COIN-OR::LEMON - Graph Library

source: lemon-1.0/lemon/bfs.h @ 167:d57ae6f0a335

Last change on this file since 167:d57ae6f0a335 was 158:500f3cbff9e4, checked in by Balazs Dezso <deba@…>, 11 years ago

Wrong member variable settings bug fix. (Ticket #95)

File size: 47.9 KB
Line 
1/* -*- C++ -*-
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/graph_utils.h>
28#include <lemon/bits/path_dump.h>
29#include <lemon/bits/invalid.h>
30#include <lemon/error.h>
31#include <lemon/maps.h>
32
33namespace lemon {
34
35
36 
37  ///Default traits class of Bfs class.
38
39  ///Default traits class of Bfs class.
40  ///\tparam GR Digraph type.
41  template<class GR>
42  struct BfsDefaultTraits
43  {
44    ///The digraph type the algorithm runs on.
45    typedef GR Digraph;
46    ///\brief The type of the map that stores the last
47    ///arcs of the shortest paths.
48    ///
49    ///The type of the map that stores the last
50    ///arcs of the shortest paths.
51    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
52    ///
53    typedef typename Digraph::template NodeMap<typename GR::Arc> PredMap;
54    ///Instantiates a PredMap.
55 
56    ///This function instantiates a \ref PredMap.
57    ///\param G is the digraph, to which we would like to define the PredMap.
58    ///\todo The digraph alone may be insufficient to initialize
59    static PredMap *createPredMap(const GR &G)
60    {
61      return new PredMap(G);
62    }
63    ///The type of the map that indicates which nodes are processed.
64 
65    ///The type of the map that indicates which nodes are processed.
66    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
67    ///\todo named parameter to set this type, function to read and write.
68    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
69    ///Instantiates a ProcessedMap.
70 
71    ///This function instantiates a \ref ProcessedMap.
72    ///\param g is the digraph, to which
73    ///we would like to define the \ref ProcessedMap
74#ifdef DOXYGEN
75    static ProcessedMap *createProcessedMap(const GR &g)
76#else
77    static ProcessedMap *createProcessedMap(const GR &)
78#endif
79    {
80      return new ProcessedMap();
81    }
82    ///The type of the map that indicates which nodes are reached.
83 
84    ///The type of the map that indicates which nodes are reached.
85    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
86    ///\todo named parameter to set this type, function to read and write.
87    typedef typename Digraph::template NodeMap<bool> ReachedMap;
88    ///Instantiates a ReachedMap.
89 
90    ///This function instantiates a \ref ReachedMap.
91    ///\param G is the digraph, to which
92    ///we would like to define the \ref ReachedMap.
93    static ReachedMap *createReachedMap(const GR &G)
94    {
95      return new ReachedMap(G);
96    }
97    ///The type of the map that stores the dists of the nodes.
98 
99    ///The type of the map that stores the dists of the nodes.
100    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
101    ///
102    typedef typename Digraph::template NodeMap<int> DistMap;
103    ///Instantiates a DistMap.
104 
105    ///This function instantiates a \ref DistMap.
106    ///\param G is the digraph, to which we would like to define 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 the \ref DistMap
829#ifdef DOXYGEN
830    static DistMap *createDistMap(const GR &g)
831#else
832    static DistMap *createDistMap(const GR &)
833#endif
834    {
835      return new DistMap();
836    }
837  };
838 
839  /// Default traits used by \ref BfsWizard
840
841  /// To make it easier to use Bfs algorithm
842  ///we have created a wizard class.
843  /// This \ref BfsWizard class needs default traits,
844  ///as well as the \ref Bfs class.
845  /// The \ref BfsWizardBase is a class to be the default traits of the
846  /// \ref BfsWizard class.
847  template<class GR>
848  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
849  {
850
851    typedef BfsWizardDefaultTraits<GR> Base;
852  protected:
853    /// Type of the nodes in the digraph.
854    typedef typename Base::Digraph::Node Node;
855
856    /// Pointer to the underlying digraph.
857    void *_g;
858    ///Pointer to the map of reached nodes.
859    void *_reached;
860    ///Pointer to the map of processed nodes.
