COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/bfs.h

Last change on this file was 2611:b526b87d8c2f, checked in by Balazs Dezso, 11 years ago

Fixing bug in named parameters (Back port bug fix of ticket #95)

File size: 47.8 KB
Line 
1/* -*- C++ -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library
4 *
5 * Copyright (C) 2003-2008
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19#ifndef LEMON_BFS_H
20#define LEMON_BFS_H
21
22///\ingroup search
23///\file
24///\brief Bfs algorithm.
25
26#include <lemon/list_graph.h>
27#include <lemon/graph_utils.h>
28#include <lemon/bits/path_dump.h>
29#include <lemon/bits/invalid.h>
30#include <lemon/error.h>
31#include <lemon/maps.h>
32
33namespace lemon {
34
35
36 
37  ///Default traits class of Bfs class.
38
39  ///Default traits class of Bfs class.
40  ///\param GR Graph type.
41  template<class GR>
42  struct BfsDefaultTraits
43  {
44    ///The graph type the algorithm runs on.
45    typedef GR Graph;
46    ///\brief The type of the map that stores the last
47    ///edges of the shortest paths.
48    ///
49    ///The type of the map that stores the last
50    ///edges of the shortest paths.
51    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
52    ///
53    typedef typename Graph::template NodeMap<typename GR::Edge> PredMap;
54    ///Instantiates a PredMap.
55 
56    ///This function instantiates a \ref PredMap.
57    ///\param G is the graph, to which we would like to define the PredMap.
58    ///\todo The graph alone may be insufficient to initialize
59    static PredMap *createPredMap(const GR &G)
60    {
61      return new PredMap(G);
62    }
63    ///The type of the map that indicates which nodes are processed.
64 
65    ///The type of the map that indicates which nodes are processed.
66    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
67    ///\todo named parameter to set this type, function to read and write.
68    typedef NullMap<typename Graph::Node,bool> ProcessedMap;
69    ///Instantiates a ProcessedMap.
70 
71    ///This function instantiates a \ref ProcessedMap.
72    ///\param g is the graph, to which
73    ///we would like to define the \ref ProcessedMap
74#ifdef DOXYGEN
75    static ProcessedMap *createProcessedMap(const GR &g)
76#else
77    static ProcessedMap *createProcessedMap(const GR &)
78#endif
79    {
80      return new ProcessedMap();
81    }
82    ///The type of the map that indicates which nodes are reached.
83 
84    ///The type of the map that indicates which nodes are reached.
85    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
86    ///\todo named parameter to set this type, function to read and write.
87    typedef typename Graph::template NodeMap<bool> ReachedMap;
88    ///Instantiates a ReachedMap.
89 
90    ///This function instantiates a \ref ReachedMap.
91    ///\param G is the graph, to which
92    ///we would like to define the \ref ReachedMap.
93    static ReachedMap *createReachedMap(const GR &G)
94    {
95      return new ReachedMap(G);
96    }
97    ///The type of the map that stores the dists of the nodes.
98 
99    ///The type of the map that stores the dists of the nodes.
100    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
101    ///
102    typedef typename Graph::template NodeMap<int> DistMap;
103    ///Instantiates a DistMap.
104 
105    ///This function instantiates a \ref DistMap.
106    ///\param G is the graph, to which we would like to define the \ref DistMap
107    static DistMap *createDistMap(const GR &G)
108    {
109      return new DistMap(G);
110    }
111  };
112 
113  ///%BFS algorithm class.
114 
115  ///\ingroup search
116  ///This class provides an efficient implementation of the %BFS algorithm.
117  ///
118  ///\param GR The graph type the algorithm runs on. The default value is
119  ///\ref ListGraph. The value of GR is not used directly by Bfs, it
120  ///is only passed to \ref BfsDefaultTraits.
121  ///\param TR Traits class to set various data types used by the algorithm.
122  ///The default traits class is
123  ///\ref BfsDefaultTraits "BfsDefaultTraits<GR>".
124  ///See \ref BfsDefaultTraits for the documentation of
125  ///a Bfs traits class.
126  ///
127  ///\author Alpar Juttner
128
129#ifdef DOXYGEN
130  template <typename GR,
131            typename TR>
132#else
133  template <typename GR=ListGraph,
134            typename TR=BfsDefaultTraits<GR> >
135#endif
136  class Bfs {
137  public:
138    /**
139     * \brief \ref Exception for uninitialized parameters.
140     *
141     * This error represents problems in the initialization
142     * of the parameters of the algorithms.
143     */
144    class UninitializedParameter : public lemon::UninitializedParameter {
145    public:
146      virtual const char* what() const throw() {
147        return "lemon::Bfs::UninitializedParameter";
148      }
149    };
150
151    typedef TR Traits;
152    ///The type of the underlying graph.
153    typedef typename TR::Graph Graph;
154   
155    ///\brief The type of the map that stores the last
156    ///edges of the shortest paths.
157    typedef typename TR::PredMap PredMap;
158    ///The type of the map indicating which nodes are reached.
159    typedef typename TR::ReachedMap ReachedMap;
160    ///The type of the map indicating which nodes are processed.
161    typedef typename TR::ProcessedMap ProcessedMap;
162    ///The type of the map that stores the dists of the nodes.
163    typedef typename TR::DistMap DistMap;
164  private:
165
166    typedef typename Graph::Node Node;
167    typedef typename Graph::NodeIt NodeIt;
168    typedef typename Graph::Edge Edge;
169    typedef typename Graph::OutEdgeIt OutEdgeIt;
170
171    /// Pointer to the underlying graph.
172    const Graph *G;
173    ///Pointer to the map of predecessors edges.
174    PredMap *_pred;
175    ///Indicates if \ref _pred is locally allocated (\c true) or not.
176    bool local_pred;
177    ///Pointer to the map of distances.
178    DistMap *_dist;
179    ///Indicates if \ref _dist is locally allocated (\c true) or not.
180    bool local_dist;
181    ///Pointer to the map of reached status of the nodes.
182    ReachedMap *_reached;
183    ///Indicates if \ref _reached is locally allocated (\c true) or not.
184    bool local_reached;
185    ///Pointer to the map of processed status of the nodes.
186    ProcessedMap *_processed;
187    ///Indicates if \ref _processed is locally allocated (\c true) or not.
