COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/bfs.h @ 2443:14abfa02bf42

Last change on this file since 2443:14abfa02bf42 was 2443:14abfa02bf42, checked in by Balazs Dezso, 12 years ago

Patch for retrieving reached/processed node in dijkstra, bfs and dfs

Patch from Peter Kovacs

File size: 47.7 KB
Line 
1/* -*- C++ -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library
4 *
5 * Copyright (C) 2003-2007
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    ///\e
155    typedef typename Graph::Node Node;
156    ///\e
157    typedef typename Graph::NodeIt NodeIt;
158    ///\e
159    typedef typename Graph::Edge Edge;
160    ///\e
161    typedef typename Graph::OutEdgeIt OutEdgeIt;
162   
163    ///\brief The type of the map that stores the last
164    ///edges of the shortest paths.
165    typedef typename TR::PredMap PredMap;
166    ///The type of the map indicating which nodes are reached.
167    typedef typename TR::ReachedMap ReachedMap;
168    ///The type of the map indicating which nodes are processed.
169    typedef typename TR::ProcessedMap ProcessedMap;
170    ///The type of the map that stores the dists of the nodes.
171    typedef typename TR::DistMap DistMap;
172  private:
173    /// Pointer to the underlying graph.
174    const Graph *G;
175    ///Pointer to the map of predecessors edges.
176    PredMap *_pred;
177    ///Indicates if \ref _pred is locally allocated (\c true) or not.
178    bool local_pred;
179    ///Pointer to the map of distances.
180    DistMap *_dist;
181    ///Indicates if \ref _dist is locally allocated (\c true) or not.
182    bool local_dist;
183    ///Pointer to the map of reached status of the nodes.
184    ReachedMap *_reached;
185    ///Indicates if \ref _reached is locally allocated (\c true) or not.
186    bool local_reached;
187    ///Pointer to the map of processed status of the nodes.
188    ProcessedMap *_processed;
189    ///Indicates if \ref _processed is locally allocated (\c true) or not.
190    bool local_processed;
191
192    std::vector<typename Graph::Node> _queue;
193    int _queue_head,_queue_tail,_queue_next_dist;
194    int _curr_dist;
195
196    ///Creates the maps if necessary.
197   
198    ///\todo Better memory allocation (instead of new).
199    void create_maps()
200    {
201      if(!_pred) {
202        local_pred = true;
203        _pred = Traits::createPredMap(*G);
204      }
205      if(!_dist) {
206        local_dist = true;
207        _dist = Traits::createDistMap(*G);
208      }
209      if(!_reached) {
210        local_reached = true;
211        _reached = Traits::createReachedMap(*G);
212      }
213      if(!_processed) {
214        local_processed = true;
215        _processed = Traits::createProcessedMap(*G);
216      }
217    }
218
219  protected:
220   
221    Bfs() {}
222   
223  public:
224 
225    typedef Bfs Create;
226
227    ///\name Named template parameters
228
229    ///@{
230
231    template <class T>
232    struct DefPredMapTraits : public Traits {
233      typedef T PredMap;
234      static PredMap *createPredMap(const Graph &)
235      {
236        throw UninitializedParameter();
237      }
238    };
239    ///\ref named-templ-param "Named parameter" for setting PredMap type
240
241    ///\ref named-templ-param "Named parameter" for setting PredMap type
242    ///
243    template <class T>
244    struct DefPredMap : public Bfs< Graph, DefPredMapTraits<T> > {
245      typedef Bfs< Graph, DefPredMapTraits<T> > Create;
246    };
247   
248    template <class T>
249    struct DefDistMapTraits : public Traits {
250      typedef T DistMap;
251      static DistMap *createDistMap(const Graph &)
252      {
253        throw UninitializedParameter();
254      }
255    };
256    ///\ref named-templ-param "Named parameter" for setting 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    ///\ref named-templ-param "Named parameter" for setting ReachedMap type
274
275    ///\ref named-templ-param "Named parameter" for setting ReachedMap type
276    ///
277    template <class T>
278    struct DefReachedMap : public Bfs< Graph, DefReachedMapTraits<T> > {
279      typedef Bfs< Graph, DefReachedMapTraits<T> > Create;
280    };
281   
282    template <class T>
283    struct DefProcessedMapTraits : public Traits {
284      typedef T ProcessedMap;
285      static ProcessedMap *createProcessedMap(const Graph &)
286      {
287        throw UninitializedParameter();
288      }
289    };
290    ///\ref named-templ-param "Named parameter" for setting ProcessedMap type
291
292    ///\ref named-templ-param "Named parameter" for setting ProcessedMap type
293    ///
294    template <class T>
295    struct DefProcessedMap : public Bfs< Graph, DefProcessedMapTraits<T> > {
296      typedef Bfs< Graph, DefProcessedMapTraits<T> > Create;
297    };
298   
299    struct DefGraphProcessedMapTraits : public Traits {
300      typedef typename Graph::template NodeMap<bool> ProcessedMap;
301      static ProcessedMap *createProcessedMap(const Graph &G)
302      {
303        return new ProcessedMap(G);
304      }
305    };
306    ///\brief \ref named-templ-param "Named parameter"
307    ///for setting the ProcessedMap type to be Graph::NodeMap<bool>.
308    ///
309    ///\ref named-templ-param "Named parameter"
310    ///for setting the ProcessedMap type to be Graph::NodeMap<bool>.
311    ///If you don't set it explicitly, it will be automatically allocated.
312    template <class T>
313    struct DefProcessedMapToBeDefaultMap :
314      public Bfs< Graph, DefGraphProcessedMapTraits> {
315      typedef Bfs< Graph, DefGraphProcessedMapTraits> Create;
316    };
317   
318    ///@}
319
320  public:     
321   
322    ///Constructor.
323   
324    ///\param _G the graph the algorithm will run on.
