490    ///\param target The target node.
491    ///\retval reach Indicates that the target node is reached.
492    ///\return The processed node.
493    ///
494    ///\warning The queue must not be empty!
495    Node processNextNode(Node target, bool& reach)
496    {
497      if(_queue_tail==_queue_next_dist) {
498        _curr_dist++;
499        _queue_next_dist=_queue_head;
500      }
501      Node n=_queue[_queue_tail++];
502      _processed->set(n,true);
503      Node m;
504      for(OutArcIt e(*G,n);e!=INVALID;++e)
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);
510          reach = reach || (target == m);
511        }
512      return n;
513    }
514
515    ///Processes the next node.
516
517    ///Processes the next node. And checks that at least one of
518    ///reached node has true value in the \c nm node map. If one node
519    ///with true value is reachable from the processed node then the
520    ///rnode parameter will be set to the first of such nodes.
521    ///
522    ///\param nm The node map of possible targets.
523    ///\retval rnode The reached target node.
524    ///\return The processed node.
525    ///
526    ///\warning The queue must not be empty!
527    template<class NM>
528    Node processNextNode(const NM& nm, Node& rnode)
529    {
530      if(_queue_tail==_queue_next_dist) {
531        _curr_dist++;
532        _queue_next_dist=_queue_head;
533      }
534      Node n=_queue[_queue_tail++];
535      _processed->set(n,true);
536      Node m;
537      for(OutArcIt e(*G,n);e!=INVALID;++e)
538        if(!(*_reached)[m=G->target(e)]) {
539          _queue[_queue_head++]=m;
540          _reached->set(m,true);
541          _pred->set(m,e);
542          _dist->set(m,_curr_dist);
543          if (nm[m] && rnode == INVALID) rnode = m;
544        }
545      return n;
546    }
547
548    ///Next node to be processed.
549
550    ///Next node to be processed.
551    ///
552    ///\return The next node to be processed or INVALID if the queue is
553    /// empty.
554    Node nextNode()
555    {
556      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
557    }
558
559    ///\brief Returns \c false if there are nodes
560    ///to be processed in the queue
561    ///
562    ///Returns \c false if there are nodes
563    ///to be processed in the queue
564    bool emptyQueue() { return _queue_tail==_queue_head; }
565    ///Returns the number of the nodes to be processed.
566
567    ///Returns the number of the nodes to be processed in the queue.
568    int queueSize() { return _queue_head-_queue_tail; }
569
570    ///Executes the algorithm.
571
572    ///Executes the algorithm.
573    ///
574    ///\pre init() must be called and at least one node should be added
575    ///with addSource() before using this function.
576    ///
577    ///This method runs the %BFS algorithm from the root node(s)
578    ///in order to
579    ///compute the
580    ///shortest path to each node. The algorithm computes
581    ///- The shortest path tree.
582    ///- The distance of each node from the root(s).
583    void start()
584    {
585      while ( !emptyQueue() ) processNextNode();
586    }
587
588    ///Executes the algorithm until \c dest is reached.
589
590    ///Executes the algorithm until \c dest is reached.
591    ///
592    ///\pre init() must be called and at least one node should be added
593    ///with addSource() before using this function.
594    ///
595    ///This method runs the %BFS algorithm from the root node(s)
596    ///in order to compute the shortest path to \c dest.
597    ///The algorithm computes
598    ///- The shortest path to \c  dest.
599    ///- The distance of \c dest from the root(s).
600    void start(Node dest)
601    {
602      bool reach = false;
603      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
604    }
605
606    ///Executes the algorithm until a condition is met.
607
608    ///Executes the algorithm until a condition is met.
609    ///
610    ///\pre init() must be called and at least one node should be added
611    ///with addSource() before using this function.
612    ///
613    ///\param nm must be a bool (or convertible) node map. The
614    ///algorithm will stop when it reaches a node \c v with
615    /// <tt>nm[v]</tt> true.
616    ///
617    ///\return The reached node \c v with <tt>nm[v]</tt> true or
618    ///\c INVALID if no such node was found.
619    template<class NM>
620    Node start(const NM &nm)
621    {
622      Node rnode = INVALID;
623      while ( !emptyQueue() && rnode == INVALID ) {
624        processNextNode(nm, rnode);
625      }
626      return rnode;
627    }
628
629    ///Runs %BFS algorithm from node \c s.
630
631    ///This method runs the %BFS algorithm from a root node \c s
632    ///in order to
633    ///compute the
634    ///shortest path to each node. The algorithm computes
635    ///- The shortest path tree.
636    ///- The distance of each node from the root.
