COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/bfs.h @ 1761:896464fe9fbb

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1/* -*- C++ -*-
2 * lemon/bfs.h - Part of LEMON, a generic C++ optimization library
3 *
4 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Research Group on Combinatorial Optimization, EGRES).
6 *
7 * Permission to use, modify and distribute this software is granted
8 * provided that this copyright notice appears in all copies. For
9 * precise terms see the accompanying LICENSE file.
10 *
11 * This software is provided "AS IS" with no warranty of any kind,
12 * express or implied, and with no claim as to its suitability for any
13 * purpose.
14 *
15 */
16
17#ifndef LEMON_BFS_H
18#define LEMON_BFS_H
19
20///\ingroup flowalgs
21///\file
22///\brief Bfs algorithm.
23
24#include <lemon/list_graph.h>
25#include <lemon/graph_utils.h>
26#include <lemon/invalid.h>
27#include <lemon/error.h>
28#include <lemon/maps.h>
29
30namespace lemon {
31
32
33 
34  ///Default traits class of Bfs class.
35
36  ///Default traits class of Bfs class.
37  ///\param GR Graph type.
38  template<class GR>
39  struct BfsDefaultTraits
40  {
41    ///The graph type the algorithm runs on.
42    typedef GR Graph;
43    ///\brief The type of the map that stores the last
44    ///edges of the shortest paths.
45    ///
46    ///The type of the map that stores the last
47    ///edges of the shortest paths.
48    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
49    ///
50    typedef typename Graph::template NodeMap<typename GR::Edge> PredMap;
51    ///Instantiates a PredMap.
52 
53    ///This function instantiates a \ref PredMap.
54    ///\param G is the graph, to which we would like to define the PredMap.
55    ///\todo The graph alone may be insufficient to initialize
56    static PredMap *createPredMap(const GR &G)
57    {
58      return new PredMap(G);
59    }
60    ///The type of the map that indicates which nodes are processed.
61 
62    ///The type of the map that indicates which nodes are processed.
63    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
64    ///\todo named parameter to set this type, function to read and write.
65    typedef NullMap<typename Graph::Node,bool> ProcessedMap;
66    ///Instantiates a ProcessedMap.
67 
68    ///This function instantiates a \ref ProcessedMap.
69    ///\param g is the graph, to which
70    ///we would like to define the \ref ProcessedMap
71#ifdef DOXYGEN
72    static ProcessedMap *createProcessedMap(const GR &g)
73#else
74    static ProcessedMap *createProcessedMap(const GR &)
75#endif
76    {
77      return new ProcessedMap();
78    }
79    ///The type of the map that indicates which nodes are reached.
80 
81    ///The type of the map that indicates which nodes are reached.
82    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
83    ///\todo named parameter to set this type, function to read and write.
84    typedef typename Graph::template NodeMap<bool> ReachedMap;
85    ///Instantiates a ReachedMap.
86 
87    ///This function instantiates a \ref ReachedMap.
88    ///\param G is the graph, to which
89    ///we would like to define the \ref ReachedMap.
90    static ReachedMap *createReachedMap(const GR &G)
91    {
92      return new ReachedMap(G);
93    }
94    ///The type of the map that stores the dists of the nodes.
95 
96    ///The type of the map that stores the dists of the nodes.
97    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
98    ///
99    typedef typename Graph::template NodeMap<int> DistMap;
100    ///Instantiates a DistMap.
101 
102    ///This function instantiates a \ref DistMap.
103    ///\param G is the graph, to which we would like to define the \ref DistMap
104    static DistMap *createDistMap(const GR &G)
105    {
106      return new DistMap(G);
107    }
108  };
109 
110  ///%BFS algorithm class.
111 
112  ///\ingroup flowalgs
113  ///This class provides an efficient implementation of the %BFS algorithm.
114  ///
115  ///\param GR The graph type the algorithm runs on. The default value is
116  ///\ref ListGraph. The value of GR is not used directly by Bfs, it
117  ///is only passed to \ref BfsDefaultTraits.
118  ///\param TR Traits class to set various data types used by the algorithm.
119  ///The default traits class is
120  ///\ref BfsDefaultTraits "BfsDefaultTraits<GR>".
