COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/bfs.h @ 2126:2c8adbee9fa6

Last change on this file since 2126:2c8adbee9fa6 was 2033:7bf1f64962c2, checked in by Balazs Dezso, 14 years ago

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1/* -*- C++ -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library
4 *
5 * Copyright (C) 2003-2006
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 flowalgs
23///\file
24///\brief Bfs algorithm.
25
26#include <lemon/list_graph.h>
27#include <lemon/graph_utils.h>
28#include <lemon/bits/invalid.h>
29#include <lemon/error.h>
30#include <lemon/maps.h>
31
32namespace lemon {
33
34
35 
36  ///Default traits class of Bfs class.
37
38  ///Default traits class of Bfs class.
39  ///\param GR Graph type.
40  template<class GR>
41  struct BfsDefaultTraits
42  {
43    ///The graph type the algorithm runs on.
44    typedef GR Graph;
45    ///\brief The type of the map that stores the last
46    ///edges of the shortest paths.
47    ///
48    ///The type of the map that stores the last
49    ///edges of the shortest paths.
50    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
51    ///
52    typedef typename Graph::template NodeMap<typename GR::Edge> PredMap;
53    ///Instantiates a PredMap.
54 
55    ///This function instantiates a \ref PredMap.
56    ///\param G is the graph, to which we would like to define the PredMap.
57    ///\todo The graph alone may be insufficient to initialize
58    static PredMap *createPredMap(const GR &G)
59    {
60      return new PredMap(G);
61    }
62    ///The type of the map that indicates which nodes are processed.
63 
64    ///The type of the map that indicates which nodes are processed.
65    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
66    ///\todo named parameter to set this type, function to read and write.
67    typedef NullMap<typename Graph::Node,bool> ProcessedMap;
68    ///Instantiates a ProcessedMap.
69 
70    ///This function instantiates a \ref ProcessedMap.
71    ///\param g is the graph, to which
72    ///we would like to define the \ref ProcessedMap
73#ifdef DOXYGEN
74    static ProcessedMap *createProcessedMap(const GR &g)
75#else
76    static ProcessedMap *createProcessedMap(const GR &)
77#endif
78    {
79      return new ProcessedMap();
80    }
81    ///The type of the map that indicates which nodes are reached.
82 
83    ///The type of the map that indicates which nodes are reached.
84    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
85    ///\todo named parameter to set this type, function to read and write.
86    typedef typename Graph::template NodeMap<bool> ReachedMap;
87    ///Instantiates a ReachedMap.
88 
89    ///This function instantiates a \ref ReachedMap.
90    ///\param G is the graph, to which
91    ///we would like to define the \ref ReachedMap.
92    static ReachedMap *createReachedMap(const GR &G)
93    {
94      return new ReachedMap(G);
95    }
96    ///The type of the map that stores the dists of the nodes.
97 
98    ///The type of the map that stores the dists of the nodes.
99    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
100    ///
101    typedef typename Graph::template NodeMap<int> DistMap;
102    ///Instantiates a DistMap.
103 
104    ///This function instantiates a \ref DistMap.
105    ///\param G is the graph, to which we would like to define the \ref DistMap
106    static DistMap *createDistMap(const GR &G)
107    {
108      return new DistMap(G);
109    }
110  };
111 
112  ///%BFS algorithm class.
113 
114  ///\ingroup flowalgs
115  ///This class provides an efficient implementation of the %BFS algorithm.
116  ///
117  ///\param GR The graph type the algorithm runs on. The default value is
118  ///\ref ListGraph. The value of GR is not used directly by Bfs, it
119  ///is only passed to \ref BfsDefaultTraits.
120  ///\param TR Traits class to set various data types used by the algorithm.
121  ///The default traits class is
122  ///\ref BfsDefaultTraits "BfsDefaultTraits<GR>".
123  ///See \ref BfsDefaultTraits for the documentation of
124  ///a Bfs traits class.
125  ///
126  ///\author Alpar Juttner
127
128#ifdef DOXYGEN
129  template <typename GR,
130            typename TR>
131#else
132  template <typename GR=ListGraph,
133            typename TR=BfsDefaultTraits<GR> >
134#endif
135  class Bfs {
136  public:
137    /**
138     * \brief \ref Exception for uninitialized parameters.
