COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/bfs.h @ 825:75e6020b19b1

Last change on this file since 825:75e6020b19b1 was 825:75e6020b19b1, checked in by Peter Kovacs <kpeter@…>, 10 years ago

Add doc for the traits class parameters (#315)

File size: 54.2 KB
Line 
1/* -*- mode: C++; indent-tabs-mode: nil; -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library.
4 *
5 * Copyright (C) 2003-2009
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 the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
86    typedef typename Digraph::template NodeMap<bool> ReachedMap;
87    ///Instantiates a \c ReachedMap.
88
89    ///This function instantiates a \ref ReachedMap.
90    ///\param g is the digraph, to which
91    ///we would like to define the \ref ReachedMap.
92    static ReachedMap *createReachedMap(const Digraph &g)
93    {
94      return new ReachedMap(g);
95    }
96
97    ///The type of the map that stores the distances of the nodes.
98
99    ///The type of the map that stores the distances of the nodes.
100    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
101    typedef typename Digraph::template NodeMap<int> DistMap;
102    ///Instantiates a \c DistMap.
103
104    ///This function instantiates a \ref DistMap.
105    ///\param g is the digraph, to which we would like to define the
106    ///\ref DistMap.
107    static DistMap *createDistMap(const Digraph &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  ///There is also a \ref bfs() "function-type interface" for the BFS
119  ///algorithm, which is convenient in the simplier cases and it can be
120  ///used easier.
121  ///
122  ///\tparam GR The type of the digraph the algorithm runs on.
123  ///The default type is \ref ListDigraph.
124  ///\tparam TR The traits class that defines various types used by the
125  ///algorithm. By default, it is \ref BfsDefaultTraits
126  ///"BfsDefaultTraits<GR>".
127  ///In most cases, this parameter should not be set directly,
128  ///consider to use the named template parameters instead.
129#ifdef DOXYGEN
130  template <typename GR,
131            typename TR>
132#else
133  template <typename GR=ListDigraph,
134            typename TR=BfsDefaultTraits<GR> >
135#endif
136  class Bfs {
137  public:
138
139    ///The type of the digraph the algorithm runs on.
140    typedef typename TR::Digraph Digraph;
141
142    ///\brief The type of the map that stores the predecessor arcs of the
143    ///shortest paths.
144    typedef typename TR::PredMap PredMap;
145    ///The type of the map that stores the distances of the nodes.
146    typedef typename TR::DistMap DistMap;
147    ///The type of the map that indicates which nodes are reached.
148    typedef typename TR::ReachedMap ReachedMap;
149    ///The type of the map that indicates which nodes are processed.
150    typedef typename TR::ProcessedMap ProcessedMap;
151    ///The type of the paths.
152    typedef PredMapPath<Digraph, PredMap> Path;
153
154    ///The \ref BfsDefaultTraits "traits class" of the algorithm.
155    typedef TR Traits;
156
157  private:
158
159    typedef typename Digraph::Node Node;
160    typedef typename Digraph::NodeIt NodeIt;
161    typedef typename Digraph::Arc Arc;
162    typedef typename Digraph::OutArcIt OutArcIt;
163
164    //Pointer to the underlying digraph.
165    const Digraph *G;
166    //Pointer to the map of predecessor arcs.
167    PredMap *_pred;
168    //Indicates if _pred is locally allocated (true) or not.
169    bool local_pred;
170    //Pointer to the map of distances.
171    DistMap *_dist;
172    //Indicates if _dist is locally allocated (true) or not.
173    bool local_dist;
174    //Pointer to the map of reached status of the nodes.
175    ReachedMap *_reached;
176    //Indicates if _reached is locally allocated (true) or not.
177    bool local_reached;
178    //Pointer to the map of processed status of the nodes.
179    ProcessedMap *_processed;
180    //Indicates if _processed is locally allocated (true) or not.
181    bool local_processed;
182
183    std::vector<typename Digraph::Node> _queue;
184    int _queue_head,_queue_tail,_queue_next_dist;
185    int _curr_dist;
186
187    //Creates the maps if necessary.
188    void create_maps()
189    {
190      if(!_pred) {
191        local_pred = true;
192        _pred = Traits::createPredMap(*G);
193      }
194      if(!_dist) {
195        local_dist = true;
196        _dist = Traits::createDistMap(*G);
197      }
198      if(!_reached) {
199        local_reached = true;
200        _reached = Traits::createReachedMap(*G);
201      }
202      if(!_processed) {
203        local_processed = true;
204        _processed = Traits::createProcessedMap(*G);
205      }
206    }
207
208  protected:
209
210    Bfs() {}
211
212  public:
213
214    typedef Bfs Create;
215
216    ///\name Named Template Parameters
217
218    ///@{
219
220    template <class T>
221    struct SetPredMapTraits : public Traits {
222      typedef T PredMap;
223      static PredMap *createPredMap(const Digraph &)
224      {
225        LEMON_ASSERT(false, "PredMap is not initialized");
226        return 0; // ignore warnings
227      }
228    };
229    ///\brief \ref named-templ-param "Named parameter" for setting
230    ///\c PredMap type.
231    ///
232    ///\ref named-templ-param "Named parameter" for setting
233    ///\c PredMap type.
234    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
235    template <class T>
236    struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > {
237      typedef Bfs< Digraph, SetPredMapTraits<T> > Create;
238    };
239
240    template <class T>
241    struct SetDistMapTraits : public Traits {
242      typedef T DistMap;
243      static DistMap *createDistMap(const Digraph &)
244      {
245        LEMON_ASSERT(false, "DistMap is not initialized");
246        return 0; // ignore warnings
247      }
248    };
249    ///\brief \ref named-templ-param "Named parameter" for setting
250    ///\c DistMap type.
251    ///
252    ///\ref named-templ-param "Named parameter" for setting
253    ///\c DistMap type.
254    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
255    template <class T>
256    struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > {
257      typedef Bfs< Digraph, SetDistMapTraits<T> > Create;
258    };
259
260    template <class T>
261    struct SetReachedMapTraits : public Traits {
262      typedef T ReachedMap;
263      static ReachedMap *createReachedMap(const Digraph &)
264      {
265        LEMON_ASSERT(false, "ReachedMap is not initialized");
266        return 0; // ignore warnings
267      }
268    };
269    ///\brief \ref named-templ-param "Named parameter" for setting
270    ///\c ReachedMap type.
271    ///
272    ///\ref named-templ-param "Named parameter" for setting
273    ///\c ReachedMap type.
274    ///It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
275    template <class T>
276    struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > {
277      typedef Bfs< Digraph, SetReachedMapTraits<T> > Create;
278    };
279
280    template <class T>
281    struct SetProcessedMapTraits : public Traits {
282      typedef T ProcessedMap;
283      static ProcessedMap *createProcessedMap(const Digraph &)
284      {
285        LEMON_ASSERT(false, "ProcessedMap is not initialized");
286        return 0; // ignore warnings
287      }
288    };
289    ///\brief \ref named-templ-param "Named parameter" for setting
290    ///\c ProcessedMap type.