121  ///See \ref BfsDefaultTraits for the documentation of
122  ///a Bfs traits class.
123  ///
124  ///\author Alpar Juttner
125
126#ifdef DOXYGEN
127  template <typename GR,
128            typename TR>
129#else
130  template <typename GR=ListGraph,
131            typename TR=BfsDefaultTraits<GR> >
132#endif
133  class Bfs {
134  public:
135    /**
136     * \brief \ref Exception for uninitialized parameters.
137     *
138     * This error represents problems in the initialization
139     * of the parameters of the algorithms.
140     */
141    class UninitializedParameter : public lemon::UninitializedParameter {
142    public:
143      virtual const char* exceptionName() const {
144        return "lemon::Bfs::UninitializedParameter";
145      }
146    };
147
148    typedef TR Traits;
149    ///The type of the underlying graph.
150    typedef typename TR::Graph Graph;
151    ///\e
152    typedef typename Graph::Node Node;
153    ///\e
154    typedef typename Graph::NodeIt NodeIt;
155    ///\e
156    typedef typename Graph::Edge Edge;
157    ///\e
158    typedef typename Graph::OutEdgeIt OutEdgeIt;
159   
160    ///\brief The type of the map that stores the last
161    ///edges of the shortest paths.
162    typedef typename TR::PredMap PredMap;
163    ///The type of the map indicating which nodes are reached.
164    typedef typename TR::ReachedMap ReachedMap;
165    ///The type of the map indicating which nodes are processed.
166    typedef typename TR::ProcessedMap ProcessedMap;
167    ///The type of the map that stores the dists of the nodes.
168    typedef typename TR::DistMap DistMap;
169  private:
170    /// Pointer to the underlying graph.
171    const Graph *G;
172    ///Pointer to the map of predecessors edges.
173    PredMap *_pred;
174    ///Indicates if \ref _pred is locally allocated (\c true) or not.
175    bool local_pred;
176    ///Pointer to the map of distances.
177    DistMap *_dist;
178    ///Indicates if \ref _dist is locally allocated (\c true) or not.
179    bool local_dist;
180    ///Pointer to the map of reached status of the nodes.
181    ReachedMap *_reached;
182    ///Indicates if \ref _reached is locally allocated (\c true) or not.
183    bool local_reached;
184    ///Pointer to the map of processed status of the nodes.
185    ProcessedMap *_processed;
186    ///Indicates if \ref _processed is locally allocated (\c true) or not.
187    bool local_processed;
188
189    std::vector<typename Graph::Node> _queue;
190    int _queue_head,_queue_tail,_queue_next_dist;
191    int _curr_dist;
192
193    ///Creates the maps if necessary.
194   
195    ///\todo Error if \c G are \c NULL.
196    ///\todo Better memory allocation (instead of new).
197    void create_maps()
198    {
199      if(!_pred) {
200        local_pred = true;
201        _pred = Traits::createPredMap(*G);
202      }
203      if(!_dist) {
204        local_dist = true;
205        _dist = Traits::createDistMap(*G);
206      }
207      if(!_reached) {
208        local_reached = true;
209        _reached = Traits::createReachedMap(*G);
210      }
211      if(!_processed) {
212        local_processed = true;
213        _processed = Traits::createProcessedMap(*G);
214      }
215    }
216
217  protected:
218   
219    Bfs() {}
220   
221  public:
222 
223    typedef Bfs Create;
224
225    ///\name Named template parameters
226
227    ///@{
228
229    template <class T>
230    struct DefPredMapTraits : public Traits {
231      typedef T PredMap;
232      static PredMap *createPredMap(const Graph &G)
233      {
234        throw UninitializedParameter();
235      }
236    };
237    ///\ref named-templ-param "Named parameter" for setting PredMap type
238
239    ///\ref named-templ-param "Named parameter" for setting PredMap type
240    ///
241    template <class T>
242    struct DefPredMap : public Bfs< Graph, DefPredMapTraits<T> > {
243      typedef Bfs< Graph, DefPredMapTraits<T> > Create;
244    };
245   
246    template <class T>
247    struct DefDistMapTraits : public Traits {
248      typedef T DistMap;
249      static DistMap *createDistMap(const Graph &G)
250      {