139     *
140     * This error represents problems in the initialization
141     * of the parameters of the algorithms.
142     */
143    class UninitializedParameter : public lemon::UninitializedParameter {
144    public:
145      virtual const char* exceptionName() const {
146        return "lemon::Bfs::UninitializedParameter";
147      }
148    };
149
150    typedef TR Traits;
151    ///The type of the underlying graph.
152    typedef typename TR::Graph Graph;
153    ///\e
154    typedef typename Graph::Node Node;
155    ///\e
156    typedef typename Graph::NodeIt NodeIt;
157    ///\e
158    typedef typename Graph::Edge Edge;
159    ///\e
160    typedef typename Graph::OutEdgeIt OutEdgeIt;
161   
162    ///\brief The type of the map that stores the last
163    ///edges of the shortest paths.
164    typedef typename TR::PredMap PredMap;
165    ///The type of the map indicating which nodes are reached.
166    typedef typename TR::ReachedMap ReachedMap;
167    ///The type of the map indicating which nodes are processed.
168    typedef typename TR::ProcessedMap ProcessedMap;
169    ///The type of the map that stores the dists of the nodes.
170    typedef typename TR::DistMap DistMap;
171  private:
172    /// Pointer to the underlying graph.
173    const Graph *G;
174    ///Pointer to the map of predecessors edges.
175    PredMap *_pred;
176    ///Indicates if \ref _pred is locally allocated (\c true) or not.
177    bool local_pred;
178    ///Pointer to the map of distances.
179    DistMap *_dist;
180    ///Indicates if \ref _dist is locally allocated (\c true) or not.
181    bool local_dist;
182    ///Pointer to the map of reached status of the nodes.
183    ReachedMap *_reached;
184    ///Indicates if \ref _reached is locally allocated (\c true) or not.
185    bool local_reached;
186    ///Pointer to the map of processed status of the nodes.
187    ProcessedMap *_processed;
188    ///Indicates if \ref _processed is locally allocated (\c true) or not.
189    bool local_processed;
190
191    std::vector<typename Graph::Node> _queue;
192    int _queue_head,_queue_tail,_queue_next_dist;
193    int _curr_dist;
194
195    ///Creates the maps if necessary.
196   
197    ///\todo Better memory allocation (instead of new).
198    void create_maps()
199    {
200      if(!_pred) {
201        local_pred = true;
202        _pred = Traits::createPredMap(*G);
203      }
204      if(!_dist) {
205        local_dist = true;
206        _dist = Traits::createDistMap(*G);
207      }
208      if(!_reached) {
209        local_reached = true;
210        _reached = Traits::createReachedMap(*G);
211      }
212      if(!_processed) {
213        local_processed = true;
214        _processed = Traits::createProcessedMap(*G);
215      }
216    }
217
218  protected:
219   
220    Bfs() {}
221   
222  public:
223 
224    typedef Bfs Create;
225
226    ///\name Named template parameters
227
228    ///@{
229
230    template <class T>
231    struct DefPredMapTraits : public Traits {
232      typedef T PredMap;
233      static PredMap *createPredMap(const Graph &)
234      {
235        throw UninitializedParameter();
236      }
237    };
238    ///\ref named-templ-param "Named parameter" for setting PredMap type
239
240    ///\ref named-templ-param "Named parameter" for setting PredMap type
241    ///
242    template <class T>
243    struct DefPredMap : public Bfs< Graph, DefPredMapTraits<T> > {
244      typedef Bfs< Graph, DefPredMapTraits<T> > Create;
245    };
246   
247    template <class T>
248    struct DefDistMapTraits : public Traits {
249      typedef T DistMap;
250      static DistMap *createDistMap(const Graph &)
251      {
252        throw UninitializedParameter();
253      }
254    };
255    ///\ref named-templ-param "Named parameter" for setting DistMap type
256
257    ///\ref named-templ-param "Named parameter" for setting DistMap type
258    ///
259    template <class T>
260    struct DefDistMap : public Bfs< Graph, DefDistMapTraits<T> > {
261      typedef Bfs< Graph, DefDistMapTraits<T> > Create;
262    };
263   
264    template <class T>
265    struct DefReachedMapTraits : public Traits {
266      typedef T ReachedMap;
