COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/bfs.h @ 909:f112c18bc304

Last change on this file since 909:f112c18bc304 was 877:141f9c0db4a3, checked in by Alpar Juttner <alpar@…>, 10 years ago

Unify the sources (#339)

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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) 2003-2010
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#include <lemon/path.h>
32
33namespace lemon {
34
35  ///Default traits class of Bfs class.
36
37  ///Default traits class of Bfs class.
38  ///\tparam GR Digraph type.
39  template<class GR>
40  struct BfsDefaultTraits
41  {
42    ///The type of the digraph the algorithm runs on.
43    typedef GR Digraph;
44
45    ///\brief The type of the map that stores the predecessor
46    ///arcs of the shortest paths.
47    ///
48    ///The type of the map that stores the predecessor
49    ///arcs of the shortest paths.
50    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
51    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
52    ///Instantiates a \c PredMap.
53
54    ///This function instantiates a \ref PredMap.
55    ///\param g is the digraph, to which we would like to define the
56    ///\ref PredMap.
57    static PredMap *createPredMap(const Digraph &g)
58    {
59      return new PredMap(g);
60    }
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 conform to the \ref concepts::WriteMap "WriteMap" concept.
66    ///By default, it is a NullMap.
67    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
68    ///Instantiates a \c 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 Digraph &g)
75#else
76    static ProcessedMap *createProcessedMap(const Digraph &)
77#endif
78    {
79      return new ProcessedMap();
80    }
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 conform to
86    ///the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
87    typedef typename Digraph::template NodeMap<bool> ReachedMap;
88    ///Instantiates a \c 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 Digraph &g)
94    {
95      return new ReachedMap(g);
96    }
97
98    ///The type of the map that stores the distances of the nodes.
99
100    ///The type of the map that stores the distances of the nodes.
101    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
102    typedef typename Digraph::template NodeMap<int> DistMap;
103    ///Instantiates a \c DistMap.
104
105    ///This function instantiates a \ref DistMap.
106    ///\param g is the digraph, to which we would like to define the
107    ///\ref DistMap.
108    static DistMap *createDistMap(const Digraph &g)
109    {
110      return new DistMap(g);
111    }
112  };
113
114  ///%BFS algorithm class.
115
116  ///\ingroup search
117  ///This class provides an efficient implementation of the %BFS algorithm.
118  ///
119  ///There is also a \ref bfs() "function-type interface" for the BFS
120  ///algorithm, which is convenient in the simplier cases and it can be
121  ///used easier.
122  ///
123  ///\tparam GR The type of the digraph the algorithm runs on.
124  ///The default type is \ref ListDigraph.
125  ///\tparam TR The traits class that defines various types used by the
126  ///algorithm. By default, it is \ref BfsDefaultTraits
127  ///"BfsDefaultTraits<GR>".
128  ///In most cases, this parameter should not be set directly,
129  ///consider to use the named template parameters instead.
130#ifdef DOXYGEN
131  template <typename GR,
132            typename TR>
133#else
134  template <typename GR=ListDigraph,
135            typename TR=BfsDefaultTraits<GR> >
136#endif
137  class Bfs {
138  public:
139
140    ///The type of the digraph the algorithm runs on.
141    typedef typename TR::Digraph Digraph;
142
143    ///\brief The type of the map that stores the predecessor arcs of the
144    ///shortest paths.
145    typedef typename TR::PredMap PredMap;
146    ///The type of the map that stores the distances of the nodes.
147    typedef typename TR::DistMap DistMap;
148    ///The type of the map that indicates which nodes are reached.
149    typedef typename TR::ReachedMap ReachedMap;
150    ///The type of the map that indicates which nodes are processed.
151    typedef typename TR::ProcessedMap ProcessedMap;
152    ///The type of the paths.
153    typedef PredMapPath<Digraph, PredMap> Path;
154
155    ///The \ref BfsDefaultTraits "traits class" of the algorithm.
156    typedef TR Traits;
157
158  private:
159
160    typedef typename Digraph::Node Node;
161    typedef typename Digraph::NodeIt NodeIt;
162    typedef typename Digraph::Arc Arc;
163    typedef typename Digraph::OutArcIt OutArcIt;
164
165    //Pointer to the underlying digraph.
166    const Digraph *G;
167    //Pointer to the map of predecessor arcs.
168    PredMap *_pred;
169    //Indicates if _pred is locally allocated (true) or not.
170    bool local_pred;
171    //Pointer to the map of distances.
172    DistMap *_dist;
173    //Indicates if _dist is locally allocated (true) or not.
174    bool local_dist;
175    //Pointer to the map of reached status of the nodes.
176    ReachedMap *_reached;
177    //Indicates if _reached is locally allocated (true) or not.
178    bool local_reached;
179    //Pointer to the map of processed status of the nodes.
180    ProcessedMap *_processed;
181    //Indicates if _processed is locally allocated (true) or not.
182    bool local_processed;
183
184    std::vector<typename Digraph::Node> _queue;
185    int _queue_head,_queue_tail,_queue_next_dist;
186    int _curr_dist;
187
188    //Creates the maps if necessary.
189    void create_maps()
190    {
191      if(!_pred) {
192        local_pred = true;
193        _pred = Traits::createPredMap(*G);
194      }
195      if(!_dist) {
196        local_dist = true;
197        _dist = Traits::createDistMap(*G);
198      }
199      if(!_reached) {
200        local_reached = true;
201        _reached = Traits::createReachedMap(*G);
202      }
203      if(!_processed) {
204        local_processed = true;
205        _processed = Traits::createProcessedMap(*G);
206      }
207    }
208
209  protected:
210
211    Bfs() {}
212
213  public:
214
215    typedef Bfs Create;
216
217    ///\name Named Template Parameters
218
219    ///@{
220
221    template <class T>
222    struct SetPredMapTraits : public Traits {
223      typedef T PredMap;
224      static PredMap *createPredMap(const Digraph &)
225      {
226        LEMON_ASSERT(false, "PredMap is not initialized");
227        return 0; // ignore warnings
228      }
229    };
230    ///\brief \ref named-templ-param "Named parameter" for setting
231    ///\c PredMap type.
232    ///
233    ///\ref named-templ-param "Named parameter" for setting
234    ///\c PredMap type.
235    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
236    template <class T>
237    struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > {
238      typedef Bfs< Digraph, SetPredMapTraits<T> > Create;
239    };
240
241    template <class T>
242    struct SetDistMapTraits : public Traits {
243      typedef T DistMap;
244      static DistMap *createDistMap(const Digraph &)
245      {
246        LEMON_ASSERT(false, "DistMap is not initialized");
247        return 0; // ignore warnings
248      }
249    };
250    ///\brief \ref named-templ-param "Named parameter" for setting
251    ///\c DistMap type.
252    ///
253    ///\ref named-templ-param "Named parameter" for setting
254    ///\c DistMap type.