251        throw UninitializedParameter();
252      }
253    };
254    ///\ref named-templ-param "Named parameter" for setting DistMap type
255
256    ///\ref named-templ-param "Named parameter" for setting DistMap type
257    ///
258    template <class T>
259    struct DefDistMap : public Bfs< Graph, DefDistMapTraits<T> > {
260      typedef Bfs< Graph, DefDistMapTraits<T> > Create;
261    };
262   
263    template <class T>
264    struct DefReachedMapTraits : public Traits {
265      typedef T ReachedMap;
266      static ReachedMap *createReachedMap(const Graph &G)
267      {
268        throw UninitializedParameter();
269      }
270    };
271    ///\ref named-templ-param "Named parameter" for setting ReachedMap type
272
273    ///\ref named-templ-param "Named parameter" for setting ReachedMap type
274    ///
275    template <class T>
276    struct DefReachedMap : public Bfs< Graph, DefReachedMapTraits<T> > {
277      typedef Bfs< Graph, DefReachedMapTraits<T> > Create;
278    };
279   
280    template <class T>
281    struct DefProcessedMapTraits : public Traits {
282      typedef T ProcessedMap;
283      static ProcessedMap *createProcessedMap(const Graph &G)
284      {
285        throw UninitializedParameter();
286      }
287    };
288    ///\ref named-templ-param "Named parameter" for setting ProcessedMap type
289
290    ///\ref named-templ-param "Named parameter" for setting ProcessedMap type
291    ///
292    template <class T>
293    struct DefProcessedMap : public Bfs< Graph, DefProcessedMapTraits<T> > {
294      typedef Bfs< Graph, DefProcessedMapTraits<T> > Create;
295    };
296   
297    struct DefGraphProcessedMapTraits : public Traits {
298      typedef typename Graph::template NodeMap<bool> ProcessedMap;
299      static ProcessedMap *createProcessedMap(const Graph &G)
300      {
301        return new ProcessedMap(G);
302      }
303    };
304    ///\brief \ref named-templ-param "Named parameter"
305    ///for setting the ProcessedMap type to be Graph::NodeMap<bool>.
306    ///
307    ///\ref named-templ-param "Named parameter"
308    ///for setting the ProcessedMap type to be Graph::NodeMap<bool>.
309    ///If you don't set it explicitly, it will be automatically allocated.
310    template <class T>
311    struct DefProcessedMapToBeDefaultMap :
312      public Bfs< Graph, DefGraphProcessedMapTraits> {
313      typedef Bfs< Graph, DefGraphProcessedMapTraits> Create;
314    };
315   
316    ///@}
317
318  public:     
319   
320    ///Constructor.
321   
322    ///\param _G the graph the algorithm will run on.
323    ///
324    Bfs(const Graph& _G) :
325      G(&_G),
326      _pred(NULL), local_pred(false),
327      _dist(NULL), local_dist(false),
328      _reached(NULL), local_reached(false),
329      _processed(NULL), local_processed(false)
330    { }
331   
332    ///Destructor.
333    ~Bfs()
334    {
335      if(local_pred) delete _pred;
336      if(local_dist) delete _dist;
337      if(local_reached) delete _reached;
338      if(local_processed) delete _processed;
339    }
340
341    ///Sets the map storing the predecessor edges.
342
343    ///Sets the map storing the predecessor edges.
344    ///If you don't use this function before calling \ref run(),
345    ///it will allocate one. The destructor deallocates this
346    ///automatically allocated map, of course.
347    ///\return <tt> (*this) </tt>
348    Bfs &predMap(PredMap &m)
349    {
350      if(local_pred) {
351        delete _pred;
352        local_pred=false;
353      }
354      _pred = &m;
355      return *this;
356    }
357
358    ///Sets the map indicating the reached nodes.
359
360    ///Sets the map indicating the reached nodes.
361    ///If you don't use this function before calling \ref run(),
362    ///it will allocate one. The destructor deallocates this
363    ///automatically allocated map, of course.
364    ///\return <tt> (*this) </tt>
365    Bfs &reachedMap(ReachedMap &m)
366    {
367      if(local_reached) {
368        delete _reached;
369        local_reached=false;
370      }
371      _reached = &m;
372      return *this;
373    }
374
375    ///Sets the map indicating the processed nodes.