637    ///
638    ///\note b.run(s) is just a shortcut of the following code.
639    ///\code
640    ///  b.init();
641    ///  b.addSource(s);
642    ///  b.start();
643    ///\endcode
644    void run(Node s) {
645      init();
646      addSource(s);
647      start();
648    }
649
650    ///Finds the shortest path between \c s and \c t.
651
652    ///Finds the shortest path between \c s and \c t.
653    ///
654    ///\return The length of the shortest s---t path if there exists one,
655    ///0 otherwise.
656    ///\note Apart from the return value, b.run(s) is
657    ///just a shortcut of the following code.
658    ///\code
659    ///  b.init();
660    ///  b.addSource(s);
661    ///  b.start(t);
662    ///\endcode
663    int run(Node s,Node t) {
664      init();
665      addSource(s);
666      start(t);
667      return reached(t) ? _curr_dist : 0;
668    }
669
670    ///@}
671
672    ///\name Query Functions
673    ///The result of the %BFS algorithm can be obtained using these
674    ///functions.\n
675    ///Before the use of these functions,
676    ///either run() or start() must be calleb.
677
678    ///@{
679
680    typedef PredMapPath<Digraph, PredMap> Path;
681
682    ///Gives back the shortest path.
683
684    ///Gives back the shortest path.
685    ///\pre The \c t should be reachable from the source.
686    Path path(Node t)
687    {
688      return Path(*G, *_pred, t);
689    }
690
691    ///The distance of a node from the root(s).
692
693    ///Returns the distance of a node from the root(s).
694    ///\pre \ref run() must be called before using this function.
695    ///\warning If node \c v in unreachable from the root(s) the return value
696    ///of this function is undefined.
697    int dist(Node v) const { return (*_dist)[v]; }
698
699    ///Returns the 'previous arc' of the shortest path tree.
700
701    ///For a node \c v it returns the 'previous arc'
702    ///of the shortest path tree,
703    ///i.e. it returns the last arc of a shortest path from the root(s) to \c
704    ///v. It is \ref INVALID
705    ///if \c v is unreachable from the root(s) or \c v is a root. The
706    ///shortest path tree used here is equal to the shortest path tree used in
707    ///\ref predNode().
708    ///\pre Either \ref run() or \ref start() must be called before using
709    ///this function.
710    Arc predArc(Node v) const { return (*_pred)[v];}
711
712    ///Returns the 'previous node' of the shortest path tree.
713
714    ///For a node \c v it returns the 'previous node'
715    ///of the shortest path tree,
716    ///i.e. it returns the last but one node from a shortest path from the
717    ///root(a) to \c /v.
718    ///It is INVALID if \c v is unreachable from the root(s) or
719    ///if \c v itself a root.
720    ///The shortest path tree used here is equal to the shortest path
721    ///tree used in \ref predArc().
722    ///\pre Either \ref run() or \ref start() must be called before
723    ///using this function.
724    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
725                                  G->source((*_pred)[v]); }
726
727    ///Returns a reference to the NodeMap of distances.
728
729    ///Returns a reference to the NodeMap of distances.
730    ///\pre Either \ref run() or \ref init() must
731    ///be called before using this function.
732    const DistMap &distMap() const { return *_dist;}
733
734    ///Returns a reference to the shortest path tree map.
735
736    ///Returns a reference to the NodeMap of the arcs of the
737    ///shortest path tree.
738    ///\pre Either \ref run() or \ref init()
739    ///must be called before using this function.
740    const PredMap &predMap() const { return *_pred;}
741
742    ///Checks if a node is reachable from the root.
743
744    ///Returns \c true if \c v is reachable from the root.
745    ///\warning The source nodes are indicated as unreached.
746    ///\pre Either \ref run() or \ref start()
747    ///must be called before using this function.
748    ///
749    bool reached(Node v) { return (*_reached)[v]; }
750
751    ///@}
752  };
753
754  ///Default traits class of Bfs function.
755
756  ///Default traits class of Bfs function.
757  ///\tparam GR Digraph type.
758  template<class GR>
759  struct BfsWizardDefaultTraits
760  {
761    ///The digraph type the algorithm runs on.
762    typedef GR Digraph;
763    ///\brief The type of the map that stores the last
764    ///arcs of the shortest paths.
765    ///
766    ///The type of the map that stores the last
767    ///arcs of the shortest paths.
768    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
769    ///
770    typedef NullMap<typename Digraph::Node,typename GR::Arc> PredMap;
771    ///Instantiates a PredMap.
772
773    ///This function instantiates a \ref PredMap.
