COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/bfs.h @ 2300:69330d717235

Last change on this file since 2300:69330d717235 was 2300:69330d717235, checked in by Balazs Dezso, 14 years ago

Conditional execution until the target is reached
/previous implementation: until the target is the next to process/

todo: query the target when we give nodemap as condition

File size: 33.0 KB
Line 
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 concepts::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 concepts::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 concepts::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 concepts::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* what() const throw() {
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    ///Processes the next node.
483
484    ///Processes the next node. And checks that the given target node
485    ///is reached. If the target node is reachable from the processed
486    ///node then the reached parameter will be set true. The reached
487    ///parameter should be initially false.
488    ///
489    ///\param target The target node.
490    ///\retval reached Indicates that the target node is reached.
491    ///\return The processed node.
492    ///
493    ///\warning The queue must not be empty!
494    Node processNextNode(Node target, bool& reached)
495    {
496      if(_queue_tail==_queue_next_dist) {
497        _curr_dist++;
498        _queue_next_dist=_queue_head;
499      }
500      Node n=_queue[_queue_tail++];
501      _processed->set(n,true);
502      Node m;
503      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
504        if(!(*_reached)[m=G->target(e)]) {
505          _queue[_queue_head++]=m;
506          _reached->set(m,true);
507          _pred->set(m,e);
508          _dist->set(m,_curr_dist);
509          reached = reached || (target == m);
510        }
511      return n;
512    }
513
514    ///Processes the next node.
515
516    ///Processes the next node. And checks that at least one of
517    ///reached node has true value in the \c nm nodemap. If one node
518    ///with true value is reachable from the processed node then the
519    ///reached parameter will be set true. The reached parameter
520    ///should be initially false.
521    ///
522    ///\param target The nodemaps of possible targets.
523    ///\retval reached Indicates that one of the target nodes is reached.
524    ///\return The processed node.
525    ///
526    ///\warning The queue must not be empty!
527    template<class NM>
528    Node processNextNode(const NM& nm, bool& reached)
529    {
530      if(_queue_tail==_queue_next_dist) {
531        _curr_dist++;
532        _queue_next_dist=_queue_head;
533      }
534      Node n=_queue[_queue_tail++];
535      _processed->set(n,true);
536      Node m;
537      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
538        if(!(*_reached)[m=G->target(e)]) {
539          _queue[_queue_head++]=m;
540          _reached->set(m,true);
541          _pred->set(m,e);
542          _dist->set(m,_curr_dist);
543          reached = reached || nm[m];
544        }
545      return n;
546    }
547     
548    ///Next node to be processed.
549
550    ///Next node to be processed.
551    ///
552    ///\return The next node to be processed or INVALID if the queue is
553    /// empty.
554    Node nextNode()
555    {
556      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
557    }
558 
559    ///\brief Returns \c false if there are nodes
560    ///to be processed in the queue
561    ///
562    ///Returns \c false if there are nodes
563    ///to be processed in the queue
564    bool emptyQueue() { return _queue_tail==_queue_head; }
565    ///Returns the number of the nodes to be processed.
566   
567    ///Returns the number of the nodes to be processed in the queue.
568    ///
569    int queueSize() { return _queue_head-_queue_tail; }
570   
571    ///Executes the algorithm.
572
573    ///Executes the algorithm.
574    ///
575    ///\pre init() must be called and at least one node should be added
576    ///with addSource() before using this function.
577    ///
578    ///This method runs the %BFS algorithm from the root node(s)
579    ///in order to
580    ///compute the
581    ///shortest path to each node. The algorithm computes
582    ///- The shortest path tree.
583    ///- The distance of each node from the root(s).
584    ///
585    void start()
586    {
587      while ( !emptyQueue() ) processNextNode();
588    }
589   
590    ///Executes the algorithm until \c dest is reached.
591
592    ///Executes the algorithm until \c dest is reached.
593    ///
594    ///\pre init() must be called and at least one node should be added
595    ///with addSource() before using this function.
596    ///
597    ///This method runs the %BFS algorithm from the root node(s)
598    ///in order to
599    ///compute the
600    ///shortest path to \c dest. The algorithm computes
601    ///- The shortest path to \c  dest.
602    ///- The distance of \c dest from the root(s).