267      static ReachedMap *createReachedMap(const Graph &)
268      {
269        throw UninitializedParameter();
270      }
271    };
272    ///\ref named-templ-param "Named parameter" for setting ReachedMap type
273
274    ///\ref named-templ-param "Named parameter" for setting ReachedMap type
275    ///
276    template <class T>
277    struct DefReachedMap : public Bfs< Graph, DefReachedMapTraits<T> > {
278      typedef Bfs< Graph, DefReachedMapTraits<T> > Create;
279    };
280   
281    template <class T>
282    struct DefProcessedMapTraits : public Traits {
283      typedef T ProcessedMap;
284      static ProcessedMap *createProcessedMap(const Graph &)
285      {
286        throw UninitializedParameter();
287      }
288    };
289    ///\ref named-templ-param "Named parameter" for setting ProcessedMap type
290
291    ///\ref named-templ-param "Named parameter" for setting ProcessedMap type
292    ///
293    template <class T>
294    struct DefProcessedMap : public Bfs< Graph, DefProcessedMapTraits<T> > {
295      typedef Bfs< Graph, DefProcessedMapTraits<T> > Create;
296    };
297   
298    struct DefGraphProcessedMapTraits : public Traits {
299      typedef typename Graph::template NodeMap<bool> ProcessedMap;
300      static ProcessedMap *createProcessedMap(const Graph &G)
301      {
302        return new ProcessedMap(G);
303      }
304    };
305    ///\brief \ref named-templ-param "Named parameter"
306    ///for setting the ProcessedMap type to be Graph::NodeMap<bool>.
307    ///
308    ///\ref named-templ-param "Named parameter"
309    ///for setting the ProcessedMap type to be Graph::NodeMap<bool>.
310    ///If you don't set it explicitly, it will be automatically allocated.
311    template <class T>
312    struct DefProcessedMapToBeDefaultMap :
313      public Bfs< Graph, DefGraphProcessedMapTraits> {
314      typedef Bfs< Graph, DefGraphProcessedMapTraits> Create;
315    };
316   
317    ///@}
318
319  public:     
320   
321    ///Constructor.
322   
323    ///\param _G the graph the algorithm will run on.
324    ///
325    Bfs(const Graph& _G) :
326      G(&_G),
327      _pred(NULL), local_pred(false),
328      _dist(NULL), local_dist(false),
329      _reached(NULL), local_reached(false),
330      _processed(NULL), local_processed(false)
331    { }
332   
333    ///Destructor.
334    ~Bfs()
335    {
336      if(local_pred) delete _pred;
337      if(local_dist) delete _dist;
338      if(local_reached) delete _reached;
339      if(local_processed) delete _processed;
340    }
341
342    ///Sets the map storing the predecessor edges.
343
344    ///Sets the map storing the predecessor edges.
345    ///If you don't use this function before calling \ref run(),
346    ///it will allocate one. The destructor deallocates this
347    ///automatically allocated map, of course.
348    ///\return <tt> (*this) </tt>
349    Bfs &predMap(PredMap &m)
350    {
351      if(local_pred) {
352        delete _pred;
353        local_pred=false;
354      }
355      _pred = &m;
356      return *this;
357    }
358
359    ///Sets the map indicating the reached nodes.
360
361    ///Sets the map indicating the reached nodes.
362    ///If you don't use this function before calling \ref run(),
363    ///it will allocate one. The destructor deallocates this
364    ///automatically allocated map, of course.
365    ///\return <tt> (*this) </tt>
366    Bfs &reachedMap(ReachedMap &m)
367    {
368      if(local_reached) {
369        delete _reached;
370        local_reached=false;
371      }
372      _reached = &m;
373      return *this;
374    }
375
376    ///Sets the map indicating the processed nodes.
377
378    ///Sets the map indicating the processed nodes.
379    ///If you don't use this function before calling \ref run(),
380    ///it will allocate one. The destructor deallocates this
381    ///automatically allocated map, of course.
382    ///\return <tt> (*this) </tt>
383    Bfs &processedMap(ProcessedMap &m)
384    {
385      if(local_processed) {
386        delete _processed;
387        local_processed=false;
388      }
389      _processed = &m;
390      return *this;
391    }
392
393    ///Sets the map storing the distances calculated by the algorithm.