774    ///\param g is the digraph, to which we would like to define the PredMap.
775    ///\todo The digraph alone may be insufficient to initialize
776#ifdef DOXYGEN
777    static PredMap *createPredMap(const GR &g)
778#else
779    static PredMap *createPredMap(const GR &)
780#endif
781    {
782      return new PredMap();
783    }
784
785    ///The type of the map that indicates which nodes are processed.
786
787    ///The type of the map that indicates which nodes are processed.
788    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
789    ///\todo named parameter to set this type, function to read and write.
790    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
791    ///Instantiates a ProcessedMap.
792
793    ///This function instantiates a \ref ProcessedMap.
794    ///\param g is the digraph, to which
795    ///we would like to define the \ref ProcessedMap
796#ifdef DOXYGEN
797    static ProcessedMap *createProcessedMap(const GR &g)
798#else
799    static ProcessedMap *createProcessedMap(const GR &)
800#endif
801    {
802      return new ProcessedMap();
803    }
804    ///The type of the map that indicates which nodes are reached.
805
806    ///The type of the map that indicates which nodes are reached.
807    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
808    ///\todo named parameter to set this type, function to read and write.
809    typedef typename Digraph::template NodeMap<bool> ReachedMap;
810    ///Instantiates a ReachedMap.
811
812    ///This function instantiates a \ref ReachedMap.
813    ///\param G is the digraph, to which
814    ///we would like to define the \ref ReachedMap.
815    static ReachedMap *createReachedMap(const GR &G)
816    {
817      return new ReachedMap(G);
818    }
819    ///The type of the map that stores the dists of the nodes.
820
821    ///The type of the map that stores the dists of the nodes.
822    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
823    ///
824    typedef NullMap<typename Digraph::Node,int> DistMap;
825    ///Instantiates a DistMap.
826
827    ///This function instantiates a \ref DistMap.
828    ///\param g is the digraph, to which we would like to define
829    ///the \ref DistMap
830#ifdef DOXYGEN
831    static DistMap *createDistMap(const GR &g)
832#else
833    static DistMap *createDistMap(const GR &)
834#endif
835    {
836      return new DistMap();
837    }
838  };
839
840  /// Default traits used by \ref BfsWizard
841
842  /// To make it easier to use Bfs algorithm
843  ///we have created a wizard class.
844  /// This \ref BfsWizard class needs default traits,
845  ///as well as the \ref Bfs class.
846  /// The \ref BfsWizardBase is a class to be the default traits of the
847  /// \ref BfsWizard class.
848  template<class GR>
849  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
850  {
851
852    typedef BfsWizardDefaultTraits<GR> Base;
853  protected:
854    /// Type of the nodes in the digraph.
855    typedef typename Base::Digraph::Node Node;
856
857    /// Pointer to the underlying digraph.
858    void *_g;
859    ///Pointer to the map of reached nodes.
860    void *_reached;
861    ///Pointer to the map of processed nodes.
862    void *_processed;
863    ///Pointer to the map of predecessors arcs.
864    void *_pred;
865    ///Pointer to the map of distances.
866    void *_dist;
867    ///Pointer to the source node.
868    Node _source;
869
870    public:
871    /// Constructor.
872
873    /// This constructor does not require parameters, therefore it initiates
874    /// all of the attributes to default values (0, INVALID).
875    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
876                           _dist(0), _source(INVALID) {}
877
878    /// Constructor.
879
880    /// This constructor requires some parameters,
881    /// listed in the parameters list.
882    /// Others are initiated to 0.
883    /// \param g is the initial value of  \ref _g
884    /// \param s is the initial value of  \ref _source
885    BfsWizardBase(const GR &g, Node s=INVALID) :
886      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
887      _reached(0), _processed(0), _pred(0), _dist(0), _source(s) {}
888
889  };
890
891  /// A class to make the usage of Bfs algorithm easier
892
893  /// This class is created to make it easier to use Bfs algorithm.
894  /// It uses the functions and features of the plain \ref Bfs,
895  /// but it is much simpler to use it.
896  ///
897  /// Simplicity means that the way to change the types defined
898  /// in the traits class is based on functions that returns the new class
899  /// and not on templatable built-in classes.
900  /// When using the plain \ref Bfs
901  /// the new class with the modified type comes from
902  /// the original class by using the ::
903  /// operator. In the case of \ref BfsWizard only
904  /// a function have to be called and it will
905  /// return the needed class.
906  ///
907  /// It does not have own \ref run method. When its \ref run method is called
908  /// it initiates a plain \ref Bfs class, and calls the \ref Bfs::run
909  /// method of it.