188    bool local_processed;
189
190    std::vector<typename Graph::Node> _queue;
191    int _queue_head,_queue_tail,_queue_next_dist;
192    int _curr_dist;
193
194    ///Creates the maps if necessary.
195   
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 &)
233      {
234        throw UninitializedParameter();
235      }
236    };
237    ///\brief \ref named-templ-param "Named parameter" for setting
238    ///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    ///\brief \ref named-templ-param "Named parameter" for setting
256    ///DistMap type
257    ///
258    ///\ref named-templ-param "Named parameter" for setting DistMap type
259    ///
260    template <class T>
261    struct DefDistMap : public Bfs< Graph, DefDistMapTraits<T> > {
262      typedef Bfs< Graph, DefDistMapTraits<T> > Create;
263    };
264   
265    template <class T>
266    struct DefReachedMapTraits : public Traits {
267      typedef T ReachedMap;
268      static ReachedMap *createReachedMap(const Graph &)
269      {
270        throw UninitializedParameter();
271      }
272    };
273    ///\brief \ref named-templ-param "Named parameter" for setting
274    ///ReachedMap type
275    ///
276    ///\ref named-templ-param "Named parameter" for setting ReachedMap type
277    ///
278    template <class T>
279    struct DefReachedMap : public Bfs< Graph, DefReachedMapTraits<T> > {
280      typedef Bfs< Graph, DefReachedMapTraits<T> > Create;
281    };
282   
283    template <class T>
284    struct DefProcessedMapTraits : public Traits {
285      typedef T ProcessedMap;
286      static ProcessedMap *createProcessedMap(const Graph &)
287      {
288        throw UninitializedParameter();
289      }
290    };
291    ///\brief \ref named-templ-param "Named parameter" for setting
292    ///ProcessedMap type
293    ///
294    ///\ref named-templ-param "Named parameter" for setting ProcessedMap type
295    ///
296    template <class T>
297    struct DefProcessedMap : public Bfs< Graph, DefProcessedMapTraits<T> > {
298      typedef Bfs< Graph, DefProcessedMapTraits<T> > Create;
299    };
300   
301    struct DefGraphProcessedMapTraits : public Traits {
302      typedef typename Graph::template NodeMap<bool> ProcessedMap;
303      static ProcessedMap *createProcessedMap(const Graph &G)
304      {
305        return new ProcessedMap(G);
306      }
307    };
308    ///\brief \ref named-templ-param "Named parameter"
309    ///for setting the ProcessedMap type to be Graph::NodeMap<bool>.
310    ///
311    ///\ref named-templ-param "Named parameter"
312    ///for setting the ProcessedMap type to be Graph::NodeMap<bool>.
313    ///If you don't set it explicitly, it will be automatically allocated.
314    template <class T>
315    struct DefProcessedMapToBeDefaultMap :
316      public Bfs< Graph, DefGraphProcessedMapTraits> {
317      typedef Bfs< Graph, DefGraphProcessedMapTraits> Create;
318    };
319   
320    ///@}
321
322  public:     
323   
324    ///Constructor.
325   
326    ///\param _G the graph the algorithm will run on.
327    ///
328    Bfs(const Graph& _G) :
329      G(&_G),
330      _pred(NULL), local_pred(false),
331      _dist(NULL), local_dist(false),
332      _reached(NULL), local_reached(false),
333      _processed(NULL), local_processed(false)
334    { }
335   
336    ///Destructor.
337    ~Bfs()
338    {
339      if(local_pred) delete _pred;
340      if(local_dist) delete _dist;
341      if(local_reached) delete _reached;
342      if(local_processed) delete _processed;
343    }
344
345    ///Sets the map storing the predecessor edges.
346
347    ///Sets the map storing the predecessor edges.
348    ///If you don't use this function before calling \ref run(),
349    ///it will allocate one. The destructor deallocates this
350    ///automatically allocated map, of course.
351    ///\return <tt> (*this) </tt>
352    Bfs &predMap(PredMap &m)
353    {
354      if(local_pred) {
355        delete _pred;
356        local_pred=false;
357      }
358      _pred = &m;
359      return *this;
360    }
361
362    ///Sets the map indicating the reached nodes.
363
364    ///Sets the map indicating the reached nodes.
365    ///If you don't use this function before calling \ref run(),
366    ///it will allocate one. The destructor deallocates this
367    ///automatically allocated map, of course.
368    ///\return <tt> (*this) </tt>
369    Bfs &reachedMap(ReachedMap &m)
370    {
371      if(local_reached) {
372        delete _reached;
373        local_reached=false;
374      }
375      _reached = &m;
376      return *this;
377    }
378
379    ///Sets the map indicating the processed nodes.
380
381    ///Sets the map indicating the processed nodes.
382    ///If you don't use this function before calling \ref run(),
383    ///it will allocate one. The destructor deallocates this
384    ///automatically allocated map, of course.
385    ///\return <tt> (*this) </tt>
386    Bfs &processedMap(ProcessedMap &m)
387    {
388      if(local_processed) {
389        delete _processed;
390        local_processed=false;
391      }
392      _processed = &m;
393      return *this;
394    }
395
396    ///Sets the map storing the distances calculated by the algorithm.
397
398    ///Sets the map storing the distances calculated by the algorithm.
399    ///If you don't use this function before calling \ref run(),
400    ///it will allocate one. The destructor deallocates this
401    ///automatically allocated map, of course.
402    ///\return <tt> (*this) </tt>
403    Bfs &distMap(DistMap &m)
404    {
405      if(local_dist) {
406        delete _dist;
407        local_dist=false;
408      }
409      _dist = &m;
410      return *this;
411    }
412
413  public:
414    ///\name Execution control
415    ///The simplest way to execute the algorithm is to use
416    ///one of the member functions called \c run(...).
417    ///\n
418    ///If you need more control on the execution,
419    ///first you must call \ref init(), then you can add several source nodes
420    ///with \ref addSource().
421    ///Finally \ref start() will perform the actual path
422    ///computation.
423
424    ///@{
425
426    ///\brief Initializes the internal data structures.
427    ///
428    ///Initializes the internal data structures.
429    ///
430    void init()
431    {
432      create_maps();
433      _queue.resize(countNodes(*G));
434      _queue_head=_queue_tail=0;
435      _curr_dist=1;
436      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
437        _pred->set(u,INVALID);
438        _reached->set(u,false);
439        _processed->set(u,false);
440      }
441    }
442   
443    ///Adds a new source node.