603    ///
604    void start(Node dest)
605    {
606      bool reached = false;
607      while ( !emptyQueue() && !reached) processNextNode(dest, reached);
608    }
609   
610    ///Executes the algorithm until a condition is met.
611
612    ///Executes the algorithm until a condition is met.
613    ///
614    ///\pre init() must be called and at least one node should be added
615    ///with addSource() before using this function.
616    ///
617    ///\param nm must be a bool (or convertible) node map. The algorithm
618    ///will stop when it reaches a node \c v with <tt>nm[v]==true</tt>.
619    ///\todo query the reached target
620    template<class NM>
621    void start(const NM &nm)
622    {
623      bool reached = false;
624      while ( !emptyQueue() && !reached) processNextNode(nm, reached);
625    }
626   
627    ///Runs %BFS algorithm from node \c s.
628   
629    ///This method runs the %BFS algorithm from a root node \c s
630    ///in order to
631    ///compute the
632    ///shortest path to each node. The algorithm computes
633    ///- The shortest path tree.
634    ///- The distance of each node from the root.
635    ///
636    ///\note d.run(s) is just a shortcut of the following code.
637    ///\code
638    ///  d.init();
639    ///  d.addSource(s);
640    ///  d.start();
641    ///\endcode
642    void run(Node s) {
643      init();
644      addSource(s);
645      start();
646    }
647   
648    ///Finds the shortest path between \c s and \c t.
649   
650    ///Finds the shortest path between \c s and \c t.
651    ///
652    ///\return The length of the shortest s---t path if there exists one,
653    ///0 otherwise.
654    ///\note Apart from the return value, d.run(s) is
655    ///just a shortcut of the following code.
656    ///\code
657    ///  d.init();
658    ///  d.addSource(s);
659    ///  d.start(t);
660    ///\endcode
661    int run(Node s,Node t) {
662      init();
663      addSource(s);
664      start(t);
665      return reached(t)? _curr_dist : 0;
666    }
667   
668    ///@}
669
670    ///\name Query Functions
671    ///The result of the %BFS algorithm can be obtained using these
672    ///functions.\n
673    ///Before the use of these functions,
674    ///either run() or start() must be called.
675   
676    ///@{
677
678    ///Copies the shortest path to \c t into \c p
679   
680    ///This function copies the shortest path to \c t into \c p.
681    ///If \c t is a source itself or unreachable, then it does not
682    ///alter \c p.
683    ///\return Returns \c true if a path to \c t was actually copied to \c p,
684    ///\c false otherwise.
685    ///\sa DirPath
686    template<class P>
687    bool getPath(P &p,Node t)
688    {
689      if(reached(t)) {
690        p.clear();
691        typename P::Builder b(p);
692        for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
693          b.pushFront(predEdge(t));
694        b.commit();
695        return true;
696      }
697      return false;
698    }
699
700    ///The distance of a node from the root(s).
701
702    ///Returns the distance of a node from the root(s).
703    ///\pre \ref run() must be called before using this function.
704    ///\warning If node \c v in unreachable from the root(s) the return value
705    ///of this function is undefined.
706    int dist(Node v) const { return (*_dist)[v]; }
707
708    ///Returns the 'previous edge' of the shortest path tree.
709
710    ///For a node \c v it returns the 'previous edge'
711    ///of the shortest path tree,
712    ///i.e. it returns the last edge of a shortest path from the root(s) to \c
713    ///v. It is \ref INVALID
714    ///if \c v is unreachable from the root(s) or \c v is a root. The
715    ///shortest path tree used here is equal to the shortest path tree used in
716    ///\ref predNode().
717    ///\pre Either \ref run() or \ref start() must be called before using
718    ///this function.
719    Edge predEdge(Node v) const { return (*_pred)[v];}
720
721    ///Returns the 'previous node' of the shortest path tree.
722
723    ///For a node \c v it returns the 'previous node'
724    ///of the shortest path tree,
725    ///i.e. it returns the last but one node from a shortest path from the
726    ///root(a) to \c /v.
727    ///It is INVALID if \c v is unreachable from the root(s) or
728    ///if \c v itself a root.
729    ///The shortest path tree used here is equal to the shortest path
730    ///tree used in \ref predEdge().
731    ///\pre Either \ref run() or \ref start() must be called before
732    ///using this function.
733    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
734                                  G->source((*_pred)[v]); }
735   
736    ///Returns a reference to the NodeMap of distances.