910  template<class TR>
911  class BfsWizard : public TR
912  {
913    typedef TR Base;
914
915    ///The type of the underlying digraph.
916    typedef typename TR::Digraph Digraph;
917    //\e
918    typedef typename Digraph::Node Node;
919    //\e
920    typedef typename Digraph::NodeIt NodeIt;
921    //\e
922    typedef typename Digraph::Arc Arc;
923    //\e
924    typedef typename Digraph::OutArcIt OutArcIt;
925
926    ///\brief The type of the map that stores
927    ///the reached nodes
928    typedef typename TR::ReachedMap ReachedMap;
929    ///\brief The type of the map that stores
930    ///the processed nodes
931    typedef typename TR::ProcessedMap ProcessedMap;
932    ///\brief The type of the map that stores the last
933    ///arcs of the shortest paths.
934    typedef typename TR::PredMap PredMap;
935    ///The type of the map that stores the dists of the nodes.
936    typedef typename TR::DistMap DistMap;
937
938  public:
939    /// Constructor.
940    BfsWizard() : TR() {}
941
942    /// Constructor that requires parameters.
943
944    /// Constructor that requires parameters.
945    /// These parameters will be the default values for the traits class.
946    BfsWizard(const Digraph &g, Node s=INVALID) :
947      TR(g,s) {}
948
949    ///Copy constructor
950    BfsWizard(const TR &b) : TR(b) {}
951
952    ~BfsWizard() {}
953
954    ///Runs Bfs algorithm from a given node.
955
956    ///Runs Bfs algorithm from a given node.
957    ///The node can be given by the \ref source function.
958    void run()
959    {
960      if(Base::_source==INVALID) throw UninitializedParameter();
961      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
962      if(Base::_reached)
963        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
964      if(Base::_processed)
965        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
966      if(Base::_pred)
967        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
968      if(Base::_dist)
969        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
970      alg.run(Base::_source);
971    }
972
973    ///Runs Bfs algorithm from the given node.
974
975    ///Runs Bfs algorithm from the given node.
976    ///\param s is the given source.
977    void run(Node s)
978    {
979      Base::_source=s;
980      run();
981    }
982
983    template<class T>
984    struct DefPredMapBase : public Base {
985      typedef T PredMap;
986      static PredMap *createPredMap(const Digraph &) { return 0; };
987      DefPredMapBase(const TR &b) : TR(b) {}
988    };
989
990    ///\brief \ref named-templ-param "Named parameter"
991    ///function for setting PredMap
992    ///
993    /// \ref named-templ-param "Named parameter"
994    ///function for setting PredMap
995    ///
996    template<class T>
997    BfsWizard<DefPredMapBase<T> > predMap(const T &t)
998    {
999      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1000      return BfsWizard<DefPredMapBase<T> >(*this);
1001    }
1002
1003
1004    template<class T>
1005    struct DefReachedMapBase : public Base {
1006      typedef T ReachedMap;
1007      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
1008      DefReachedMapBase(const TR &b) : TR(b) {}
1009    };
1010
1011    ///\brief \ref named-templ-param "Named parameter"
1012    ///function for setting ReachedMap
1013    ///
1014    /// \ref named-templ-param "Named parameter"
1015    ///function for setting ReachedMap
1016    ///
1017    template<class T>
1018    BfsWizard<DefReachedMapBase<T> > reachedMap(const T &t)
1019    {
1020      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
1021      return BfsWizard<DefReachedMapBase<T> >(*this);
1022    }
1023
1024
1025    template<class T>
1026    struct DefProcessedMapBase : public Base {
1027      typedef T ProcessedMap;
1028      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
1029      DefProcessedMapBase(const TR &b) : TR(b) {}
1030    };
1031
1032    ///\brief \ref named-templ-param "Named parameter"
1033    ///function for setting ProcessedMap
1034    ///
1035    /// \ref named-templ-param "Named parameter"
1036    ///function for setting ProcessedMap
1037    ///
1038    template<class T>
1039    BfsWizard<DefProcessedMapBase<T> > processedMap(const T &t)
1040    {
1041      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
1042      return BfsWizard<DefProcessedMapBase<T> >(*this);
1043    }
1044
1045
1046    template<class T>
1047    struct DefDistMapBase : public Base {
1048      typedef T DistMap;
1049      static DistMap *createDistMap(const Digraph &) { return 0; };
1050      DefDistMapBase(const TR &b) : TR(b) {}
1051    };
1052
1053    ///\brief \ref named-templ-param "Named parameter"
1054    ///function for setting DistMap type
1055    ///
1056    /// \ref named-templ-param "Named parameter"
1057    ///function for setting DistMap type
1058    ///
1059    template<class T>
1060    BfsWizard<DefDistMapBase<T> > distMap(const T &t)
1061    {
1062      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1063      return BfsWizard<DefDistMapBase<T> >(*this);
1064    }
1065
1066    /// Sets the source node, from which the Bfs algorithm runs.