444
445    ///Adds a new source node to the set of nodes to be processed.
446    ///
447    void addSource(Node s)
448    {
449      if(!(*_reached)[s])
450        {
451          _reached->set(s,true);
452          _pred->set(s,INVALID);
453          _dist->set(s,0);
454          _queue[_queue_head++]=s;
455          _queue_next_dist=_queue_head;
456        }
457    }
458   
459    ///Processes the next node.
460
461    ///Processes the next node.
462    ///
463    ///\return The processed node.
464    ///
465    ///\warning The queue must not be empty!
466    Node processNextNode()
467    {
468      if(_queue_tail==_queue_next_dist) {
469        _curr_dist++;
470        _queue_next_dist=_queue_head;
471      }
472      Node n=_queue[_queue_tail++];
473      _processed->set(n,true);
474      Node m;
475      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
476        if(!(*_reached)[m=G->target(e)]) {
477          _queue[_queue_head++]=m;
478          _reached->set(m,true);
479          _pred->set(m,e);
480          _dist->set(m,_curr_dist);
481        }
482      return n;
483    }
484
485    ///Processes the next node.
486
487    ///Processes the next node. And checks that the given target node
488    ///is reached. If the target node is reachable from the processed
489    ///node then the reached parameter will be set true. The reached
490    ///parameter should be initially false.
491    ///
492    ///\param target The target node.
493    ///\retval reach Indicates that the target node is reached.
494    ///\return The processed node.
495    ///
496    ///\warning The queue must not be empty!
497    Node processNextNode(Node target, bool& reach)
498    {
499      if(_queue_tail==_queue_next_dist) {
500        _curr_dist++;
501        _queue_next_dist=_queue_head;
502      }
503      Node n=_queue[_queue_tail++];
504      _processed->set(n,true);
505      Node m;
506      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
507        if(!(*_reached)[m=G->target(e)]) {
508          _queue[_queue_head++]=m;
509          _reached->set(m,true);
510          _pred->set(m,e);
511          _dist->set(m,_curr_dist);
512          reach = reach || (target == m);
513        }
514      return n;
515    }
516
517    ///Processes the next node.
518
519    ///Processes the next node. And checks that at least one of
520    ///reached node has true value in the \c nm node map. If one node
521    ///with true value is reachable from the processed node then the
522    ///rnode parameter will be set to the first of such nodes.
523    ///
524    ///\param nm The node map of possible targets.
525    ///\retval rnode The reached target node.
526    ///\return The processed node.
527    ///
528    ///\warning The queue must not be empty!
529    template<class NM>
530    Node processNextNode(const NM& nm, Node& rnode)
531    {
532      if(_queue_tail==_queue_next_dist) {
533        _curr_dist++;
534        _queue_next_dist=_queue_head;
535      }
536      Node n=_queue[_queue_tail++];
537      _processed->set(n,true);
538      Node m;
539      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
540        if(!(*_reached)[m=G->target(e)]) {
541          _queue[_queue_head++]=m;
542          _reached->set(m,true);
543          _pred->set(m,e);
544          _dist->set(m,_curr_dist);
545          if (nm[m] && rnode == INVALID) rnode = m;
546        }
547      return n;
548    }
549     
550    ///Next node to be processed.
551
552    ///Next node to be processed.
553    ///
554    ///\return The next node to be processed or INVALID if the queue is
555    /// empty.
556    Node nextNode()
557    {
558      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
559    }
560 
561    ///\brief Returns \c false if there are nodes
562    ///to be processed in the queue
563    ///
564    ///Returns \c false if there are nodes
565    ///to be processed in the queue
566    bool emptyQueue() { return _queue_tail==_queue_head; }
567    ///Returns the number of the nodes to be processed.
568   
569    ///Returns the number of the nodes to be processed in the queue.
570    int queueSize() { return _queue_head-_queue_tail; }
571   
572    ///Executes the algorithm.
573
574    ///Executes the algorithm.
575    ///
576    ///\pre init() must be called and at least one node should be added
577    ///with addSource() before using this function.
578    ///
579    ///This method runs the %BFS algorithm from the root node(s)
580    ///in order to
581    ///compute the
582    ///shortest path to each node. The algorithm computes
583    ///- The shortest path tree.
584    ///- The distance of each node from the root(s).
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 compute the shortest path to \c dest.
599    ///The algorithm computes
600    ///- The shortest path to \c  dest.
601    ///- The distance of \c dest from the root(s).
602    void start(Node dest)
603    {
604      bool reach = false;
605      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
606    }
607   
608    ///Executes the algorithm until a condition is met.
609
610    ///Executes the algorithm until a condition is met.
611    ///
612    ///\pre init() must be called and at least one node should be added
613    ///with addSource() before using this function.
614    ///
615    ///\param nm must be a bool (or convertible) node map. The
616    ///algorithm will stop when it reaches a node \c v with
617    /// <tt>nm[v]</tt> true.
618    ///
619    ///\return The reached node \c v with <tt>nm[v]</tt> true or
620    ///\c INVALID if no such node was found.
621    template<class NM>
622    Node start(const NM &nm)
623    {
624      Node rnode = INVALID;
625      while ( !emptyQueue() && rnode == INVALID ) {
626        processNextNode(nm, rnode);
627      }
628      return rnode;
629    }
630   
631    ///Runs %BFS algorithm from node \c s.
632   
633    ///This method runs the %BFS algorithm from a root node \c s
634    ///in order to
635    ///compute the
636    ///shortest path to each node. The algorithm computes
637    ///- The shortest path tree.
638    ///- The distance of each node from the root.
639    ///
640    ///\note b.run(s) is just a shortcut of the following code.
641    ///\code
642    ///  b.init();
643    ///  b.addSource(s);
644    ///  b.start();
645    ///\endcode
646    void run(Node s) {
647      init();
648      addSource(s);
649      start();
650    }
651   
652    ///Finds the shortest path between \c s and \c t.
653   
654    ///Finds the shortest path between \c s and \c t.
655    ///
656    ///\return The length of the shortest s---t path if there exists one,
657    ///0 otherwise.
658    ///\note Apart from the return value, b.run(s) is
659    ///just a shortcut of the following code.