291    ///
292    ///\ref named-templ-param "Named parameter" for setting
293    ///\c ProcessedMap type.
294    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
295    template <class T>
296    struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > {
297      typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create;
298    };
299
300    struct SetStandardProcessedMapTraits : public Traits {
301      typedef typename Digraph::template NodeMap<bool> ProcessedMap;
302      static ProcessedMap *createProcessedMap(const Digraph &g)
303      {
304        return new ProcessedMap(g);
305        return 0; // ignore warnings
306      }
307    };
308    ///\brief \ref named-templ-param "Named parameter" for setting
309    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
310    ///
311    ///\ref named-templ-param "Named parameter" for setting
312    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
313    ///If you don't set it explicitly, it will be automatically allocated.
314    struct SetStandardProcessedMap :
315      public Bfs< Digraph, SetStandardProcessedMapTraits > {
316      typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create;
317    };
318
319    ///@}
320
321  public:
322
323    ///Constructor.
324
325    ///Constructor.
326    ///\param g The digraph the algorithm runs on.
327    Bfs(const Digraph &g) :
328      G(&g),
329      _pred(NULL), local_pred(false),
330      _dist(NULL), local_dist(false),
331      _reached(NULL), local_reached(false),
332      _processed(NULL), local_processed(false)
333    { }
334
335    ///Destructor.
336    ~Bfs()
337    {
338      if(local_pred) delete _pred;
339      if(local_dist) delete _dist;
340      if(local_reached) delete _reached;
341      if(local_processed) delete _processed;
342    }
343
344    ///Sets the map that stores the predecessor arcs.
345
346    ///Sets the map that stores the predecessor arcs.
347    ///If you don't use this function before calling \ref run(Node) "run()"
348    ///or \ref init(), an instance will be allocated automatically.
349    ///The destructor deallocates this automatically allocated map,
350    ///of course.
351    ///\return <tt> (*this) </tt>
352    Bfs &predMap(PredMap &m)
353    {
354      if(local_pred) {
355        delete _pred;
356        local_pred=false;
357      }
358      _pred = &m;
359      return *this;
360    }
361
362    ///Sets the map that indicates which nodes are reached.
363
364    ///Sets the map that indicates which nodes are reached.
365    ///If you don't use this function before calling \ref run(Node) "run()"
366    ///or \ref init(), an instance will be allocated automatically.
367    ///The destructor deallocates this automatically allocated map,
368    ///of course.
369    ///\return <tt> (*this) </tt>
370    Bfs &reachedMap(ReachedMap &m)
371    {
372      if(local_reached) {
373        delete _reached;
374        local_reached=false;
375      }
376      _reached = &m;
377      return *this;
378    }
379
380    ///Sets the map that indicates which nodes are processed.
381
382    ///Sets the map that indicates which nodes are processed.
383    ///If you don't use this function before calling \ref run(Node) "run()"
384    ///or \ref init(), an instance will be allocated automatically.
385    ///The destructor deallocates this automatically allocated map,
386    ///of course.
387    ///\return <tt> (*this) </tt>
388    Bfs &processedMap(ProcessedMap &m)
389    {
390      if(local_processed) {
391        delete _processed;
392        local_processed=false;
393      }
394      _processed = &m;
395      return *this;
396    }
397
398    ///Sets the map that stores the distances of the nodes.
399
400    ///Sets the map that stores the distances of the nodes calculated by
401    ///the algorithm.
402    ///If you don't use this function before calling \ref run(Node) "run()"
403    ///or \ref init(), an instance will be allocated automatically.
404    ///The destructor deallocates this automatically allocated map,
405    ///of course.
406    ///\return <tt> (*this) </tt>
407    Bfs &distMap(DistMap &m)
408    {
409      if(local_dist) {
410        delete _dist;
411        local_dist=false;
412      }
413      _dist = &m;
414      return *this;
415    }
416
417  public:
418
419    ///\name Execution Control
420    ///The simplest way to execute the BFS algorithm is to use one of the
421    ///member functions called \ref run(Node) "run()".\n
422    ///If you need better control on the execution, you have to call
423    ///\ref init() first, then you can add several source nodes with
424    ///\ref addSource(). Finally the actual path computation can be
425    ///performed with one of the \ref start() functions.
426
427    ///@{
428
429    ///\brief Initializes the internal data structures.
430    ///
431    ///Initializes the internal data structures.
432    void init()
433    {
434      create_maps();
435      _queue.resize(countNodes(*G));
436      _queue_head=_queue_tail=0;
437      _curr_dist=1;
438      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
439        _pred->set(u,INVALID);
440        _reached->set(u,false);
441        _processed->set(u,false);
442      }
443    }
444
445    ///Adds a new source node.
446
447    ///Adds a new source node to the set of nodes to be processed.
448    ///
449    void addSource(Node s)
450    {
451      if(!(*_reached)[s])
452        {
453          _reached->set(s,true);
454          _pred->set(s,INVALID);
455          _dist->set(s,0);
456          _queue[_queue_head++]=s;
457          _queue_next_dist=_queue_head;
458        }
459    }
460
461    ///Processes the next node.
462
463    ///Processes the next node.
464    ///
465    ///\return The processed node.
466    ///
467    ///\pre The queue must not be empty.
468    Node processNextNode()
469    {
470      if(_queue_tail==_queue_next_dist) {
471        _curr_dist++;
472        _queue_next_dist=_queue_head;
473      }
474      Node n=_queue[_queue_tail++];
475      _processed->set(n,true);
476      Node m;
477      for(OutArcIt e(*G,n);e!=INVALID;++e)
478        if(!(*_reached)[m=G->target(e)]) {
479          _queue[_queue_head++]=m;
480          _reached->set(m,true);
481          _pred->set(m,e);
482          _dist->set(m,_curr_dist);
483        }
484      return n;
485    }
486
487    ///Processes the next node.
488
489    ///Processes the next node and checks if the given target node
490    ///is reached. If the target node is reachable from the processed
491    ///node, then the \c reach parameter will be set to \c true.
492    ///
493    ///\param target The target node.
494    ///\retval reach Indicates if the target node is reached.
495    ///It should be initially \c false.
496    ///
497    ///\return The processed node.
498    ///
499    ///\pre The queue must not be empty.
500    Node processNextNode(Node target, bool& reach)
501    {
502      if(_queue_tail==_queue_next_dist) {
503        _curr_dist++;
504        _queue_next_dist=_queue_head;
505      }
506      Node n=_queue[_queue_tail++];
507      _processed->set(n,true);
508      Node m;
509      for(OutArcIt e(*G,n);e!=INVALID;++e)
510        if(!(*_reached)[m=G->target(e)]) {
511          _queue[_queue_head++]=m;
512          _reached->set(m,true);
513          _pred->set(m,e);
514          _dist->set(m,_curr_dist);
515          reach = reach || (target == m);
516        }
517      return n;
518    }
519
520    ///Processes the next node.
