COIN-OR::LEMON - Graph Library

source: lemon-1.2/lemon/bfs.h @ 953:b873350e6258

Last change on this file since 953:b873350e6258 was 953:b873350e6258, checked in by Alpar Juttner <alpar@…>, 8 years ago

Intel C++ compatibility fixes

File size: 54.3 KB
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1/* -*- mode: C++; indent-tabs-mode: nil; -*-
2 *
3 * This file is a part of LEMON, a generic C++ optimization library.
4 *
5 * Copyright (C) 2003-2009
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/bits/path_dump.h>
28#include <lemon/core.h>
29#include <lemon/error.h>
30#include <lemon/maps.h>
31#include <lemon/path.h>
32
33namespace lemon {
34
35  ///Default traits class of Bfs class.
36
37  ///Default traits class of Bfs class.
38  ///\tparam GR Digraph type.
39  template<class GR>
40  struct BfsDefaultTraits
41  {
42    ///The type of the digraph the algorithm runs on.
43    typedef GR Digraph;
44
45    ///\brief The type of the map that stores the predecessor
46    ///arcs of the shortest paths.
47    ///
48    ///The type of the map that stores the predecessor
49    ///arcs of the shortest paths.
50    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
51    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
52    ///Instantiates a \c PredMap.
53
54    ///This function instantiates a \ref PredMap.
55    ///\param g is the digraph, to which we would like to define the
56    ///\ref PredMap.
57    static PredMap *createPredMap(const Digraph &g)
58    {
59      return new PredMap(g);
60    }
61
62    ///The type of the map that indicates which nodes are processed.
63
64    ///The type of the map that indicates which nodes are processed.
65    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
66    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
67    ///Instantiates a \c ProcessedMap.
68
69    ///This function instantiates a \ref ProcessedMap.
70    ///\param g is the digraph, to which
71    ///we would like to define the \ref ProcessedMap
72#ifdef DOXYGEN
73    static ProcessedMap *createProcessedMap(const Digraph &g)
74#else
75    static ProcessedMap *createProcessedMap(const Digraph &)
76#endif
77    {
78      return new ProcessedMap();
79    }
80
81    ///The type of the map that indicates which nodes are reached.
82
83    ///The type of the map that indicates which nodes are reached.
84    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
85    typedef typename Digraph::template NodeMap<bool> ReachedMap;
86    ///Instantiates a \c ReachedMap.
87
88    ///This function instantiates a \ref ReachedMap.
89    ///\param g is the digraph, to which
90    ///we would like to define the \ref ReachedMap.
91    static ReachedMap *createReachedMap(const Digraph &g)
92    {
93      return new ReachedMap(g);
94    }
95
96    ///The type of the map that stores the distances of the nodes.
97
98    ///The type of the map that stores the distances of the nodes.
99    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
100    typedef typename Digraph::template NodeMap<int> DistMap;
101    ///Instantiates a \c DistMap.
102
103    ///This function instantiates a \ref DistMap.
104    ///\param g is the digraph, to which we would like to define the
105    ///\ref DistMap.
106    static DistMap *createDistMap(const Digraph &g)
107    {
108      return new DistMap(g);
109    }
110  };
111
112  ///%BFS algorithm class.
113
114  ///\ingroup search
115  ///This class provides an efficient implementation of the %BFS algorithm.
116  ///
117  ///There is also a \ref bfs() "function-type interface" for the BFS
118  ///algorithm, which is convenient in the simplier cases and it can be
119  ///used easier.
120  ///
121  ///\tparam GR The type of the digraph the algorithm runs on.
122  ///The default type is \ref ListDigraph.
123#ifdef DOXYGEN
124  template <typename GR,
125            typename TR>
126#else
127  template <typename GR=ListDigraph,
128            typename TR=BfsDefaultTraits<GR> >
129#endif
130  class Bfs {
131  public:
132
133    ///The type of the digraph the algorithm runs on.
134    typedef typename TR::Digraph Digraph;
135
136    ///\brief The type of the map that stores the predecessor arcs of the
137    ///shortest paths.
138    typedef typename TR::PredMap PredMap;
139    ///The type of the map that stores the distances of the nodes.
140    typedef typename TR::DistMap DistMap;
141    ///The type of the map that indicates which nodes are reached.