737
738    ///Returns a reference to the NodeMap of distances.
739    ///\pre Either \ref run() or \ref init() must
740    ///be called before using this function.
741    const DistMap &distMap() const { return *_dist;}
742 
743    ///Returns a reference to the shortest path tree map.
744
745    ///Returns a reference to the NodeMap of the edges of the
746    ///shortest path tree.
747    ///\pre Either \ref run() or \ref init()
748    ///must be called before using this function.
749    const PredMap &predMap() const { return *_pred;}
750 
751    ///Checks if a node is reachable from the root.
752
753    ///Returns \c true if \c v is reachable from the root.
754    ///\warning The source nodes are indicated as unreached.
755    ///\pre Either \ref run() or \ref start()
756    ///must be called before using this function.
757    ///
758    bool reached(Node v) { return (*_reached)[v]; }
759   
760    ///@}
761  };
762
763  ///Default traits class of Bfs function.
764
765  ///Default traits class of Bfs function.
766  ///\param GR Graph type.
767  template<class GR>
768  struct BfsWizardDefaultTraits
769  {
770    ///The graph type the algorithm runs on.
771    typedef GR Graph;
772    ///\brief The type of the map that stores the last
773    ///edges of the shortest paths.
774    ///
775    ///The type of the map that stores the last
776    ///edges of the shortest paths.
777    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
778    ///
779    typedef NullMap<typename Graph::Node,typename GR::Edge> PredMap;
780    ///Instantiates a PredMap.
781 
782    ///This function instantiates a \ref PredMap.
783    ///\param g is the graph, to which we would like to define the PredMap.
784    ///\todo The graph alone may be insufficient to initialize
785#ifdef DOXYGEN
786    static PredMap *createPredMap(const GR &g)
787#else
788    static PredMap *createPredMap(const GR &)
789#endif
790    {
791      return new PredMap();
792    }
793
794    ///The type of the map that indicates which nodes are processed.
795 
796    ///The type of the map that indicates which nodes are processed.
797    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
798    ///\todo named parameter to set this type, function to read and write.
799    typedef NullMap<typename Graph::Node,bool> ProcessedMap;
800    ///Instantiates a ProcessedMap.
801 
802    ///This function instantiates a \ref ProcessedMap.
803    ///\param g is the graph, to which
804    ///we would like to define the \ref ProcessedMap
805#ifdef DOXYGEN
806    static ProcessedMap *createProcessedMap(const GR &g)
807#else
808    static ProcessedMap *createProcessedMap(const GR &)
809#endif
810    {
811      return new ProcessedMap();
812    }
813    ///The type of the map that indicates which nodes are reached.
814 
815    ///The type of the map that indicates which nodes are reached.
816    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
817    ///\todo named parameter to set this type, function to read and write.
818    typedef typename Graph::template NodeMap<bool> ReachedMap;
819    ///Instantiates a ReachedMap.
820 
821    ///This function instantiates a \ref ReachedMap.
822    ///\param G is the graph, to which
823    ///we would like to define the \ref ReachedMap.
824    static ReachedMap *createReachedMap(const GR &G)
825    {
826      return new ReachedMap(G);
827    }
828    ///The type of the map that stores the dists of the nodes.
829 
830    ///The type of the map that stores the dists of the nodes.
831    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
832    ///
833    typedef NullMap<typename Graph::Node,int> DistMap;
834    ///Instantiates a DistMap.
835 
836    ///This function instantiates a \ref DistMap.
837    ///\param g is the graph, to which we would like to define the \ref DistMap
838#ifdef DOXYGEN
839    static DistMap *createDistMap(const GR &g)
840#else
841    static DistMap *createDistMap(const GR &)
842#endif
843    {
844      return new DistMap();
845    }
846  };
847 
848  /// Default traits used by \ref BfsWizard
849
850  /// To make it easier to use Bfs algorithm
851  ///we have created a wizard class.
852  /// This \ref BfsWizard class needs default traits,
853  ///as well as the \ref Bfs class.
854  /// The \ref BfsWizardBase is a class to be the default traits of the
855  /// \ref BfsWizard class.
856  template<class GR>
857  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
858  {
859
860    typedef BfsWizardDefaultTraits<GR> Base;
861  protected:
862    /// Type of the nodes in the graph.