394
395    ///Sets the map storing the distances calculated by the algorithm.
396    ///If you don't use this function before calling \ref run(),
397    ///it will allocate one. The destructor deallocates this
398    ///automatically allocated map, of course.
399    ///\return <tt> (*this) </tt>
400    Bfs &distMap(DistMap &m)
401    {
402      if(local_dist) {
403        delete _dist;
404        local_dist=false;
405      }
406      _dist = &m;
407      return *this;
408    }
409
410  public:
411    ///\name Execution control
412    ///The simplest way to execute the algorithm is to use
413    ///one of the member functions called \c run(...).
414    ///\n
415    ///If you need more control on the execution,
416    ///first you must call \ref init(), then you can add several source nodes
417    ///with \ref addSource().
418    ///Finally \ref start() will perform the actual path
419    ///computation.
420
421    ///@{
422
423    ///Initializes the internal data structures.
424
425    ///Initializes the internal data structures.
426    ///
427    void init()
428    {
429      create_maps();
430      _queue.resize(countNodes(*G));
431      _queue_head=_queue_tail=0;
432      _curr_dist=1;
433      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
434        _pred->set(u,INVALID);
435        _reached->set(u,false);
436        _processed->set(u,false);
437      }
438    }
439   
440    ///Adds a new source node.
441
442    ///Adds a new source node to the set of nodes to be processed.
443    ///
444    void addSource(Node s)
445    {
446      if(!(*_reached)[s])
447        {
448          _reached->set(s,true);
449          _pred->set(s,INVALID);
450          _dist->set(s,0);
451          _queue[_queue_head++]=s;
452          _queue_next_dist=_queue_head;
453        }
454    }
455   
456    ///Processes the next node.
457
458    ///Processes the next node.
459    ///
460    ///\return The processed node.
461    ///
462    ///\warning The queue must not be empty!
463    Node processNextNode()
464    {
465      if(_queue_tail==_queue_next_dist) {
466        _curr_dist++;
467        _queue_next_dist=_queue_head;
468      }
469      Node n=_queue[_queue_tail++];
470      _processed->set(n,true);
471      Node m;
472      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
473        if(!(*_reached)[m=G->target(e)]) {
474          _queue[_queue_head++]=m;
475          _reached->set(m,true);
476          _pred->set(m,e);
477          _dist->set(m,_curr_dist);
478        }
479      return n;
480    }
481     
482    ///Next node to be processed.
483
484    ///Next node to be processed.
485    ///
486    ///\return The next node to be processed or INVALID if the queue is
487    /// empty.
488    Node nextNode()
489    {
490      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
491    }
492 
493    ///\brief Returns \c false if there are nodes
494    ///to be processed in the queue
495    ///
496    ///Returns \c false if there are nodes
497    ///to be processed in the queue
498    bool emptyQueue() { return _queue_tail==_queue_head; }
499    ///Returns the number of the nodes to be processed.
500   
501    ///Returns the number of the nodes to be processed in the queue.
502    ///
503    int queueSize() { return _queue_head-_queue_tail; }
504   
505    ///Executes the algorithm.
506
507    ///Executes the algorithm.
508    ///
509    ///\pre init() must be called and at least one node should be added
510    ///with addSource() before using this function.
511    ///
512    ///This method runs the %BFS algorithm from the root node(s)
513    ///in order to
514    ///compute the
515    ///shortest path to each node. The algorithm computes
516    ///- The shortest path tree.
517    ///- The distance of each node from the root(s).
518    ///
519    void start()
520    {
521      while ( !emptyQueue() ) processNextNode();
522    }
523   
524    ///Executes the algorithm until \c dest is reached.
525
526    ///Executes the algorithm until \c dest is reached.
527    ///
528    ///\pre init() must be called and at least one node should be added
529    ///with addSource() before using this function.
530    ///
531    ///This method runs the %BFS algorithm from the root node(s)
532    ///in order to
533    ///compute the
534    ///shortest path to \c dest. The algorithm computes
535    ///- The shortest path to \c  dest.
536    ///- The distance of \c dest from the root(s).
537    ///
538    void start(Node dest)
539    {
540      while ( !emptyQueue() && _queue[_queue_tail]!=dest ) processNextNode();
541    }
542   
543    ///Executes the algorithm until a condition is met.