325    ///
326    Bfs(const Graph& _G) :
327      G(&_G),
328      _pred(NULL), local_pred(false),
329      _dist(NULL), local_dist(false),
330      _reached(NULL), local_reached(false),
331      _processed(NULL), local_processed(false)
332    { }
333   
334    ///Destructor.
335    ~Bfs()
336    {
337      if(local_pred) delete _pred;
338      if(local_dist) delete _dist;
339      if(local_reached) delete _reached;
340      if(local_processed) delete _processed;
341    }
342
343    ///Sets the map storing the predecessor edges.
344
345    ///Sets the map storing the predecessor edges.
346    ///If you don't use this function before calling \ref run(),
347    ///it will allocate one. The destructor deallocates this
348    ///automatically allocated map, of course.
349    ///\return <tt> (*this) </tt>
350    Bfs &predMap(PredMap &m)
351    {
352      if(local_pred) {
353        delete _pred;
354        local_pred=false;
355      }
356      _pred = &m;
357      return *this;
358    }
359
360    ///Sets the map indicating the reached nodes.
361
362    ///Sets the map indicating the reached nodes.
363    ///If you don't use this function before calling \ref run(),
364    ///it will allocate one. The destructor deallocates this
365    ///automatically allocated map, of course.
366    ///\return <tt> (*this) </tt>
367    Bfs &reachedMap(ReachedMap &m)
368    {
369      if(local_reached) {
370        delete _reached;
371        local_reached=false;
372      }
373      _reached = &m;
374      return *this;
375    }
376
377    ///Sets the map indicating the processed nodes.
378
379    ///Sets the map indicating the processed nodes.
380    ///If you don't use this function before calling \ref run(),
381    ///it will allocate one. The destructor deallocates this
382    ///automatically allocated map, of course.
383    ///\return <tt> (*this) </tt>
384    Bfs &processedMap(ProcessedMap &m)
385    {
386      if(local_processed) {
387        delete _processed;
388        local_processed=false;
389      }
390      _processed = &m;
391      return *this;
392    }
393
394    ///Sets the map storing the distances calculated by the algorithm.
395
396    ///Sets the map storing the distances calculated by the algorithm.
397    ///If you don't use this function before calling \ref run(),
398    ///it will allocate one. The destructor deallocates this
399    ///automatically allocated map, of course.
400    ///\return <tt> (*this) </tt>
401    Bfs &distMap(DistMap &m)
402    {
403      if(local_dist) {
404        delete _dist;
405        local_dist=false;
406      }
407      _dist = &m;
408      return *this;
409    }
410
411  public:
412    ///\name Execution control
413    ///The simplest way to execute the algorithm is to use
414    ///one of the member functions called \c run(...).
415    ///\n
416    ///If you need more control on the execution,
417    ///first you must call \ref init(), then you can add several source nodes
418    ///with \ref addSource().
419    ///Finally \ref start() will perform the actual path
420    ///computation.
421
422    ///@{
423
424    ///Initializes the internal data structures.
425
426    ///Initializes the internal data structures.
427    ///
428    void init()
429    {
430      create_maps();
431      _queue.resize(countNodes(*G));
432      _queue_head=_queue_tail=0;
433      _curr_dist=1;
434      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
435        _pred->set(u,INVALID);
436        _reached->set(u,false);
437        _processed->set(u,false);
438      }
439    }
440   
441    ///Adds a new source node.
442
443    ///Adds a new source node to the set of nodes to be processed.
444    ///
445    void addSource(Node s)
446    {
447      if(!(*_reached)[s])
448        {
449          _reached->set(s,true);
450          _pred->set(s,INVALID);
451          _dist->set(s,0);
452          _queue[_queue_head++]=s;
453          _queue_next_dist=_queue_head;
454        }
455    }
456   
457    ///Processes the next node.
458
459    ///Processes the next node.
460    ///
461    ///\return The processed node.
462    ///
463    ///\warning The queue must not be empty!
464    Node processNextNode()
465    {
466      if(_queue_tail==_queue_next_dist) {
467        _curr_dist++;
468        _queue_next_dist=_queue_head;
469      }
470      Node n=_queue[_queue_tail++];
471      _processed->set(n,true);
472      Node m;
473      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
474        if(!(*_reached)[m=G->target(e)]) {
475          _queue[_queue_head++]=m;
476          _reached->set(m,true);
477          _pred->set(m,e);
478          _dist->set(m,_curr_dist);
479        }
480      return n;
481    }
482
483    ///Processes the next node.
484
485    ///Processes the next node. And checks that the given target node
486    ///is reached. If the target node is reachable from the processed
487    ///node then the reached parameter will be set true. The reached
488    ///parameter should be initially false.
489    ///
490    ///\param target The target node.
491    ///\retval reach Indicates that the target node is reached.
492    ///\return The processed node.
493    ///
494    ///\warning The queue must not be empty!
495    Node processNextNode(Node target, bool& reach)
496    {
497      if(_queue_tail==_queue_next_dist) {
498        _curr_dist++;
499        _queue_next_dist=_queue_head;
500      }
501      Node n=_queue[_queue_tail++];
502      _processed->set(n,true);
503      Node m;
504      for(OutEdgeIt e(*G,n);e!=INVALID;++e)
505        if(!(*_reached)[m=G->target(e)]) {
506          _queue[_queue_head++]=m;
507          _reached->set(m,true);
508          _pred->set(m,e);
509          _dist->set(m,_curr_dist);
510          reach = reach || (target == m);
511        }
512      return n;
513    }
514
515    ///Processes the next node.
516
517    ///Processes the next node. And checks that at least one of
518    ///reached node has true value in the \c nm node map. If one node
519    ///with true value is reachable from the processed node then the
520    ///rnode parameter will be set to the first of such nodes.
521    ///
522    ///\param nm The node map of possible targets.
523    ///\retval rnode The reached target node.