863    typedef typename Base::Graph::Node Node;
864
865    /// Pointer to the underlying graph.
866    void *_g;
867    ///Pointer to the map of reached nodes.
868    void *_reached;
869    ///Pointer to the map of processed nodes.
870    void *_processed;
871    ///Pointer to the map of predecessors edges.
872    void *_pred;
873    ///Pointer to the map of distances.
874    void *_dist;
875    ///Pointer to the source node.
876    Node _source;
877   
878    public:
879    /// Constructor.
880   
881    /// This constructor does not require parameters, therefore it initiates
882    /// all of the attributes to default values (0, INVALID).
883    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
884                           _dist(0), _source(INVALID) {}
885
886    /// Constructor.
887   
888    /// This constructor requires some parameters,
889    /// listed in the parameters list.
890    /// Others are initiated to 0.
891    /// \param g is the initial value of  \ref _g
892    /// \param s is the initial value of  \ref _source
893    BfsWizardBase(const GR &g, Node s=INVALID) :
894      _g((void *)&g), _reached(0), _processed(0), _pred(0),
895      _dist(0), _source(s) {}
896
897  };
898 
899  /// A class to make the usage of Bfs algorithm easier
900
901  /// This class is created to make it easier to use Bfs algorithm.
902  /// It uses the functions and features of the plain \ref Bfs,
903  /// but it is much simpler to use it.
904  ///
905  /// Simplicity means that the way to change the types defined
906  /// in the traits class is based on functions that returns the new class
907  /// and not on templatable built-in classes.
908  /// When using the plain \ref Bfs
909  /// the new class with the modified type comes from
910  /// the original class by using the ::
911  /// operator. In the case of \ref BfsWizard only
912  /// a function have to be called and it will
913  /// return the needed class.
914  ///
915  /// It does not have own \ref run method. When its \ref run method is called
916  /// it initiates a plain \ref Bfs class, and calls the \ref Bfs::run
917  /// method of it.
918  template<class TR>
919  class BfsWizard : public TR
920  {
921    typedef TR Base;
922
923    ///The type of the underlying graph.
924    typedef typename TR::Graph Graph;
925    //\e
926    typedef typename Graph::Node Node;
927    //\e
928    typedef typename Graph::NodeIt NodeIt;
929    //\e
930    typedef typename Graph::Edge Edge;
931    //\e
932    typedef typename Graph::OutEdgeIt OutEdgeIt;
933   
934    ///\brief The type of the map that stores
935    ///the reached nodes
936    typedef typename TR::ReachedMap ReachedMap;
937    ///\brief The type of the map that stores
938    ///the processed nodes
939    typedef typename TR::ProcessedMap ProcessedMap;
940    ///\brief The type of the map that stores the last
941    ///edges of the shortest paths.
942    typedef typename TR::PredMap PredMap;
943    ///The type of the map that stores the dists of the nodes.
944    typedef typename TR::DistMap DistMap;
945
946public:
947    /// Constructor.
948    BfsWizard() : TR() {}
949
950    /// Constructor that requires parameters.
951
952    /// Constructor that requires parameters.
953    /// These parameters will be the default values for the traits class.
954    BfsWizard(const Graph &g, Node s=INVALID) :
955      TR(g,s) {}
956
957    ///Copy constructor
958    BfsWizard(const TR &b) : TR(b) {}
959
960    ~BfsWizard() {}
961
962    ///Runs Bfs algorithm from a given node.
963   
964    ///Runs Bfs algorithm from a given node.
965    ///The node can be given by the \ref source function.
966    void run()
967    {
968      if(Base::_source==INVALID) throw UninitializedParameter();
969      Bfs<Graph,TR> alg(*(Graph*)Base::_g);
970      if(Base::_reached)
971        alg.reachedMap(*(ReachedMap*)Base::_reached);
972      if(Base::_processed) alg.processedMap(*(ProcessedMap*)Base::_processed);
973      if(Base::_pred) alg.predMap(*(PredMap*)Base::_pred);
974      if(Base::_dist) alg.distMap(*(DistMap*)Base::_dist);
975      alg.run(Base::_source);
976    }
977
978    ///Runs Bfs algorithm from the given node.
979
980    ///Runs Bfs algorithm from the given node.
981    ///\param s is the given source.