255    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
256    template <class T>
257    struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > {
258      typedef Bfs< Digraph, SetDistMapTraits<T> > Create;
259    };
260
261    template <class T>
262    struct SetReachedMapTraits : public Traits {
263      typedef T ReachedMap;
264      static ReachedMap *createReachedMap(const Digraph &)
265      {
266        LEMON_ASSERT(false, "ReachedMap is not initialized");
267        return 0; // ignore warnings
268      }
269    };
270    ///\brief \ref named-templ-param "Named parameter" for setting
271    ///\c ReachedMap type.
272    ///
273    ///\ref named-templ-param "Named parameter" for setting
274    ///\c ReachedMap type.
275    ///It must conform to
276    ///the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
277    template <class T>
278    struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > {
279      typedef Bfs< Digraph, SetReachedMapTraits<T> > Create;
280    };
281
282    template <class T>
283    struct SetProcessedMapTraits : public Traits {
284      typedef T ProcessedMap;
285      static ProcessedMap *createProcessedMap(const Digraph &)
286      {
287        LEMON_ASSERT(false, "ProcessedMap is not initialized");
288        return 0; // ignore warnings
289      }
290    };
291    ///\brief \ref named-templ-param "Named parameter" for setting
292    ///\c ProcessedMap type.
293    ///
294    ///\ref named-templ-param "Named parameter" for setting
295    ///\c ProcessedMap type.
296    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
297    template <class T>
298    struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > {
299      typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create;
300    };
301
302    struct SetStandardProcessedMapTraits : public Traits {
303      typedef typename Digraph::template NodeMap<bool> ProcessedMap;
304      static ProcessedMap *createProcessedMap(const Digraph &g)
305      {
306        return new ProcessedMap(g);
307        return 0; // ignore warnings
308      }
309    };
310    ///\brief \ref named-templ-param "Named parameter" for setting
311    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
312    ///
313    ///\ref named-templ-param "Named parameter" for setting
314    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
315    ///If you don't set it explicitly, it will be automatically allocated.
316    struct SetStandardProcessedMap :
317      public Bfs< Digraph, SetStandardProcessedMapTraits > {
318      typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create;
319    };
320
321    ///@}
322
323  public:
324
325    ///Constructor.
326
327    ///Constructor.
328    ///\param g The digraph the algorithm runs on.
329    Bfs(const Digraph &g) :
330      G(&g),
331      _pred(NULL), local_pred(false),
332      _dist(NULL), local_dist(false),
333      _reached(NULL), local_reached(false),
334      _processed(NULL), local_processed(false)
335    { }
336
337    ///Destructor.
338    ~Bfs()
339    {
340      if(local_pred) delete _pred;
341      if(local_dist) delete _dist;
342      if(local_reached) delete _reached;
343      if(local_processed) delete _processed;
344    }
345
346    ///Sets the map that stores the predecessor arcs.
347
348    ///Sets the map that stores the predecessor arcs.
349    ///If you don't use this function before calling \ref run(Node) "run()"
350    ///or \ref init(), an instance will be allocated automatically.
351    ///The destructor deallocates this automatically allocated map,
352    ///of course.
353    ///\return <tt> (*this) </tt>
354    Bfs &predMap(PredMap &m)
355    {
356      if(local_pred) {
357        delete _pred;
358        local_pred=false;
359      }
360      _pred = &m;
361      return *this;
362    }
363
364    ///Sets the map that indicates which nodes are reached.
365
366    ///Sets the map that indicates which nodes are reached.
367    ///If you don't use this function before calling \ref run(Node) "run()"
368    ///or \ref init(), an instance will be allocated automatically.
369    ///The destructor deallocates this automatically allocated map,
370    ///of course.
371    ///\return <tt> (*this) </tt>
372    Bfs &reachedMap(ReachedMap &m)
373    {
374      if(local_reached) {
375        delete _reached;
376        local_reached=false;
377      }
378      _reached = &m;
379      return *this;
380    }
381
382    ///Sets the map that indicates which nodes are processed.
383
384    ///Sets the map that indicates which nodes are processed.
385    ///If you don't use this function before calling \ref run(Node) "run()"
386    ///or \ref init(), an instance will be allocated automatically.
387    ///The destructor deallocates this automatically allocated map,
388    ///of course.
389    ///\return <tt> (*this) </tt>
390    Bfs &processedMap(ProcessedMap &m)
391    {
392      if(local_processed) {
393        delete _processed;
394        local_processed=false;
395      }
396      _processed = &m;
397      return *this;
398    }
399
400    ///Sets the map that stores the distances of the nodes.
401
402    ///Sets the map that stores the distances of the nodes calculated by
403    ///the algorithm.
404    ///If you don't use this function before calling \ref run(Node) "run()"
405    ///or \ref init(), an instance will be allocated automatically.
406    ///The destructor deallocates this automatically allocated map,
407    ///of course.
408    ///\return <tt> (*this) </tt>
409    Bfs &distMap(DistMap &m)
410    {
411      if(local_dist) {
412        delete _dist;
413        local_dist=false;
414      }
415      _dist = &m;
416      return *this;
417    }
418
419  public:
420
421    ///\name Execution Control
422    ///The simplest way to execute the BFS algorithm is to use one of the
423    ///member functions called \ref run(Node) "run()".\n
424    ///If you need better control on the execution, you have to call
425    ///\ref init() first, then you can add several source nodes with
426    ///\ref addSource(). Finally the actual path computation can be
427    ///performed with one of the \ref start() functions.
428
429    ///@{
430
431    ///\brief Initializes the internal data structures.
432    ///
433    ///Initializes the internal data structures.
434    void init()
435    {
436      create_maps();
437      _queue.resize(countNodes(*G));
438      _queue_head=_queue_tail=0;
439      _curr_dist=1;
440      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
441        _pred->set(u,INVALID);
442        _reached->set(u,false);
443        _processed->set(u,false);
444      }
445    }
446
447    ///Adds a new source node.
448
449    ///Adds a new source node to the set of nodes to be processed.
450    ///
451    void addSource(Node s)
452    {
453      if(!(*_reached)[s])
454        {
455          _reached->set(s,true);
456          _pred->set(s,INVALID);
457          _dist->set(s,0);
458          _queue[_queue_head++]=s;
459          _queue_next_dist=_queue_head;
460        }
461    }
462
463    ///Processes the next node.
464
465    ///Processes the next node.
466    ///
467    ///\return The processed node.
468    ///
469    ///\pre The queue must not be empty.
470    Node processNextNode()
471    {
472      if(_queue_tail==_queue_next_dist) {
473        _curr_dist++;
474        _queue_next_dist=_queue_head;
475      }
476      Node n=_queue[_queue_tail++];
477      _processed->set(n,true);
478      Node m;
479      for(OutArcIt e(*G,n);e!=INVALID;++e)
480        if(!(*_reached)[m=G->target(e)]) {
481          _queue[_queue_head++]=m;
482          _reached->set(m,true);
483          _pred->set(m,e);
484          _dist->set(m,_curr_dist);
485        }
486      return n;
487    }
488
489    ///Processes the next node.