544
545    ///Executes the algorithm until a condition is met.
546    ///
547    ///\pre init() must be called and at least one node should be added
548    ///with addSource() before using this function.
549    ///
550    ///\param nm must be a bool (or convertible) node map. The algorithm
551    ///will stop when it reaches a node \c v with <tt>nm[v]==true</tt>.
552    template<class NM>
553    void start(const NM &nm)
554    {
555      while ( !emptyQueue() && !nm[_queue[_queue_tail]] ) processNextNode();
556    }
557   
558    ///Runs %BFS algorithm from node \c s.
559   
560    ///This method runs the %BFS algorithm from a root node \c s
561    ///in order to
562    ///compute the
563    ///shortest path to each node. The algorithm computes
564    ///- The shortest path tree.
565    ///- The distance of each node from the root.
566    ///
567    ///\note d.run(s) is just a shortcut of the following code.
568    ///\code
569    ///  d.init();
570    ///  d.addSource(s);
571    ///  d.start();
572    ///\endcode
573    void run(Node s) {
574      init();
575      addSource(s);
576      start();
577    }
578   
579    ///Finds the shortest path between \c s and \c t.
580   
581    ///Finds the shortest path between \c s and \c t.
582    ///
583    ///\return The length of the shortest s---t path if there exists one,
584    ///0 otherwise.
585    ///\note Apart from the return value, d.run(s) is
586    ///just a shortcut of the following code.
587    ///\code
588    ///  d.init();
589    ///  d.addSource(s);
590    ///  d.start(t);
591    ///\endcode
592    int run(Node s,Node t) {
593      init();
594      addSource(s);
595      start(t);
596      return reached(t)?_curr_dist-1+(_queue_tail==_queue_next_dist):0;
597    }
598   
599    ///@}
600
601    ///\name Query Functions
602    ///The result of the %BFS algorithm can be obtained using these
603    ///functions.\n
604    ///Before the use of these functions,
605    ///either run() or start() must be called.
606   
607    ///@{
608
609    ///Copies the shortest path to \c t into \c p
610   
611    ///This function copies the shortest path to \c t into \c p.
612    ///If \c t is a source itself or unreachable, then it does not
613    ///alter \c p.
614    ///\return Returns \c true if a path to \c t was actually copied to \c p,
615    ///\c false otherwise.
616    ///\sa DirPath
617    template<class P>
618    bool getPath(P &p,Node t)
619    {
620      if(reached(t)) {
621        p.clear();
622        typename P::Builder b(p);
623        for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
624          b.pushFront(predEdge(t));
625        b.commit();
626        return true;
627      }
628      return false;
629    }
630
631    ///The distance of a node from the root(s).
632
633    ///Returns the distance of a node from the root(s).
634    ///\pre \ref run() must be called before using this function.
635    ///\warning If node \c v in unreachable from the root(s) the return value
636    ///of this function is undefined.
637    int dist(Node v) const { return (*_dist)[v]; }
638
639    ///Returns the 'previous edge' of the shortest path tree.
640
641    ///For a node \c v it returns the 'previous edge'
642    ///of the shortest path tree,
643    ///i.e. it returns the last edge of a shortest path from the root(s) to \c
644    ///v. It is \ref INVALID
645    ///if \c v is unreachable from the root(s) or \c v is a root. The
646    ///shortest path tree used here is equal to the shortest path tree used in
647    ///\ref predNode().
648    ///\pre Either \ref run() or \ref start() must be called before using
649    ///this function.
650    Edge predEdge(Node v) const { return (*_pred)[v];}
651
652    ///Returns the 'previous node' of the shortest path tree.
653
654    ///For a node \c v it returns the 'previous node'
655    ///of the shortest path tree,
656    ///i.e. it returns the last but one node from a shortest path from the
657    ///root(a) to \c /v.
658    ///It is INVALID if \c v is unreachable from the root(s) or
659    ///if \c v itself a root.
660    ///The shortest path tree used here is equal to the shortest path
661    ///tree used in \ref predEdge().
662    ///\pre Either \ref run() or \ref start() must be called before
663    ///using this function.
664    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
665                                  G->source((*_pred)[v]); }
666   
667    ///Returns a reference to the NodeMap of distances.