1067
1068    /// Sets the source node, from which the Bfs algorithm runs.
1069    /// \param s is the source node.
1070    BfsWizard<TR> &source(Node s)
1071    {
1072      Base::_source=s;
1073      return *this;
1074    }
1075
1076  };
1077
1078  ///Function type interface for Bfs algorithm.
1079
1080  /// \ingroup search
1081  ///Function type interface for Bfs algorithm.
1082  ///
1083  ///This function also has several
1084  ///\ref named-templ-func-param "named parameters",
1085  ///they are declared as the members of class \ref BfsWizard.
1086  ///The following
1087  ///example shows how to use these parameters.
1088  ///\code
1089  ///  bfs(g,source).predMap(preds).run();
1090  ///\endcode
1091  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1092  ///to the end of the parameter list.
1093  ///\sa BfsWizard
1094  ///\sa Bfs
1095  template<class GR>
1096  BfsWizard<BfsWizardBase<GR> >
1097  bfs(const GR &g,typename GR::Node s=INVALID)
1098  {
1099    return BfsWizard<BfsWizardBase<GR> >(g,s);
1100  }
1101
1102#ifdef DOXYGEN
1103  /// \brief Visitor class for bfs.
1104  ///
1105  /// This class defines the interface of the BfsVisit events, and
1106  /// it could be the base of a real Visitor class.
1107  template <typename _Digraph>
1108  struct BfsVisitor {
1109    typedef _Digraph Digraph;
1110    typedef typename Digraph::Arc Arc;
1111    typedef typename Digraph::Node Node;
1112    /// \brief Called when the arc reach a node.
1113    ///
1114    /// It is called when the bfs find an arc which target is not
1115    /// reached yet.
1116    void discover(const Arc& arc) {}
1117    /// \brief Called when the node reached first time.
1118    ///
1119    /// It is Called when the node reached first time.
1120    void reach(const Node& node) {}
1121    /// \brief Called when the arc examined but target of the arc
1122    /// already discovered.
1123    ///
1124    /// It called when the arc examined but the target of the arc
1125    /// already discovered.
1126    void examine(const Arc& arc) {}
1127    /// \brief Called for the source node of the bfs.
1128    ///
1129    /// It is called for the source node of the bfs.
1130    void start(const Node& node) {}
1131    /// \brief Called when the node processed.
1132    ///
1133    /// It is Called when the node processed.
1134    void process(const Node& node) {}
1135  };
1136#else
1137  template <typename _Digraph>
1138  struct BfsVisitor {
1139    typedef _Digraph Digraph;
1140    typedef typename Digraph::Arc Arc;
1141    typedef typename Digraph::Node Node;
1142    void discover(const Arc&) {}
1143    void reach(const Node&) {}
1144    void examine(const Arc&) {}
1145    void start(const Node&) {}
1146    void process(const Node&) {}
1147
1148    template <typename _Visitor>
1149    struct Constraints {
1150      void constraints() {
1151        Arc arc;
1152        Node node;
1153        visitor.discover(arc);
1154        visitor.reach(node);
1155        visitor.examine(arc);
1156        visitor.start(node);
1157        visitor.process(node);
1158      }
1159      _Visitor& visitor;
1160    };
1161  };
1162#endif
1163
1164  /// \brief Default traits class of BfsVisit class.
1165  ///
1166  /// Default traits class of BfsVisit class.
1167  /// \tparam _Digraph Digraph type.
1168  template<class _Digraph>
1169  struct BfsVisitDefaultTraits {
1170
1171    /// \brief The digraph type the algorithm runs on.
1172    typedef _Digraph Digraph;
1173
1174    /// \brief The type of the map that indicates which nodes are reached.
1175    ///
1176    /// The type of the map that indicates which nodes are reached.
1177    /// It must meet the \ref concepts::WriteMap "WriteMap" concept.
1178    /// \todo named parameter to set this type, function to read and write.
1179    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1180
1181    /// \brief Instantiates a ReachedMap.
1182    ///
1183    /// This function instantiates a \ref ReachedMap.
1184    /// \param digraph is the digraph, to which
1185    /// we would like to define the \ref ReachedMap.