490
491    ///Processes the next node and checks if the given target node
492    ///is reached. If the target node is reachable from the processed
493    ///node, then the \c reach parameter will be set to \c true.
494    ///
495    ///\param target The target node.
496    ///\retval reach Indicates if the target node is reached.
497    ///It should be initially \c false.
498    ///
499    ///\return The processed node.
500    ///
501    ///\pre The queue must not be empty.
502    Node processNextNode(Node target, bool& reach)
503    {
504      if(_queue_tail==_queue_next_dist) {
505        _curr_dist++;
506        _queue_next_dist=_queue_head;
507      }
508      Node n=_queue[_queue_tail++];
509      _processed->set(n,true);
510      Node m;
511      for(OutArcIt e(*G,n);e!=INVALID;++e)
512        if(!(*_reached)[m=G->target(e)]) {
513          _queue[_queue_head++]=m;
514          _reached->set(m,true);
515          _pred->set(m,e);
516          _dist->set(m,_curr_dist);
517          reach = reach || (target == m);
518        }
519      return n;
520    }
521
522    ///Processes the next node.
523
524    ///Processes the next node and checks if at least one of reached
525    ///nodes has \c true value in the \c nm node map. If one node
526    ///with \c true value is reachable from the processed node, then the
527    ///\c rnode parameter will be set to the first of such nodes.
528    ///
529    ///\param nm A \c bool (or convertible) node map that indicates the
530    ///possible targets.
531    ///\retval rnode The reached target node.
532    ///It should be initially \c INVALID.
533    ///
534    ///\return The processed node.
535    ///
536    ///\pre The queue must not be empty.
537    template<class NM>
538    Node processNextNode(const NM& nm, Node& rnode)
539    {
540      if(_queue_tail==_queue_next_dist) {
541        _curr_dist++;
542        _queue_next_dist=_queue_head;
543      }
544      Node n=_queue[_queue_tail++];
545      _processed->set(n,true);
546      Node m;
547      for(OutArcIt e(*G,n);e!=INVALID;++e)
548        if(!(*_reached)[m=G->target(e)]) {
549          _queue[_queue_head++]=m;
550          _reached->set(m,true);
551          _pred->set(m,e);
552          _dist->set(m,_curr_dist);
553          if (nm[m] && rnode == INVALID) rnode = m;
554        }
555      return n;
556    }
557
558    ///The next node to be processed.
559
560    ///Returns the next node to be processed or \c INVALID if the queue
561    ///is empty.
562    Node nextNode() const
563    {
564      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
565    }
566
567    ///Returns \c false if there are nodes to be processed.
568
569    ///Returns \c false if there are nodes to be processed
570    ///in the queue.
571    bool emptyQueue() const { return _queue_tail==_queue_head; }
572
573    ///Returns the number of the nodes to be processed.
574
575    ///Returns the number of the nodes to be processed
576    ///in the queue.
577    int queueSize() const { return _queue_head-_queue_tail; }
578
579    ///Executes the algorithm.
580
581    ///Executes the algorithm.
582    ///
583    ///This method runs the %BFS algorithm from the root node(s)
584    ///in order to compute the shortest path to each node.
585    ///
586    ///The algorithm computes
587    ///- the shortest path tree (forest),
588    ///- the distance of each node from the root(s).
589    ///
590    ///\pre init() must be called and at least one root node should be
591    ///added with addSource() before using this function.
592    ///
593    ///\note <tt>b.start()</tt> is just a shortcut of the following code.
594    ///\code
595    ///  while ( !b.emptyQueue() ) {
596    ///    b.processNextNode();
597    ///  }
598    ///\endcode
599    void start()
600    {
601      while ( !emptyQueue() ) processNextNode();
602    }
603
604    ///Executes the algorithm until the given target node is reached.
605
606    ///Executes the algorithm until the given target node is reached.
607    ///
608    ///This method runs the %BFS algorithm from the root node(s)
609    ///in order to compute the shortest path to \c t.
610    ///
611    ///The algorithm computes
612    ///- the shortest path to \c t,
613    ///- the distance of \c t from the root(s).
614    ///
615    ///\pre init() must be called and at least one root node should be
616    ///added with addSource() before using this function.
617    ///
618    ///\note <tt>b.start(t)</tt> is just a shortcut of the following code.
619    ///\code
620    ///  bool reach = false;
621    ///  while ( !b.emptyQueue() && !reach ) {
622    ///    b.processNextNode(t, reach);
623    ///  }
624    ///\endcode
625    void start(Node t)
626    {
627      bool reach = false;
628      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
629    }
630
631    ///Executes the algorithm until a condition is met.
632
633    ///Executes the algorithm until a condition is met.
634    ///
635    ///This method runs the %BFS algorithm from the root node(s) in
636    ///order to compute the shortest path to a node \c v with
637    /// <tt>nm[v]</tt> true, if such a node can be found.
638    ///
639    ///\param nm A \c bool (or convertible) node map. The algorithm
640    ///will stop when it reaches a node \c v with <tt>nm[v]</tt> true.
641    ///
642    ///\return The reached node \c v with <tt>nm[v]</tt> true or
643    ///\c INVALID if no such node was found.
644    ///
645    ///\pre init() must be called and at least one root node should be
646    ///added with addSource() before using this function.
647    ///
648    ///\note <tt>b.start(nm)</tt> is just a shortcut of the following code.
649    ///\code
650    ///  Node rnode = INVALID;
651    ///  while ( !b.emptyQueue() && rnode == INVALID ) {
652    ///    b.processNextNode(nm, rnode);
653    ///  }
654    ///  return rnode;
655    ///\endcode
656    template<class NodeBoolMap>
657    Node start(const NodeBoolMap &nm)
658    {
659      Node rnode = INVALID;
660      while ( !emptyQueue() && rnode == INVALID ) {
661        processNextNode(nm, rnode);
662      }
663      return rnode;
664    }
665
666    ///Runs the algorithm from the given source node.
667
668    ///This method runs the %BFS algorithm from node \c s
669    ///in order to compute the shortest path to each node.
670    ///
671    ///The algorithm computes
672    ///- the shortest path tree,
673    ///- the distance of each node from the root.
674    ///
675    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
676    ///\code
677    ///  b.init();
678    ///  b.addSource(s);
679    ///  b.start();
680    ///\endcode
681    void run(Node s) {
682      init();
683      addSource(s);
684      start();
685    }
686
687    ///Finds the shortest path between \c s and \c t.
688
689    ///This method runs the %BFS algorithm from node \c s
690    ///in order to compute the shortest path to node \c t
691    ///(it stops searching when \c t is processed).
692    ///
693    ///\return \c true if \c t is reachable form \c s.
694    ///
695    ///\note Apart from the return value, <tt>b.run(s,t)</tt> is just a
696    ///shortcut of the following code.
697    ///\code
698    ///  b.init();
699    ///  b.addSource(s);
700    ///  b.start(t);
701    ///\endcode
702    bool run(Node s,Node t) {
703      init();
704      addSource(s);
705      start(t);
706      return reached(t);
707    }
708
709    ///Runs the algorithm to visit all nodes in the digraph.