142    typedef typename TR::ReachedMap ReachedMap;
143    ///The type of the map that indicates which nodes are processed.
144    typedef typename TR::ProcessedMap ProcessedMap;
145    ///The type of the paths.
146    typedef PredMapPath<Digraph, PredMap> Path;
147
148    ///The \ref BfsDefaultTraits "traits class" of the algorithm.
149    typedef TR Traits;
150
151  private:
152
153    typedef typename Digraph::Node Node;
154    typedef typename Digraph::NodeIt NodeIt;
155    typedef typename Digraph::Arc Arc;
156    typedef typename Digraph::OutArcIt OutArcIt;
157
158    //Pointer to the underlying digraph.
159    const Digraph *G;
160    //Pointer to the map of predecessor arcs.
161    PredMap *_pred;
162    //Indicates if _pred is locally allocated (true) or not.
163    bool local_pred;
164    //Pointer to the map of distances.
165    DistMap *_dist;
166    //Indicates if _dist is locally allocated (true) or not.
167    bool local_dist;
168    //Pointer to the map of reached status of the nodes.
169    ReachedMap *_reached;
170    //Indicates if _reached is locally allocated (true) or not.
171    bool local_reached;
172    //Pointer to the map of processed status of the nodes.
173    ProcessedMap *_processed;
174    //Indicates if _processed is locally allocated (true) or not.
175    bool local_processed;
176
177    std::vector<typename Digraph::Node> _queue;
178    int _queue_head,_queue_tail,_queue_next_dist;
179    int _curr_dist;
180
181    //Creates the maps if necessary.
182    void create_maps()
183    {
184      if(!_pred) {
185        local_pred = true;
186        _pred = Traits::createPredMap(*G);
187      }
188      if(!_dist) {
189        local_dist = true;
190        _dist = Traits::createDistMap(*G);
191      }
192      if(!_reached) {
193        local_reached = true;
194        _reached = Traits::createReachedMap(*G);
195      }
196      if(!_processed) {
197        local_processed = true;
198        _processed = Traits::createProcessedMap(*G);
199      }
200    }
201
202  protected:
203
204    Bfs() {}
205
206  public:
207
208    typedef Bfs Create;
209
210    ///\name Named Template Parameters
211
212    ///@{
213
214    template <class T>
215    struct SetPredMapTraits : public Traits {
216      typedef T PredMap;
217      static PredMap *createPredMap(const Digraph &)
218      {
219        LEMON_ASSERT(false, "PredMap is not initialized");
220        return 0; // ignore warnings
221      }
222    };
223    ///\brief \ref named-templ-param "Named parameter" for setting
224    ///\c PredMap type.
225    ///
226    ///\ref named-templ-param "Named parameter" for setting
227    ///\c PredMap type.
228    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
229    template <class T>
230    struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > {
231      typedef Bfs< Digraph, SetPredMapTraits<T> > Create;
232    };
233
234    template <class T>
235    struct SetDistMapTraits : public Traits {
236      typedef T DistMap;
237      static DistMap *createDistMap(const Digraph &)
238      {
239        LEMON_ASSERT(false, "DistMap is not initialized");
240        return 0; // ignore warnings
241      }
242    };
243    ///\brief \ref named-templ-param "Named parameter" for setting
244    ///\c DistMap type.
245    ///
246    ///\ref named-templ-param "Named parameter" for setting
247    ///\c DistMap type.
248    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
249    template <class T>
250    struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > {
251      typedef Bfs< Digraph, SetDistMapTraits<T> > Create;
252    };
253
254    template <class T>
255    struct SetReachedMapTraits : public Traits {
256      typedef T ReachedMap;
257      static ReachedMap *createReachedMap(const Digraph &)
258      {
259        LEMON_ASSERT(false, "ReachedMap is not initialized");
260        return 0; // ignore warnings
261      }
262    };
263    ///\brief \ref named-templ-param "Named parameter" for setting
264    ///\c ReachedMap type.
265    ///
266    ///\ref named-templ-param "Named parameter" for setting
267    ///\c ReachedMap type.
268    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
269    template <class T>
270    struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > {
271      typedef Bfs< Digraph, SetReachedMapTraits<T> > Create;
272    };
273
274    template <class T>
275    struct SetProcessedMapTraits : public Traits {
276      typedef T ProcessedMap;
277      static ProcessedMap *createProcessedMap(const Digraph &)
278      {
279        LEMON_ASSERT(false, "ProcessedMap is not initialized");
280        return 0; // ignore warnings
281      }
282    };
283    ///\brief \ref named-templ-param "Named parameter" for setting
284    ///\c ProcessedMap type.