861    void *_processed;
862    ///Pointer to the map of predecessors arcs.
863    void *_pred;
864    ///Pointer to the map of distances.
865    void *_dist;
866    ///Pointer to the source node.
867    Node _source;
868   
869    public:
870    /// Constructor.
871   
872    /// This constructor does not require parameters, therefore it initiates
873    /// all of the attributes to default values (0, INVALID).
874    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
875                           _dist(0), _source(INVALID) {}
876
877    /// Constructor.
878   
879    /// This constructor requires some parameters,
880    /// listed in the parameters list.
881    /// Others are initiated to 0.
882    /// \param g is the initial value of  \ref _g
883    /// \param s is the initial value of  \ref _source
884    BfsWizardBase(const GR &g, Node s=INVALID) :
885      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
886      _reached(0), _processed(0), _pred(0), _dist(0), _source(s) {}
887
888  };
889 
890  /// A class to make the usage of Bfs algorithm easier
891
892  /// This class is created to make it easier to use Bfs algorithm.
893  /// It uses the functions and features of the plain \ref Bfs,
894  /// but it is much simpler to use it.
895  ///
896  /// Simplicity means that the way to change the types defined
897  /// in the traits class is based on functions that returns the new class
898  /// and not on templatable built-in classes.
899  /// When using the plain \ref Bfs
900  /// the new class with the modified type comes from
901  /// the original class by using the ::
902  /// operator. In the case of \ref BfsWizard only
903  /// a function have to be called and it will
904  /// return the needed class.
905  ///
906  /// It does not have own \ref run method. When its \ref run method is called
907  /// it initiates a plain \ref Bfs class, and calls the \ref Bfs::run
908  /// method of it.
909  template<class TR>
910  class BfsWizard : public TR
911  {
912    typedef TR Base;
913
914    ///The type of the underlying digraph.
915    typedef typename TR::Digraph Digraph;
916    //\e
917    typedef typename Digraph::Node Node;
918    //\e
919    typedef typename Digraph::NodeIt NodeIt;
920    //\e
921    typedef typename Digraph::Arc Arc;
922    //\e
923    typedef typename Digraph::OutArcIt OutArcIt;
924   
925    ///\brief The type of the map that stores
926    ///the reached nodes
927    typedef typename TR::ReachedMap ReachedMap;
928    ///\brief The type of the map that stores
929    ///the processed nodes
930    typedef typename TR::ProcessedMap ProcessedMap;
931    ///\brief The type of the map that stores the last
932    ///arcs of the shortest paths.
933    typedef typename TR::PredMap PredMap;
934    ///The type of the map that stores the dists of the nodes.
935    typedef typename TR::DistMap DistMap;
936
937  public:
938    /// Constructor.
939    BfsWizard() : TR() {}
940
941    /// Constructor that requires parameters.
942
943    /// Constructor that requires parameters.
944    /// These parameters will be the default values for the traits class.
945    BfsWizard(const Digraph &g, Node s=INVALID) :
946      TR(g,s) {}
947
948    ///Copy constructor
949    BfsWizard(const TR &b) : TR(b) {}
950
951    ~BfsWizard() {}
952
953    ///Runs Bfs algorithm from a given node.
954   
955    ///Runs Bfs algorithm from a given node.
956    ///The node can be given by the \ref source function.
957    void run()
958    {
959      if(Base::_source==INVALID) throw UninitializedParameter();
960      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
961      if(Base::_reached)
962        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
963      if(Base::_processed)
964        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
965      if(Base::_pred)
966        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
967      if(Base::_dist)
968        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
969      alg.run(Base::_source);
970    }
971
972    ///Runs Bfs algorithm from the given node.
973
974    ///Runs Bfs algorithm from the given node.
975    ///\param s is the given source.