376
377    ///Sets the map indicating the processed nodes.
378    ///If you don't use this function before calling \ref run(),
379    ///it will allocate one. The destructor deallocates this
380    ///automatically allocated map, of course.
381    ///\return <tt> (*this) </tt>
382    Bfs &processedMap(ProcessedMap &m)
383    {
384      if(local_processed) {
385        delete _processed;
386        local_processed=false;
387      }
388      _processed = &m;
389      return *this;
390    }
391
392    ///Sets the map storing the distances calculated by the algorithm.
393
394    ///Sets the map storing the distances calculated by the algorithm.
395    ///If you don't use this function before calling \ref run(),
396    ///it will allocate one. The destructor deallocates this
397    ///automatically allocated map, of course.
398    ///\return <tt> (*this) </tt>
399    Bfs &distMap(DistMap &m)
400    {
401      if(local_dist) {
402        delete _dist;
403        local_dist=false;
404      }
405      _dist = &m;
406      return *this;
407    }
408
409  public:
410    ///\name Execution control
411    ///The simplest way to execute the algorithm is to use
412    ///one of the member functions called \c run(...).
413    ///\n
414    ///If you need more control on the execution,
415    ///first you must call \ref init(), then you can add several source nodes
416    ///with \ref addSource().
417    ///Finally \ref start() will perform the actual path
418    ///computation.
419
420    ///@{
421
422    ///Initializes the internal data structures.
423
424    ///Initializes the internal data structures.
425    ///
426    void init()
427    {
428      create_maps();
429      _queue.resize(countNodes(*G));
430      _queue_head=_queue_tail=0;
431      _curr_dist=1;
432      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
433        _pred->set(u,INVALID);
434        _reached->set(u,false);
435        _processed->set(u,false);
436      }
437    }
438   
439    ///Adds a new source node.
440
441    ///Adds a new source node to the set of nodes to be processed.
442    ///
443    void addSource(Node s)
444    {
445      if(!(*_reached)[s])
446        {
447          _reached->set(s,true);
448          _pred->set(s,INVALID);
449          _dist->set(s,0);
450          _queue[_queue_head++]=s;
451          _queue_next_dist=_queue_head;
452        }
453    }
454   
455    ///Processes the next node.
456
457    ///Processes the next node.
458    ///
459    ///\return The processed node.
460    ///
461    ///\warning The queue must not be empty!
462    Node processNextNode()
463    {
464      if(_queue_tail==_queue_next_dist) {
465        _curr_dist++;
466        _queue_next_dist=_queue_head;
467      }
468      Node n=_queue[_queue_tail++];
469      _processed->set(n,true);
470      Node m;
471      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
472        if(!(*_reached)[m=G->target(e)]) {
473          _queue[_queue_head++]=m;
474          _reached->set(m,true);
475          _pred->set(m,e);
476          _dist->set(m,_curr_dist);
477        }
478      return n;
479    }
480     
481    ///Next node to be processed.
482
483    ///Next node to be processed.
484    ///
485    ///\return The next node to be processed or INVALID if the queue is
486    /// empty.
487    Node nextNode()
488    {
489      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
490    }
491 
492    ///\brief Returns \c false if there are nodes
493    ///to be processed in the queue
494    ///
495    ///Returns \c false if there are nodes
496    ///to be processed in the queue
497    bool emptyQueue() { return _queue_tail==_queue_head; }
498    ///Returns the number of the nodes to be processed.
499   
500    ///Returns the number of the nodes to be processed in the queue.
501    ///
502    int queueSize() { return _queue_head-_queue_tail; }
503   
504    ///Executes the algorithm.
505
506    ///Executes the algorithm.
507    ///
508    ///\pre init() must be called and at least one node should be added
509    ///with addSource() before using this function.
510    ///
511    ///This method runs the %BFS algorithm from the root node(s)
512    ///in order to
513    ///compute the
514    ///shortest path to each node. The algorithm computes
515    ///- The shortest path tree.
516    ///- The distance of each node from the root(s).