660    ///\code
661    ///  b.init();
662    ///  b.addSource(s);
663    ///  b.start(t);
664    ///\endcode
665    int run(Node s,Node t) {
666      init();
667      addSource(s);
668      start(t);
669      return reached(t) ? _curr_dist : 0;
670    }
671   
672    ///@}
673
674    ///\name Query Functions
675    ///The result of the %BFS algorithm can be obtained using these
676    ///functions.\n
677    ///Before the use of these functions,
678    ///either run() or start() must be calleb.
679   
680    ///@{
681
682    typedef PredMapPath<Graph, PredMap> Path;
683
684    ///Gives back the shortest path.
685   
686    ///Gives back the shortest path.
687    ///\pre The \c t should be reachable from the source.
688    Path path(Node t)
689    {
690      return Path(*G, *_pred, t);
691    }
692
693    ///The distance of a node from the root(s).
694
695    ///Returns the distance of a node from the root(s).
696    ///\pre \ref run() must be called before using this function.
697    ///\warning If node \c v in unreachable from the root(s) the return value
698    ///of this function is undefined.
699    int dist(Node v) const { return (*_dist)[v]; }
700
701    ///Returns the 'previous edge' of the shortest path tree.
702
703    ///For a node \c v it returns the 'previous edge'
704    ///of the shortest path tree,
705    ///i.e. it returns the last edge of a shortest path from the root(s) to \c
706    ///v. It is \ref INVALID
707    ///if \c v is unreachable from the root(s) or \c v is a root. The
708    ///shortest path tree used here is equal to the shortest path tree used in
709    ///\ref predNode().
710    ///\pre Either \ref run() or \ref start() must be called before using
711    ///this function.
712    Edge predEdge(Node v) const { return (*_pred)[v];}
713
714    ///Returns the 'previous node' of the shortest path tree.
715
716    ///For a node \c v it returns the 'previous node'
717    ///of the shortest path tree,
718    ///i.e. it returns the last but one node from a shortest path from the
719    ///root(a) to \c /v.
720    ///It is INVALID if \c v is unreachable from the root(s) or
721    ///if \c v itself a root.
722    ///The shortest path tree used here is equal to the shortest path
723    ///tree used in \ref predEdge().
724    ///\pre Either \ref run() or \ref start() must be called before
725    ///using this function.
726    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
727                                  G->source((*_pred)[v]); }
728   
729    ///Returns a reference to the NodeMap of distances.
730
731    ///Returns a reference to the NodeMap of distances.
732    ///\pre Either \ref run() or \ref init() must
733    ///be called before using this function.
734    const DistMap &distMap() const { return *_dist;}
735 
736    ///Returns a reference to the shortest path tree map.
737
738    ///Returns a reference to the NodeMap of the edges of the
739    ///shortest path tree.
740    ///\pre Either \ref run() or \ref init()
741    ///must be called before using this function.
742    const PredMap &predMap() const { return *_pred;}
743 
744    ///Checks if a node is reachable from the root.
745
746    ///Returns \c true if \c v is reachable from the root.
747    ///\warning The source nodes are indicated as unreached.
748    ///\pre Either \ref run() or \ref start()
749    ///must be called before using this function.
750    ///
751    bool reached(Node v) { return (*_reached)[v]; }
752   
753    ///@}
754  };
755
756  ///Default traits class of Bfs function.
757
758  ///Default traits class of Bfs function.
759  ///\param GR Graph type.
760  template<class GR>
761  struct BfsWizardDefaultTraits
762  {
763    ///The graph type the algorithm runs on.
764    typedef GR Graph;
765    ///\brief The type of the map that stores the last
766    ///edges of the shortest paths.
767    ///
768    ///The type of the map that stores the last
769    ///edges of the shortest paths.
770    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
771    ///
772    typedef NullMap<typename Graph::Node,typename GR::Edge> PredMap;
773    ///Instantiates a PredMap.
774 
775    ///This function instantiates a \ref PredMap.
776    ///\param g is the graph, to which we would like to define the PredMap.
777    ///\todo The graph alone may be insufficient to initialize
778#ifdef DOXYGEN
779    static PredMap *createPredMap(const GR &g)
780#else
781    static PredMap *createPredMap(const GR &)
782#endif
783    {
784      return new PredMap();
785    }
786
787    ///The type of the map that indicates which nodes are processed.
788 
789    ///The type of the map that indicates which nodes are processed.
790    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
791    ///\todo named parameter to set this type, function to read and write.
792    typedef NullMap<typename Graph::Node,bool> ProcessedMap;
793    ///Instantiates a ProcessedMap.
794 
795    ///This function instantiates a \ref ProcessedMap.
796    ///\param g is the graph, to which
797    ///we would like to define the \ref ProcessedMap
798#ifdef DOXYGEN
799    static ProcessedMap *createProcessedMap(const GR &g)
800#else
801    static ProcessedMap *createProcessedMap(const GR &)
802#endif
803    {
804      return new ProcessedMap();
805    }
806    ///The type of the map that indicates which nodes are reached.
807 
808    ///The type of the map that indicates which nodes are reached.
809    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
810    ///\todo named parameter to set this type, function to read and write.
811    typedef typename Graph::template NodeMap<bool> ReachedMap;
812    ///Instantiates a ReachedMap.
813 
814    ///This function instantiates a \ref ReachedMap.
815    ///\param G is the graph, to which
816    ///we would like to define the \ref ReachedMap.
817    static ReachedMap *createReachedMap(const GR &G)
818    {
819      return new ReachedMap(G);
820    }
821    ///The type of the map that stores the dists of the nodes.
822 
823    ///The type of the map that stores the dists of the nodes.
824    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
825    ///
826    typedef NullMap<typename Graph::Node,int> DistMap;
827    ///Instantiates a DistMap.
828 
829    ///This function instantiates a \ref DistMap.
830    ///\param g is the graph, to which we would like to define the \ref DistMap
831#ifdef DOXYGEN
832    static DistMap *createDistMap(const GR &g)
833#else
834    static DistMap *createDistMap(const GR &)
835#endif
836    {
837      return new DistMap();
838    }
839  };
840 
841  /// Default traits used by \ref BfsWizard
842
843  /// To make it easier to use Bfs algorithm
844  ///we have created a wizard class.
845  /// This \ref BfsWizard class needs default traits,
846  ///as well as the \ref Bfs class.
847  /// The \ref BfsWizardBase is a class to be the default traits of the
848  /// \ref BfsWizard class.