976    void run(Node s)
977    {
978      Base::_source=s;
979      run();
980    }
981
982    template<class T>
983    struct DefPredMapBase : public Base {
984      typedef T PredMap;
985      static PredMap *createPredMap(const Digraph &) { return 0; };
986      DefPredMapBase(const TR &b) : TR(b) {}
987    };
988   
989    ///\brief \ref named-templ-param "Named parameter"
990    ///function for setting PredMap
991    ///
992    /// \ref named-templ-param "Named parameter"
993    ///function for setting PredMap
994    ///
995    template<class T>
996    BfsWizard<DefPredMapBase<T> > predMap(const T &t)
997    {
998      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
999      return BfsWizard<DefPredMapBase<T> >(*this);
1000    }
1001   
1002 
1003    template<class T>
1004    struct DefReachedMapBase : public Base {
1005      typedef T ReachedMap;
1006      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
1007      DefReachedMapBase(const TR &b) : TR(b) {}
1008    };
1009   
1010    ///\brief \ref named-templ-param "Named parameter"
1011    ///function for setting ReachedMap
1012    ///
1013    /// \ref named-templ-param "Named parameter"
1014    ///function for setting ReachedMap
1015    ///
1016    template<class T>
1017    BfsWizard<DefReachedMapBase<T> > reachedMap(const T &t)
1018    {
1019      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
1020      return BfsWizard<DefReachedMapBase<T> >(*this);
1021    }
1022   
1023
1024    template<class T>
1025    struct DefProcessedMapBase : public Base {
1026      typedef T ProcessedMap;
1027      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
1028      DefProcessedMapBase(const TR &b) : TR(b) {}
1029    };
1030   
1031    ///\brief \ref named-templ-param "Named parameter"
1032    ///function for setting ProcessedMap
1033    ///
1034    /// \ref named-templ-param "Named parameter"
1035    ///function for setting ProcessedMap
1036    ///
1037    template<class T>
1038    BfsWizard<DefProcessedMapBase<T> > processedMap(const T &t)
1039    {
1040      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
1041      return BfsWizard<DefProcessedMapBase<T> >(*this);
1042    }
1043   
1044   
1045    template<class T>
1046    struct DefDistMapBase : public Base {
1047      typedef T DistMap;
1048      static DistMap *createDistMap(const Digraph &) { return 0; };
1049      DefDistMapBase(const TR &b) : TR(b) {}
1050    };
1051   
1052    ///\brief \ref named-templ-param "Named parameter"
1053    ///function for setting DistMap type
1054    ///
1055    /// \ref named-templ-param "Named parameter"
1056    ///function for setting DistMap type
1057    ///
1058    template<class T>
1059    BfsWizard<DefDistMapBase<T> > distMap(const T &t)
1060    {
1061      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1062      return BfsWizard<DefDistMapBase<T> >(*this);
1063    }
1064   
1065    /// Sets the source node, from which the Bfs algorithm runs.
1066
1067    /// Sets the source node, from which the Bfs algorithm runs.
1068    /// \param s is the source node.
1069    BfsWizard<TR> &source(Node s)
1070    {
1071      Base::_source=s;
1072      return *this;
1073    }
1074   
1075  };
1076 
1077  ///Function type interface for Bfs algorithm.
1078
1079  /// \ingroup search
1080  ///Function type interface for Bfs algorithm.
1081  ///
1082  ///This function also has several
1083  ///\ref named-templ-func-param "named parameters",
1084  ///they are declared as the members of class \ref BfsWizard.
1085  ///The following
1086  ///example shows how to use these parameters.
1087  ///\code
1088  ///  bfs(g,source).predMap(preds).run();
1089  ///\endcode
1090  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1091  ///to the end of the parameter list.
1092  ///\sa BfsWizard
1093  ///\sa Bfs
1094  template<class GR>
1095  BfsWizard<BfsWizardBase<GR> >
1096  bfs(const GR &g,typename GR::Node s=INVALID)
1097  {
1098    return BfsWizard<BfsWizardBase<GR> >(g,s);
1099  }
1100
1101#ifdef DOXYGEN
1102  /// \brief Visitor class for bfs.
1103  /// 
1104  /// This class defines the interface of the BfsVisit events, and
1105  /// it could be the base of a real Visitor class.
1106  template <typename _Digraph>
1107  struct BfsVisitor {
1108    typedef _Digraph Digraph;
1109    typedef typename Digraph::Arc Arc;
1110    typedef typename Digraph::Node Node;
1111    /// \brief Called when the arc reach a node.