524    ///\return The processed node.
525    ///
526    ///\warning The queue must not be empty!
527    template<class NM>
528    Node processNextNode(const NM& nm, Node& rnode)
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          if (nm[m] && rnode == INVALID) rnode = 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    int queueSize() { return _queue_head-_queue_tail; }
569   
570    ///Executes the algorithm.
571
572    ///Executes the algorithm.
573    ///
574    ///\pre init() must be called and at least one node should be added
575    ///with addSource() before using this function.
576    ///
577    ///This method runs the %BFS algorithm from the root node(s)
578    ///in order to
579    ///compute the
580    ///shortest path to each node. The algorithm computes
581    ///- The shortest path tree.
582    ///- The distance of each node from the root(s).
583    void start()
584    {
585      while ( !emptyQueue() ) processNextNode();
586    }
587   
588    ///Executes the algorithm until \c dest is reached.
589
590    ///Executes the algorithm until \c dest is reached.
591    ///
592    ///\pre init() must be called and at least one node should be added
593    ///with addSource() before using this function.
594    ///
595    ///This method runs the %BFS algorithm from the root node(s)
596    ///in order to
597    ///compute the
598    ///shortest path to \c dest. The algorithm computes
599    ///- The shortest path to \c  dest.
600    ///- The distance of \c dest from the root(s).
601    void start(Node dest)
602    {
603      bool reach = false;
604      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
605    }
606   
607    ///Executes the algorithm until a condition is met.
608
609    ///Executes the algorithm until a condition is met.
610    ///
611    ///\pre init() must be called and at least one node should be added
612    ///with addSource() before using this function.
613    ///
614    ///\param nm must be a bool (or convertible) node map. The
615    ///algorithm will stop when it reaches a node \c v with
616    /// <tt>nm[v]</tt> true.
617    ///
618    ///\return The reached node \c v with <tt>nm[v]<\tt> true or
619    ///\c INVALID if no such node was found.
620    template<class NM>
621    Node start(const NM &nm)
622    {
623      Node rnode = INVALID;
624      while ( !emptyQueue() && rnode == INVALID ) {
625        processNextNode(nm, rnode);
626      }
627      return rnode;
628    }
629   
630    ///Runs %BFS algorithm from node \c s.
631   
632    ///This method runs the %BFS algorithm from a root node \c s
633    ///in order to
634    ///compute the
635    ///shortest path to each node. The algorithm computes
636    ///- The shortest path tree.
637    ///- The distance of each node from the root.
638    ///
639    ///\note b.run(s) is just a shortcut of the following code.
640    ///\code
641    ///  b.init();
642    ///  b.addSource(s);
643    ///  b.start();
644    ///\endcode
645    void run(Node s) {
646      init();
647      addSource(s);
648      start();
649    }
650   
651    ///Finds the shortest path between \c s and \c t.
652   
653    ///Finds the shortest path between \c s and \c t.
654    ///
655    ///\return The length of the shortest s---t path if there exists one,
656    ///0 otherwise.
657    ///\note Apart from the return value, b.run(s) is
658    ///just a shortcut of the following code.
659    ///\code
660    ///  b.init();
661    ///  b.addSource(s);
662    ///  b.start(t);
663    ///\endcode
664    int run(Node s,Node t) {
665      init();
666      addSource(s);
667      start(t);
668      return reached(t) ? _curr_dist : 0;
669    }
670   
671    ///@}
672
673    ///\name Query Functions
674    ///The result of the %BFS algorithm can be obtained using these
675    ///functions.\n
676    ///Before the use of these functions,
677    ///either run() or start() must be calleb.
678   
679    ///@{
680
681    typedef PredMapPath<Graph, PredMap> Path;
682
683    ///Gives back the shortest path.
684   
685    ///Gives back the shortest path.
686    ///\pre The \c t should be reachable from the source.
687    Path path(Node t)
688    {
689      return Path(*G, *_pred, t);
690    }
691
692    ///The distance of a node from the root(s).
693
694    ///Returns the distance of a node from the root(s).
695    ///\pre \ref run() must be called before using this function.
696    ///\warning If node \c v in unreachable from the root(s) the return value
697    ///of this function is undefined.
698    int dist(Node v) const { return (*_dist)[v]; }
699
700    ///Returns the 'previous edge' of the shortest path tree.
701
702    ///For a node \c v it returns the 'previous edge'
703    ///of the shortest path tree,
704    ///i.e. it returns the last edge of a shortest path from the root(s) to \c
705    ///v. It is \ref INVALID
706    ///if \c v is unreachable from the root(s) or \c v is a root. The
707    ///shortest path tree used here is equal to the shortest path tree used in
708    ///\ref predNode().
709    ///\pre Either \ref run() or \ref start() must be called before using
710    ///this function.
711    Edge predEdge(Node v) const { return (*_pred)[v];}
712
713    ///Returns the 'previous node' of the shortest path tree.
714
715    ///For a node \c v it returns the 'previous node'
716    ///of the shortest path tree,
717    ///i.e. it returns the last but one node from a shortest path from the
718    ///root(a) to \c /v.
719    ///It is INVALID if \c v is unreachable from the root(s) or
720    ///if \c v itself a root.
721    ///The shortest path tree used here is equal to the shortest path
722    ///tree used in \ref predEdge().
723    ///\pre Either \ref run() or \ref start() must be called before
724    ///using this function.
725    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
726                                  G->source((*_pred)[v]); }
727   
728    ///Returns a reference to the NodeMap of distances.
729
730    ///Returns a reference to the NodeMap of distances.
731    ///\pre Either \ref run() or \ref init() must
732    ///be called before using this function.
733    const DistMap &distMap() const { return *_dist;}
734 
735    ///Returns a reference to the shortest path tree map.
736
737    ///Returns a reference to the NodeMap of the edges of the
738    ///shortest path tree.