521
522    ///Processes the next node and checks if at least one of reached
523    ///nodes has \c true value in the \c nm node map. If one node
524    ///with \c true value is reachable from the processed node, then the
525    ///\c rnode parameter will be set to the first of such nodes.
526    ///
527    ///\param nm A \c bool (or convertible) node map that indicates the
528    ///possible targets.
529    ///\retval rnode The reached target node.
530    ///It should be initially \c INVALID.
531    ///
532    ///\return The processed node.
533    ///
534    ///\pre The queue must not be empty.
535    template<class NM>
536    Node processNextNode(const NM& nm, Node& rnode)
537    {
538      if(_queue_tail==_queue_next_dist) {
539        _curr_dist++;
540        _queue_next_dist=_queue_head;
541      }
542      Node n=_queue[_queue_tail++];
543      _processed->set(n,true);
544      Node m;
545      for(OutArcIt e(*G,n);e!=INVALID;++e)
546        if(!(*_reached)[m=G->target(e)]) {
547          _queue[_queue_head++]=m;
548          _reached->set(m,true);
549          _pred->set(m,e);
550          _dist->set(m,_curr_dist);
551          if (nm[m] && rnode == INVALID) rnode = m;
552        }
553      return n;
554    }
555
556    ///The next node to be processed.
557
558    ///Returns the next node to be processed or \c INVALID if the queue
559    ///is empty.
560    Node nextNode() const
561    {
562      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
563    }
564
565    ///Returns \c false if there are nodes to be processed.
566
567    ///Returns \c false if there are nodes to be processed
568    ///in the queue.
569    bool emptyQueue() const { return _queue_tail==_queue_head; }
570
571    ///Returns the number of the nodes to be processed.
572
573    ///Returns the number of the nodes to be processed
574    ///in the queue.
575    int queueSize() const { return _queue_head-_queue_tail; }
576
577    ///Executes the algorithm.
578
579    ///Executes the algorithm.
580    ///
581    ///This method runs the %BFS algorithm from the root node(s)
582    ///in order to compute the shortest path to each node.
583    ///
584    ///The algorithm computes
585    ///- the shortest path tree (forest),
586    ///- the distance of each node from the root(s).
587    ///
588    ///\pre init() must be called and at least one root node should be
589    ///added with addSource() before using this function.
590    ///
591    ///\note <tt>b.start()</tt> is just a shortcut of the following code.
592    ///\code
593    ///  while ( !b.emptyQueue() ) {
594    ///    b.processNextNode();
595    ///  }
596    ///\endcode
597    void start()
598    {
599      while ( !emptyQueue() ) processNextNode();
600    }
601
602    ///Executes the algorithm until the given target node is reached.
603
604    ///Executes the algorithm until the given target node is reached.
605    ///
606    ///This method runs the %BFS algorithm from the root node(s)
607    ///in order to compute the shortest path to \c t.
608    ///
609    ///The algorithm computes
610    ///- the shortest path to \c t,
611    ///- the distance of \c t from the root(s).
612    ///
613    ///\pre init() must be called and at least one root node should be
614    ///added with addSource() before using this function.
615    ///
616    ///\note <tt>b.start(t)</tt> is just a shortcut of the following code.
617    ///\code
618    ///  bool reach = false;
619    ///  while ( !b.emptyQueue() && !reach ) {
620    ///    b.processNextNode(t, reach);
621    ///  }
622    ///\endcode
623    void start(Node t)
624    {
625      bool reach = false;
626      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
627    }
628
629    ///Executes the algorithm until a condition is met.
630
631    ///Executes the algorithm until a condition is met.
632    ///
633    ///This method runs the %BFS algorithm from the root node(s) in
634    ///order to compute the shortest path to a node \c v with
635    /// <tt>nm[v]</tt> true, if such a node can be found.
636    ///
637    ///\param nm A \c bool (or convertible) node map. The algorithm
638    ///will stop when it reaches a node \c v with <tt>nm[v]</tt> true.
639    ///
640    ///\return The reached node \c v with <tt>nm[v]</tt> true or
641    ///\c INVALID if no such node was found.
642    ///
643    ///\pre init() must be called and at least one root node should be
644    ///added with addSource() before using this function.
645    ///
646    ///\note <tt>b.start(nm)</tt> is just a shortcut of the following code.
647    ///\code
648    ///  Node rnode = INVALID;
649    ///  while ( !b.emptyQueue() && rnode == INVALID ) {
650    ///    b.processNextNode(nm, rnode);
651    ///  }
652    ///  return rnode;
653    ///\endcode
654    template<class NodeBoolMap>
655    Node start(const NodeBoolMap &nm)
656    {
657      Node rnode = INVALID;
658      while ( !emptyQueue() && rnode == INVALID ) {
659        processNextNode(nm, rnode);
660      }
661      return rnode;
662    }
663
664    ///Runs the algorithm from the given source node.
665
666    ///This method runs the %BFS algorithm from node \c s
667    ///in order to compute the shortest path to each node.
668    ///
669    ///The algorithm computes
670    ///- the shortest path tree,
671    ///- the distance of each node from the root.
672    ///
673    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
674    ///\code
675    ///  b.init();
676    ///  b.addSource(s);
677    ///  b.start();
678    ///\endcode
679    void run(Node s) {
680      init();
681      addSource(s);
682      start();
683    }
684
685    ///Finds the shortest path between \c s and \c t.
686
687    ///This method runs the %BFS algorithm from node \c s
688    ///in order to compute the shortest path to node \c t
689    ///(it stops searching when \c t is processed).
690    ///
691    ///\return \c true if \c t is reachable form \c s.
692    ///
693    ///\note Apart from the return value, <tt>b.run(s,t)</tt> is just a
694    ///shortcut of the following code.
695    ///\code
696    ///  b.init();
697    ///  b.addSource(s);
698    ///  b.start(t);
699    ///\endcode
700    bool run(Node s,Node t) {
701      init();
702      addSource(s);
703      start(t);
704      return reached(t);
705    }
706
707    ///Runs the algorithm to visit all nodes in the digraph.
708
709    ///This method runs the %BFS algorithm in order to visit all nodes
710    ///in the digraph.
711    ///
712    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
713    ///\code
714    ///  b.init();
715    ///  for (NodeIt n(gr); n != INVALID; ++n) {
716    ///    if (!b.reached(n)) {
717    ///      b.addSource(n);
718    ///      b.start();
719    ///    }
720    ///  }
721    ///\endcode
722    void run() {
723      init();
724      for (NodeIt n(*G); n != INVALID; ++n) {
725        if (!reached(n)) {
726          addSource(n);
727          start();
728        }
729      }
730    }
731
732    ///@}
733
734    ///\name Query Functions
735    ///The results of the BFS algorithm can be obtained using these
736    ///functions.\n
737    ///Either \ref run(Node) "run()" or \ref start() should be called
738    ///before using them.