1112    ///
1113    /// It is called when the bfs find an arc which target is not
1114    /// reached yet.
1115    void discover(const Arc& arc) {}
1116    /// \brief Called when the node reached first time.
1117    ///
1118    /// It is Called when the node reached first time.
1119    void reach(const Node& node) {}
1120    /// \brief Called when the arc examined but target of the arc
1121    /// already discovered.
1122    ///
1123    /// It called when the arc examined but the target of the arc
1124    /// already discovered.
1125    void examine(const Arc& arc) {}
1126    /// \brief Called for the source node of the bfs.
1127    ///
1128    /// It is called for the source node of the bfs.
1129    void start(const Node& node) {}
1130    /// \brief Called when the node processed.
1131    ///
1132    /// It is Called when the node processed.
1133    void process(const Node& node) {}
1134  };
1135#else
1136  template <typename _Digraph>
1137  struct BfsVisitor {
1138    typedef _Digraph Digraph;
1139    typedef typename Digraph::Arc Arc;
1140    typedef typename Digraph::Node Node;
1141    void discover(const Arc&) {}
1142    void reach(const Node&) {}
1143    void examine(const Arc&) {}
1144    void start(const Node&) {}
1145    void process(const Node&) {}
1146
1147    template <typename _Visitor>
1148    struct Constraints {
1149      void constraints() {
1150        Arc arc;
1151        Node node;
1152        visitor.discover(arc);
1153        visitor.reach(node);
1154        visitor.examine(arc);
1155        visitor.start(node);
1156        visitor.process(node);
1157      }
1158      _Visitor& visitor;
1159    };
1160  };
1161#endif
1162
1163  /// \brief Default traits class of BfsVisit class.
1164  ///
1165  /// Default traits class of BfsVisit class.
1166  /// \tparam _Digraph Digraph type.
1167  template<class _Digraph>
1168  struct BfsVisitDefaultTraits {
1169
1170    /// \brief The digraph type the algorithm runs on.
1171    typedef _Digraph Digraph;
1172
1173    /// \brief The type of the map that indicates which nodes are reached.
1174    ///
1175    /// The type of the map that indicates which nodes are reached.
1176    /// It must meet the \ref concepts::WriteMap "WriteMap" concept.
1177    /// \todo named parameter to set this type, function to read and write.
1178    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1179
1180    /// \brief Instantiates a ReachedMap.
1181    ///
1182    /// This function instantiates a \ref ReachedMap.
1183    /// \param digraph is the digraph, to which
1184    /// we would like to define the \ref ReachedMap.
1185    static ReachedMap *createReachedMap(const Digraph &digraph) {
1186      return new ReachedMap(digraph);
1187    }
1188
1189  };
1190
1191  /// \ingroup search
1192  /// 
1193  /// \brief %BFS Visit algorithm class.
1194  /// 
1195  /// This class provides an efficient implementation of the %BFS algorithm
1196  /// with visitor interface.
1197  ///
1198  /// The %BfsVisit class provides an alternative interface to the Bfs
1199  /// class. It works with callback mechanism, the BfsVisit object calls
1200  /// on every bfs event the \c Visitor class member functions.
1201  ///
1202  /// \tparam _Digraph The digraph type the algorithm runs on. The default value is
1203  /// \ref ListDigraph. The value of _Digraph is not used directly by Bfs, it
1204  /// is only passed to \ref BfsDefaultTraits.
1205  /// \tparam _Visitor The Visitor object for the algorithm. The
1206  /// \ref BfsVisitor "BfsVisitor<_Digraph>" is an empty Visitor which
1207  /// does not observe the Bfs events. If you want to observe the bfs
1208  /// events you should implement your own Visitor class.
1209  /// \tparam _Traits Traits class to set various data types used by the
1210  /// algorithm. The default traits class is
1211  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<_Digraph>".
1212  /// See \ref BfsVisitDefaultTraits for the documentation of
1213  /// a Bfs visit traits class.