517    ///
518    void start()
519    {
520      while ( !emptyQueue() ) processNextNode();
521    }
522   
523    ///Executes the algorithm until \c dest is reached.
524
525    ///Executes the algorithm until \c dest is reached.
526    ///
527    ///\pre init() must be called and at least one node should be added
528    ///with addSource() before using this function.
529    ///
530    ///This method runs the %BFS algorithm from the root node(s)
531    ///in order to
532    ///compute the
533    ///shortest path to \c dest. The algorithm computes
534    ///- The shortest path to \c  dest.
535    ///- The distance of \c dest from the root(s).
536    ///
537    void start(Node dest)
538    {
539      while ( !emptyQueue() && _queue[_queue_tail]!=dest ) processNextNode();
540    }
541   
542    ///Executes the algorithm until a condition is met.
543
544    ///Executes the algorithm until a condition is met.
545    ///
546    ///\pre init() must be called and at least one node should be added
547    ///with addSource() before using this function.
548    ///
549    ///\param nm must be a bool (or convertible) node map. The algorithm
550    ///will stop when it reaches a node \c v with <tt>nm[v]==true</tt>.
551    template<class NM>
552    void start(const NM &nm)
553    {
554      while ( !emptyQueue() && !nm[_queue[_queue_tail]] ) processNextNode();
555    }
556   
557    ///Runs %BFS algorithm from node \c s.
558   
559    ///This method runs the %BFS algorithm from a root node \c s
560    ///in order to
561    ///compute the
562    ///shortest path to each node. The algorithm computes
563    ///- The shortest path tree.
564    ///- The distance of each node from the root.
565    ///
566    ///\note d.run(s) is just a shortcut of the following code.
567    ///\code
568    ///  d.init();
569    ///  d.addSource(s);
570    ///  d.start();
571    ///\endcode
572    void run(Node s) {
573      init();
574      addSource(s);
575      start();
576    }
577   
578    ///Finds the shortest path between \c s and \c t.
579   
580    ///Finds the shortest path between \c s and \c t.
581    ///
582    ///\return The length of the shortest s---t path if there exists one,
583    ///0 otherwise.
584    ///\note Apart from the return value, d.run(s) is
585    ///just a shortcut of the following code.
586    ///\code
587    ///  d.init();
588    ///  d.addSource(s);
589    ///  d.start(t);
590    ///\endcode
591    int run(Node s,Node t) {
592      init();
593      addSource(s);
594      start(t);
595      return reached(t)?_curr_dist-1+(_queue_tail==_queue_next_dist):0;
596    }
597   
598    ///@}
599
600    ///\name Query Functions
601    ///The result of the %BFS algorithm can be obtained using these
602    ///functions.\n
603    ///Before the use of these functions,
604    ///either run() or start() must be called.
605   
606    ///@{
607
608    ///Copies the shortest path to \c t into \c p
609   
610    ///This function copies the shortest path to \c t into \c p.
611    ///If \c t is a source itself or unreachable, then it does not
612    ///alter \c p.
613    ///\todo Is it the right way to handle unreachable nodes?
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);pred(t)!=INVALID;t=predNode(t))
624          b.pushFront(pred(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    ///\todo predEdge could be a better name.
651    Edge pred(Node v) const { return (*_pred)[v];}
652
653    ///Returns the 'previous node' of the shortest path tree.
654
655    ///For a node \c v it returns the 'previous node'
656    ///of the shortest path tree,
657    ///i.e. it returns the last but one node from a shortest path from the
658    ///root(a) to \c /v.
659    ///It is INVALID if \c v is unreachable from the root(s) or
660    ///if \c v itself a root.
661    ///The shortest path tree used here is equal to the shortest path
662    ///tree used in \ref pred().
663    ///\pre Either \ref run() or \ref start() must be called before
664    ///using this function.
665    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
666                                  G->source((*_pred)[v]); }
667   
668    ///Returns a reference to the NodeMap of distances.
669
670    ///Returns a reference to the NodeMap of distances.
671    ///\pre Either \ref run() or \ref init() must
672    ///be called before using this function.
673    const DistMap &distMap() const { return *_dist;}
674 
675    ///Returns a reference to the shortest path tree map.