668
669    ///Returns a reference to the NodeMap of distances.
670    ///\pre Either \ref run() or \ref init() must
671    ///be called before using this function.
672    const DistMap &distMap() const { return *_dist;}
673 
674    ///Returns a reference to the shortest path tree map.
675
676    ///Returns a reference to the NodeMap of the edges of the
677    ///shortest path tree.
678    ///\pre Either \ref run() or \ref init()
679    ///must be called before using this function.
680    const PredMap &predMap() const { return *_pred;}
681 
682    ///Checks if a node is reachable from the root.
683
684    ///Returns \c true if \c v is reachable from the root.
685    ///\warning The source nodes are indicated as unreached.
686    ///\pre Either \ref run() or \ref start()
687    ///must be called before using this function.
688    ///
689    bool reached(Node v) { return (*_reached)[v]; }
690   
691    ///@}
692  };
693
694  ///Default traits class of Bfs function.
695
696  ///Default traits class of Bfs function.
697  ///\param GR Graph type.
698  template<class GR>
699  struct BfsWizardDefaultTraits
700  {
701    ///The graph type the algorithm runs on.
702    typedef GR Graph;
703    ///\brief The type of the map that stores the last
704    ///edges of the shortest paths.
705    ///
706    ///The type of the map that stores the last
707    ///edges of the shortest paths.
708    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
709    ///
710    typedef NullMap<typename Graph::Node,typename GR::Edge> PredMap;
711    ///Instantiates a PredMap.
712 
713    ///This function instantiates a \ref PredMap.
714    ///\param g is the graph, to which we would like to define the PredMap.
715    ///\todo The graph alone may be insufficient to initialize
716#ifdef DOXYGEN
717    static PredMap *createPredMap(const GR &g)
718#else
719    static PredMap *createPredMap(const GR &)
720#endif
721    {
722      return new PredMap();
723    }
724
725    ///The type of the map that indicates which nodes are processed.
726 
727    ///The type of the map that indicates which nodes are processed.
728    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
729    ///\todo named parameter to set this type, function to read and write.
730    typedef NullMap<typename Graph::Node,bool> ProcessedMap;
731    ///Instantiates a ProcessedMap.
732 
733    ///This function instantiates a \ref ProcessedMap.
734    ///\param g is the graph, to which
735    ///we would like to define the \ref ProcessedMap
736#ifdef DOXYGEN
737    static ProcessedMap *createProcessedMap(const GR &g)
738#else
739    static ProcessedMap *createProcessedMap(const GR &)
740#endif
741    {
742      return new ProcessedMap();
743    }
744    ///The type of the map that indicates which nodes are reached.
745 
746    ///The type of the map that indicates which nodes are reached.
747    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
748    ///\todo named parameter to set this type, function to read and write.
749    typedef typename Graph::template NodeMap<bool> ReachedMap;
750    ///Instantiates a ReachedMap.
751 
752    ///This function instantiates a \ref ReachedMap.
753    ///\param G is the graph, to which
754    ///we would like to define the \ref ReachedMap.
755    static ReachedMap *createReachedMap(const GR &G)
756    {
757      return new ReachedMap(G);
758    }
759    ///The type of the map that stores the dists of the nodes.
760 
761    ///The type of the map that stores the dists of the nodes.
762    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
763    ///
764    typedef NullMap<typename Graph::Node,int> DistMap;
765    ///Instantiates a DistMap.
766 
767    ///This function instantiates a \ref DistMap.
768    ///\param g is the graph, to which we would like to define the \ref DistMap
769#ifdef DOXYGEN
770    static DistMap *createDistMap(const GR &g)
771#else
772    static DistMap *createDistMap(const GR &)
773#endif
774    {
775      return new DistMap();
776    }
777  };
778 
779  /// Default traits used by \ref BfsWizard
780
781  /// To make it easier to use Bfs algorithm
782  ///we have created a wizard class.
783  /// This \ref BfsWizard class needs default traits,
784  ///as well as the \ref Bfs class.
785  /// The \ref BfsWizardBase is a class to be the default traits of the
786  /// \ref BfsWizard class.
787  template<class GR>
788  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
789  {
790
791    typedef BfsWizardDefaultTraits<GR> Base;
792  protected:
793    /// Type of the nodes in the graph.