739
740    ///@{
741
742    ///The shortest path to the given node.
743
744    ///Returns the shortest path to the given node from the root(s).
745    ///
746    ///\warning \c t should be reached from the root(s).
747    ///
748    ///\pre Either \ref run(Node) "run()" or \ref init()
749    ///must be called before using this function.
750    Path path(Node t) const { return Path(*G, *_pred, t); }
751
752    ///The distance of the given node from the root(s).
753
754    ///Returns the distance of the given node from the root(s).
755    ///
756    ///\warning If node \c v is not reached from the root(s), then
757    ///the return value of this function is undefined.
758    ///
759    ///\pre Either \ref run(Node) "run()" or \ref init()
760    ///must be called before using this function.
761    int dist(Node v) const { return (*_dist)[v]; }
762
763    ///\brief Returns the 'previous arc' of the shortest path tree for
764    ///the given node.
765    ///
766    ///This function returns the 'previous arc' of the shortest path
767    ///tree for the node \c v, i.e. it returns the last arc of a
768    ///shortest path from a root to \c v. It is \c INVALID if \c v
769    ///is not reached from the root(s) or if \c v is a root.
770    ///
771    ///The shortest path tree used here is equal to the shortest path
772    ///tree used in \ref predNode() and \ref predMap().
773    ///
774    ///\pre Either \ref run(Node) "run()" or \ref init()
775    ///must be called before using this function.
776    Arc predArc(Node v) const { return (*_pred)[v];}
777
778    ///\brief Returns the 'previous node' of the shortest path tree for
779    ///the given node.
780    ///
781    ///This function returns the 'previous node' of the shortest path
782    ///tree for the node \c v, i.e. it returns the last but one node
783    ///of a shortest path from a root to \c v. It is \c INVALID
784    ///if \c v is not reached from the root(s) or if \c v is a root.
785    ///
786    ///The shortest path tree used here is equal to the shortest path
787    ///tree used in \ref predArc() and \ref predMap().
788    ///
789    ///\pre Either \ref run(Node) "run()" or \ref init()
790    ///must be called before using this function.
791    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
792                                  G->source((*_pred)[v]); }
793
794    ///\brief Returns a const reference to the node map that stores the
795    /// distances of the nodes.
796    ///
797    ///Returns a const reference to the node map that stores the distances
798    ///of the nodes calculated by the algorithm.
799    ///
800    ///\pre Either \ref run(Node) "run()" or \ref init()
801    ///must be called before using this function.
802    const DistMap &distMap() const { return *_dist;}
803
804    ///\brief Returns a const reference to the node map that stores the
805    ///predecessor arcs.
806    ///
807    ///Returns a const reference to the node map that stores the predecessor
808    ///arcs, which form the shortest path tree (forest).
809    ///
810    ///\pre Either \ref run(Node) "run()" or \ref init()
811    ///must be called before using this function.
812    const PredMap &predMap() const { return *_pred;}
813
814    ///Checks if the given node is reached from the root(s).
815
816    ///Returns \c true if \c v is reached from the root(s).
817    ///
818    ///\pre Either \ref run(Node) "run()" or \ref init()
819    ///must be called before using this function.
820    bool reached(Node v) const { return (*_reached)[v]; }
821
822    ///@}
823  };
824
825  ///Default traits class of bfs() function.
826
827  ///Default traits class of bfs() function.
828  ///\tparam GR Digraph type.
829  template<class GR>
830  struct BfsWizardDefaultTraits
831  {
832    ///The type of the digraph the algorithm runs on.
833    typedef GR Digraph;
834
835    ///\brief The type of the map that stores the predecessor
836    ///arcs of the shortest paths.
837    ///
838    ///The type of the map that stores the predecessor
839    ///arcs of the shortest paths.
840    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
841    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
842    ///Instantiates a PredMap.
843
844    ///This function instantiates a PredMap.
845    ///\param g is the digraph, to which we would like to define the
846    ///PredMap.
847    static PredMap *createPredMap(const Digraph &g)
848    {
849      return new PredMap(g);
850    }
851
852    ///The type of the map that indicates which nodes are processed.
853
854    ///The type of the map that indicates which nodes are processed.
855    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
856    ///By default, it is a NullMap.
857    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
858    ///Instantiates a ProcessedMap.
859
860    ///This function instantiates a ProcessedMap.
861    ///\param g is the digraph, to which
862    ///we would like to define the ProcessedMap.
863#ifdef DOXYGEN
864    static ProcessedMap *createProcessedMap(const Digraph &g)
865#else
866    static ProcessedMap *createProcessedMap(const Digraph &)
867#endif
868    {
869      return new ProcessedMap();
870    }
871
872    ///The type of the map that indicates which nodes are reached.
873
874    ///The type of the map that indicates which nodes are reached.
875    ///It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
876    typedef typename Digraph::template NodeMap<bool> ReachedMap;
877    ///Instantiates a ReachedMap.
878
879    ///This function instantiates a ReachedMap.
880    ///\param g is the digraph, to which
881    ///we would like to define the ReachedMap.
882    static ReachedMap *createReachedMap(const Digraph &g)
883    {
884      return new ReachedMap(g);
885    }
886
887    ///The type of the map that stores the distances of the nodes.
888
889    ///The type of the map that stores the distances of the nodes.
890    ///It must conform to the \ref concepts::WriteMap "WriteMap" concept.
891    typedef typename Digraph::template NodeMap<int> DistMap;
892    ///Instantiates a DistMap.
893
894    ///This function instantiates a DistMap.
895    ///\param g is the digraph, to which we would like to define
896    ///the DistMap
897    static DistMap *createDistMap(const Digraph &g)
898    {
899      return new DistMap(g);
900    }
901
902    ///The type of the shortest paths.
903
904    ///The type of the shortest paths.
905    ///It must conform to the \ref concepts::Path "Path" concept.
906    typedef lemon::Path<Digraph> Path;
907  };
908
909  /// Default traits class used by BfsWizard
910
911  /// Default traits class used by BfsWizard.
912  /// \tparam GR The type of the digraph.
913  template<class GR>
914  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
915  {
916
917    typedef BfsWizardDefaultTraits<GR> Base;
918  protected:
919    //The type of the nodes in the digraph.
920    typedef typename Base::Digraph::Node Node;
921
922    //Pointer to the digraph the algorithm runs on.
923    void *_g;
924    //Pointer to the map of reached nodes.
925    void *_reached;
926    //Pointer to the map of processed nodes.
927    void *_processed;
928    //Pointer to the map of predecessors arcs.
929    void *_pred;
930    //Pointer to the map of distances.
931    void *_dist;
932    //Pointer to the shortest path to the target node.