1186    static ReachedMap *createReachedMap(const Digraph &digraph) {
1187      return new ReachedMap(digraph);
1188    }
1189
1190  };
1191
1192  /// \ingroup search
1193  ///
1194  /// \brief %BFS Visit algorithm class.
1195  ///
1196  /// This class provides an efficient implementation of the %BFS algorithm
1197  /// with visitor interface.
1198  ///
1199  /// The %BfsVisit class provides an alternative interface to the Bfs
1200  /// class. It works with callback mechanism, the BfsVisit object calls
1201  /// on every bfs event the \c Visitor class member functions.
1202  ///
1203  /// \tparam _Digraph The digraph type the algorithm runs on.
1204  /// The default value is
1205  /// \ref ListDigraph. The value of _Digraph is not used directly by Bfs, it
1206  /// is only passed to \ref BfsDefaultTraits.
1207  /// \tparam _Visitor The Visitor object for the algorithm. The
1208  /// \ref BfsVisitor "BfsVisitor<_Digraph>" is an empty Visitor which
1209  /// does not observe the Bfs events. If you want to observe the bfs
1210  /// events you should implement your own Visitor class.
1211  /// \tparam _Traits Traits class to set various data types used by the
1212  /// algorithm. The default traits class is
1213  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<_Digraph>".
1214  /// See \ref BfsVisitDefaultTraits for the documentation of
1215  /// a Bfs visit traits class.
1216#ifdef DOXYGEN
1217  template <typename _Digraph, typename _Visitor, typename _Traits>
1218#else
1219  template <typename _Digraph = ListDigraph,
1220            typename _Visitor = BfsVisitor<_Digraph>,
1221            typename _Traits = BfsDefaultTraits<_Digraph> >
1222#endif
1223  class BfsVisit {
1224  public:
1225
1226    /// \brief \ref Exception for uninitialized parameters.
1227    ///
1228    /// This error represents problems in the initialization
1229    /// of the parameters of the algorithms.
1230    class UninitializedParameter : public lemon::UninitializedParameter {
1231    public:
1232      virtual const char* what() const throw()
1233      {
1234        return "lemon::BfsVisit::UninitializedParameter";
1235      }
1236    };
1237
1238    typedef _Traits Traits;
1239
1240    typedef typename Traits::Digraph Digraph;
1241
1242    typedef _Visitor Visitor;
1243
1244    ///The type of the map indicating which nodes are reached.
1245    typedef typename Traits::ReachedMap ReachedMap;
1246
1247  private:
1248
1249    typedef typename Digraph::Node Node;
1250    typedef typename Digraph::NodeIt NodeIt;
1251    typedef typename Digraph::Arc Arc;
1252    typedef typename Digraph::OutArcIt OutArcIt;
1253
1254    /// Pointer to the underlying digraph.
1255    const Digraph *_digraph;
1256    /// Pointer to the visitor object.
1257    Visitor *_visitor;
1258    ///Pointer to the map of reached status of the nodes.
1259    ReachedMap *_reached;
1260    ///Indicates if \ref _reached is locally allocated (\c true) or not.
1261    bool local_reached;
1262
1263    std::vector<typename Digraph::Node> _list;
1264    int _list_front, _list_back;
1265
1266    /// \brief Creates the maps if necessary.
1267    ///
1268    /// Creates the maps if necessary.
1269    void create_maps() {
1270      if(!_reached) {
1271        local_reached = true;
1272        _reached = Traits::createReachedMap(*_digraph);
1273      }
1274    }
1275
1276  protected:
1277
1278    BfsVisit() {}
1279
1280  public:
1281
1282    typedef BfsVisit Create;
1283
1284    /// \name Named template parameters
1285
1286    ///@{
1287    template <class T>
1288    struct DefReachedMapTraits : public Traits {
1289      typedef T ReachedMap;
1290      static ReachedMap *createReachedMap(const Digraph &digraph) {
1291        throw UninitializedParameter();
1292      }
1293    };
1294    /// \brief \ref named-templ-param "Named parameter" for setting
1295    /// ReachedMap type
1296    ///
1297    /// \ref named-templ-param "Named parameter" for setting ReachedMap type
1298    template <class T>
1299    struct DefReachedMap : public BfsVisit< Digraph, Visitor,
1300                                            DefReachedMapTraits<T> > {
1301      typedef BfsVisit< Digraph, Visitor, DefReachedMapTraits<T> > Create;
1302    };
1303    ///@}
1304
1305  public:
1306
1307    /// \brief Constructor.
1308    ///
1309    /// Constructor.
1310    ///
1311    /// \param digraph the digraph the algorithm will run on.
1312    /// \param visitor The visitor of the algorithm.