794    typedef typename Base::Graph::Node Node;
795
796    /// Pointer to the underlying graph.
797    void *_g;
798    ///Pointer to the map of reached nodes.
799    void *_reached;
800    ///Pointer to the map of processed nodes.
801    void *_processed;
802    ///Pointer to the map of predecessors edges.
803    void *_pred;
804    ///Pointer to the map of distances.
805    void *_dist;
806    ///Pointer to the source node.
807    Node _source;
808   
809    public:
810    /// Constructor.
811   
812    /// This constructor does not require parameters, therefore it initiates
813    /// all of the attributes to default values (0, INVALID).
814    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
815                           _dist(0), _source(INVALID) {}
816
817    /// Constructor.
818   
819    /// This constructor requires some parameters,
820    /// listed in the parameters list.
821    /// Others are initiated to 0.
822    /// \param g is the initial value of  \ref _g
823    /// \param s is the initial value of  \ref _source
824    BfsWizardBase(const GR &g, Node s=INVALID) :
825      _g((void *)&g), _reached(0), _processed(0), _pred(0),
826      _dist(0), _source(s) {}
827
828  };
829 
830  /// A class to make the usage of Bfs algorithm easier
831
832  /// This class is created to make it easier to use Bfs algorithm.
833  /// It uses the functions and features of the plain \ref Bfs,
834  /// but it is much simpler to use it.
835  ///
836  /// Simplicity means that the way to change the types defined
837  /// in the traits class is based on functions that returns the new class
838  /// and not on templatable built-in classes.
839  /// When using the plain \ref Bfs
840  /// the new class with the modified type comes from
841  /// the original class by using the ::
842  /// operator. In the case of \ref BfsWizard only
843  /// a function have to be called and it will
844  /// return the needed class.
845  ///
846  /// It does not have own \ref run method. When its \ref run method is called
847  /// it initiates a plain \ref Bfs class, and calls the \ref Bfs::run
848  /// method of it.
849  template<class TR>
850  class BfsWizard : public TR
851  {
852    typedef TR Base;
853
854    ///The type of the underlying graph.
855    typedef typename TR::Graph Graph;
856    //\e
857    typedef typename Graph::Node Node;
858    //\e
859    typedef typename Graph::NodeIt NodeIt;
860    //\e
861    typedef typename Graph::Edge Edge;
862    //\e
863    typedef typename Graph::OutEdgeIt OutEdgeIt;
864   
865    ///\brief The type of the map that stores
866    ///the reached nodes
867    typedef typename TR::ReachedMap ReachedMap;
868    ///\brief The type of the map that stores
869    ///the processed nodes
870    typedef typename TR::ProcessedMap ProcessedMap;
871    ///\brief The type of the map that stores the last
872    ///edges of the shortest paths.
873    typedef typename TR::PredMap PredMap;
874    ///The type of the map that stores the dists of the nodes.
875    typedef typename TR::DistMap DistMap;
876
877public:
878    /// Constructor.
879    BfsWizard() : TR() {}
880
881    /// Constructor that requires parameters.
882
883    /// Constructor that requires parameters.
884    /// These parameters will be the default values for the traits class.
885    BfsWizard(const Graph &g, Node s=INVALID) :
886      TR(g,s) {}
887
888    ///Copy constructor
889    BfsWizard(const TR &b) : TR(b) {}
890
891    ~BfsWizard() {}
892
893    ///Runs Bfs algorithm from a given node.
894   
895    ///Runs Bfs algorithm from a given node.
896    ///The node can be given by the \ref source function.
897    void run()
898    {
899      if(Base::_source==INVALID) throw UninitializedParameter();
900      Bfs<Graph,TR> alg(*(Graph*)Base::_g);
901      if(Base::_reached)
902        alg.reachedMap(*(ReachedMap*)Base::_reached);
903      if(Base::_processed) alg.processedMap(*(ProcessedMap*)Base::_processed);
904      if(Base::_pred) alg.predMap(*(PredMap*)Base::_pred);
905      if(Base::_dist) alg.distMap(*(DistMap*)Base::_dist);
906      alg.run(Base::_source);
907    }
908
909    ///Runs Bfs algorithm from the given node.
910
911    ///Runs Bfs algorithm from the given node.
912    ///\param s is the given source.