739    ///\pre Either \ref run() or \ref init()
740    ///must be called before using this function.
741    const PredMap &predMap() const { return *_pred;}
742 
743    ///Checks if a node is reachable from the root.
744
745    ///Returns \c true if \c v is reachable from the root.
746    ///\warning The source nodes are indicated as unreached.
747    ///\pre Either \ref run() or \ref start()
748    ///must be called before using this function.
749    ///
750    bool reached(Node v) { return (*_reached)[v]; }
751   
752    ///@}
753  };
754
755  ///Default traits class of Bfs function.
756
757  ///Default traits class of Bfs function.
758  ///\param GR Graph type.
759  template<class GR>
760  struct BfsWizardDefaultTraits
761  {
762    ///The graph type the algorithm runs on.
763    typedef GR Graph;
764    ///\brief The type of the map that stores the last
765    ///edges of the shortest paths.
766    ///
767    ///The type of the map that stores the last
768    ///edges of the shortest paths.
769    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
770    ///
771    typedef NullMap<typename Graph::Node,typename GR::Edge> PredMap;
772    ///Instantiates a PredMap.
773 
774    ///This function instantiates a \ref PredMap.
775    ///\param g is the graph, to which we would like to define the PredMap.
776    ///\todo The graph alone may be insufficient to initialize
777#ifdef DOXYGEN
778    static PredMap *createPredMap(const GR &g)
779#else
780    static PredMap *createPredMap(const GR &)
781#endif
782    {
783      return new PredMap();
784    }
785
786    ///The type of the map that indicates which nodes are processed.
787 
788    ///The type of the map that indicates which nodes are processed.
789    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
790    ///\todo named parameter to set this type, function to read and write.
791    typedef NullMap<typename Graph::Node,bool> ProcessedMap;
792    ///Instantiates a ProcessedMap.
793 
794    ///This function instantiates a \ref ProcessedMap.
795    ///\param g is the graph, to which
796    ///we would like to define the \ref ProcessedMap
797#ifdef DOXYGEN
798    static ProcessedMap *createProcessedMap(const GR &g)
799#else
800    static ProcessedMap *createProcessedMap(const GR &)
801#endif
802    {
803      return new ProcessedMap();
804    }
805    ///The type of the map that indicates which nodes are reached.
806 
807    ///The type of the map that indicates which nodes are reached.
808    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
809    ///\todo named parameter to set this type, function to read and write.
810    typedef typename Graph::template NodeMap<bool> ReachedMap;
811    ///Instantiates a ReachedMap.
812 
813    ///This function instantiates a \ref ReachedMap.
814    ///\param G is the graph, to which
815    ///we would like to define the \ref ReachedMap.
816    static ReachedMap *createReachedMap(const GR &G)
817    {
818      return new ReachedMap(G);
819    }
820    ///The type of the map that stores the dists of the nodes.
821 
822    ///The type of the map that stores the dists of the nodes.
823    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
824    ///
825    typedef NullMap<typename Graph::Node,int> DistMap;
826    ///Instantiates a DistMap.
827 
828    ///This function instantiates a \ref DistMap.
829    ///\param g is the graph, to which we would like to define the \ref DistMap
830#ifdef DOXYGEN
831    static DistMap *createDistMap(const GR &g)
832#else
833    static DistMap *createDistMap(const GR &)
834#endif
835    {
836      return new DistMap();
837    }
838  };
839 
840  /// Default traits used by \ref BfsWizard
841
842  /// To make it easier to use Bfs algorithm
843  ///we have created a wizard class.
844  /// This \ref BfsWizard class needs default traits,
845  ///as well as the \ref Bfs class.
846  /// The \ref BfsWizardBase is a class to be the default traits of the
847  /// \ref BfsWizard class.
848  template<class GR>
849  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
850  {
851
852    typedef BfsWizardDefaultTraits<GR> Base;
853  protected:
854    /// Type of the nodes in the graph.
855    typedef typename Base::Graph::Node Node;
856
857    /// Pointer to the underlying graph.
858    void *_g;
859    ///Pointer to the map of reached nodes.
860    void *_reached;
861    ///Pointer to the map of processed nodes.
862    void *_processed;
863    ///Pointer to the map of predecessors edges.
864    void *_pred;
865    ///Pointer to the map of distances.
866    void *_dist;
867    ///Pointer to the source node.
868    Node _source;
869   
870    public:
871    /// Constructor.
872   
873    /// This constructor does not require parameters, therefore it initiates
874    /// all of the attributes to default values (0, INVALID).
875    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
876                           _dist(0), _source(INVALID) {}
877
878    /// Constructor.
879   
880    /// This constructor requires some parameters,
881    /// listed in the parameters list.
882    /// Others are initiated to 0.
883    /// \param g is the initial value of  \ref _g
884    /// \param s is the initial value of  \ref _source
885    BfsWizardBase(const GR &g, Node s=INVALID) :
886      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
887      _reached(0), _processed(0), _pred(0), _dist(0), _source(s) {}
888
889  };
890 
891  /// A class to make the usage of Bfs algorithm easier
892
893  /// This class is created to make it easier to use Bfs algorithm.
894  /// It uses the functions and features of the plain \ref Bfs,
895  /// but it is much simpler to use it.
896  ///
897  /// Simplicity means that the way to change the types defined
898  /// in the traits class is based on functions that returns the new class
899  /// and not on templatable built-in classes.
900  /// When using the plain \ref Bfs
901  /// the new class with the modified type comes from
902  /// the original class by using the ::
903  /// operator. In the case of \ref BfsWizard only
904  /// a function have to be called and it will
905  /// return the needed class.
906  ///
907  /// It does not have own \ref run method. When its \ref run method is called
908  /// it initiates a plain \ref Bfs class, and calls the \ref Bfs::run
909  /// method of it.