285    ///
286    ///\ref named-templ-param "Named parameter" for setting
287    ///\c ProcessedMap type.
288    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
289    template <class T>
290    struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > {
291      typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create;
292    };
293
294    struct SetStandardProcessedMapTraits : public Traits {
295      typedef typename Digraph::template NodeMap<bool> ProcessedMap;
296      static ProcessedMap *createProcessedMap(const Digraph &g)
297      {
298        return new ProcessedMap(g);
299        return 0; // ignore warnings
300      }
301    };
302    ///\brief \ref named-templ-param "Named parameter" for setting
303    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
304    ///
305    ///\ref named-templ-param "Named parameter" for setting
306    ///\c ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
307    ///If you don't set it explicitly, it will be automatically allocated.
308    struct SetStandardProcessedMap :
309      public Bfs< Digraph, SetStandardProcessedMapTraits > {
310      typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create;
311    };
312
313    ///@}
314
315  public:
316
317    ///Constructor.
318
319    ///Constructor.
320    ///\param g The digraph the algorithm runs on.
321    Bfs(const Digraph &g) :
322      G(&g),
323      _pred(NULL), local_pred(false),
324      _dist(NULL), local_dist(false),
325      _reached(NULL), local_reached(false),
326      _processed(NULL), local_processed(false)
327    { }
328
329    ///Destructor.
330    ~Bfs()
331    {
332      if(local_pred) delete _pred;
333      if(local_dist) delete _dist;
334      if(local_reached) delete _reached;
335      if(local_processed) delete _processed;
336    }
337
338    ///Sets the map that stores the predecessor arcs.
339
340    ///Sets the map that stores the predecessor arcs.
341    ///If you don't use this function before calling \ref run(Node) "run()"
342    ///or \ref init(), an instance will be allocated automatically.
343    ///The destructor deallocates this automatically allocated map,
344    ///of course.
345    ///\return <tt> (*this) </tt>
346    Bfs &predMap(PredMap &m)
347    {
348      if(local_pred) {
349        delete _pred;
350        local_pred=false;
351      }
352      _pred = &m;
353      return *this;
354    }
355
356    ///Sets the map that indicates which nodes are reached.
357
358    ///Sets the map that indicates which nodes are reached.
359    ///If you don't use this function before calling \ref run(Node) "run()"
360    ///or \ref init(), an instance will be allocated automatically.
361    ///The destructor deallocates this automatically allocated map,
362    ///of course.
363    ///\return <tt> (*this) </tt>
364    Bfs &reachedMap(ReachedMap &m)
365    {
366      if(local_reached) {
367        delete _reached;
368        local_reached=false;
369      }
370      _reached = &m;
371      return *this;
372    }
373
374    ///Sets the map that indicates which nodes are processed.
375
376    ///Sets the map that indicates which nodes are processed.
377    ///If you don't use this function before calling \ref run(Node) "run()"
378    ///or \ref init(), an instance will be allocated automatically.
379    ///The destructor deallocates this automatically allocated map,
380    ///of course.
381    ///\return <tt> (*this) </tt>
382    Bfs &processedMap(ProcessedMap &m)
383    {
384      if(local_processed) {
385        delete _processed;
386        local_processed=false;
387      }
388      _processed = &m;
389      return *this;
390    }
391
392    ///Sets the map that stores the distances of the nodes.
393
394    ///Sets the map that stores the distances of the nodes calculated by
395    ///the algorithm.
396    ///If you don't use this function before calling \ref run(Node) "run()"
397    ///or \ref init(), an instance will be allocated automatically.
398    ///The destructor deallocates this automatically allocated map,
399    ///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
413    ///\name Execution Control
414    ///The simplest way to execute the BFS algorithm is to use one of the
415    ///member functions called \ref run(Node) "run()".\n
416    ///If you need more control on the execution, first you have to call
417    ///\ref init(), then you can add several source nodes with
418    ///\ref addSource(). Finally the actual path computation can be
419    ///performed with one of the \ref start() functions.
420
421    ///@{
422
423    ///\brief Initializes the internal data structures.