849  template<class GR>
850  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
851  {
852
853    typedef BfsWizardDefaultTraits<GR> Base;
854  protected:
855    /// Type of the nodes in the graph.
856    typedef typename Base::Graph::Node Node;
857
858    /// Pointer to the underlying graph.
859    void *_g;
860    ///Pointer to the map of reached nodes.
861    void *_reached;
862    ///Pointer to the map of processed nodes.
863    void *_processed;
864    ///Pointer to the map of predecessors edges.
865    void *_pred;
866    ///Pointer to the map of distances.
867    void *_dist;
868    ///Pointer to the source node.
869    Node _source;
870   
871    public:
872    /// Constructor.
873   
874    /// This constructor does not require parameters, therefore it initiates
875    /// all of the attributes to default values (0, INVALID).
876    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
877                           _dist(0), _source(INVALID) {}
878
879    /// Constructor.
880   
881    /// This constructor requires some parameters,
882    /// listed in the parameters list.
883    /// Others are initiated to 0.
884    /// \param g is the initial value of  \ref _g
885    /// \param s is the initial value of  \ref _source
886    BfsWizardBase(const GR &g, Node s=INVALID) :
887      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
888      _reached(0), _processed(0), _pred(0), _dist(0), _source(s) {}
889
890  };
891 
892  /// A class to make the usage of Bfs algorithm easier
893
894  /// This class is created to make it easier to use Bfs algorithm.
895  /// It uses the functions and features of the plain \ref Bfs,
896  /// but it is much simpler to use it.
897  ///
898  /// Simplicity means that the way to change the types defined
899  /// in the traits class is based on functions that returns the new class
900  /// and not on templatable built-in classes.
901  /// When using the plain \ref Bfs
902  /// the new class with the modified type comes from
903  /// the original class by using the ::
904  /// operator. In the case of \ref BfsWizard only
905  /// a function have to be called and it will
906  /// return the needed class.
907  ///
908  /// It does not have own \ref run method. When its \ref run method is called
909  /// it initiates a plain \ref Bfs class, and calls the \ref Bfs::run
910  /// method of it.
911  template<class TR>
912  class BfsWizard : public TR
913  {
914    typedef TR Base;
915
916    ///The type of the underlying graph.
917    typedef typename TR::Graph Graph;
918    //\e
919    typedef typename Graph::Node Node;
920    //\e
921    typedef typename Graph::NodeIt NodeIt;
922    //\e
923    typedef typename Graph::Edge Edge;
924    //\e
925    typedef typename Graph::OutEdgeIt OutEdgeIt;
926   
927    ///\brief The type of the map that stores
928    ///the reached nodes
929    typedef typename TR::ReachedMap ReachedMap;
930    ///\brief The type of the map that stores
931    ///the processed nodes
932    typedef typename TR::ProcessedMap ProcessedMap;
933    ///\brief The type of the map that stores the last
934    ///edges of the shortest paths.
935    typedef typename TR::PredMap PredMap;
936    ///The type of the map that stores the dists of the nodes.
937    typedef typename TR::DistMap DistMap;
938
939  public:
940    /// Constructor.
941    BfsWizard() : TR() {}
942
943    /// Constructor that requires parameters.
944
945    /// Constructor that requires parameters.
946    /// These parameters will be the default values for the traits class.
947    BfsWizard(const Graph &g, Node s=INVALID) :
948      TR(g,s) {}
949
950    ///Copy constructor
951    BfsWizard(const TR &b) : TR(b) {}
952
953    ~BfsWizard() {}
954
955    ///Runs Bfs algorithm from a given node.
956   
957    ///Runs Bfs algorithm from a given node.
958    ///The node can be given by the \ref source function.
959    void run()
960    {
961      if(Base::_source==INVALID) throw UninitializedParameter();
962      Bfs<Graph,TR> alg(*reinterpret_cast<const Graph*>(Base::_g));
963      if(Base::_reached)
964        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
965      if(Base::_processed)
966        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
967      if(Base::_pred)
968        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
969      if(Base::_dist)
970        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
971      alg.run(Base::_source);
972    }
973
974    ///Runs Bfs algorithm from the given node.
975
976    ///Runs Bfs algorithm from the given node.
977    ///\param s is the given source.
978    void run(Node s)
979    {
980      Base::_source=s;
981      run();
982    }
983
984    template<class T>
985    struct DefPredMapBase : public Base {
986      typedef T PredMap;
987      static PredMap *createPredMap(const Graph &) { return 0; };
988      DefPredMapBase(const TR &b) : TR(b) {}
989    };
990   
991    ///\brief \ref named-templ-param "Named parameter"
992    ///function for setting PredMap
993    ///
994    /// \ref named-templ-param "Named parameter"
995    ///function for setting PredMap
996    ///
997    template<class T>
998    BfsWizard<DefPredMapBase<T> > predMap(const T &t)
999    {
1000      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1001      return BfsWizard<DefPredMapBase<T> >(*this);
1002    }
1003   
1004 
1005    template<class T>
1006    struct DefReachedMapBase : public Base {
1007      typedef T ReachedMap;
1008      static ReachedMap *createReachedMap(const Graph &) { return 0; };
1009      DefReachedMapBase(const TR &b) : TR(b) {}
1010    };
1011   
1012    ///\brief \ref named-templ-param "Named parameter"
1013    ///function for setting ReachedMap
1014    ///
1015    /// \ref named-templ-param "Named parameter"
1016    ///function for setting ReachedMap
1017    ///
1018    template<class T>
1019    BfsWizard<DefReachedMapBase<T> > reachedMap(const T &t)
1020    {
1021      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
1022      return BfsWizard<DefReachedMapBase<T> >(*this);
1023    }
1024   
1025
1026    template<class T>
1027    struct DefProcessedMapBase : public Base {
1028      typedef T ProcessedMap;
1029      static ProcessedMap *createProcessedMap(const Graph &) { return 0; };
1030      DefProcessedMapBase(const TR &b) : TR(b) {}
1031    };
1032   
1033    ///\brief \ref named-templ-param "Named parameter"
1034    ///function for setting ProcessedMap
1035    ///
1036    /// \ref named-templ-param "Named parameter"
1037    ///function for setting ProcessedMap
1038    ///
1039    template<class T>
1040    BfsWizard<DefProcessedMapBase<T> > processedMap(const T &t)
1041    {
1042      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
1043      return BfsWizard<DefProcessedMapBase<T> >(*this);
1044    }
1045   
1046   
1047    template<class T>
1048    struct DefDistMapBase : public Base {
1049      typedef T DistMap;
1050      static DistMap *createDistMap(const Graph &) { return 0; };
1051      DefDistMapBase(const TR &b) : TR(b) {}
1052    };
1053   
1054    ///\brief \ref named-templ-param "Named parameter"
1055    ///function for setting DistMap type
1056    ///
1057    /// \ref named-templ-param "Named parameter"
1058    ///function for setting DistMap type
1059    ///
1060    template<class T>
1061    BfsWizard<DefDistMapBase<T> > distMap(const T &t)
1062    {
1063      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1064      return BfsWizard<DefDistMapBase<T> >(*this);
1065    }
1066   
1067    /// Sets the source node, from which the Bfs algorithm runs.