1313    ///
1314    BfsVisit(const Digraph& digraph, Visitor& visitor)
1315      : _digraph(&digraph), _visitor(&visitor),
1316        _reached(0), local_reached(false) {}
1317
1318    /// \brief Destructor.
1319    ///
1320    /// Destructor.
1321    ~BfsVisit() {
1322      if(local_reached) delete _reached;
1323    }
1324
1325    /// \brief Sets the map indicating if a node is reached.
1326    ///
1327    /// Sets the map indicating if a node is reached.
1328    /// If you don't use this function before calling \ref run(),
1329    /// it will allocate one. The destuctor deallocates this
1330    /// automatically allocated map, of course.
1331    /// \return <tt> (*this) </tt>
1332    BfsVisit &reachedMap(ReachedMap &m) {
1333      if(local_reached) {
1334        delete _reached;
1335        local_reached = false;
1336      }
1337      _reached = &m;
1338      return *this;
1339    }
1340
1341  public:
1342    /// \name Execution control
1343    /// The simplest way to execute the algorithm is to use
1344    /// one of the member functions called \c run(...).
1345    /// \n
1346    /// If you need more control on the execution,
1347    /// first you must call \ref init(), then you can adda source node
1348    /// with \ref addSource().
1349    /// Finally \ref start() will perform the actual path
1350    /// computation.
1351
1352    /// @{
1353    /// \brief Initializes the internal data structures.
1354    ///
1355    /// Initializes the internal data structures.
1356    ///
1357    void init() {
1358      create_maps();
1359      _list.resize(countNodes(*_digraph));
1360      _list_front = _list_back = -1;
1361      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
1362        _reached->set(u, false);
1363      }
1364    }
1365
1366    /// \brief Adds a new source node.
1367    ///
1368    /// Adds a new source node to the set of nodes to be processed.
1369    void addSource(Node s) {
1370      if(!(*_reached)[s]) {
1371          _reached->set(s,true);
1372          _visitor->start(s);
1373          _visitor->reach(s);
1374          _list[++_list_back] = s;
1375        }
1376    }
1377
1378    /// \brief Processes the next node.
1379    ///
1380    /// Processes the next node.
1381    ///
1382    /// \return The processed node.
1383    ///
1384    /// \pre The queue must not be empty!
1385    Node processNextNode() {
1386      Node n = _list[++_list_front];
1387      _visitor->process(n);
1388      Arc e;
1389      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1390        Node m = _digraph->target(e);
1391        if (!(*_reached)[m]) {
1392          _visitor->discover(e);
1393          _visitor->reach(m);
1394          _reached->set(m, true);
1395          _list[++_list_back] = m;
1396        } else {
1397          _visitor->examine(e);
1398        }
1399      }
1400      return n;
1401    }
1402
1403    /// \brief Processes the next node.
1404    ///
1405    /// Processes the next node. And checks that the given target node
1406    /// is reached. If the target node is reachable from the processed
1407    /// node then the reached parameter will be set true. The reached
1408    /// parameter should be initially false.
1409    ///
1410    /// \param target The target node.
1411    /// \retval reach Indicates that the target node is reached.
1412    /// \return The processed node.
1413    ///
1414    /// \warning The queue must not be empty!
1415    Node processNextNode(Node target, bool& reach) {
1416      Node n = _list[++_list_front];
1417      _visitor->process(n);
1418      Arc e;
1419      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1420        Node m = _digraph->target(e);
1421        if (!(*_reached)[m]) {
1422          _visitor->discover(e);
1423          _visitor->reach(m);
1424          _reached->set(m, true);
1425          _list[++_list_back] = m;
1426          reach = reach || (target == m);
1427        } else {
1428          _visitor->examine(e);
1429        }
1430      }
1431      return n;
1432    }
1433
1434    /// \brief Processes the next node.
1435    ///
1436    /// Processes the next node. And checks that at least one of
1437    /// reached node has true value in the \c nm node map. If one node
1438    /// with true value is reachable from the processed node then the
1439    /// rnode parameter will be set to the first of such nodes.
1440    ///
1441    /// \param nm The node map of possible targets.
1442    /// \retval rnode The reached target node.
1443    /// \return The processed node.
1444    ///
1445    /// \warning The queue must not be empty!