424    ///
425    ///Initializes the internal data structures.
426    void init()
427    {
428      create_maps();
429      _queue.resize(countNodes(*G));
430      _queue_head=_queue_tail=0;
431      _curr_dist=1;
432      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
433        _pred->set(u,INVALID);
434        _reached->set(u,false);
435        _processed->set(u,false);
436      }
437    }
438
439    ///Adds a new source node.
440
441    ///Adds a new source node to the set of nodes to be processed.
442    ///
443    void addSource(Node s)
444    {
445      if(!(*_reached)[s])
446        {
447          _reached->set(s,true);
448          _pred->set(s,INVALID);
449          _dist->set(s,0);
450          _queue[_queue_head++]=s;
451          _queue_next_dist=_queue_head;
452        }
453    }
454
455    ///Processes the next node.
456
457    ///Processes the next node.
458    ///
459    ///\return The processed node.
460    ///
461    ///\pre The queue must not be empty.
462    Node processNextNode()
463    {
464      if(_queue_tail==_queue_next_dist) {
465        _curr_dist++;
466        _queue_next_dist=_queue_head;
467      }
468      Node n=_queue[_queue_tail++];
469      _processed->set(n,true);
470      Node m;
471      for(OutArcIt e(*G,n);e!=INVALID;++e)
472        if(!(*_reached)[m=G->target(e)]) {
473          _queue[_queue_head++]=m;
474          _reached->set(m,true);
475          _pred->set(m,e);
476          _dist->set(m,_curr_dist);
477        }
478      return n;
479    }
480
481    ///Processes the next node.
482
483    ///Processes the next node and checks if the given target node
484    ///is reached. If the target node is reachable from the processed
485    ///node, then the \c reach parameter will be set to \c true.
486    ///
487    ///\param target The target node.
488    ///\retval reach Indicates if the target node is reached.
489    ///It should be initially \c false.
490    ///
491    ///\return The processed node.
492    ///
493    ///\pre The queue must not be empty.
494    Node processNextNode(Node target, bool& reach)
495    {
496      if(_queue_tail==_queue_next_dist) {
497        _curr_dist++;
498        _queue_next_dist=_queue_head;
499      }
500      Node n=_queue[_queue_tail++];
501      _processed->set(n,true);
502      Node m;
503      for(OutArcIt e(*G,n);e!=INVALID;++e)
504        if(!(*_reached)[m=G->target(e)]) {
505          _queue[_queue_head++]=m;
506          _reached->set(m,true);
507          _pred->set(m,e);
508          _dist->set(m,_curr_dist);
509          reach = reach || (target == m);
510        }
511      return n;
512    }
513
514    ///Processes the next node.
515
516    ///Processes the next node and checks if at least one of reached
517    ///nodes has \c true value in the \c nm node map. If one node
518    ///with \c true value is reachable from the processed node, then the
519    ///\c rnode parameter will be set to the first of such nodes.
520    ///
521    ///\param nm A \c bool (or convertible) node map that indicates the
522    ///possible targets.
523    ///\retval rnode The reached target node.
524    ///It should be initially \c INVALID.
525    ///
526    ///\return The processed node.
527    ///
528    ///\pre 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(OutArcIt 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    ///The next node to be processed.
551
552    ///Returns the next node to be processed or \c INVALID if the queue
553    ///is empty.
554    Node nextNode() const
555    {
556      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
557    }
558
559    ///Returns \c false if there are nodes to be processed.
560
561    ///Returns \c false if there are nodes to be processed
562    ///in the queue.
563    bool emptyQueue() const { return _queue_tail==_queue_head; }
564
565    ///Returns the number of the nodes to be processed.
566
567    ///Returns the number of the nodes to be processed
568    ///in the queue.
569    int queueSize() const { return _queue_head-_queue_tail; }
570
571    ///Executes the algorithm.
572
573    ///Executes the algorithm.
574    ///
575    ///This method runs the %BFS algorithm from the root node(s)
576    ///in order to compute the shortest path to each node.
577    ///
578    ///The algorithm computes
579    ///- the shortest path tree (forest),
580    ///- the distance of each node from the root(s).
581    ///
582    ///\pre init() must be called and at least one root node should be
583    ///added with addSource() before using this function.
584    ///
585    ///\note <tt>b.start()</tt> is just a shortcut of the following code.