910  template<class TR>
911  class BfsWizard : public TR
912  {
913    typedef TR Base;
914
915    ///The type of the underlying graph.
916    typedef typename TR::Graph Graph;
917    //\e
918    typedef typename Graph::Node Node;
919    //\e
920    typedef typename Graph::NodeIt NodeIt;
921    //\e
922    typedef typename Graph::Edge Edge;
923    //\e
924    typedef typename Graph::OutEdgeIt OutEdgeIt;
925   
926    ///\brief The type of the map that stores
927    ///the reached nodes
928    typedef typename TR::ReachedMap ReachedMap;
929    ///\brief The type of the map that stores
930    ///the processed nodes
931    typedef typename TR::ProcessedMap ProcessedMap;
932    ///\brief The type of the map that stores the last
933    ///edges of the shortest paths.
934    typedef typename TR::PredMap PredMap;
935    ///The type of the map that stores the dists of the nodes.
936    typedef typename TR::DistMap DistMap;
937
938  public:
939    /// Constructor.
940    BfsWizard() : TR() {}
941
942    /// Constructor that requires parameters.
943
944    /// Constructor that requires parameters.
945    /// These parameters will be the default values for the traits class.
946    BfsWizard(const Graph &g, Node s=INVALID) :
947      TR(g,s) {}
948
949    ///Copy constructor
950    BfsWizard(const TR &b) : TR(b) {}
951
952    ~BfsWizard() {}
953
954    ///Runs Bfs algorithm from a given node.
955   
956    ///Runs Bfs algorithm from a given node.
957    ///The node can be given by the \ref source function.
958    void run()
959    {
960      if(Base::_source==INVALID) throw UninitializedParameter();
961      Bfs<Graph,TR> alg(*reinterpret_cast<const Graph*>(Base::_g));
962      if(Base::_reached)
963        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
964      if(Base::_processed)
965        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
966      if(Base::_pred)
967        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
968      if(Base::_dist)
969        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
970      alg.run(Base::_source);
971    }
972
973    ///Runs Bfs algorithm from the given node.
974
975    ///Runs Bfs algorithm from the given node.
976    ///\param s is the given source.
977    void run(Node s)
978    {
979      Base::_source=s;
980      run();
981    }
982
983    template<class T>
984    struct DefPredMapBase : public Base {
985      typedef T PredMap;
986      static PredMap *createPredMap(const Graph &) { return 0; };
987      DefPredMapBase(const TR &b) : TR(b) {}
988    };
989   
990    ///\brief \ref named-templ-param "Named parameter"
991    ///function for setting PredMap
992    ///
993    /// \ref named-templ-param "Named parameter"
994    ///function for setting PredMap
995    ///
996    template<class T>
997    BfsWizard<DefPredMapBase<T> > predMap(const T &t)
998    {
999      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1000      return BfsWizard<DefPredMapBase<T> >(*this);
1001    }
1002   
1003 
1004    template<class T>
1005    struct DefReachedMapBase : public Base {
1006      typedef T ReachedMap;
1007      static ReachedMap *createReachedMap(const Graph &) { return 0; };
1008      DefReachedMapBase(const TR &b) : TR(b) {}
1009    };
1010   
1011    ///\brief \ref named-templ-param "Named parameter"
1012    ///function for setting ReachedMap
1013    ///
1014    /// \ref named-templ-param "Named parameter"
1015    ///function for setting ReachedMap
1016    ///
1017    template<class T>
1018    BfsWizard<DefReachedMapBase<T> > reachedMap(const T &t)
1019    {
1020      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1021      return BfsWizard<DefReachedMapBase<T> >(*this);
1022    }
1023   
1024
1025    template<class T>
1026    struct DefProcessedMapBase : public Base {
1027      typedef T ProcessedMap;
1028      static ProcessedMap *createProcessedMap(const Graph &) { return 0; };
1029      DefProcessedMapBase(const TR &b) : TR(b) {}
1030    };
1031   
1032    ///\brief \ref named-templ-param "Named parameter"
1033    ///function for setting ProcessedMap
1034    ///
1035    /// \ref named-templ-param "Named parameter"
1036    ///function for setting ProcessedMap
1037    ///
1038    template<class T>
1039    BfsWizard<DefProcessedMapBase<T> > processedMap(const T &t)
1040    {
1041      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1042      return BfsWizard<DefProcessedMapBase<T> >(*this);
1043    }
1044   
1045   
1046    template<class T>
1047    struct DefDistMapBase : public Base {
1048      typedef T DistMap;
1049      static DistMap *createDistMap(const Graph &) { return 0; };
1050      DefDistMapBase(const TR &b) : TR(b) {}
1051    };
1052   
1053    ///\brief \ref named-templ-param "Named parameter"
1054    ///function for setting DistMap type
1055    ///
1056    /// \ref named-templ-param "Named parameter"
1057    ///function for setting DistMap type
1058    ///
1059    template<class T>
1060    BfsWizard<DefDistMapBase<T> > distMap(const T &t)
1061    {
1062      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1063      return BfsWizard<DefDistMapBase<T> >(*this);
1064    }
1065   
1066    /// Sets the source node, from which the Bfs algorithm runs.
1067
1068    /// Sets the source node, from which the Bfs algorithm runs.
1069    /// \param s is the source node.
1070    BfsWizard<TR> &source(Node s)
1071    {
1072      Base::_source=s;
1073      return *this;
1074    }
1075   
1076  };
1077 
1078  ///Function type interface for Bfs algorithm.
1079
1080  /// \ingroup search
1081  ///Function type interface for Bfs algorithm.
1082  ///
1083  ///This function also has several
1084  ///\ref named-templ-func-param "named parameters",
1085  ///they are declared as the members of class \ref BfsWizard.
1086  ///The following
1087  ///example shows how to use these parameters.
1088  ///\code
1089  ///  bfs(g,source).predMap(preds).run();
1090  ///\endcode
1091  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1092  ///to the end of the parameter list.