676
677    ///Returns a reference to the NodeMap of the edges of the
678    ///shortest path tree.
679    ///\pre Either \ref run() or \ref init()
680    ///must be called before using this function.
681    const PredMap &predMap() const { return *_pred;}
682 
683    ///Checks if a node is reachable from the root.
684
685    ///Returns \c true if \c v is reachable from the root.
686    ///\warning The source nodes are indicated as unreached.
687    ///\pre Either \ref run() or \ref start()
688    ///must be called before using this function.
689    ///
690    bool reached(Node v) { return (*_reached)[v]; }
691   
692    ///@}
693  };
694
695  ///Default traits class of Bfs function.
696
697  ///Default traits class of Bfs function.
698  ///\param GR Graph type.
699  template<class GR>
700  struct BfsWizardDefaultTraits
701  {
702    ///The graph type the algorithm runs on.
703    typedef GR Graph;
704    ///\brief The type of the map that stores the last
705    ///edges of the shortest paths.
706    ///
707    ///The type of the map that stores the last
708    ///edges of the shortest paths.
709    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
710    ///
711    typedef NullMap<typename Graph::Node,typename GR::Edge> PredMap;
712    ///Instantiates a PredMap.
713 
714    ///This function instantiates a \ref PredMap.
715    ///\param g is the graph, to which we would like to define the PredMap.
716    ///\todo The graph alone may be insufficient to initialize
717#ifdef DOXYGEN
718    static PredMap *createPredMap(const GR &g)
719#else
720    static PredMap *createPredMap(const GR &)
721#endif
722    {
723      return new PredMap();
724    }
725
726    ///The type of the map that indicates which nodes are processed.
727 
728    ///The type of the map that indicates which nodes are processed.
729    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
730    ///\todo named parameter to set this type, function to read and write.
731    typedef NullMap<typename Graph::Node,bool> ProcessedMap;
732    ///Instantiates a ProcessedMap.
733 
734    ///This function instantiates a \ref ProcessedMap.
735    ///\param g is the graph, to which
736    ///we would like to define the \ref ProcessedMap
737#ifdef DOXYGEN
738    static ProcessedMap *createProcessedMap(const GR &g)
739#else
740    static ProcessedMap *createProcessedMap(const GR &)
741#endif
742    {
743      return new ProcessedMap();
744    }
745    ///The type of the map that indicates which nodes are reached.
746 
747    ///The type of the map that indicates which nodes are reached.
748    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
749    ///\todo named parameter to set this type, function to read and write.
750    typedef typename Graph::template NodeMap<bool> ReachedMap;
751    ///Instantiates a ReachedMap.
752 
753    ///This function instantiates a \ref ReachedMap.
754    ///\param G is the graph, to which
755    ///we would like to define the \ref ReachedMap.
756    static ReachedMap *createReachedMap(const GR &G)
757    {
758      return new ReachedMap(G);
759    }
760    ///The type of the map that stores the dists of the nodes.
761 
762    ///The type of the map that stores the dists of the nodes.
763    ///It must meet the \ref concept::WriteMap "WriteMap" concept.
764    ///
765    typedef NullMap<typename Graph::Node,int> DistMap;
766    ///Instantiates a DistMap.
767 
768    ///This function instantiates a \ref DistMap.
769    ///\param g is the graph, to which we would like to define the \ref DistMap
770#ifdef DOXYGEN
771    static DistMap *createDistMap(const GR &g)
772#else
773    static DistMap *createDistMap(const GR &)
774#endif
775    {
776      return new DistMap();
777    }
778  };
779 
780  /// Default traits used by \ref BfsWizard
781
782  /// To make it easier to use Bfs algorithm
783  ///we have created a wizard class.
784  /// This \ref BfsWizard class needs default traits,
785  ///as well as the \ref Bfs class.
786  /// The \ref BfsWizardBase is a class to be the default traits of the
787  /// \ref BfsWizard class.
788  template<class GR>
789  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
790  {
791
792    typedef BfsWizardDefaultTraits<GR> Base;
793  protected:
794    /// Type of the nodes in the graph.
795    typedef typename Base::Graph::Node Node;
796
797    /// Pointer to the underlying graph.
798    void *_g;
799    ///Pointer to the map of reached nodes.