933    void *_path;
934    //Pointer to the distance of the target node.
935    int *_di;
936
937    public:
938    /// Constructor.
939
940    /// This constructor does not require parameters, it initiates
941    /// all of the attributes to \c 0.
942    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
943                      _dist(0), _path(0), _di(0) {}
944
945    /// Constructor.
946
947    /// This constructor requires one parameter,
948    /// others are initiated to \c 0.
949    /// \param g The digraph the algorithm runs on.
950    BfsWizardBase(const GR &g) :
951      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
952      _reached(0), _processed(0), _pred(0), _dist(0),  _path(0), _di(0) {}
953
954  };
955
956  /// Auxiliary class for the function-type interface of BFS algorithm.
957
958  /// This auxiliary class is created to implement the
959  /// \ref bfs() "function-type interface" of \ref Bfs algorithm.
960  /// It does not have own \ref run(Node) "run()" method, it uses the
961  /// functions and features of the plain \ref Bfs.
962  ///
963  /// This class should only be used through the \ref bfs() function,
964  /// which makes it easier to use the algorithm.
965  ///
966  /// \tparam TR The traits class that defines various types used by the
967  /// algorithm.
968  template<class TR>
969  class BfsWizard : public TR
970  {
971    typedef TR Base;
972
973    typedef typename TR::Digraph Digraph;
974
975    typedef typename Digraph::Node Node;
976    typedef typename Digraph::NodeIt NodeIt;
977    typedef typename Digraph::Arc Arc;
978    typedef typename Digraph::OutArcIt OutArcIt;
979
980    typedef typename TR::PredMap PredMap;
981    typedef typename TR::DistMap DistMap;
982    typedef typename TR::ReachedMap ReachedMap;
983    typedef typename TR::ProcessedMap ProcessedMap;
984    typedef typename TR::Path Path;
985
986  public:
987
988    /// Constructor.
989    BfsWizard() : TR() {}
990
991    /// Constructor that requires parameters.
992
993    /// Constructor that requires parameters.
994    /// These parameters will be the default values for the traits class.
995    /// \param g The digraph the algorithm runs on.
996    BfsWizard(const Digraph &g) :
997      TR(g) {}
998
999    ///Copy constructor
1000    BfsWizard(const TR &b) : TR(b) {}
1001
1002    ~BfsWizard() {}
1003
1004    ///Runs BFS algorithm from the given source node.
1005
1006    ///This method runs BFS algorithm from node \c s
1007    ///in order to compute the shortest path to each node.
1008    void run(Node s)
1009    {
1010      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1011      if (Base::_pred)
1012        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1013      if (Base::_dist)
1014        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1015      if (Base::_reached)
1016        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1017      if (Base::_processed)
1018        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1019      if (s!=INVALID)
1020        alg.run(s);
1021      else
1022        alg.run();
1023    }
1024
1025    ///Finds the shortest path between \c s and \c t.
1026
1027    ///This method runs BFS algorithm from node \c s
1028    ///in order to compute the shortest path to node \c t
1029    ///(it stops searching when \c t is processed).
1030    ///
1031    ///\return \c true if \c t is reachable form \c s.
1032    bool run(Node s, Node t)
1033    {
1034      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1035      if (Base::_pred)
1036        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1037      if (Base::_dist)
1038        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1039      if (Base::_reached)
1040        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1041      if (Base::_processed)
1042        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1043      alg.run(s,t);
1044      if (Base::_path)
1045        *reinterpret_cast<Path*>(Base::_path) = alg.path(t);
1046      if (Base::_di)
1047        *Base::_di = alg.dist(t);
1048      return alg.reached(t);
1049    }
1050
1051    ///Runs BFS algorithm to visit all nodes in the digraph.
1052
1053    ///This method runs BFS algorithm in order to visit all nodes
1054    ///in the digraph.
1055    void run()
1056    {
1057      run(INVALID);
1058    }
1059
1060    template<class T>
1061    struct SetPredMapBase : public Base {
1062      typedef T PredMap;
1063      static PredMap *createPredMap(const Digraph &) { return 0; };
1064      SetPredMapBase(const TR &b) : TR(b) {}
1065    };
1066
1067    ///\brief \ref named-templ-param "Named parameter" for setting
1068    ///the predecessor map.
1069    ///
1070    ///\ref named-templ-param "Named parameter" function for setting
1071    ///the map that stores the predecessor arcs of the nodes.
1072    template<class T>
1073    BfsWizard<SetPredMapBase<T> > predMap(const T &t)
1074    {
1075      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1076      return BfsWizard<SetPredMapBase<T> >(*this);
1077    }
1078
1079    template<class T>
1080    struct SetReachedMapBase : public Base {
1081      typedef T ReachedMap;
1082      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
1083      SetReachedMapBase(const TR &b) : TR(b) {}
1084    };
1085
1086    ///\brief \ref named-templ-param "Named parameter" for setting
1087    ///the reached map.
1088    ///
1089    ///\ref named-templ-param "Named parameter" function for setting
1090    ///the map that indicates which nodes are reached.
1091    template<class T>
1092    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)
1093    {
1094      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
1095      return BfsWizard<SetReachedMapBase<T> >(*this);
1096    }
1097
1098    template<class T>
1099    struct SetDistMapBase : public Base {
1100      typedef T DistMap;
1101      static DistMap *createDistMap(const Digraph &) { return 0; };
1102      SetDistMapBase(const TR &b) : TR(b) {}
1103    };
1104
1105    ///\brief \ref named-templ-param "Named parameter" for setting
1106    ///the distance map.
1107    ///
1108    ///\ref named-templ-param "Named parameter" function for setting
1109    ///the map that stores the distances of the nodes calculated
1110    ///by the algorithm.
1111    template<class T>
1112    BfsWizard<SetDistMapBase<T> > distMap(const T &t)
1113    {
1114      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1115      return BfsWizard<SetDistMapBase<T> >(*this);
1116    }
1117
1118    template<class T>
1119    struct SetProcessedMapBase : public Base {
1120      typedef T ProcessedMap;
1121      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
1122      SetProcessedMapBase(const TR &b) : TR(b) {}
1123    };
1124
1125    ///\brief \ref named-func-param "Named parameter" for setting
1126    ///the processed map.
1127    ///
1128    ///\ref named-templ-param "Named parameter" function for setting
1129    ///the map that indicates which nodes are processed.
1130    template<class T>
1131    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)
1132    {
1133      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
1134      return BfsWizard<SetProcessedMapBase<T> >(*this);
1135    }
1136
1137    template<class T>
1138    struct SetPathBase : public Base {
1139      typedef T Path;
1140      SetPathBase(const TR &b) : TR(b) {}
1141    };
1142    ///\brief \ref named-func-param "Named parameter"
1143    ///for getting the shortest path to the target node.
1144    ///
1145    ///\ref named-func-param "Named parameter"
1146    ///for getting the shortest path to the target node.