1093  ///\sa BfsWizard
1094  ///\sa Bfs
1095  template<class GR>
1096  BfsWizard<BfsWizardBase<GR> >
1097  bfs(const GR &g,typename GR::Node s=INVALID)
1098  {
1099    return BfsWizard<BfsWizardBase<GR> >(g,s);
1100  }
1101
1102#ifdef DOXYGEN
1103  /// \brief Visitor class for bfs.
1104  /// 
1105  /// It gives a simple interface for a functional interface for bfs
1106  /// traversal. The traversal on a linear data structure.
1107  template <typename _Graph>
1108  struct BfsVisitor {
1109    typedef _Graph Graph;
1110    typedef typename Graph::Edge Edge;
1111    typedef typename Graph::Node Node;
1112    /// \brief Called when the edge reach a node.
1113    ///
1114    /// It is called when the bfs find an edge which target is not
1115    /// reached yet.
1116    void discover(const Edge& edge) {}
1117    /// \brief Called when the node reached first time.
1118    ///
1119    /// It is Called when the node reached first time.
1120    void reach(const Node& node) {}
1121    /// \brief Called when the edge examined but target of the edge
1122    /// already discovered.
1123    ///
1124    /// It called when the edge examined but the target of the edge
1125    /// already discovered.
1126    void examine(const Edge& edge) {}
1127    /// \brief Called for the source node of the bfs.
1128    ///
1129    /// It is called for the source node of the bfs.
1130    void start(const Node& node) {}
1131    /// \brief Called when the node processed.
1132    ///
1133    /// It is Called when the node processed.
1134    void process(const Node& node) {}
1135  };
1136#else
1137  template <typename _Graph>
1138  struct BfsVisitor {
1139    typedef _Graph Graph;
1140    typedef typename Graph::Edge Edge;
1141    typedef typename Graph::Node Node;
1142    void discover(const Edge&) {}
1143    void reach(const Node&) {}
1144    void examine(const Edge&) {}
1145    void start(const Node&) {}
1146    void process(const Node&) {}
1147
1148    template <typename _Visitor>
1149    struct Constraints {
1150      void constraints() {
1151        Edge edge;
1152        Node node;
1153        visitor.discover(edge);
1154        visitor.reach(node);
1155        visitor.examine(edge);
1156        visitor.start(node);
1157        visitor.process(node);
1158      }
1159      _Visitor& visitor;
1160    };
1161  };
1162#endif
1163
1164  /// \brief Default traits class of BfsVisit class.
1165  ///
1166  /// Default traits class of BfsVisit class.
1167  /// \param _Graph Graph type.
1168  template<class _Graph>
1169  struct BfsVisitDefaultTraits {
1170
1171    /// \brief The graph type the algorithm runs on.
1172    typedef _Graph Graph;
1173
1174    /// \brief The type of the map that indicates which nodes are reached.
1175    ///
1176    /// The type of the map that indicates which nodes are reached.
1177    /// It must meet the \ref concepts::WriteMap "WriteMap" concept.
1178    /// \todo named parameter to set this type, function to read and write.
1179    typedef typename Graph::template NodeMap<bool> ReachedMap;
1180
1181    /// \brief Instantiates a ReachedMap.
1182    ///
1183    /// This function instantiates a \ref ReachedMap.
1184    /// \param graph is the graph, to which
1185    /// we would like to define the \ref ReachedMap.
1186    static ReachedMap *createReachedMap(const Graph &graph) {
1187      return new ReachedMap(graph);
1188    }
1189
1190  };
1191 
1192  /// %BFS Visit algorithm class.
1193 
1194  /// \ingroup search
1195  /// This class provides an efficient implementation of the %BFS algorithm
1196  /// with visitor interface.
1197  ///
1198  /// The %BfsVisit class provides an alternative interface to the Bfs
1199  /// class. It works with callback mechanism, the BfsVisit object calls
1200  /// on every bfs event the \c Visitor class member functions.
1201  ///
1202  /// \param _Graph The graph type the algorithm runs on. The default value is
1203  /// \ref ListGraph. The value of _Graph is not used directly by Bfs, it
1204  /// is only passed to \ref BfsDefaultTraits.
1205  /// \param _Visitor The Visitor object for the algorithm. The
1206  /// \ref BfsVisitor "BfsVisitor<_Graph>" is an empty Visitor which
1207  /// does not observe the Bfs events. If you want to observe the bfs
1208  /// events you should implement your own Visitor class.
1209  /// \param _Traits Traits class to set various data types used by the
1210  /// algorithm. The default traits class is
1211  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<_Graph>".
1212  /// See \ref BfsVisitDefaultTraits for the documentation of
1213  /// a Bfs visit traits class.
1214  ///
1215  /// \author Jacint Szabo, Alpar Juttner and Balazs Dezso
1216#ifdef DOXYGEN
1217  template <typename _Graph, typename _Visitor, typename _Traits>
1218#else
1219  template <typename _Graph = ListGraph,
1220            typename _Visitor = BfsVisitor<_Graph>,
1221            typename _Traits = BfsDefaultTraits<_Graph> >
1222#endif
1223  class BfsVisit {
1224  public:
1225   
1226    /// \brief \ref Exception for uninitialized parameters.
1227    ///
1228    /// This error represents problems in the initialization
1229    /// of the parameters of the algorithms.
1230    class UninitializedParameter : public lemon::UninitializedParameter {
1231    public:
1232      virtual const char* what() const throw()
1233      {
1234        return "lemon::BfsVisit::UninitializedParameter";
1235      }
1236    };
1237
1238    typedef _Traits Traits;
1239
1240    typedef typename Traits::Graph Graph;
1241
1242    typedef _Visitor Visitor;
1243
1244    ///The type of the map indicating which nodes are reached.