586    ///\code
587    ///  while ( !b.emptyQueue() ) {
588    ///    b.processNextNode();
589    ///  }
590    ///\endcode
591    void start()
592    {
593      while ( !emptyQueue() ) processNextNode();
594    }
595
596    ///Executes the algorithm until the given target node is reached.
597
598    ///Executes the algorithm until the given target node is reached.
599    ///
600    ///This method runs the %BFS algorithm from the root node(s)
601    ///in order to compute the shortest path to \c t.
602    ///
603    ///The algorithm computes
604    ///- the shortest path to \c t,
605    ///- the distance of \c t from the root(s).
606    ///
607    ///\pre init() must be called and at least one root node should be
608    ///added with addSource() before using this function.
609    ///
610    ///\note <tt>b.start(t)</tt> is just a shortcut of the following code.
611    ///\code
612    ///  bool reach = false;
613    ///  while ( !b.emptyQueue() && !reach ) {
614    ///    b.processNextNode(t, reach);
615    ///  }
616    ///\endcode
617    void start(Node t)
618    {
619      bool reach = false;
620      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
621    }
622
623    ///Executes the algorithm until a condition is met.
624
625    ///Executes the algorithm until a condition is met.
626    ///
627    ///This method runs the %BFS algorithm from the root node(s) in
628    ///order to compute the shortest path to a node \c v with
629    /// <tt>nm[v]</tt> true, if such a node can be found.
630    ///
631    ///\param nm A \c bool (or convertible) node map. The algorithm
632    ///will stop when it reaches a node \c v with <tt>nm[v]</tt> true.
633    ///
634    ///\return The reached node \c v with <tt>nm[v]</tt> true or
635    ///\c INVALID if no such node was found.
636    ///
637    ///\pre init() must be called and at least one root node should be
638    ///added with addSource() before using this function.
639    ///
640    ///\note <tt>b.start(nm)</tt> is just a shortcut of the following code.
641    ///\code
642    ///  Node rnode = INVALID;
643    ///  while ( !b.emptyQueue() && rnode == INVALID ) {
644    ///    b.processNextNode(nm, rnode);
645    ///  }
646    ///  return rnode;
647    ///\endcode
648    template<class NodeBoolMap>
649    Node start(const NodeBoolMap &nm)
650    {
651      Node rnode = INVALID;
652      while ( !emptyQueue() && rnode == INVALID ) {
653        processNextNode(nm, rnode);
654      }
655      return rnode;
656    }
657
658    ///Runs the algorithm from the given source node.
659
660    ///This method runs the %BFS algorithm from node \c s
661    ///in order to compute the shortest path to each node.
662    ///
663    ///The algorithm computes
664    ///- the shortest path tree,
665    ///- the distance of each node from the root.
666    ///
667    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
668    ///\code
669    ///  b.init();
670    ///  b.addSource(s);
671    ///  b.start();
672    ///\endcode
673    void run(Node s) {
674      init();
675      addSource(s);
676      start();
677    }
678
679    ///Finds the shortest path between \c s and \c t.
680
681    ///This method runs the %BFS algorithm from node \c s
682    ///in order to compute the shortest path to node \c t
683    ///(it stops searching when \c t is processed).
684    ///
685    ///\return \c true if \c t is reachable form \c s.
686    ///
687    ///\note Apart from the return value, <tt>b.run(s,t)</tt> is just a
688    ///shortcut of the following code.
689    ///\code
690    ///  b.init();
691    ///  b.addSource(s);
692    ///  b.start(t);
693    ///\endcode
694    bool run(Node s,Node t) {
695      init();
696      addSource(s);
697      start(t);
698      return reached(t);
699    }
700
701    ///Runs the algorithm to visit all nodes in the digraph.
702
703    ///This method runs the %BFS algorithm in order to
704    ///compute the shortest path to each node.
705    ///
706    ///The algorithm computes
707    ///- the shortest path tree (forest),
708    ///- the distance of each node from the root(s).