1147    template<class T>
1148    BfsWizard<SetPathBase<T> > path(const T &t)
1149    {
1150      Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t));
1151      return BfsWizard<SetPathBase<T> >(*this);
1152    }
1153
1154    ///\brief \ref named-func-param "Named parameter"
1155    ///for getting the distance of the target node.
1156    ///
1157    ///\ref named-func-param "Named parameter"
1158    ///for getting the distance of the target node.
1159    BfsWizard dist(const int &d)
1160    {
1161      Base::_di=const_cast<int*>(&d);
1162      return *this;
1163    }
1164
1165  };
1166
1167  ///Function-type interface for BFS algorithm.
1168
1169  /// \ingroup search
1170  ///Function-type interface for BFS algorithm.
1171  ///
1172  ///This function also has several \ref named-func-param "named parameters",
1173  ///they are declared as the members of class \ref BfsWizard.
1174  ///The following examples show how to use these parameters.
1175  ///\code
1176  ///  // Compute shortest path from node s to each node
1177  ///  bfs(g).predMap(preds).distMap(dists).run(s);
1178  ///
1179  ///  // Compute shortest path from s to t
1180  ///  bool reached = bfs(g).path(p).dist(d).run(s,t);
1181  ///\endcode
1182  ///\warning Don't forget to put the \ref BfsWizard::run(Node) "run()"
1183  ///to the end of the parameter list.
1184  ///\sa BfsWizard
1185  ///\sa Bfs
1186  template<class GR>
1187  BfsWizard<BfsWizardBase<GR> >
1188  bfs(const GR &digraph)
1189  {
1190    return BfsWizard<BfsWizardBase<GR> >(digraph);
1191  }
1192
1193#ifdef DOXYGEN
1194  /// \brief Visitor class for BFS.
1195  ///
1196  /// This class defines the interface of the BfsVisit events, and
1197  /// it could be the base of a real visitor class.
1198  template <typename GR>
1199  struct BfsVisitor {
1200    typedef GR Digraph;
1201    typedef typename Digraph::Arc Arc;
1202    typedef typename Digraph::Node Node;
1203    /// \brief Called for the source node(s) of the BFS.
1204    ///
1205    /// This function is called for the source node(s) of the BFS.
1206    void start(const Node& node) {}
1207    /// \brief Called when a node is reached first time.
1208    ///
1209    /// This function is called when a node is reached first time.
1210    void reach(const Node& node) {}
1211    /// \brief Called when a node is processed.
1212    ///
1213    /// This function is called when a node is processed.
1214    void process(const Node& node) {}
1215    /// \brief Called when an arc reaches a new node.
1216    ///
1217    /// This function is called when the BFS finds an arc whose target node
1218    /// is not reached yet.
1219    void discover(const Arc& arc) {}
1220    /// \brief Called when an arc is examined but its target node is
1221    /// already discovered.
1222    ///
1223    /// This function is called when an arc is examined but its target node is
1224    /// already discovered.
1225    void examine(const Arc& arc) {}
1226  };
1227#else
1228  template <typename GR>
1229  struct BfsVisitor {
1230    typedef GR Digraph;
1231    typedef typename Digraph::Arc Arc;
1232    typedef typename Digraph::Node Node;
1233    void start(const Node&) {}
1234    void reach(const Node&) {}
1235    void process(const Node&) {}
1236    void discover(const Arc&) {}
1237    void examine(const Arc&) {}
1238
1239    template <typename _Visitor>
1240    struct Constraints {
1241      void constraints() {
1242        Arc arc;
1243        Node node;
1244        visitor.start(node);
1245        visitor.reach(node);
1246        visitor.process(node);
1247        visitor.discover(arc);
1248        visitor.examine(arc);
1249      }
1250      _Visitor& visitor;
1251    };
1252  };
1253#endif
1254
1255  /// \brief Default traits class of BfsVisit class.
1256  ///
1257  /// Default traits class of BfsVisit class.
1258  /// \tparam GR The type of the digraph the algorithm runs on.
1259  template<class GR>
1260  struct BfsVisitDefaultTraits {
1261
1262    /// \brief The type of the digraph the algorithm runs on.
1263    typedef GR Digraph;
1264
1265    /// \brief The type of the map that indicates which nodes are reached.
1266    ///
1267    /// The type of the map that indicates which nodes are reached.
1268    /// It must conform to the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
1269    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1270
1271    /// \brief Instantiates a ReachedMap.
1272    ///
1273    /// This function instantiates a ReachedMap.
1274    /// \param digraph is the digraph, to which
1275    /// we would like to define the ReachedMap.
1276    static ReachedMap *createReachedMap(const Digraph &digraph) {
1277      return new ReachedMap(digraph);
1278    }
1279
1280  };
1281
1282  /// \ingroup search
1283  ///
1284  /// \brief BFS algorithm class with visitor interface.
1285  ///
1286  /// This class provides an efficient implementation of the BFS algorithm
1287  /// with visitor interface.
1288  ///
1289  /// The BfsVisit class provides an alternative interface to the Bfs
1290  /// class. It works with callback mechanism, the BfsVisit object calls
1291  /// the member functions of the \c Visitor class on every BFS event.
1292  ///
1293  /// This interface of the BFS algorithm should be used in special cases
1294  /// when extra actions have to be performed in connection with certain
1295  /// events of the BFS algorithm. Otherwise consider to use Bfs or bfs()
1296  /// instead.
1297  ///
1298  /// \tparam GR The type of the digraph the algorithm runs on.
1299  /// The default type is \ref ListDigraph.
1300  /// The value of GR is not used directly by \ref BfsVisit,
1301  /// it is only passed to \ref BfsVisitDefaultTraits.
1302  /// \tparam VS The Visitor type that is used by the algorithm.
1303  /// \ref BfsVisitor "BfsVisitor<GR>" is an empty visitor, which
1304  /// does not observe the BFS events. If you want to observe the BFS
1305  /// events, you should implement your own visitor class.
1306  /// \tparam TR The traits class that defines various types used by the
1307  /// algorithm. By default, it is \ref BfsVisitDefaultTraits
1308  /// "BfsVisitDefaultTraits<GR>".
1309  /// In most cases, this parameter should not be set directly,
1310  /// consider to use the named template parameters instead.
1311#ifdef DOXYGEN
1312  template <typename GR, typename VS, typename TR>
1313#else
1314  template <typename GR = ListDigraph,
1315            typename VS = BfsVisitor<GR>,
1316            typename TR = BfsVisitDefaultTraits<GR> >
1317#endif
1318  class BfsVisit {
1319  public:
1320
1321    ///The traits class.
1322    typedef TR Traits;
1323
1324    ///The type of the digraph the algorithm runs on.
1325    typedef typename Traits::Digraph Digraph;
1326
1327    ///The visitor type used by the algorithm.
1328    typedef VS Visitor;
1329
1330    ///The type of the map that indicates which nodes are reached.