1245    typedef typename Traits::ReachedMap ReachedMap;
1246
1247  private:
1248
1249    typedef typename Graph::Node Node;
1250    typedef typename Graph::NodeIt NodeIt;
1251    typedef typename Graph::Edge Edge;
1252    typedef typename Graph::OutEdgeIt OutEdgeIt;
1253
1254    /// Pointer to the underlying graph.
1255    const Graph *_graph;
1256    /// Pointer to the visitor object.
1257    Visitor *_visitor;
1258    ///Pointer to the map of reached status of the nodes.
1259    ReachedMap *_reached;
1260    ///Indicates if \ref _reached is locally allocated (\c true) or not.
1261    bool local_reached;
1262
1263    std::vector<typename Graph::Node> _list;
1264    int _list_front, _list_back;
1265
1266    /// \brief Creates the maps if necessary.
1267    ///
1268    /// Creates the maps if necessary.
1269    void create_maps() {
1270      if(!_reached) {
1271        local_reached = true;
1272        _reached = Traits::createReachedMap(*_graph);
1273      }
1274    }
1275
1276  protected:
1277
1278    BfsVisit() {}
1279   
1280  public:
1281
1282    typedef BfsVisit Create;
1283
1284    /// \name Named template parameters
1285
1286    ///@{
1287    template <class T>
1288    struct DefReachedMapTraits : public Traits {
1289      typedef T ReachedMap;
1290      static ReachedMap *createReachedMap(const Graph &graph) {
1291        throw UninitializedParameter();
1292      }
1293    };
1294    /// \brief \ref named-templ-param "Named parameter" for setting
1295    /// ReachedMap type
1296    ///
1297    /// \ref named-templ-param "Named parameter" for setting ReachedMap type
1298    template <class T>
1299    struct DefReachedMap : public BfsVisit< Graph, Visitor,
1300                                            DefReachedMapTraits<T> > {
1301      typedef BfsVisit< Graph, Visitor, DefReachedMapTraits<T> > Create;
1302    };
1303    ///@}
1304
1305  public:     
1306   
1307    /// \brief Constructor.
1308    ///
1309    /// Constructor.
1310    ///
1311    /// \param graph the graph the algorithm will run on.
1312    /// \param visitor The visitor of the algorithm.
1313    ///
1314    BfsVisit(const Graph& graph, Visitor& visitor)
1315      : _graph(&graph), _visitor(&visitor),
1316        _reached(0), local_reached(false) {}
1317   
1318    /// \brief Destructor.
1319    ///
1320    /// Destructor.
1321    ~BfsVisit() {
1322      if(local_reached) delete _reached;
1323    }
1324
1325    /// \brief Sets the map indicating if a node is reached.
1326    ///
1327    /// Sets the map indicating if a node is reached.
1328    /// If you don't use this function before calling \ref run(),
1329    /// it will allocate one. The destuctor deallocates this
1330    /// automatically allocated map, of course.
1331    /// \return <tt> (*this) </tt>
1332    BfsVisit &reachedMap(ReachedMap &m) {
1333      if(local_reached) {
1334        delete _reached;
1335        local_reached = false;
1336      }
1337      _reached = &m;
1338      return *this;
1339    }
1340
1341  public:
1342    /// \name Execution control
1343    /// The simplest way to execute the algorithm is to use
1344    /// one of the member functions called \c run(...).
1345    /// \n
1346    /// If you need more control on the execution,
1347    /// first you must call \ref init(), then you can adda source node
1348    /// with \ref addSource().
1349    /// Finally \ref start() will perform the actual path
1350    /// computation.
1351
1352    /// @{
1353    /// \brief Initializes the internal data structures.
1354    ///
1355    /// Initializes the internal data structures.
1356    ///
1357    void init() {
1358      create_maps();
1359      _list.resize(countNodes(*_graph));
1360      _list_front = _list_back = -1;
1361      for (NodeIt u(*_graph) ; u != INVALID ; ++u) {
1362        _reached->set(u, false);
1363      }
1364    }
1365   
1366    /// \brief Adds a new source node.
1367    ///
1368    /// Adds a new source node to the set of nodes to be processed.
1369    void addSource(Node s) {
1370      if(!(*_reached)[s]) {
1371          _reached->set(s,true);
1372          _visitor->start(s);
1373          _visitor->reach(s);
1374          _list[++_list_back] = s;
1375        }
1376    }
1377   
1378    /// \brief Processes the next node.
1379    ///
1380    /// Processes the next node.
1381    ///
1382    /// \return The processed node.
1383    ///
1384    /// \pre The queue must not be empty!
1385    Node processNextNode() {
1386      Node n = _list[++_list_front];
1387      _visitor->process(n);
1388      Edge e;
1389      for (_graph->firstOut(e, n); e != INVALID; _graph->nextOut(e)) {
1390        Node m = _graph->target(e);
1391        if (!(*_reached)[m]) {
1392          _visitor->discover(e);
1393          _visitor->reach(m);
1394          _reached->set(m, true);
1395          _list[++_list_back] = m;
1396        } else {
1397          _visitor->examine(e);
1398        }
1399      }
1400      return n;
1401    }
1402
1403    /// \brief Processes the next node.
1404    ///
1405    /// Processes the next node. And checks that the given target node
1406    /// is reached. If the target node is reachable from the processed
1407    /// node then the reached parameter will be set true. The reached
1408    /// parameter should be initially false.
1409    ///
1410    /// \param target The target node.
1411    /// \retval reach Indicates that the target node is reached.
1412    /// \return The processed node.
1413    ///
1414    /// \warning The queue must not be empty!