800    void *_reached;
801    ///Pointer to the map of processed nodes.
802    void *_processed;
803    ///Pointer to the map of predecessors edges.
804    void *_pred;
805    ///Pointer to the map of distances.
806    void *_dist;
807    ///Pointer to the source node.
808    Node _source;
809   
810    public:
811    /// Constructor.
812   
813    /// This constructor does not require parameters, therefore it initiates
814    /// all of the attributes to default values (0, INVALID).
815    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
816                           _dist(0), _source(INVALID) {}
817
818    /// Constructor.
819   
820    /// This constructor requires some parameters,
821    /// listed in the parameters list.
822    /// Others are initiated to 0.
823    /// \param g is the initial value of  \ref _g
824    /// \param s is the initial value of  \ref _source
825    BfsWizardBase(const GR &g, Node s=INVALID) :
826      _g((void *)&g), _reached(0), _processed(0), _pred(0),
827      _dist(0), _source(s) {}
828
829  };
830 
831  /// A class to make the usage of Bfs algorithm easier
832
833  /// This class is created to make it easier to use Bfs algorithm.
834  /// It uses the functions and features of the plain \ref Bfs,
835  /// but it is much simpler to use it.
836  ///
837  /// Simplicity means that the way to change the types defined
838  /// in the traits class is based on functions that returns the new class
839  /// and not on templatable built-in classes.
840  /// When using the plain \ref Bfs
841  /// the new class with the modified type comes from
842  /// the original class by using the ::
843  /// operator. In the case of \ref BfsWizard only
844  /// a function have to be called and it will
845  /// return the needed class.
846  ///
847  /// It does not have own \ref run method. When its \ref run method is called
848  /// it initiates a plain \ref Bfs class, and calls the \ref Bfs::run
849  /// method of it.
850  template<class TR>
851  class BfsWizard : public TR
852  {
853    typedef TR Base;
854
855    ///The type of the underlying graph.
856    typedef typename TR::Graph Graph;
857    //\e
858    typedef typename Graph::Node Node;
859    //\e
860    typedef typename Graph::NodeIt NodeIt;
861    //\e
862    typedef typename Graph::Edge Edge;
863    //\e
864    typedef typename Graph::OutEdgeIt OutEdgeIt;
865   
866    ///\brief The type of the map that stores
867    ///the reached nodes
868    typedef typename TR::ReachedMap ReachedMap;
869    ///\brief The type of the map that stores
870    ///the processed nodes
871    typedef typename TR::ProcessedMap ProcessedMap;
872    ///\brief The type of the map that stores the last
873    ///edges of the shortest paths.
874    typedef typename TR::PredMap PredMap;
875    ///The type of the map that stores the dists of the nodes.
876    typedef typename TR::DistMap DistMap;
877
878public:
879    /// Constructor.
880    BfsWizard() : TR() {}
881
882    /// Constructor that requires parameters.
883
884    /// Constructor that requires parameters.
885    /// These parameters will be the default values for the traits class.
886    BfsWizard(const Graph &g, Node s=INVALID) :
887      TR(g,s) {}
888
889    ///Copy constructor
890    BfsWizard(const TR &b) : TR(b) {}
891
892    ~BfsWizard() {}
893
894    ///Runs Bfs algorithm from a given node.
895   
896    ///Runs Bfs algorithm from a given node.
897    ///The node can be given by the \ref source function.
898    void run()
899    {
900      if(Base::_source==INVALID) throw UninitializedParameter();
901      Bfs<Graph,TR> alg(*(Graph*)Base::_g);
902      if(Base::_reached)
903        alg.reachedMap(*(ReachedMap*)Base::_reached);
904      if(Base::_processed) alg.processedMap(*(ProcessedMap*)Base::_processed);
905      if(Base::_pred) alg.predMap(*(PredMap*)Base::_pred);
906      if(Base::_dist) alg.distMap(*(DistMap*)Base::_dist);
907      alg.run(Base::_source);
908    }
909
910    ///Runs Bfs algorithm from the given node.
911
912    ///Runs Bfs algorithm from the given node.
913    ///\param s is the given source.