1068
1069    /// Sets the source node, from which the Bfs algorithm runs.
1070    /// \param s is the source node.
1071    BfsWizard<TR> &source(Node s)
1072    {
1073      Base::_source=s;
1074      return *this;
1075    }
1076   
1077  };
1078 
1079  ///Function type interface for Bfs algorithm.
1080
1081  /// \ingroup search
1082  ///Function type interface for Bfs algorithm.
1083  ///
1084  ///This function also has several
1085  ///\ref named-templ-func-param "named parameters",
1086  ///they are declared as the members of class \ref BfsWizard.
1087  ///The following
1088  ///example shows how to use these parameters.
1089  ///\code
1090  ///  bfs(g,source).predMap(preds).run();
1091  ///\endcode
1092  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1093  ///to the end of the parameter list.
1094  ///\sa BfsWizard
1095  ///\sa Bfs
1096  template<class GR>
1097  BfsWizard<BfsWizardBase<GR> >
1098  bfs(const GR &g,typename GR::Node s=INVALID)
1099  {
1100    return BfsWizard<BfsWizardBase<GR> >(g,s);
1101  }
1102
1103#ifdef DOXYGEN
1104  /// \brief Visitor class for bfs.
1105  /// 
1106  /// This class defines the interface of the BfsVisit events, and
1107  /// it could be the base of a real Visitor class.
1108  template <typename _Graph>
1109  struct BfsVisitor {
1110    typedef _Graph Graph;
1111    typedef typename Graph::Edge Edge;
1112    typedef typename Graph::Node Node;
1113    /// \brief Called when the edge reach a node.
1114    ///
1115    /// It is called when the bfs find an edge which target is not
1116    /// reached yet.
1117    void discover(const Edge& edge) {}
1118    /// \brief Called when the node reached first time.
1119    ///
1120    /// It is Called when the node reached first time.
1121    void reach(const Node& node) {}
1122    /// \brief Called when the edge examined but target of the edge
1123    /// already discovered.
1124    ///
1125    /// It called when the edge examined but the target of the edge
1126    /// already discovered.
1127    void examine(const Edge& edge) {}
1128    /// \brief Called for the source node of the bfs.
1129    ///
1130    /// It is called for the source node of the bfs.
1131    void start(const Node& node) {}
1132    /// \brief Called when the node processed.
1133    ///
1134    /// It is Called when the node processed.
1135    void process(const Node& node) {}
1136  };
1137#else
1138  template <typename _Graph>
1139  struct BfsVisitor {
1140    typedef _Graph Graph;
1141    typedef typename Graph::Edge Edge;
1142    typedef typename Graph::Node Node;
1143    void discover(const Edge&) {}
1144    void reach(const Node&) {}
1145    void examine(const Edge&) {}
1146    void start(const Node&) {}
1147    void process(const Node&) {}
1148
1149    template <typename _Visitor>
1150    struct Constraints {
1151      void constraints() {
1152        Edge edge;
1153        Node node;
1154        visitor.discover(edge);
1155        visitor.reach(node);
1156        visitor.examine(edge);
1157        visitor.start(node);
1158        visitor.process(node);
1159      }
1160      _Visitor& visitor;
1161    };
1162  };
1163#endif
1164
1165  /// \brief Default traits class of BfsVisit class.
1166  ///
1167  /// Default traits class of BfsVisit class.
1168  /// \param _Graph Graph type.
1169  template<class _Graph>
1170  struct BfsVisitDefaultTraits {
1171
1172    /// \brief The graph type the algorithm runs on.
1173    typedef _Graph Graph;
1174
1175    /// \brief The type of the map that indicates which nodes are reached.
1176    ///
1177    /// The type of the map that indicates which nodes are reached.
1178    /// It must meet the \ref concepts::WriteMap "WriteMap" concept.
1179    /// \todo named parameter to set this type, function to read and write.
1180    typedef typename Graph::template NodeMap<bool> ReachedMap;
1181
1182    /// \brief Instantiates a ReachedMap.
1183    ///
1184    /// This function instantiates a \ref ReachedMap.
1185    /// \param graph is the graph, to which
1186    /// we would like to define the \ref ReachedMap.
1187    static ReachedMap *createReachedMap(const Graph &graph) {
1188      return new ReachedMap(graph);
1189    }
1190
1191  };
1192
1193  /// \ingroup search
1194  /// 
1195  /// \brief %BFS Visit algorithm class.
1196  /// 
1197  /// This class provides an efficient implementation of the %BFS algorithm
1198  /// with visitor interface.
1199  ///
1200  /// The %BfsVisit class provides an alternative interface to the Bfs
1201  /// class. It works with callback mechanism, the BfsVisit object calls
1202  /// on every bfs event the \c Visitor class member functions.
1203  ///
1204  /// \param _Graph The graph type the algorithm runs on. The default value is
1205  /// \ref ListGraph. The value of _Graph is not used directly by Bfs, it
1206  /// is only passed to \ref BfsDefaultTraits.
1207  /// \param _Visitor The Visitor object for the algorithm. The
1208  /// \ref BfsVisitor "BfsVisitor<_Graph>" is an empty Visitor which
1209  /// does not observe the Bfs events. If you want to observe the bfs
1210  /// events you should implement your own Visitor class.
1211  /// \param _Traits Traits class to set various data types used by the
1212  /// algorithm. The default traits class is
1213  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<_Graph>".
1214  /// See \ref BfsVisitDefaultTraits for the documentation of
1215  /// a Bfs visit traits class.