1446    template <typename NM>
1447    Node processNextNode(const NM& nm, Node& rnode) {
1448      Node n = _list[++_list_front];
1449      _visitor->process(n);
1450      Arc e;
1451      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1452        Node m = _digraph->target(e);
1453        if (!(*_reached)[m]) {
1454          _visitor->discover(e);
1455          _visitor->reach(m);
1456          _reached->set(m, true);
1457          _list[++_list_back] = m;
1458          if (nm[m] && rnode == INVALID) rnode = m;
1459        } else {
1460          _visitor->examine(e);
1461        }
1462      }
1463      return n;
1464    }
1465
1466    /// \brief Next node to be processed.
1467    ///
1468    /// Next node to be processed.
1469    ///
1470    /// \return The next node to be processed or INVALID if the stack is
1471    /// empty.
1472    Node nextNode() {
1473      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1474    }
1475
1476    /// \brief Returns \c false if there are nodes
1477    /// to be processed in the queue
1478    ///
1479    /// Returns \c false if there are nodes
1480    /// to be processed in the queue
1481    bool emptyQueue() { return _list_front == _list_back; }
1482
1483    /// \brief Returns the number of the nodes to be processed.
1484    ///
1485    /// Returns the number of the nodes to be processed in the queue.
1486    int queueSize() { return _list_back - _list_front; }
1487
1488    /// \brief Executes the algorithm.
1489    ///
1490    /// Executes the algorithm.
1491    ///
1492    /// \pre init() must be called and at least one node should be added
1493    /// with addSource() before using this function.
1494    void start() {
1495      while ( !emptyQueue() ) processNextNode();
1496    }
1497
1498    /// \brief Executes the algorithm until \c dest is reached.
1499    ///
1500    /// Executes the algorithm until \c dest is reached.
1501    ///
1502    /// \pre init() must be called and at least one node should be added
1503    /// with addSource() before using this function.
1504    void start(Node dest) {
1505      bool reach = false;
1506      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
1507    }
1508
1509    /// \brief Executes the algorithm until a condition is met.
1510    ///
1511    /// Executes the algorithm until a condition is met.
1512    ///
1513    /// \pre init() must be called and at least one node should be added
1514    /// with addSource() before using this function.
1515    ///
1516    ///\param nm must be a bool (or convertible) node map. The
1517    ///algorithm will stop when it reaches a node \c v with
1518    /// <tt>nm[v]</tt> true.
1519    ///
1520    ///\return The reached node \c v with <tt>nm[v]</tt> true or
1521    ///\c INVALID if no such node was found.
1522    template <typename NM>
1523    Node start(const NM &nm) {
1524      Node rnode = INVALID;
1525      while ( !emptyQueue() && rnode == INVALID ) {
1526        processNextNode(nm, rnode);
1527      }
1528      return rnode;
1529    }
1530
1531    /// \brief Runs %BFSVisit algorithm from node \c s.
1532    ///
1533    /// This method runs the %BFS algorithm from a root node \c s.
1534    /// \note b.run(s) is just a shortcut of the following code.
1535    ///\code
1536    ///   b.init();
1537    ///   b.addSource(s);
1538    ///   b.start();
1539    ///\endcode
1540    void run(Node s) {
1541      init();
1542      addSource(s);
1543      start();
1544    }
1545
1546    /// \brief Runs %BFSVisit algorithm to visit all nodes in the digraph.
1547    ///
1548    /// This method runs the %BFS algorithm in order to
1549    /// compute the %BFS path to each node. The algorithm computes
1550    /// - The %BFS tree.
1551    /// - The distance of each node from the root in the %BFS tree.
1552    ///
1553    ///\note b.run() is just a shortcut of the following code.
1554    ///\code
1555    ///  b.init();
1556    ///  for (NodeIt it(digraph); it != INVALID; ++it) {
1557    ///    if (!b.reached(it)) {
1558    ///      b.addSource(it);
1559    ///      b.start();
1560    ///    }
1561    ///  }
1562    ///\endcode
1563    void run() {
1564      init();
1565      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1566        if (!reached(it)) {
1567          addSource(it);
1568          start();
1569        }
1570      }
1571    }
1572    ///@}
1573
1574    /// \name Query Functions
1575    /// The result of the %BFS algorithm can be obtained using these
1576    /// functions.\n
1577    /// Before the use of these functions,
1578    /// either run() or start() must be called.
1579    ///@{
1580
1581    /// \brief Checks if a node is reachable from the root.
1582    ///
1583    /// Returns \c true if \c v is reachable from the root(s).
1584    /// \warning The source nodes are inditated as unreachable.
1585    /// \pre Either \ref run() or \ref start()
1586    /// must be called before using this function.
1587    ///
1588    bool reached(Node v) { return (*_reached)[v]; }
1589    ///@}
1590  };
1591
1592} //END OF NAMESPACE LEMON
1593
1594#endif
1595
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