710
711    ///This method runs the %BFS algorithm in order to visit all nodes
712    ///in the digraph.
713    ///
714    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
715    ///\code
716    ///  b.init();
717    ///  for (NodeIt n(gr); n != INVALID; ++n) {
718    ///    if (!b.reached(n)) {
719    ///      b.addSource(n);
720    ///      b.start();
721    ///    }
722    ///  }
723    ///\endcode
724    void run() {
725      init();
726      for (NodeIt n(*G); n != INVALID; ++n) {
727        if (!reached(n)) {
728          addSource(n);
729          start();
730        }
731      }
732    }
733
734    ///@}
735
736    ///\name Query Functions
737    ///The results of the BFS algorithm can be obtained using these
738    ///functions.\n
739    ///Either \ref run(Node) "run()" or \ref start() should be called
740    ///before using them.
741
742    ///@{
743
744    ///The shortest path to the given node.
745
746    ///Returns the shortest path to the given node from the root(s).
747    ///
748    ///\warning \c t should be reached from the root(s).
749    ///
750    ///\pre Either \ref run(Node) "run()" or \ref init()
751    ///must be called before using this function.
752    Path path(Node t) const { return Path(*G, *_pred, t); }
753
754    ///The distance of the given node from the root(s).
755
756    ///Returns the distance of the given node from the root(s).
757    ///
758    ///\warning If node \c v is not reached from the root(s), then
759    ///the return value of this function is undefined.
760    ///
761    ///\pre Either \ref run(Node) "run()" or \ref init()
762    ///must be called before using this function.
763    int dist(Node v) const { return (*_dist)[v]; }
764
765    ///\brief Returns the 'previous arc' of the shortest path tree for
766    ///the given node.
767    ///
768    ///This function returns the 'previous arc' of the shortest path
769    ///tree for the node \c v, i.e. it returns the last arc of a
770    ///shortest path from a root to \c v. It is \c INVALID if \c v
771    ///is not reached from the root(s) or if \c v is a root.
772    ///
773    ///The shortest path tree used here is equal to the shortest path
774    ///tree used in \ref predNode() and \ref predMap().
775    ///
776    ///\pre Either \ref run(Node) "run()" or \ref init()
777    ///must be called before using this function.
778    Arc predArc(Node v) const { return (*_pred)[v];}
779
780    ///\brief Returns the 'previous node' of the shortest path tree for
781    ///the given node.
782    ///
783    ///This function returns the 'previous node' of the shortest path
784    ///tree for the node \c v, i.e. it returns the last but one node
785    ///of a shortest path from a root to \c v. It is \c INVALID
786    ///if \c v is not reached from the root(s) or if \c v is a root.
787    ///
788    ///The shortest path tree used here is equal to the shortest path
789    ///tree used in \ref predArc() and \ref predMap().
790    ///
791    ///\pre Either \ref run(Node) "run()" or \ref init()
792    ///must be called before using this function.
793    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
794                                  G->source((*_pred)[v]); }
795
796    ///\brief Returns a const reference to the node map that stores the
797    /// distances of the nodes.
798    ///
799    ///Returns a const reference to the node map that stores the distances
800    ///of the nodes calculated by the algorithm.
801    ///
802    ///\pre Either \ref run(Node) "run()" or \ref init()
803    ///must be called before using this function.
804    const DistMap &distMap() const { return *_dist;}
805
806    ///\brief Returns a const reference to the node map that stores the
807    ///predecessor arcs.
808    ///
809    ///Returns a const reference to the node map that stores the predecessor
810    ///arcs, which form the shortest path tree (forest).
811    ///
812    ///\pre Either \ref run(Node) "run()" or \ref init()
813    ///must be called before using this function.
814    const PredMap &predMap() const { return *_pred;}
815
816    ///Checks if the given node is reached from the root(s).
817
818    ///Returns \c true if \c v is reached from the root(s).
819    ///
820    ///\pre Either \ref run(Node) "run()" or \ref init()
821    ///must be called before using this function.
822    bool reached(Node v) const { return (*_reached)[v]; }
823
824    ///@}
825  };
826
827  ///Default traits class of bfs() function.
828
829  ///Default traits class of bfs() function.
830  ///\tparam GR Digraph type.
831  template<class GR>
832  struct BfsWizardDefaultTraits
833  {
834    ///The type of the digraph the algorithm runs on.
835    typedef GR Digraph;
836
837    ///\brief The type of the map that stores the predecessor
838    ///arcs of the shortest paths.
839    ///
840    ///The type of the map that stores the predecessor
841    ///arcs of the shortest paths.
842    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
843    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
844    ///Instantiates a PredMap.
845
846    ///This function instantiates a PredMap.
847    ///\param g is the digraph, to which we would like to define the
848    ///PredMap.
849    static PredMap *createPredMap(const Digraph &g)
850    {
851      return new PredMap(g);
852    }
853
854    ///The type of the map that indicates which nodes are processed.
855
856    ///The type of the map that indicates which nodes are processed.
857    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
858    ///By default, it is a NullMap.
859    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
860    ///Instantiates a ProcessedMap.
861
862    ///This function instantiates a ProcessedMap.
863    ///\param g is the digraph, to which
864    ///we would like to define the ProcessedMap.
865#ifdef DOXYGEN
866    static ProcessedMap *createProcessedMap(const Digraph &g)
867#else
868    static ProcessedMap *createProcessedMap(const Digraph &)
869#endif
870    {
871      return new ProcessedMap();
872    }
873
874    ///The type of the map that indicates which nodes are reached.
875
876    ///The type of the map that indicates which nodes are reached.
877    ///It must conform to
878    ///the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
879    typedef typename Digraph::template NodeMap<bool> ReachedMap;
880    ///Instantiates a ReachedMap.
881
882    ///This function instantiates a ReachedMap.
883    ///\param g is the digraph, to which
884    ///we would like to define the ReachedMap.
885    static ReachedMap *createReachedMap(const Digraph &g)
886    {
887      return new ReachedMap(g);
888    }
889
890    ///The type of the map that stores the distances of the nodes.
891
892    ///The type of the map that stores the distances of the nodes.
893    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
894    typedef typename Digraph::template NodeMap<int> DistMap;
895    ///Instantiates a DistMap.
896
897    ///This function instantiates a DistMap.
898    ///\param g is the digraph, to which we would like to define
899    ///the DistMap
900    static DistMap *createDistMap(const Digraph &g)
901    {
902      return new DistMap(g);
903    }
904
905    ///The type of the shortest paths.
906
907    ///The type of the shortest paths.
908    ///It must conform to the \ref concepts::Path "Path" concept.
909    typedef lemon::Path<Digraph> Path;
910  };
911
912  /// Default traits class used by BfsWizard
913
914  /// Default traits class used by BfsWizard.
915  /// \tparam GR The type of the digraph.
916  template<class GR>
917  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
918  {
919
920    typedef BfsWizardDefaultTraits<GR> Base;
921  protected:
922    //The type of the nodes in the digraph.