913    void run(Node s)
914    {
915      Base::_source=s;
916      run();
917    }
918
919    template<class T>
920    struct DefPredMapBase : public Base {
921      typedef T PredMap;
922      static PredMap *createPredMap(const Graph &) { return 0; };
923      DefPredMapBase(const TR &b) : TR(b) {}
924    };
925   
926    ///\brief \ref named-templ-param "Named parameter"
927    ///function for setting PredMap
928    ///
929    /// \ref named-templ-param "Named parameter"
930    ///function for setting PredMap
931    ///
932    template<class T>
933    BfsWizard<DefPredMapBase<T> > predMap(const T &t)
934    {
935      Base::_pred=(void *)&t;
936      return BfsWizard<DefPredMapBase<T> >(*this);
937    }
938   
939 
940    template<class T>
941    struct DefReachedMapBase : public Base {
942      typedef T ReachedMap;
943      static ReachedMap *createReachedMap(const Graph &) { return 0; };
944      DefReachedMapBase(const TR &b) : TR(b) {}
945    };
946   
947    ///\brief \ref named-templ-param "Named parameter"
948    ///function for setting ReachedMap
949    ///
950    /// \ref named-templ-param "Named parameter"
951    ///function for setting ReachedMap
952    ///
953    template<class T>
954    BfsWizard<DefReachedMapBase<T> > reachedMap(const T &t)
955    {
956      Base::_pred=(void *)&t;
957      return BfsWizard<DefReachedMapBase<T> >(*this);
958    }
959   
960
961    template<class T>
962    struct DefProcessedMapBase : public Base {
963      typedef T ProcessedMap;
964      static ProcessedMap *createProcessedMap(const Graph &) { return 0; };
965      DefProcessedMapBase(const TR &b) : TR(b) {}
966    };
967   
968    ///\brief \ref named-templ-param "Named parameter"
969    ///function for setting ProcessedMap
970    ///
971    /// \ref named-templ-param "Named parameter"
972    ///function for setting ProcessedMap
973    ///
974    template<class T>
975    BfsWizard<DefProcessedMapBase<T> > processedMap(const T &t)
976    {
977      Base::_pred=(void *)&t;
978      return BfsWizard<DefProcessedMapBase<T> >(*this);
979    }
980   
981   
982    template<class T>
983    struct DefDistMapBase : public Base {
984      typedef T DistMap;
985      static DistMap *createDistMap(const Graph &) { return 0; };
986      DefDistMapBase(const TR &b) : TR(b) {}
987    };
988   
989    ///\brief \ref named-templ-param "Named parameter"
990    ///function for setting DistMap type
991    ///
992    /// \ref named-templ-param "Named parameter"
993    ///function for setting DistMap type
994    ///
995    template<class T>
996    BfsWizard<DefDistMapBase<T> > distMap(const T &t)
997    {
998      Base::_dist=(void *)&t;
999      return BfsWizard<DefDistMapBase<T> >(*this);
1000    }
1001   
1002    /// Sets the source node, from which the Bfs algorithm runs.
1003
1004    /// Sets the source node, from which the Bfs algorithm runs.
1005    /// \param s is the source node.
1006    BfsWizard<TR> &source(Node s)
1007    {
1008      Base::_source=s;
1009      return *this;
1010    }
1011   
1012  };
1013 
1014  ///Function type interface for Bfs algorithm.
1015
1016  /// \ingroup flowalgs
1017  ///Function type interface for Bfs algorithm.
1018  ///
1019  ///This function also has several
1020  ///\ref named-templ-func-param "named parameters",
1021  ///they are declared as the members of class \ref BfsWizard.
1022  ///The following
1023  ///example shows how to use these parameters.
1024  ///\code
1025  ///  bfs(g,source).predMap(preds).run();
1026  ///\endcode
1027  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1028  ///to the end of the parameter list.
1029  ///\sa BfsWizard
1030  ///\sa Bfs
1031  template<class GR>
1032  BfsWizard<BfsWizardBase<GR> >
1033  bfs(const GR &g,typename GR::Node s=INVALID)
1034  {
1035    return BfsWizard<BfsWizardBase<GR> >(g,s);
1036  }
1037
1038} //END OF NAMESPACE LEMON
1039
1040#endif
1041
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