982    void run(Node s)
983    {
984      Base::_source=s;
985      run();
986    }
987
988    template<class T>
989    struct DefPredMapBase : public Base {
990      typedef T PredMap;
991      static PredMap *createPredMap(const Graph &) { return 0; };
992      DefPredMapBase(const TR &b) : TR(b) {}
993    };
994   
995    ///\brief \ref named-templ-param "Named parameter"
996    ///function for setting PredMap
997    ///
998    /// \ref named-templ-param "Named parameter"
999    ///function for setting PredMap
1000    ///
1001    template<class T>
1002    BfsWizard<DefPredMapBase<T> > predMap(const T &t)
1003    {
1004      Base::_pred=(void *)&t;
1005      return BfsWizard<DefPredMapBase<T> >(*this);
1006    }
1007   
1008 
1009    template<class T>
1010    struct DefReachedMapBase : public Base {
1011      typedef T ReachedMap;
1012      static ReachedMap *createReachedMap(const Graph &) { return 0; };
1013      DefReachedMapBase(const TR &b) : TR(b) {}
1014    };
1015   
1016    ///\brief \ref named-templ-param "Named parameter"
1017    ///function for setting ReachedMap
1018    ///
1019    /// \ref named-templ-param "Named parameter"
1020    ///function for setting ReachedMap
1021    ///
1022    template<class T>
1023    BfsWizard<DefReachedMapBase<T> > reachedMap(const T &t)
1024    {
1025      Base::_pred=(void *)&t;
1026      return BfsWizard<DefReachedMapBase<T> >(*this);
1027    }
1028   
1029
1030    template<class T>
1031    struct DefProcessedMapBase : public Base {
1032      typedef T ProcessedMap;
1033      static ProcessedMap *createProcessedMap(const Graph &) { return 0; };
1034      DefProcessedMapBase(const TR &b) : TR(b) {}
1035    };
1036   
1037    ///\brief \ref named-templ-param "Named parameter"
1038    ///function for setting ProcessedMap
1039    ///
1040    /// \ref named-templ-param "Named parameter"
1041    ///function for setting ProcessedMap
1042    ///
1043    template<class T>
1044    BfsWizard<DefProcessedMapBase<T> > processedMap(const T &t)
1045    {
1046      Base::_pred=(void *)&t;
1047      return BfsWizard<DefProcessedMapBase<T> >(*this);
1048    }
1049   
1050   
1051    template<class T>
1052    struct DefDistMapBase : public Base {
1053      typedef T DistMap;
1054      static DistMap *createDistMap(const Graph &) { return 0; };
1055      DefDistMapBase(const TR &b) : TR(b) {}
1056    };
1057   
1058    ///\brief \ref named-templ-param "Named parameter"
1059    ///function for setting DistMap type
1060    ///
1061    /// \ref named-templ-param "Named parameter"
1062    ///function for setting DistMap type
1063    ///
1064    template<class T>
1065    BfsWizard<DefDistMapBase<T> > distMap(const T &t)
1066    {
1067      Base::_dist=(void *)&t;
1068      return BfsWizard<DefDistMapBase<T> >(*this);
1069    }
1070   
1071    /// Sets the source node, from which the Bfs algorithm runs.
1072
1073    /// Sets the source node, from which the Bfs algorithm runs.
1074    /// \param s is the source node.
1075    BfsWizard<TR> &source(Node s)
1076    {
1077      Base::_source=s;
1078      return *this;
1079    }
1080   
1081  };
1082 
1083  ///Function type interface for Bfs algorithm.
1084
1085  /// \ingroup flowalgs
1086  ///Function type interface for Bfs algorithm.
1087  ///
1088  ///This function also has several
1089  ///\ref named-templ-func-param "named parameters",
1090  ///they are declared as the members of class \ref BfsWizard.
1091  ///The following
1092  ///example shows how to use these parameters.
1093  ///\code
1094  ///  bfs(g,source).predMap(preds).run();
1095  ///\endcode
1096  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1097  ///to the end of the parameter list.
1098  ///\sa BfsWizard
1099  ///\sa Bfs
1100  template<class GR>
1101  BfsWizard<BfsWizardBase<GR> >
1102  bfs(const GR &g,typename GR::Node s=INVALID)
1103  {
1104    return BfsWizard<BfsWizardBase<GR> >(g,s);
1105  }
1106
1107} //END OF NAMESPACE LEMON
1108
1109#endif
1110
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