1214#ifdef DOXYGEN
1215  template <typename _Digraph, typename _Visitor, typename _Traits>
1216#else
1217  template <typename _Digraph = ListDigraph,
1218            typename _Visitor = BfsVisitor<_Digraph>,
1219            typename _Traits = BfsDefaultTraits<_Digraph> >
1220#endif
1221  class BfsVisit {
1222  public:
1223   
1224    /// \brief \ref Exception for uninitialized parameters.
1225    ///
1226    /// This error represents problems in the initialization
1227    /// of the parameters of the algorithms.
1228    class UninitializedParameter : public lemon::UninitializedParameter {
1229    public:
1230      virtual const char* what() const throw()
1231      {
1232        return "lemon::BfsVisit::UninitializedParameter";
1233      }
1234    };
1235
1236    typedef _Traits Traits;
1237
1238    typedef typename Traits::Digraph Digraph;
1239
1240    typedef _Visitor Visitor;
1241
1242    ///The type of the map indicating which nodes are reached.
1243    typedef typename Traits::ReachedMap ReachedMap;
1244
1245  private:
1246
1247    typedef typename Digraph::Node Node;
1248    typedef typename Digraph::NodeIt NodeIt;
1249    typedef typename Digraph::Arc Arc;
1250    typedef typename Digraph::OutArcIt OutArcIt;
1251
1252    /// Pointer to the underlying digraph.
1253    const Digraph *_digraph;
1254    /// Pointer to the visitor object.
1255    Visitor *_visitor;
1256    ///Pointer to the map of reached status of the nodes.
1257    ReachedMap *_reached;
1258    ///Indicates if \ref _reached is locally allocated (\c true) or not.
1259    bool local_reached;
1260
1261    std::vector<typename Digraph::Node> _list;
1262    int _list_front, _list_back;
1263
1264    /// \brief Creates the maps if necessary.
1265    ///
1266    /// Creates the maps if necessary.
1267    void create_maps() {
1268      if(!_reached) {
1269        local_reached = true;
1270        _reached = Traits::createReachedMap(*_digraph);
1271      }
1272    }
1273
1274  protected:
1275
1276    BfsVisit() {}
1277   
1278  public:
1279
1280    typedef BfsVisit Create;
1281
1282    /// \name Named template parameters
1283
1284    ///@{
1285    template <class T>
1286    struct DefReachedMapTraits : public Traits {
1287      typedef T ReachedMap;
1288      static ReachedMap *createReachedMap(const Digraph &digraph) {
1289        throw UninitializedParameter();
1290      }
1291    };
1292    /// \brief \ref named-templ-param "Named parameter" for setting
1293    /// ReachedMap type
1294    ///
1295    /// \ref named-templ-param "Named parameter" for setting ReachedMap type
1296    template <class T>
1297    struct DefReachedMap : public BfsVisit< Digraph, Visitor,
1298                                            DefReachedMapTraits<T> > {
1299      typedef BfsVisit< Digraph, Visitor, DefReachedMapTraits<T> > Create;
1300    };
1301    ///@}
1302
1303  public:     
1304   
1305    /// \brief Constructor.
1306    ///
1307    /// Constructor.
1308    ///
1309    /// \param digraph the digraph the algorithm will run on.
1310    /// \param visitor The visitor of the algorithm.
1311    ///
1312    BfsVisit(const Digraph& digraph, Visitor& visitor)
1313      : _digraph(&digraph), _visitor(&visitor),
1314        _reached(0), local_reached(false) {}
1315   
1316    /// \brief Destructor.
1317    ///
1318    /// Destructor.
1319    ~BfsVisit() {
1320      if(local_reached) delete _reached;
1321    }
1322
1323    /// \brief Sets the map indicating if a node is reached.
1324    ///
1325    /// Sets the map indicating if a node is reached.
1326    /// If you don't use this function before calling \ref run(),
1327    /// it will allocate one. The destuctor deallocates this
1328    /// automatically allocated map, of course.
1329    /// \return <tt> (*this) </tt>
1330    BfsVisit &reachedMap(ReachedMap &m) {
1331      if(local_reached) {
1332        delete _reached;
1333        local_reached = false;
1334      }
1335      _reached = &m;
1336      return *this;
1337    }
1338
1339  public:
1340    /// \name Execution control
1341    /// The simplest way to execute the algorithm is to use
1342    /// one of the member functions called \c run(...).