1331    typedef typename Traits::ReachedMap ReachedMap;
1332
1333  private:
1334
1335    typedef typename Digraph::Node Node;
1336    typedef typename Digraph::NodeIt NodeIt;
1337    typedef typename Digraph::Arc Arc;
1338    typedef typename Digraph::OutArcIt OutArcIt;
1339
1340    //Pointer to the underlying digraph.
1341    const Digraph *_digraph;
1342    //Pointer to the visitor object.
1343    Visitor *_visitor;
1344    //Pointer to the map of reached status of the nodes.
1345    ReachedMap *_reached;
1346    //Indicates if _reached is locally allocated (true) or not.
1347    bool local_reached;
1348
1349    std::vector<typename Digraph::Node> _list;
1350    int _list_front, _list_back;
1351
1352    //Creates the maps if necessary.
1353    void create_maps() {
1354      if(!_reached) {
1355        local_reached = true;
1356        _reached = Traits::createReachedMap(*_digraph);
1357      }
1358    }
1359
1360  protected:
1361
1362    BfsVisit() {}
1363
1364  public:
1365
1366    typedef BfsVisit Create;
1367
1368    /// \name Named Template Parameters
1369
1370    ///@{
1371    template <class T>
1372    struct SetReachedMapTraits : public Traits {
1373      typedef T ReachedMap;
1374      static ReachedMap *createReachedMap(const Digraph &digraph) {
1375        LEMON_ASSERT(false, "ReachedMap is not initialized");
1376        return 0; // ignore warnings
1377      }
1378    };
1379    /// \brief \ref named-templ-param "Named parameter" for setting
1380    /// ReachedMap type.
1381    ///
1382    /// \ref named-templ-param "Named parameter" for setting ReachedMap type.
1383    template <class T>
1384    struct SetReachedMap : public BfsVisit< Digraph, Visitor,
1385                                            SetReachedMapTraits<T> > {
1386      typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create;
1387    };
1388    ///@}
1389
1390  public:
1391
1392    /// \brief Constructor.
1393    ///
1394    /// Constructor.
1395    ///
1396    /// \param digraph The digraph the algorithm runs on.
1397    /// \param visitor The visitor object of the algorithm.
1398    BfsVisit(const Digraph& digraph, Visitor& visitor)
1399      : _digraph(&digraph), _visitor(&visitor),
1400        _reached(0), local_reached(false) {}
1401
1402    /// \brief Destructor.
1403    ~BfsVisit() {
1404      if(local_reached) delete _reached;
1405    }
1406
1407    /// \brief Sets the map that indicates which nodes are reached.
1408    ///
1409    /// Sets the map that indicates which nodes are reached.
1410    /// If you don't use this function before calling \ref run(Node) "run()"
1411    /// or \ref init(), an instance will be allocated automatically.
1412    /// The destructor deallocates this automatically allocated map,
1413    /// of course.
1414    /// \return <tt> (*this) </tt>
1415    BfsVisit &reachedMap(ReachedMap &m) {
1416      if(local_reached) {
1417        delete _reached;
1418        local_reached = false;
1419      }
1420      _reached = &m;
1421      return *this;
1422    }
1423
1424  public:
1425
1426    /// \name Execution Control
1427    /// The simplest way to execute the BFS algorithm is to use one of the
1428    /// member functions called \ref run(Node) "run()".\n
1429    /// If you need better control on the execution, you have to call
1430    /// \ref init() first, then you can add several source nodes with
1431    /// \ref addSource(). Finally the actual path computation can be
1432    /// performed with one of the \ref start() functions.
1433
1434    /// @{
1435
1436    /// \brief Initializes the internal data structures.
1437    ///
1438    /// Initializes the internal data structures.
1439    void init() {
1440      create_maps();
1441      _list.resize(countNodes(*_digraph));
1442      _list_front = _list_back = -1;
1443      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
1444        _reached->set(u, false);
1445      }
1446    }
1447
1448    /// \brief Adds a new source node.
1449    ///
1450    /// Adds a new source node to the set of nodes to be processed.
1451    void addSource(Node s) {
1452      if(!(*_reached)[s]) {
1453          _reached->set(s,true);
1454          _visitor->start(s);
1455          _visitor->reach(s);
1456          _list[++_list_back] = s;
1457        }
1458    }
1459
1460    /// \brief Processes the next node.
1461    ///
1462    /// Processes the next node.
1463    ///
1464    /// \return The processed node.
1465    ///
1466    /// \pre The queue must not be empty.
1467    Node processNextNode() {
1468      Node n = _list[++_list_front];
1469      _visitor->process(n);
1470      Arc e;
1471      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1472        Node m = _digraph->target(e);
1473        if (!(*_reached)[m]) {
1474          _visitor->discover(e);
1475          _visitor->reach(m);
1476          _reached->set(m, true);
1477          _list[++_list_back] = m;
1478        } else {
1479          _visitor->examine(e);
1480        }
1481      }
1482      return n;
1483    }
1484
1485    /// \brief Processes the next node.
1486    ///
1487    /// Processes the next node and checks if the given target node
1488    /// is reached. If the target node is reachable from the processed
1489    /// node, then the \c reach parameter will be set to \c true.
1490    ///
1491    /// \param target The target node.
1492    /// \retval reach Indicates if the target node is reached.
1493    /// It should be initially \c false.
1494    ///
1495    /// \return The processed node.
1496    ///
1497    /// \pre The queue must not be empty.
1498    Node processNextNode(Node target, bool& reach) {
1499      Node n = _list[++_list_front];
1500      _visitor->process(n);
1501      Arc e;
1502      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1503        Node m = _digraph->target(e);
1504        if (!(*_reached)[m]) {
1505          _visitor->discover(e);
1506          _visitor->reach(m);
1507          _reached->set(m, true);
1508          _list[++_list_back] = m;
1509          reach = reach || (target == m);
1510        } else {
1511          _visitor->examine(e);
1512        }
1513      }
1514      return n;
1515    }
1516
1517    /// \brief Processes the next node.
1518    ///
1519    /// Processes the next node and checks if at least one of reached
1520    /// nodes has \c true value in the \c nm node map. If one node
1521    /// with \c true value is reachable from the processed node, then the
1522    /// \c rnode parameter will be set to the first of such nodes.
1523    ///
1524    /// \param nm A \c bool (or convertible) node map that indicates the
1525    /// possible targets.
1526    /// \retval rnode The reached target node.
1527    /// It should be initially \c INVALID.
1528    ///
1529    /// \return The processed node.
1530    ///
1531    /// \pre The queue must not be empty.