709    ///
710    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
711    ///\code
712    ///  b.init();
713    ///  for (NodeIt n(gr); n != INVALID; ++n) {
714    ///    if (!b.reached(n)) {
715    ///      b.addSource(n);
716    ///      b.start();
717    ///    }
718    ///  }
719    ///\endcode
720    void run() {
721      init();
722      for (NodeIt n(*G); n != INVALID; ++n) {
723        if (!reached(n)) {
724          addSource(n);
725          start();
726        }
727      }
728    }
729
730    ///@}
731
732    ///\name Query Functions
733    ///The results of the BFS algorithm can be obtained using these
734    ///functions.\n
735    ///Either \ref run(Node) "run()" or \ref start() should be called
736    ///before using them.
737
738    ///@{
739
740    ///The shortest path to a node.
741
742    ///Returns the shortest path to a node.
743    ///
744    ///\warning \c t should be reached from the root(s).
745    ///
746    ///\pre Either \ref run(Node) "run()" or \ref init()
747    ///must be called before using this function.
748    Path path(Node t) const { return Path(*G, *_pred, t); }
749
750    ///The distance of a node from the root(s).
751
752    ///Returns the distance of a node from the root(s).
753    ///
754    ///\warning If node \c v is not reached from the root(s), then
755    ///the return value of this function is undefined.
756    ///
757    ///\pre Either \ref run(Node) "run()" or \ref init()
758    ///must be called before using this function.
759    int dist(Node v) const { return (*_dist)[v]; }
760
761    ///Returns the 'previous arc' of the shortest path tree for a node.
762
763    ///This function returns the 'previous arc' of the shortest path
764    ///tree for the node \c v, i.e. it returns the last arc of a
765    ///shortest path from a root to \c v. It is \c INVALID if \c v
766    ///is not reached from the root(s) or if \c v is a root.
767    ///
768    ///The shortest path tree used here is equal to the shortest path
769    ///tree used in \ref predNode().
770    ///
771    ///\pre Either \ref run(Node) "run()" or \ref init()
772    ///must be called before using this function.
773    Arc predArc(Node v) const { return (*_pred)[v];}
774
775    ///Returns the 'previous node' of the shortest path tree for a node.
776
777    ///This function returns the 'previous node' of the shortest path
778    ///tree for the node \c v, i.e. it returns the last but one node
779    ///from a shortest path from a root to \c v. It is \c INVALID
780    ///if \c v is not reached from the root(s) or if \c v is a root.
781    ///
782    ///The shortest path tree used here is equal to the shortest path
783    ///tree used in \ref predArc().
784    ///
785    ///\pre Either \ref run(Node) "run()" or \ref init()
786    ///must be called before using this function.
787    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
788                                  G->source((*_pred)[v]); }
789
790    ///\brief Returns a const reference to the node map that stores the
791    /// distances of the nodes.
792    ///
793    ///Returns a const reference to the node map that stores the distances
794    ///of the nodes calculated by the algorithm.
795    ///
796    ///\pre Either \ref run(Node) "run()" or \ref init()
797    ///must be called before using this function.
798    const DistMap &distMap() const { return *_dist;}
799
800    ///\brief Returns a const reference to the node map that stores the
801    ///predecessor arcs.
802    ///
803    ///Returns a const reference to the node map that stores the predecessor
804    ///arcs, which form the shortest path tree.
805    ///
806    ///\pre Either \ref run(Node) "run()" or \ref init()
807    ///must be called before using this function.
808    const PredMap &predMap() const { return *_pred;}
809
810    ///Checks if a node is reached from the root(s).
811
812    ///Returns \c true if \c v is reached from the root(s).
813    ///
814    ///\pre Either \ref run(Node) "run()" or \ref init()
815    ///must be called before using this function.
816    bool reached(Node v) const { return (*_reached)[v]; }
817
818    ///@}
819  };
820
821  ///Default traits class of bfs() function.
822
823  ///Default traits class of bfs() function.
824  ///\tparam GR Digraph type.
825  template<class GR>
826  struct BfsWizardDefaultTraits
827  {
828    ///The type of the digraph the algorithm runs on.
829    typedef GR Digraph;
830
831    ///\brief The type of the map that stores the predecessor
832    ///arcs of the shortest paths.
833    ///
834    ///The type of the map that stores the predecessor
835    ///arcs of the shortest paths.
836    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
837    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
838    ///Instantiates a PredMap.
839
840    ///This function instantiates a PredMap.
841    ///\param g is the digraph, to which we would like to define the
842    ///PredMap.
843    static PredMap *createPredMap(const Digraph &g)
844    {
845      return new PredMap(g);
846    }
847
848    ///The type of the map that indicates which nodes are processed.