923    typedef typename Base::Digraph::Node Node;
924
925    //Pointer to the digraph the algorithm runs on.
926    void *_g;
927    //Pointer to the map of reached nodes.
928    void *_reached;
929    //Pointer to the map of processed nodes.
930    void *_processed;
931    //Pointer to the map of predecessors arcs.
932    void *_pred;
933    //Pointer to the map of distances.
934    void *_dist;
935    //Pointer to the shortest path to the target node.
936    void *_path;
937    //Pointer to the distance of the target node.
938    int *_di;
939
940    public:
941    /// Constructor.
942
943    /// This constructor does not require parameters, it initiates
944    /// all of the attributes to \c 0.
945    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
946                      _dist(0), _path(0), _di(0) {}
947
948    /// Constructor.
949
950    /// This constructor requires one parameter,
951    /// others are initiated to \c 0.
952    /// \param g The digraph the algorithm runs on.
953    BfsWizardBase(const GR &g) :
954      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
955      _reached(0), _processed(0), _pred(0), _dist(0),  _path(0), _di(0) {}
956
957  };
958
959  /// Auxiliary class for the function-type interface of BFS algorithm.
960
961  /// This auxiliary class is created to implement the
962  /// \ref bfs() "function-type interface" of \ref Bfs algorithm.
963  /// It does not have own \ref run(Node) "run()" method, it uses the
964  /// functions and features of the plain \ref Bfs.
965  ///
966  /// This class should only be used through the \ref bfs() function,
967  /// which makes it easier to use the algorithm.
968  ///
969  /// \tparam TR The traits class that defines various types used by the
970  /// algorithm.
971  template<class TR>
972  class BfsWizard : public TR
973  {
974    typedef TR Base;
975
976    typedef typename TR::Digraph Digraph;
977
978    typedef typename Digraph::Node Node;
979    typedef typename Digraph::NodeIt NodeIt;
980    typedef typename Digraph::Arc Arc;
981    typedef typename Digraph::OutArcIt OutArcIt;
982
983    typedef typename TR::PredMap PredMap;
984    typedef typename TR::DistMap DistMap;
985    typedef typename TR::ReachedMap ReachedMap;
986    typedef typename TR::ProcessedMap ProcessedMap;
987    typedef typename TR::Path Path;
988
989  public:
990
991    /// Constructor.
992    BfsWizard() : TR() {}
993
994    /// Constructor that requires parameters.
995
996    /// Constructor that requires parameters.
997    /// These parameters will be the default values for the traits class.
998    /// \param g The digraph the algorithm runs on.
999    BfsWizard(const Digraph &g) :
1000      TR(g) {}
1001
1002    ///Copy constructor
1003    BfsWizard(const TR &b) : TR(b) {}
1004
1005    ~BfsWizard() {}
1006
1007    ///Runs BFS algorithm from the given source node.
1008
1009    ///This method runs BFS algorithm from node \c s
1010    ///in order to compute the shortest path to each node.
1011    void run(Node s)
1012    {
1013      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1014      if (Base::_pred)
1015        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1016      if (Base::_dist)
1017        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1018      if (Base::_reached)
1019        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1020      if (Base::_processed)
1021        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1022      if (s!=INVALID)
1023        alg.run(s);
1024      else
1025        alg.run();
1026    }
1027
1028    ///Finds the shortest path between \c s and \c t.
1029
1030    ///This method runs BFS algorithm from node \c s
1031    ///in order to compute the shortest path to node \c t
1032    ///(it stops searching when \c t is processed).
1033    ///
1034    ///\return \c true if \c t is reachable form \c s.
1035    bool run(Node s, Node t)
1036    {
1037      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1038      if (Base::_pred)
1039        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1040      if (Base::_dist)
1041        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1042      if (Base::_reached)
1043        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1044      if (Base::_processed)
1045        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1046      alg.run(s,t);
1047      if (Base::_path)
1048        *reinterpret_cast<Path*>(Base::_path) = alg.path(t);
1049      if (Base::_di)
1050        *Base::_di = alg.dist(t);
1051      return alg.reached(t);
1052    }
1053
1054    ///Runs BFS algorithm to visit all nodes in the digraph.
1055
1056    ///This method runs BFS algorithm in order to visit all nodes
1057    ///in the digraph.
1058    void run()
1059    {
1060      run(INVALID);
1061    }
1062
1063    template<class T>
1064    struct SetPredMapBase : public Base {
1065      typedef T PredMap;
1066      static PredMap *createPredMap(const Digraph &) { return 0; };
1067      SetPredMapBase(const TR &b) : TR(b) {}
1068    };
1069
1070    ///\brief \ref named-templ-param "Named parameter" for setting
1071    ///the predecessor map.
1072    ///
1073    ///\ref named-templ-param "Named parameter" function for setting
1074    ///the map that stores the predecessor arcs of the nodes.
1075    template<class T>
1076    BfsWizard<SetPredMapBase<T> > predMap(const T &t)
1077    {
1078      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1079      return BfsWizard<SetPredMapBase<T> >(*this);
1080    }
1081
1082    template<class T>
1083    struct SetReachedMapBase : public Base {
1084      typedef T ReachedMap;
1085      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
1086      SetReachedMapBase(const TR &b) : TR(b) {}
1087    };
1088
1089    ///\brief \ref named-templ-param "Named parameter" for setting
1090    ///the reached map.
1091    ///
1092    ///\ref named-templ-param "Named parameter" function for setting
1093    ///the map that indicates which nodes are reached.
1094    template<class T>
1095    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)
1096    {
1097      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
1098      return BfsWizard<SetReachedMapBase<T> >(*this);
1099    }
1100
1101    template<class T>
1102    struct SetDistMapBase : public Base {
1103      typedef T DistMap;
1104      static DistMap *createDistMap(const Digraph &) { return 0; };
1105      SetDistMapBase(const TR &b) : TR(b) {}
1106    };
1107
1108    ///\brief \ref named-templ-param "Named parameter" for setting
1109    ///the distance map.
1110    ///
1111    ///\ref named-templ-param "Named parameter" function for setting
1112    ///the map that stores the distances of the nodes calculated
1113    ///by the algorithm.
1114    template<class T>
1115    BfsWizard<SetDistMapBase<T> > distMap(const T &t)
1116    {
1117      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1118      return BfsWizard<SetDistMapBase<T> >(*this);
1119    }
1120
1121    template<class T>
1122    struct SetProcessedMapBase : public Base {
1123      typedef T ProcessedMap;
1124      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
1125      SetProcessedMapBase(const TR &b) : TR(b) {}
1126    };
1127
1128    ///\brief \ref named-func-param "Named parameter" for setting
1129    ///the processed map.
1130    ///
1131    ///\ref named-templ-param "Named parameter" function for setting
1132    ///the map that indicates which nodes are processed.