1532    template <typename NM>
1533    Node processNextNode(const NM& nm, Node& rnode) {
1534      Node n = _list[++_list_front];
1535      _visitor->process(n);
1536      Arc e;
1537      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1538        Node m = _digraph->target(e);
1539        if (!(*_reached)[m]) {
1540          _visitor->discover(e);
1541          _visitor->reach(m);
1542          _reached->set(m, true);
1543          _list[++_list_back] = m;
1544          if (nm[m] && rnode == INVALID) rnode = m;
1545        } else {
1546          _visitor->examine(e);
1547        }
1548      }
1549      return n;
1550    }
1551
1552    /// \brief The next node to be processed.
1553    ///
1554    /// Returns the next node to be processed or \c INVALID if the queue
1555    /// is empty.
1556    Node nextNode() const {
1557      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1558    }
1559
1560    /// \brief Returns \c false if there are nodes
1561    /// to be processed.
1562    ///
1563    /// Returns \c false if there are nodes
1564    /// to be processed in the queue.
1565    bool emptyQueue() const { return _list_front == _list_back; }
1566
1567    /// \brief Returns the number of the nodes to be processed.
1568    ///
1569    /// Returns the number of the nodes to be processed in the queue.
1570    int queueSize() const { return _list_back - _list_front; }
1571
1572    /// \brief Executes the algorithm.
1573    ///
1574    /// Executes the algorithm.
1575    ///
1576    /// This method runs the %BFS algorithm from the root node(s)
1577    /// in order to compute the shortest path to each node.
1578    ///
1579    /// The algorithm computes
1580    /// - the shortest path tree (forest),
1581    /// - the distance of each node from the root(s).
1582    ///
1583    /// \pre init() must be called and at least one root node should be added
1584    /// with addSource() before using this function.
1585    ///
1586    /// \note <tt>b.start()</tt> is just a shortcut of the following code.
1587    /// \code
1588    ///   while ( !b.emptyQueue() ) {
1589    ///     b.processNextNode();
1590    ///   }
1591    /// \endcode
1592    void start() {
1593      while ( !emptyQueue() ) processNextNode();
1594    }
1595
1596    /// \brief Executes the algorithm until the given target node is reached.
1597    ///
1598    /// Executes the algorithm until the given target node is reached.
1599    ///
1600    /// This method runs the %BFS algorithm from the root node(s)
1601    /// in order to compute the shortest path to \c t.
1602    ///
1603    /// The algorithm computes
1604    /// - the shortest path to \c t,
1605    /// - the distance of \c t from the root(s).
1606    ///
1607    /// \pre init() must be called and at least one root node should be
1608    /// added with addSource() before using this function.
1609    ///
1610    /// \note <tt>b.start(t)</tt> is just a shortcut of the following code.
1611    /// \code
1612    ///   bool reach = false;
1613    ///   while ( !b.emptyQueue() && !reach ) {
1614    ///     b.processNextNode(t, reach);
1615    ///   }
1616    /// \endcode
1617    void start(Node t) {
1618      bool reach = false;
1619      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
1620    }
1621
1622    /// \brief Executes the algorithm until a condition is met.
1623    ///
1624    /// Executes the algorithm until a condition is met.
1625    ///
1626    /// This method runs the %BFS algorithm from the root node(s) in
1627    /// order to compute the shortest path to a node \c v with
1628    /// <tt>nm[v]</tt> true, if such a node can be found.
1629    ///
1630    /// \param nm must be a bool (or convertible) node map. The
1631    /// algorithm will stop when it reaches a node \c v with
1632    /// <tt>nm[v]</tt> true.
1633    ///
1634    /// \return The reached node \c v with <tt>nm[v]</tt> true or
1635    /// \c INVALID if no such node was found.
1636    ///
1637    /// \pre init() must be called and at least one root node should be
1638    /// added with addSource() before using this function.
1639    ///
1640    /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code.
1641    /// \code
1642    ///   Node rnode = INVALID;
1643    ///   while ( !b.emptyQueue() && rnode == INVALID ) {
1644    ///     b.processNextNode(nm, rnode);
1645    ///   }
1646    ///   return rnode;
1647    /// \endcode
1648    template <typename NM>
1649    Node start(const NM &nm) {
1650      Node rnode = INVALID;
1651      while ( !emptyQueue() && rnode == INVALID ) {
1652        processNextNode(nm, rnode);
1653      }
1654      return rnode;
1655    }
1656
1657    /// \brief Runs the algorithm from the given source node.
1658    ///
1659    /// This method runs the %BFS algorithm from node \c s
1660    /// in order to compute the shortest path to each node.
1661    ///
1662    /// The algorithm computes
1663    /// - the shortest path tree,
1664    /// - the distance of each node from the root.
1665    ///
1666    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1667    ///\code
1668    ///   b.init();
1669    ///   b.addSource(s);
1670    ///   b.start();
1671    ///\endcode
1672    void run(Node s) {
1673      init();
1674      addSource(s);
1675      start();
1676    }
1677
1678    /// \brief Finds the shortest path between \c s and \c t.
1679    ///
1680    /// This method runs the %BFS algorithm from node \c s
1681    /// in order to compute the shortest path to node \c t
1682    /// (it stops searching when \c t is processed).
1683    ///
1684    /// \return \c true if \c t is reachable form \c s.
1685    ///
1686    /// \note Apart from the return value, <tt>b.run(s,t)</tt> is just a
1687    /// shortcut of the following code.
1688    ///\code
1689    ///   b.init();
1690    ///   b.addSource(s);
1691    ///   b.start(t);
1692    ///\endcode
1693    bool run(Node s,Node t) {
1694      init();
1695      addSource(s);
1696      start(t);
1697      return reached(t);
1698    }
1699
1700    /// \brief Runs the algorithm to visit all nodes in the digraph.
1701    ///
1702    /// This method runs the %BFS algorithm in order to visit all nodes
1703    /// in the digraph.
1704    ///
1705    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1706    ///\code
1707    ///  b.init();
1708    ///  for (NodeIt n(gr); n != INVALID; ++n) {
1709    ///    if (!b.reached(n)) {
1710    ///      b.addSource(n);
1711    ///      b.start();
1712    ///    }
1713    ///  }
1714    ///\endcode
1715    void run() {
1716      init();
1717      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1718        if (!reached(it)) {
1719          addSource(it);
1720          start();
1721        }
1722      }
1723    }
1724
1725    ///@}
1726
1727    /// \name Query Functions
1728    /// The results of the BFS algorithm can be obtained using these
1729    /// functions.\n
1730    /// Either \ref run(Node) "run()" or \ref start() should be called
1731    /// before using them.
1732
1733    ///@{
1734
1735    /// \brief Checks if the given node is reached from the root(s).
1736    ///
1737    /// Returns \c true if \c v is reached from the root(s).
1738    ///
1739    /// \pre Either \ref run(Node) "run()" or \ref init()
1740    /// must be called before using this function.
1741    bool reached(Node v) const { return (*_reached)[v]; }
1742
1743    ///@}
1744
1745  };
1746
1747} //END OF NAMESPACE LEMON
1748
1749#endif
Note: See TracBrowser for help on using the repository browser.