1415    Node processNextNode(Node target, bool& reach) {
1416      Node n = _list[++_list_front];
1417      _visitor->process(n);
1418      Edge e;
1419      for (_graph->firstOut(e, n); e != INVALID; _graph->nextOut(e)) {
1420        Node m = _graph->target(e);
1421        if (!(*_reached)[m]) {
1422          _visitor->discover(e);
1423          _visitor->reach(m);
1424          _reached->set(m, true);
1425          _list[++_list_back] = m;
1426          reach = reach || (target == m);
1427        } else {
1428          _visitor->examine(e);
1429        }
1430      }
1431      return n;
1432    }
1433
1434    /// \brief Processes the next node.
1435    ///
1436    /// Processes the next node. And checks that at least one of
1437    /// reached node has true value in the \c nm node map. If one node
1438    /// with true value is reachable from the processed node then the
1439    /// rnode parameter will be set to the first of such nodes.
1440    ///
1441    /// \param nm The node map of possible targets.
1442    /// \retval rnode The reached target node.
1443    /// \return The processed node.
1444    ///
1445    /// \warning The queue must not be empty!
1446    template <typename NM>
1447    Node processNextNode(const NM& nm, Node& rnode) {
1448      Node n = _list[++_list_front];
1449      _visitor->process(n);
1450      Edge e;
1451      for (_graph->firstOut(e, n); e != INVALID; _graph->nextOut(e)) {
1452        Node m = _graph->target(e);
1453        if (!(*_reached)[m]) {
1454          _visitor->discover(e);
1455          _visitor->reach(m);
1456          _reached->set(m, true);
1457          _list[++_list_back] = m;
1458          if (nm[m] && rnode == INVALID) rnode = m;
1459        } else {
1460          _visitor->examine(e);
1461        }
1462      }
1463      return n;
1464    }
1465
1466    /// \brief Next node to be processed.
1467    ///
1468    /// Next node to be processed.
1469    ///
1470    /// \return The next node to be processed or INVALID if the stack is
1471    /// empty.
1472    Node nextNode() {
1473      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1474    }
1475
1476    /// \brief Returns \c false if there are nodes
1477    /// to be processed in the queue
1478    ///
1479    /// Returns \c false if there are nodes
1480    /// to be processed in the queue
1481    bool emptyQueue() { return _list_front == _list_back; }
1482
1483    /// \brief Returns the number of the nodes to be processed.
1484    ///
1485    /// Returns the number of the nodes to be processed in the queue.
1486    int queueSize() { return _list_back - _list_front; }
1487   
1488    /// \brief Executes the algorithm.
1489    ///
1490    /// Executes the algorithm.
1491    ///
1492    /// \pre init() must be called and at least one node should be added
1493    /// with addSource() before using this function.
1494    void start() {
1495      while ( !emptyQueue() ) processNextNode();
1496    }
1497   
1498    /// \brief Executes the algorithm until \c dest is reached.
1499    ///
1500    /// Executes the algorithm until \c dest is reached.
1501    ///
1502    /// \pre init() must be called and at least one node should be added
1503    /// with addSource() before using this function.
1504    void start(Node dest) {
1505      bool reach = false;
1506      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
1507    }
1508   
1509    /// \brief Executes the algorithm until a condition is met.
1510    ///
1511    /// Executes the algorithm until a condition is met.
1512    ///
1513    /// \pre init() must be called and at least one node should be added
1514    /// with addSource() before using this function.
1515    ///
1516    ///\param nm must be a bool (or convertible) node map. The
1517    ///algorithm will stop when it reaches a node \c v with
1518    /// <tt>nm[v]</tt> true.
1519    ///
1520    ///\return The reached node \c v with <tt>nm[v]<\tt> true or
1521    ///\c INVALID if no such node was found.
1522    template <typename NM>
1523    Node start(const NM &nm) {
1524      Node rnode = INVALID;
1525      while ( !emptyQueue() && rnode == INVALID ) {
1526        processNextNode(nm, rnode);
1527      }
1528      return rnode;
1529    }
1530
1531    /// \brief Runs %BFSVisit algorithm from node \c s.
1532    ///
1533    /// This method runs the %BFS algorithm from a root node \c s.
1534    /// \note b.run(s) is just a shortcut of the following code.
1535    ///\code
1536    ///   b.init();
1537    ///   b.addSource(s);
1538    ///   b.start();
1539    ///\endcode
1540    void run(Node s) {
1541      init();
1542      addSource(s);
1543      start();
1544    }
1545
1546    /// \brief Runs %BFSVisit algorithm to visit all nodes in the graph.
1547    ///   
1548    /// This method runs the %BFS algorithm in order to
1549    /// compute the %BFS path to each node. The algorithm computes
1550    /// - The %BFS tree.
1551    /// - The distance of each node from the root in the %BFS tree.
1552    ///
1553    ///\note b.run() is just a shortcut of the following code.
1554    ///\code
1555    ///  b.init();
1556    ///  for (NodeIt it(graph); it != INVALID; ++it) {
1557    ///    if (!b.reached(it)) {
1558    ///      b.addSource(it);
1559    ///      b.start();
1560    ///    }
1561    ///  }
1562    ///\endcode
1563    void run() {
1564      init();
1565      for (NodeIt it(*_graph); it != INVALID; ++it) {
1566        if (!reached(it)) {
1567          addSource(it);
1568          start();
1569        }
1570      }
1571    }
1572    ///@}
1573
1574    /// \name Query Functions
1575    /// The result of the %BFS algorithm can be obtained using these
1576    /// functions.\n
1577    /// Before the use of these functions,
1578    /// either run() or start() must be called.
1579    ///@{
1580
1581    /// \brief Checks if a node is reachable from the root.
1582    ///
1583    /// Returns \c true if \c v is reachable from the root(s).
1584    /// \warning The source nodes are inditated as unreachable.
1585    /// \pre Either \ref run() or \ref start()
1586    /// must be called before using this function.
1587    ///
1588    bool reached(Node v) { return (*_reached)[v]; }
1589    ///@}
1590  };
1591
1592} //END OF NAMESPACE LEMON
1593
1594#endif
1595
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