1133    template<class T>
1134    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)
1135    {
1136      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
1137      return BfsWizard<SetProcessedMapBase<T> >(*this);
1138    }
1139
1140    template<class T>
1141    struct SetPathBase : public Base {
1142      typedef T Path;
1143      SetPathBase(const TR &b) : TR(b) {}
1144    };
1145    ///\brief \ref named-func-param "Named parameter"
1146    ///for getting the shortest path to the target node.
1147    ///
1148    ///\ref named-func-param "Named parameter"
1149    ///for getting the shortest path to the target node.
1150    template<class T>
1151    BfsWizard<SetPathBase<T> > path(const T &t)
1152    {
1153      Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t));
1154      return BfsWizard<SetPathBase<T> >(*this);
1155    }
1156
1157    ///\brief \ref named-func-param "Named parameter"
1158    ///for getting the distance of the target node.
1159    ///
1160    ///\ref named-func-param "Named parameter"
1161    ///for getting the distance of the target node.
1162    BfsWizard dist(const int &d)
1163    {
1164      Base::_di=const_cast<int*>(&d);
1165      return *this;
1166    }
1167
1168  };
1169
1170  ///Function-type interface for BFS algorithm.
1171
1172  /// \ingroup search
1173  ///Function-type interface for BFS algorithm.
1174  ///
1175  ///This function also has several \ref named-func-param "named parameters",
1176  ///they are declared as the members of class \ref BfsWizard.
1177  ///The following examples show how to use these parameters.
1178  ///\code
1179  ///  // Compute shortest path from node s to each node
1180  ///  bfs(g).predMap(preds).distMap(dists).run(s);
1181  ///
1182  ///  // Compute shortest path from s to t
1183  ///  bool reached = bfs(g).path(p).dist(d).run(s,t);
1184  ///\endcode
1185  ///\warning Don't forget to put the \ref BfsWizard::run(Node) "run()"
1186  ///to the end of the parameter list.
1187  ///\sa BfsWizard
1188  ///\sa Bfs
1189  template<class GR>
1190  BfsWizard<BfsWizardBase<GR> >
1191  bfs(const GR &digraph)
1192  {
1193    return BfsWizard<BfsWizardBase<GR> >(digraph);
1194  }
1195
1196#ifdef DOXYGEN
1197  /// \brief Visitor class for BFS.
1198  ///
1199  /// This class defines the interface of the BfsVisit events, and
1200  /// it could be the base of a real visitor class.
1201  template <typename GR>
1202  struct BfsVisitor {
1203    typedef GR Digraph;
1204    typedef typename Digraph::Arc Arc;
1205    typedef typename Digraph::Node Node;
1206    /// \brief Called for the source node(s) of the BFS.
1207    ///
1208    /// This function is called for the source node(s) of the BFS.
1209    void start(const Node& node) {}
1210    /// \brief Called when a node is reached first time.
1211    ///
1212    /// This function is called when a node is reached first time.
1213    void reach(const Node& node) {}
1214    /// \brief Called when a node is processed.
1215    ///
1216    /// This function is called when a node is processed.
1217    void process(const Node& node) {}
1218    /// \brief Called when an arc reaches a new node.
1219    ///
1220    /// This function is called when the BFS finds an arc whose target node
1221    /// is not reached yet.
1222    void discover(const Arc& arc) {}
1223    /// \brief Called when an arc is examined but its target node is
1224    /// already discovered.
1225    ///
1226    /// This function is called when an arc is examined but its target node is
1227    /// already discovered.
1228    void examine(const Arc& arc) {}
1229  };
1230#else
1231  template <typename GR>
1232  struct BfsVisitor {
1233    typedef GR Digraph;
1234    typedef typename Digraph::Arc Arc;
1235    typedef typename Digraph::Node Node;
1236    void start(const Node&) {}
1237    void reach(const Node&) {}
1238    void process(const Node&) {}
1239    void discover(const Arc&) {}
1240    void examine(const Arc&) {}
1241
1242    template <typename _Visitor>
1243    struct Constraints {
1244      void constraints() {
1245        Arc arc;
1246        Node node;
1247        visitor.start(node);
1248        visitor.reach(node);
1249        visitor.process(node);
1250        visitor.discover(arc);
1251        visitor.examine(arc);
1252      }
1253      _Visitor& visitor;
1254    };
1255  };
1256#endif
1257
1258  /// \brief Default traits class of BfsVisit class.
1259  ///
1260  /// Default traits class of BfsVisit class.
1261  /// \tparam GR The type of the digraph the algorithm runs on.
1262  template<class GR>
1263  struct BfsVisitDefaultTraits {
1264
1265    /// \brief The type of the digraph the algorithm runs on.
1266    typedef GR Digraph;
1267
1268    /// \brief The type of the map that indicates which nodes are reached.
1269    ///
1270    /// The type of the map that indicates which nodes are reached.
1271    /// It must conform to
1272    ///the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
1273    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1274
1275    /// \brief Instantiates a ReachedMap.
1276    ///
1277    /// This function instantiates a ReachedMap.
1278    /// \param digraph is the digraph, to which
1279    /// we would like to define the ReachedMap.
1280    static ReachedMap *createReachedMap(const Digraph &digraph) {
1281      return new ReachedMap(digraph);
1282    }
1283
1284  };
1285
1286  /// \ingroup search
1287  ///
1288  /// \brief BFS algorithm class with visitor interface.
1289  ///
1290  /// This class provides an efficient implementation of the BFS algorithm
1291  /// with visitor interface.
1292  ///
1293  /// The BfsVisit class provides an alternative interface to the Bfs
1294  /// class. It works with callback mechanism, the BfsVisit object calls
1295  /// the member functions of the \c Visitor class on every BFS event.
1296  ///
1297  /// This interface of the BFS algorithm should be used in special cases
1298  /// when extra actions have to be performed in connection with certain
1299  /// events of the BFS algorithm. Otherwise consider to use Bfs or bfs()
1300  /// instead.
1301  ///
1302  /// \tparam GR The type of the digraph the algorithm runs on.
1303  /// The default type is \ref ListDigraph.
1304  /// The value of GR is not used directly by \ref BfsVisit,
1305  /// it is only passed to \ref BfsVisitDefaultTraits.
1306  /// \tparam VS The Visitor type that is used by the algorithm.
1307  /// \ref BfsVisitor "BfsVisitor<GR>" is an empty visitor, which
1308  /// does not observe the BFS events. If you want to observe the BFS
1309  /// events, you should implement your own visitor class.
1310  /// \tparam TR The traits class that defines various types used by the
1311  /// algorithm. By default, it is \ref BfsVisitDefaultTraits
1312  /// "BfsVisitDefaultTraits<GR>".
1313  /// In most cases, this parameter should not be set directly,
1314  /// consider to use the named template parameters instead.
1315#ifdef DOXYGEN
1316  template <typename GR, typename VS, typename TR>
1317#else
1318  template <typename GR = ListDigraph,
1319            typename VS = BfsVisitor<GR>,
1320            typename TR = BfsVisitDefaultTraits<GR> >
1321#endif
1322  class BfsVisit {
1323  public:
1324
1325    ///The traits class.