1343    /// \n
1344    /// If you need more control on the execution,
1345    /// first you must call \ref init(), then you can adda source node
1346    /// with \ref addSource().
1347    /// Finally \ref start() will perform the actual path
1348    /// computation.
1349
1350    /// @{
1351    /// \brief Initializes the internal data structures.
1352    ///
1353    /// Initializes the internal data structures.
1354    ///
1355    void init() {
1356      create_maps();
1357      _list.resize(countNodes(*_digraph));
1358      _list_front = _list_back = -1;
1359      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
1360        _reached->set(u, false);
1361      }
1362    }
1363   
1364    /// \brief Adds a new source node.
1365    ///
1366    /// Adds a new source node to the set of nodes to be processed.
1367    void addSource(Node s) {
1368      if(!(*_reached)[s]) {
1369          _reached->set(s,true);
1370          _visitor->start(s);
1371          _visitor->reach(s);
1372          _list[++_list_back] = s;
1373        }
1374    }
1375   
1376    /// \brief Processes the next node.
1377    ///
1378    /// Processes the next node.
1379    ///
1380    /// \return The processed node.
1381    ///
1382    /// \pre The queue must not be empty!
1383    Node processNextNode() {
1384      Node n = _list[++_list_front];
1385      _visitor->process(n);
1386      Arc e;
1387      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1388        Node m = _digraph->target(e);
1389        if (!(*_reached)[m]) {
1390          _visitor->discover(e);
1391          _visitor->reach(m);
1392          _reached->set(m, true);
1393          _list[++_list_back] = m;
1394        } else {
1395          _visitor->examine(e);
1396        }
1397      }
1398      return n;
1399    }
1400
1401    /// \brief Processes the next node.
1402    ///
1403    /// Processes the next node. And checks that the given target node
1404    /// is reached. If the target node is reachable from the processed
1405    /// node then the reached parameter will be set true. The reached
1406    /// parameter should be initially false.
1407    ///
1408    /// \param target The target node.
1409    /// \retval reach Indicates that the target node is reached.
1410    /// \return The processed node.
1411    ///
1412    /// \warning The queue must not be empty!
1413    Node processNextNode(Node target, bool& reach) {
1414      Node n = _list[++_list_front];
1415      _visitor->process(n);
1416      Arc e;
1417      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1418        Node m = _digraph->target(e);
1419        if (!(*_reached)[m]) {
1420          _visitor->discover(e);
1421          _visitor->reach(m);
1422          _reached->set(m, true);
1423          _list[++_list_back] = m;
1424          reach = reach || (target == m);
1425        } else {
1426          _visitor->examine(e);
1427        }
1428      }
1429      return n;
1430    }
1431
1432    /// \brief Processes the next node.
1433    ///
1434    /// Processes the next node. And checks that at least one of
1435    /// reached node has true value in the \c nm node map. If one node
1436    /// with true value is reachable from the processed node then the
1437    /// rnode parameter will be set to the first of such nodes.
1438    ///
1439    /// \param nm The node map of possible targets.
1440    /// \retval rnode The reached target node.
1441    /// \return The processed node.
1442    ///
1443    /// \warning The queue must not be empty!
1444    template <typename NM>
1445    Node processNextNode(const NM& nm, Node& rnode) {
1446      Node n = _list[++_list_front];
1447      _visitor->process(n);
1448      Arc e;
1449      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1450        Node m = _digraph->target(e);
1451        if (!(*_reached)[m]) {
1452          _visitor->discover(e);
1453          _visitor->reach(m);
1454          _reached->set(m, true);
1455          _list[++_list_back] = m;
1456          if (nm[m] && rnode == INVALID) rnode = m;
1457        } else {
1458          _visitor->examine(e);
1459        }
1460      }
1461      return n;
1462    }
1463
1464    /// \brief Next node to be processed.
1465    ///
1466    /// Next node to be processed.
1467    ///
1468    /// \return The next node to be processed or INVALID if the stack is
1469    /// empty.