914    void run(Node s)
915    {
916      Base::_source=s;
917      run();
918    }
919
920    template<class T>
921    struct DefPredMapBase : public Base {
922      typedef T PredMap;
923      static PredMap *createPredMap(const Graph &) { return 0; };
924      DefPredMapBase(const TR &b) : TR(b) {}
925    };
926   
927    ///\brief \ref named-templ-param "Named parameter"
928    ///function for setting PredMap
929    ///
930    /// \ref named-templ-param "Named parameter"
931    ///function for setting PredMap
932    ///
933    template<class T>
934    BfsWizard<DefPredMapBase<T> > predMap(const T &t)
935    {
936      Base::_pred=(void *)&t;
937      return BfsWizard<DefPredMapBase<T> >(*this);
938    }
939   
940 
941    template<class T>
942    struct DefReachedMapBase : public Base {
943      typedef T ReachedMap;
944      static ReachedMap *createReachedMap(const Graph &) { return 0; };
945      DefReachedMapBase(const TR &b) : TR(b) {}
946    };
947   
948    ///\brief \ref named-templ-param "Named parameter"
949    ///function for setting ReachedMap
950    ///
951    /// \ref named-templ-param "Named parameter"
952    ///function for setting ReachedMap
953    ///
954    template<class T>
955    BfsWizard<DefReachedMapBase<T> > reachedMap(const T &t)
956    {
957      Base::_pred=(void *)&t;
958      return BfsWizard<DefReachedMapBase<T> >(*this);
959    }
960   
961
962    template<class T>
963    struct DefProcessedMapBase : public Base {
964      typedef T ProcessedMap;
965      static ProcessedMap *createProcessedMap(const Graph &) { return 0; };
966      DefProcessedMapBase(const TR &b) : TR(b) {}
967    };
968   
969    ///\brief \ref named-templ-param "Named parameter"
970    ///function for setting ProcessedMap
971    ///
972    /// \ref named-templ-param "Named parameter"
973    ///function for setting ProcessedMap
974    ///
975    template<class T>
976    BfsWizard<DefProcessedMapBase<T> > processedMap(const T &t)
977    {
978      Base::_pred=(void *)&t;
979      return BfsWizard<DefProcessedMapBase<T> >(*this);
980    }
981   
982   
983    template<class T>
984    struct DefDistMapBase : public Base {
985      typedef T DistMap;
986      static DistMap *createDistMap(const Graph &) { return 0; };
987      DefDistMapBase(const TR &b) : TR(b) {}
988    };
989   
990    ///\brief \ref named-templ-param "Named parameter"
991    ///function for setting DistMap type
992    ///
993    /// \ref named-templ-param "Named parameter"
994    ///function for setting DistMap type
995    ///
996    template<class T>
997    BfsWizard<DefDistMapBase<T> > distMap(const T &t)
998    {
999      Base::_dist=(void *)&t;
1000      return BfsWizard<DefDistMapBase<T> >(*this);
1001    }
1002   
1003    /// Sets the source node, from which the Bfs algorithm runs.
1004
1005    /// Sets the source node, from which the Bfs algorithm runs.
1006    /// \param s is the source node.
1007    BfsWizard<TR> &source(Node s)
1008    {
1009      Base::_source=s;
1010      return *this;
1011    }
1012   
1013  };
1014 
1015  ///Function type interface for Bfs algorithm.
1016
1017  /// \ingroup flowalgs
1018  ///Function type interface for Bfs algorithm.
1019  ///
1020  ///This function also has several
1021  ///\ref named-templ-func-param "named parameters",
1022  ///they are declared as the members of class \ref BfsWizard.
1023  ///The following
1024  ///example shows how to use these parameters.
1025  ///\code
1026  ///  bfs(g,source).predMap(preds).run();
1027  ///\endcode
1028  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1029  ///to the end of the parameter list.
1030  ///\sa BfsWizard
1031  ///\sa Bfs
1032  template<class GR>
1033  BfsWizard<BfsWizardBase<GR> >
1034  bfs(const GR &g,typename GR::Node s=INVALID)
1035  {
1036    return BfsWizard<BfsWizardBase<GR> >(g,s);
1037  }
1038
1039} //END OF NAMESPACE LEMON
1040
1041#endif
1042
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