1326    typedef TR Traits;
1327
1328    ///The type of the digraph the algorithm runs on.
1329    typedef typename Traits::Digraph Digraph;
1330
1331    ///The visitor type used by the algorithm.
1332    typedef VS Visitor;
1333
1334    ///The type of the map that indicates which nodes are reached.
1335    typedef typename Traits::ReachedMap ReachedMap;
1336
1337  private:
1338
1339    typedef typename Digraph::Node Node;
1340    typedef typename Digraph::NodeIt NodeIt;
1341    typedef typename Digraph::Arc Arc;
1342    typedef typename Digraph::OutArcIt OutArcIt;
1343
1344    //Pointer to the underlying digraph.
1345    const Digraph *_digraph;
1346    //Pointer to the visitor object.
1347    Visitor *_visitor;
1348    //Pointer to the map of reached status of the nodes.
1349    ReachedMap *_reached;
1350    //Indicates if _reached is locally allocated (true) or not.
1351    bool local_reached;
1352
1353    std::vector<typename Digraph::Node> _list;
1354    int _list_front, _list_back;
1355
1356    //Creates the maps if necessary.
1357    void create_maps() {
1358      if(!_reached) {
1359        local_reached = true;
1360        _reached = Traits::createReachedMap(*_digraph);
1361      }
1362    }
1363
1364  protected:
1365
1366    BfsVisit() {}
1367
1368  public:
1369
1370    typedef BfsVisit Create;
1371
1372    /// \name Named Template Parameters
1373
1374    ///@{
1375    template <class T>
1376    struct SetReachedMapTraits : public Traits {
1377      typedef T ReachedMap;
1378      static ReachedMap *createReachedMap(const Digraph &digraph) {
1379        LEMON_ASSERT(false, "ReachedMap is not initialized");
1380        return 0; // ignore warnings
1381      }
1382    };
1383    /// \brief \ref named-templ-param "Named parameter" for setting
1384    /// ReachedMap type.
1385    ///
1386    /// \ref named-templ-param "Named parameter" for setting ReachedMap type.
1387    template <class T>
1388    struct SetReachedMap : public BfsVisit< Digraph, Visitor,
1389                                            SetReachedMapTraits<T> > {
1390      typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create;
1391    };
1392    ///@}
1393
1394  public:
1395
1396    /// \brief Constructor.
1397    ///
1398    /// Constructor.
1399    ///
1400    /// \param digraph The digraph the algorithm runs on.
1401    /// \param visitor The visitor object of the algorithm.
1402    BfsVisit(const Digraph& digraph, Visitor& visitor)
1403      : _digraph(&digraph), _visitor(&visitor),
1404        _reached(0), local_reached(false) {}
1405
1406    /// \brief Destructor.
1407    ~BfsVisit() {
1408      if(local_reached) delete _reached;
1409    }
1410
1411    /// \brief Sets the map that indicates which nodes are reached.
1412    ///
1413    /// Sets the map that indicates which nodes are reached.
1414    /// If you don't use this function before calling \ref run(Node) "run()"
1415    /// or \ref init(), an instance will be allocated automatically.
1416    /// The destructor deallocates this automatically allocated map,
1417    /// of course.
1418    /// \return <tt> (*this) </tt>
1419    BfsVisit &reachedMap(ReachedMap &m) {
1420      if(local_reached) {
1421        delete _reached;
1422        local_reached = false;
1423      }
1424      _reached = &m;
1425      return *this;
1426    }
1427
1428  public:
1429
1430    /// \name Execution Control
1431    /// The simplest way to execute the BFS algorithm is to use one of the
1432    /// member functions called \ref run(Node) "run()".\n
1433    /// If you need better control on the execution, you have to call
1434    /// \ref init() first, then you can add several source nodes with
1435    /// \ref addSource(). Finally the actual path computation can be
1436    /// performed with one of the \ref start() functions.
1437
1438    /// @{
1439
1440    /// \brief Initializes the internal data structures.
1441    ///
1442    /// Initializes the internal data structures.
1443    void init() {
1444      create_maps();
1445      _list.resize(countNodes(*_digraph));
1446      _list_front = _list_back = -1;
1447      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
1448        _reached->set(u, false);
1449      }
1450    }
1451
1452    /// \brief Adds a new source node.
1453    ///
1454    /// Adds a new source node to the set of nodes to be processed.
1455    void addSource(Node s) {
1456      if(!(*_reached)[s]) {
1457          _reached->set(s,true);
1458          _visitor->start(s);
1459          _visitor->reach(s);
1460          _list[++_list_back] = s;
1461        }
1462    }
1463
1464    /// \brief Processes the next node.
1465    ///
1466    /// Processes the next node.
1467    ///
1468    /// \return The processed node.
1469    ///
1470    /// \pre The queue must not be empty.
1471    Node processNextNode() {
1472      Node n = _list[++_list_front];
1473      _visitor->process(n);
1474      Arc e;
1475      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1476        Node m = _digraph->target(e);
1477        if (!(*_reached)[m]) {
1478          _visitor->discover(e);
1479          _visitor->reach(m);
1480          _reached->set(m, true);
1481          _list[++_list_back] = m;
1482        } else {
1483          _visitor->examine(e);
1484        }
1485      }
1486      return n;
1487    }
1488
1489    /// \brief Processes the next node.
1490    ///
1491    /// Processes the next node and checks if the given target node
1492    /// is reached. If the target node is reachable from the processed
1493    /// node, then the \c reach parameter will be set to \c true.
1494    ///
1495    /// \param target The target node.
1496    /// \retval reach Indicates if the target node is reached.
1497    /// It should be initially \c false.
1498    ///
1499    /// \return The processed node.
1500    ///
1501    /// \pre The queue must not be empty.
1502    Node processNextNode(Node target, bool& reach) {
1503      Node n = _list[++_list_front];
1504      _visitor->process(n);
1505      Arc e;
1506      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1507        Node m = _digraph->target(e);
1508        if (!(*_reached)[m]) {
1509          _visitor->discover(e);
1510          _visitor->reach(m);
1511          _reached->set(m, true);
1512          _list[++_list_back] = m;
1513          reach = reach || (target == m);
1514        } else {
1515          _visitor->examine(e);
1516        }
1517      }
1518      return n;
1519    }
1520
1521    /// \brief Processes the next node.
1522    ///
1523    /// Processes the next node and checks if at least one of reached
1524    /// nodes has \c true value in the \c nm node map. If one node
1525    /// with \c true value is reachable from the processed node, then the
1526    /// \c rnode parameter will be set to the first of such nodes.
1527    ///
1528    /// \param nm A \c bool (or convertible) node map that indicates the
1529    /// possible targets.
1530    /// \retval rnode The reached target node.
1531    /// It should be initially \c INVALID.
1532    ///
1533    /// \return The processed node.
1534    ///
1535    /// \pre The queue must not be empty.