1216  ///
1217  /// \author Jacint Szabo, Alpar Juttner and Balazs Dezso
1218#ifdef DOXYGEN
1219  template <typename _Graph, typename _Visitor, typename _Traits>
1220#else
1221  template <typename _Graph = ListGraph,
1222            typename _Visitor = BfsVisitor<_Graph>,
1223            typename _Traits = BfsDefaultTraits<_Graph> >
1224#endif
1225  class BfsVisit {
1226  public:
1227   
1228    /// \brief \ref Exception for uninitialized parameters.
1229    ///
1230    /// This error represents problems in the initialization
1231    /// of the parameters of the algorithms.
1232    class UninitializedParameter : public lemon::UninitializedParameter {
1233    public:
1234      virtual const char* what() const throw()
1235      {
1236        return "lemon::BfsVisit::UninitializedParameter";
1237      }
1238    };
1239
1240    typedef _Traits Traits;
1241
1242    typedef typename Traits::Graph Graph;
1243
1244    typedef _Visitor Visitor;
1245
1246    ///The type of the map indicating which nodes are reached.
1247    typedef typename Traits::ReachedMap ReachedMap;
1248
1249  private:
1250
1251    typedef typename Graph::Node Node;
1252    typedef typename Graph::NodeIt NodeIt;
1253    typedef typename Graph::Edge Edge;
1254    typedef typename Graph::OutEdgeIt OutEdgeIt;
1255
1256    /// Pointer to the underlying graph.
1257    const Graph *_graph;
1258    /// Pointer to the visitor object.
1259    Visitor *_visitor;
1260    ///Pointer to the map of reached status of the nodes.
1261    ReachedMap *_reached;
1262    ///Indicates if \ref _reached is locally allocated (\c true) or not.
1263    bool local_reached;
1264
1265    std::vector<typename Graph::Node> _list;
1266    int _list_front, _list_back;
1267
1268    /// \brief Creates the maps if necessary.
1269    ///
1270    /// Creates the maps if necessary.
1271    void create_maps() {
1272      if(!_reached) {
1273        local_reached = true;
1274        _reached = Traits::createReachedMap(*_graph);
1275      }
1276    }
1277
1278  protected:
1279
1280    BfsVisit() {}
1281   
1282  public:
1283
1284    typedef BfsVisit Create;
1285
1286    /// \name Named template parameters
1287
1288    ///@{
1289    template <class T>
1290    struct DefReachedMapTraits : public Traits {
1291      typedef T ReachedMap;
1292      static ReachedMap *createReachedMap(const Graph &graph) {
1293        throw UninitializedParameter();
1294      }
1295    };
1296    /// \brief \ref named-templ-param "Named parameter" for setting
1297    /// ReachedMap type
1298    ///
1299    /// \ref named-templ-param "Named parameter" for setting ReachedMap type
1300    template <class T>
1301    struct DefReachedMap : public BfsVisit< Graph, Visitor,
1302                                            DefReachedMapTraits<T> > {
1303      typedef BfsVisit< Graph, Visitor, DefReachedMapTraits<T> > Create;
1304    };
1305    ///@}
1306
1307  public:     
1308   
1309    /// \brief Constructor.
1310    ///
1311    /// Constructor.
1312    ///
1313    /// \param graph the graph the algorithm will run on.
1314    /// \param visitor The visitor of the algorithm.
1315    ///
1316    BfsVisit(const Graph& graph, Visitor& visitor)
1317      : _graph(&graph), _visitor(&visitor),
1318        _reached(0), local_reached(false) {}
1319   
1320    /// \brief Destructor.
1321    ///
1322    /// Destructor.
1323    ~BfsVisit() {
1324      if(local_reached) delete _reached;
1325    }
1326
1327    /// \brief Sets the map indicating if a node is reached.
1328    ///
1329    /// Sets the map indicating if a node is reached.
1330    /// If you don't use this function before calling \ref run(),
1331    /// it will allocate one. The destuctor deallocates this
1332    /// automatically allocated map, of course.
1333    /// \return <tt> (*this) </tt>
1334    BfsVisit &reachedMap(ReachedMap &m) {
1335      if(local_reached) {
1336        delete _reached;
1337        local_reached = false;
1338      }
1339      _reached = &m;
1340      return *this;
1341    }
1342
1343  public:
1344    /// \name Execution control
1345    /// The simplest way to execute the algorithm is to use
1346    /// one of the member functions called \c run(...).
1347    /// \n
1348    /// If you need more control on the execution,
1349    /// first you must call \ref init(), then you can adda source node
1350    /// with \ref addSource().
1351    /// Finally \ref start() will perform the actual path
1352    /// computation.
1353
1354    /// @{
1355    /// \brief Initializes the internal data structures.
1356    ///
1357    /// Initializes the internal data structures.
1358    ///
1359    void init() {
1360      create_maps();
1361      _list.resize(countNodes(*_graph));
1362      _list_front = _list_back = -1;
1363      for (NodeIt u(*_graph) ; u != INVALID ; ++u) {
1364        _reached->set(u, false);
1365      }
1366    }
1367   
1368    /// \brief Adds a new source node.
1369    ///
1370    /// Adds a new source node to the set of nodes to be processed.
1371    void addSource(Node s) {
1372      if(!(*_reached)[s]) {
1373          _reached->set(s,true);
1374          _visitor->start(s);
1375          _visitor->reach(s);
1376          _list[++_list_back] = s;
1377        }
1378    }
1379   
1380    /// \brief Processes the next node.
1381    ///
1382    /// Processes the next node.
1383    ///
1384    /// \return The processed node.
1385    ///
1386    /// \pre The queue must not be empty!
1387    Node processNextNode() {
1388      Node n = _list[++_list_front];
1389      _visitor->process(n);
1390      Edge e;
1391      for (_graph->firstOut(e, n); e != INVALID; _graph->nextOut(e)) {
1392        Node m = _graph->target(e);
1393        if (!(*_reached)[m]) {
1394          _visitor->discover(e);
1395          _visitor->reach(m);
1396          _reached->set(m, true);
1397          _list[++_list_back] = m;
1398        } else {
1399          _visitor->examine(e);
1400        }
1401      }
1402      return n;
1403    }
1404
1405    /// \brief Processes the next node.
1406    ///
1407    /// Processes the next node. And checks that the given target node
1408    /// is reached. If the target node is reachable from the processed
1409    /// node then the reached parameter will be set true. The reached
1410    /// parameter should be initially false.