1470    Node nextNode() {
1471      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1472    }
1473
1474    /// \brief Returns \c false if there are nodes
1475    /// to be processed in the queue
1476    ///
1477    /// Returns \c false if there are nodes
1478    /// to be processed in the queue
1479    bool emptyQueue() { return _list_front == _list_back; }
1480
1481    /// \brief Returns the number of the nodes to be processed.
1482    ///
1483    /// Returns the number of the nodes to be processed in the queue.
1484    int queueSize() { return _list_back - _list_front; }
1485   
1486    /// \brief Executes the algorithm.
1487    ///
1488    /// Executes the algorithm.
1489    ///
1490    /// \pre init() must be called and at least one node should be added
1491    /// with addSource() before using this function.
1492    void start() {
1493      while ( !emptyQueue() ) processNextNode();
1494    }
1495   
1496    /// \brief Executes the algorithm until \c dest is reached.
1497    ///
1498    /// Executes the algorithm until \c dest is reached.
1499    ///
1500    /// \pre init() must be called and at least one node should be added
1501    /// with addSource() before using this function.
1502    void start(Node dest) {
1503      bool reach = false;
1504      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
1505    }
1506   
1507    /// \brief Executes the algorithm until a condition is met.
1508    ///
1509    /// Executes the algorithm until a condition is met.
1510    ///
1511    /// \pre init() must be called and at least one node should be added
1512    /// with addSource() before using this function.
1513    ///
1514    ///\param nm must be a bool (or convertible) node map. The
1515    ///algorithm will stop when it reaches a node \c v with
1516    /// <tt>nm[v]</tt> true.
1517    ///
1518    ///\return The reached node \c v with <tt>nm[v]</tt> true or
1519    ///\c INVALID if no such node was found.
1520    template <typename NM>
1521    Node start(const NM &nm) {
1522      Node rnode = INVALID;
1523      while ( !emptyQueue() && rnode == INVALID ) {
1524        processNextNode(nm, rnode);
1525      }
1526      return rnode;
1527    }
1528
1529    /// \brief Runs %BFSVisit algorithm from node \c s.
1530    ///
1531    /// This method runs the %BFS algorithm from a root node \c s.
1532    /// \note b.run(s) is just a shortcut of the following code.
1533    ///\code
1534    ///   b.init();
1535    ///   b.addSource(s);
1536    ///   b.start();
1537    ///\endcode
1538    void run(Node s) {
1539      init();
1540      addSource(s);
1541      start();
1542    }
1543
1544    /// \brief Runs %BFSVisit algorithm to visit all nodes in the digraph.
1545    ///   
1546    /// This method runs the %BFS algorithm in order to
1547    /// compute the %BFS path to each node. The algorithm computes
1548    /// - The %BFS tree.
1549    /// - The distance of each node from the root in the %BFS tree.
1550    ///
1551    ///\note b.run() is just a shortcut of the following code.
1552    ///\code
1553    ///  b.init();
1554    ///  for (NodeIt it(digraph); it != INVALID; ++it) {
1555    ///    if (!b.reached(it)) {
1556    ///      b.addSource(it);
1557    ///      b.start();
1558    ///    }
1559    ///  }
1560    ///\endcode
1561    void run() {
1562      init();
1563      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1564        if (!reached(it)) {
1565          addSource(it);
1566          start();
1567        }
1568      }
1569    }
1570    ///@}
1571
1572    /// \name Query Functions
1573    /// The result of the %BFS algorithm can be obtained using these
1574    /// functions.\n
1575    /// Before the use of these functions,
1576    /// either run() or start() must be called.
1577    ///@{
1578
1579    /// \brief Checks if a node is reachable from the root.
1580    ///
1581    /// Returns \c true if \c v is reachable from the root(s).
1582    /// \warning The source nodes are inditated as unreachable.
1583    /// \pre Either \ref run() or \ref start()
1584    /// must be called before using this function.
1585    ///
1586    bool reached(Node v) { return (*_reached)[v]; }
1587    ///@}
1588  };
1589
1590} //END OF NAMESPACE LEMON
1591
1592#endif
1593
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