1536    template <typename NM>
1537    Node processNextNode(const NM& nm, Node& rnode) {
1538      Node n = _list[++_list_front];
1539      _visitor->process(n);
1540      Arc e;
1541      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1542        Node m = _digraph->target(e);
1543        if (!(*_reached)[m]) {
1544          _visitor->discover(e);
1545          _visitor->reach(m);
1546          _reached->set(m, true);
1547          _list[++_list_back] = m;
1548          if (nm[m] && rnode == INVALID) rnode = m;
1549        } else {
1550          _visitor->examine(e);
1551        }
1552      }
1553      return n;
1554    }
1555
1556    /// \brief The next node to be processed.
1557    ///
1558    /// Returns the next node to be processed or \c INVALID if the queue
1559    /// is empty.
1560    Node nextNode() const {
1561      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1562    }
1563
1564    /// \brief Returns \c false if there are nodes
1565    /// to be processed.
1566    ///
1567    /// Returns \c false if there are nodes
1568    /// to be processed in the queue.
1569    bool emptyQueue() const { return _list_front == _list_back; }
1570
1571    /// \brief Returns the number of the nodes to be processed.
1572    ///
1573    /// Returns the number of the nodes to be processed in the queue.
1574    int queueSize() const { return _list_back - _list_front; }
1575
1576    /// \brief Executes the algorithm.
1577    ///
1578    /// Executes the algorithm.
1579    ///
1580    /// This method runs the %BFS algorithm from the root node(s)
1581    /// in order to compute the shortest path to each node.
1582    ///
1583    /// The algorithm computes
1584    /// - the shortest path tree (forest),
1585    /// - the distance of each node from the root(s).
1586    ///
1587    /// \pre init() must be called and at least one root node should be added
1588    /// with addSource() before using this function.
1589    ///
1590    /// \note <tt>b.start()</tt> is just a shortcut of the following code.
1591    /// \code
1592    ///   while ( !b.emptyQueue() ) {
1593    ///     b.processNextNode();
1594    ///   }
1595    /// \endcode
1596    void start() {
1597      while ( !emptyQueue() ) processNextNode();
1598    }
1599
1600    /// \brief Executes the algorithm until the given target node is reached.
1601    ///
1602    /// Executes the algorithm until the given target node is reached.
1603    ///
1604    /// This method runs the %BFS algorithm from the root node(s)
1605    /// in order to compute the shortest path to \c t.
1606    ///
1607    /// The algorithm computes
1608    /// - the shortest path to \c t,
1609    /// - the distance of \c t from the root(s).
1610    ///
1611    /// \pre init() must be called and at least one root node should be
1612    /// added with addSource() before using this function.
1613    ///
1614    /// \note <tt>b.start(t)</tt> is just a shortcut of the following code.
1615    /// \code
1616    ///   bool reach = false;
1617    ///   while ( !b.emptyQueue() && !reach ) {
1618    ///     b.processNextNode(t, reach);
1619    ///   }
1620    /// \endcode
1621    void start(Node t) {
1622      bool reach = false;
1623      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
1624    }
1625
1626    /// \brief Executes the algorithm until a condition is met.
1627    ///
1628    /// Executes the algorithm until a condition is met.
1629    ///
1630    /// This method runs the %BFS algorithm from the root node(s) in
1631    /// order to compute the shortest path to a node \c v with
1632    /// <tt>nm[v]</tt> true, if such a node can be found.
1633    ///
1634    /// \param nm must be a bool (or convertible) node map. The
1635    /// algorithm will stop when it reaches a node \c v with
1636    /// <tt>nm[v]</tt> true.
1637    ///
1638    /// \return The reached node \c v with <tt>nm[v]</tt> true or
1639    /// \c INVALID if no such node was found.
1640    ///
1641    /// \pre init() must be called and at least one root node should be
1642    /// added with addSource() before using this function.
1643    ///
1644    /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code.
1645    /// \code
1646    ///   Node rnode = INVALID;
1647    ///   while ( !b.emptyQueue() && rnode == INVALID ) {
1648    ///     b.processNextNode(nm, rnode);
1649    ///   }
1650    ///   return rnode;
1651    /// \endcode
1652    template <typename NM>
1653    Node start(const NM &nm) {
1654      Node rnode = INVALID;
1655      while ( !emptyQueue() && rnode == INVALID ) {
1656        processNextNode(nm, rnode);
1657      }
1658      return rnode;
1659    }
1660
1661    /// \brief Runs the algorithm from the given source node.
1662    ///
1663    /// This method runs the %BFS algorithm from node \c s
1664    /// in order to compute the shortest path to each node.
1665    ///
1666    /// The algorithm computes
1667    /// - the shortest path tree,
1668    /// - the distance of each node from the root.
1669    ///
1670    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1671    ///\code
1672    ///   b.init();
1673    ///   b.addSource(s);
1674    ///   b.start();
1675    ///\endcode
1676    void run(Node s) {
1677      init();
1678      addSource(s);
1679      start();
1680    }
1681
1682    /// \brief Finds the shortest path between \c s and \c t.
1683    ///
1684    /// This method runs the %BFS algorithm from node \c s
1685    /// in order to compute the shortest path to node \c t
1686    /// (it stops searching when \c t is processed).
1687    ///
1688    /// \return \c true if \c t is reachable form \c s.
1689    ///
1690    /// \note Apart from the return value, <tt>b.run(s,t)</tt> is just a
1691    /// shortcut of the following code.
1692    ///\code
1693    ///   b.init();
1694    ///   b.addSource(s);
1695    ///   b.start(t);
1696    ///\endcode
1697    bool run(Node s,Node t) {
1698      init();
1699      addSource(s);
1700      start(t);
1701      return reached(t);
1702    }
1703
1704    /// \brief Runs the algorithm to visit all nodes in the digraph.
1705    ///
1706    /// This method runs the %BFS algorithm in order to visit all nodes
1707    /// in the digraph.
1708    ///
1709    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1710    ///\code
1711    ///  b.init();
1712    ///  for (NodeIt n(gr); n != INVALID; ++n) {
1713    ///    if (!b.reached(n)) {
1714    ///      b.addSource(n);
1715    ///      b.start();
1716    ///    }
1717    ///  }
1718    ///\endcode
1719    void run() {
1720      init();
1721      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1722        if (!reached(it)) {
1723          addSource(it);
1724          start();
1725        }
1726      }
1727    }
1728
1729    ///@}
1730
1731    /// \name Query Functions
1732    /// The results of the BFS algorithm can be obtained using these
1733    /// functions.\n
1734    /// Either \ref run(Node) "run()" or \ref start() should be called
1735    /// before using them.
1736
1737    ///@{
1738
1739    /// \brief Checks if the given node is reached from the root(s).
1740    ///
1741    /// Returns \c true if \c v is reached from the root(s).
1742    ///
1743    /// \pre Either \ref run(Node) "run()" or \ref init()
1744    /// must be called before using this function.
1745    bool reached(Node v) const { return (*_reached)[v]; }
1746
1747    ///@}
1748
1749  };
1750
1751} //END OF NAMESPACE LEMON
1752
1753#endif
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