1411    ///
1412    /// \param target The target node.
1413    /// \retval reach Indicates that the target node is reached.
1414    /// \return The processed node.
1415    ///
1416    /// \warning The queue must not be empty!
1417    Node processNextNode(Node target, bool& reach) {
1418      Node n = _list[++_list_front];
1419      _visitor->process(n);
1420      Edge e;
1421      for (_graph->firstOut(e, n); e != INVALID; _graph->nextOut(e)) {
1422        Node m = _graph->target(e);
1423        if (!(*_reached)[m]) {
1424          _visitor->discover(e);
1425          _visitor->reach(m);
1426          _reached->set(m, true);
1427          _list[++_list_back] = m;
1428          reach = reach || (target == m);
1429        } else {
1430          _visitor->examine(e);
1431        }
1432      }
1433      return n;
1434    }
1435
1436    /// \brief Processes the next node.
1437    ///
1438    /// Processes the next node. And checks that at least one of
1439    /// reached node has true value in the \c nm node map. If one node
1440    /// with true value is reachable from the processed node then the
1441    /// rnode parameter will be set to the first of such nodes.
1442    ///
1443    /// \param nm The node map of possible targets.
1444    /// \retval rnode The reached target node.
1445    /// \return The processed node.
1446    ///
1447    /// \warning The queue must not be empty!
1448    template <typename NM>
1449    Node processNextNode(const NM& nm, Node& rnode) {
1450      Node n = _list[++_list_front];
1451      _visitor->process(n);
1452      Edge e;
1453      for (_graph->firstOut(e, n); e != INVALID; _graph->nextOut(e)) {
1454        Node m = _graph->target(e);
1455        if (!(*_reached)[m]) {
1456          _visitor->discover(e);
1457          _visitor->reach(m);
1458          _reached->set(m, true);
1459          _list[++_list_back] = m;
1460          if (nm[m] && rnode == INVALID) rnode = m;
1461        } else {
1462          _visitor->examine(e);
1463        }
1464      }
1465      return n;
1466    }
1467
1468    /// \brief Next node to be processed.
1469    ///
1470    /// Next node to be processed.
1471    ///
1472    /// \return The next node to be processed or INVALID if the stack is
1473    /// empty.
1474    Node nextNode() {
1475      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1476    }
1477
1478    /// \brief Returns \c false if there are nodes
1479    /// to be processed in the queue
1480    ///
1481    /// Returns \c false if there are nodes
1482    /// to be processed in the queue
1483    bool emptyQueue() { return _list_front == _list_back; }
1484
1485    /// \brief Returns the number of the nodes to be processed.
1486    ///
1487    /// Returns the number of the nodes to be processed in the queue.
1488    int queueSize() { return _list_back - _list_front; }
1489   
1490    /// \brief Executes the algorithm.
1491    ///
1492    /// Executes the algorithm.
1493    ///
1494    /// \pre init() must be called and at least one node should be added
1495    /// with addSource() before using this function.
1496    void start() {
1497      while ( !emptyQueue() ) processNextNode();
1498    }
1499   
1500    /// \brief Executes the algorithm until \c dest is reached.
1501    ///
1502    /// Executes the algorithm until \c dest is reached.
1503    ///
1504    /// \pre init() must be called and at least one node should be added
1505    /// with addSource() before using this function.
1506    void start(Node dest) {
1507      bool reach = false;
1508      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
1509    }
1510   
1511    /// \brief Executes the algorithm until a condition is met.
1512    ///
1513    /// Executes the algorithm until a condition is met.
1514    ///
1515    /// \pre init() must be called and at least one node should be added
1516    /// with addSource() before using this function.
1517    ///
1518    ///\param nm must be a bool (or convertible) node map. The
1519    ///algorithm will stop when it reaches a node \c v with
1520    /// <tt>nm[v]</tt> true.
1521    ///
1522    ///\return The reached node \c v with <tt>nm[v]</tt> true or
1523    ///\c INVALID if no such node was found.
1524    template <typename NM>
1525    Node start(const NM &nm) {
1526      Node rnode = INVALID;
1527      while ( !emptyQueue() && rnode == INVALID ) {
1528        processNextNode(nm, rnode);
1529      }
1530      return rnode;
1531    }
1532
1533    /// \brief Runs %BFSVisit algorithm from node \c s.
1534    ///
1535    /// This method runs the %BFS algorithm from a root node \c s.
1536    /// \note b.run(s) is just a shortcut of the following code.
1537    ///\code
1538    ///   b.init();
1539    ///   b.addSource(s);
1540    ///   b.start();
1541    ///\endcode
1542    void run(Node s) {
1543      init();
1544      addSource(s);
1545      start();
1546    }
1547
1548    /// \brief Runs %BFSVisit algorithm to visit all nodes in the graph.
1549    ///   
1550    /// This method runs the %BFS algorithm in order to
1551    /// compute the %BFS path to each node. The algorithm computes
1552    /// - The %BFS tree.
1553    /// - The distance of each node from the root in the %BFS tree.
1554    ///
1555    ///\note b.run() is just a shortcut of the following code.
1556    ///\code
1557    ///  b.init();
1558    ///  for (NodeIt it(graph); it != INVALID; ++it) {
1559    ///    if (!b.reached(it)) {
1560    ///      b.addSource(it);
1561    ///      b.start();
1562    ///    }
1563    ///  }
1564    ///\endcode
1565    void run() {
1566      init();
1567      for (NodeIt it(*_graph); it != INVALID; ++it) {
1568        if (!reached(it)) {
1569          addSource(it);
1570          start();
1571        }
1572      }
1573    }
1574    ///@}
1575
1576    /// \name Query Functions
1577    /// The result of the %BFS algorithm can be obtained using these
1578    /// functions.\n
1579    /// Before the use of these functions,
1580    /// either run() or start() must be called.
1581    ///@{
1582
1583    /// \brief Checks if a node is reachable from the root.
1584    ///
1585    /// Returns \c true if \c v is reachable from the root(s).
1586    /// \warning The source nodes are inditated as unreachable.
1587    /// \pre Either \ref run() or \ref start()
1588    /// must be called before using this function.
1589    ///
1590    bool reached(Node v) { return (*_reached)[v]; }
1591    ///@}
1592  };
1593
1594} //END OF NAMESPACE LEMON
1595
1596#endif
1597
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