849
850    ///The type of the map that indicates which nodes are processed.
851    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
852    ///By default it is a NullMap.
853    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
854    ///Instantiates a ProcessedMap.
855
856    ///This function instantiates a ProcessedMap.
857    ///\param g is the digraph, to which
858    ///we would like to define the ProcessedMap.
859#ifdef DOXYGEN
860    static ProcessedMap *createProcessedMap(const Digraph &g)
861#else
862    static ProcessedMap *createProcessedMap(const Digraph &)
863#endif
864    {
865      return new ProcessedMap();
866    }
867
868    ///The type of the map that indicates which nodes are reached.
869
870    ///The type of the map that indicates which nodes are reached.
871    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
872    typedef typename Digraph::template NodeMap<bool> ReachedMap;
873    ///Instantiates a ReachedMap.
874
875    ///This function instantiates a ReachedMap.
876    ///\param g is the digraph, to which
877    ///we would like to define the ReachedMap.
878    static ReachedMap *createReachedMap(const Digraph &g)
879    {
880      return new ReachedMap(g);
881    }
882
883    ///The type of the map that stores the distances of the nodes.
884
885    ///The type of the map that stores the distances of the nodes.
886    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
887    typedef typename Digraph::template NodeMap<int> DistMap;
888    ///Instantiates a DistMap.
889
890    ///This function instantiates a DistMap.
891    ///\param g is the digraph, to which we would like to define
892    ///the DistMap
893    static DistMap *createDistMap(const Digraph &g)
894    {
895      return new DistMap(g);
896    }
897
898    ///The type of the shortest paths.
899
900    ///The type of the shortest paths.
901    ///It must meet the \ref concepts::Path "Path" concept.
902    typedef lemon::Path<Digraph> Path;
903  };
904
905  /// Default traits class used by BfsWizard
906
907  /// To make it easier to use Bfs algorithm
908  /// we have created a wizard class.
909  /// This \ref BfsWizard class needs default traits,
910  /// as well as the \ref Bfs class.
911  /// The \ref BfsWizardBase is a class to be the default traits of the
912  /// \ref BfsWizard class.
913  template<class GR>
914  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
915  {
916
917    typedef BfsWizardDefaultTraits<GR> Base;
918  protected:
919    //The type of the nodes in the digraph.
920    typedef typename Base::Digraph::Node Node;
921
922    //Pointer to the digraph the algorithm runs on.
923    void *_g;
924    //Pointer to the map of reached nodes.
925    void *_reached;
926    //Pointer to the map of processed nodes.
927    void *_processed;
928    //Pointer to the map of predecessors arcs.
929    void *_pred;
930    //Pointer to the map of distances.
931    void *_dist;
932    //Pointer to the shortest path to the target node.
933    void *_path;
934    //Pointer to the distance of the target node.
935    int *_di;
936
937    public:
938    /// Constructor.
939
940    /// This constructor does not require parameters, therefore it initiates
941    /// all of the attributes to \c 0.
942    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
943                      _dist(0), _path(0), _di(0) {}
944
945    /// Constructor.
946
947    /// This constructor requires one parameter,
948    /// others are initiated to \c 0.
949    /// \param g The digraph the algorithm runs on.
950    BfsWizardBase(const GR &g) :
951      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
952      _reached(0), _processed(0), _pred(0), _dist(0),  _path(0), _di(0) {}
953
954  };
955
956  /// Auxiliary class for the function-type interface of BFS algorithm.
957
958  /// This auxiliary class is created to implement the
959  /// \ref bfs() "function-type interface" of \ref Bfs algorithm.
960  /// It does not have own \ref run(Node) "run()" method, it uses the
961  /// functions and features of the plain \ref Bfs.
962  ///
963  /// This class should only be used through the \ref bfs() function,
964  /// which makes it easier to use the algorithm.
965  template<class TR>
966  class BfsWizard : public TR
967  {
968    typedef TR Base;
969
970    ///The type of the digraph the algorithm runs on.
971    typedef typename TR::Digraph Digraph;
972
973    typedef typename Digraph::Node Node;
974    typedef typename Digraph::NodeIt NodeIt;
975    typedef typename Digraph::Arc Arc;
976    typedef typename Digraph::OutArcIt OutArcIt;
977
978    ///\brief The type of the map that stores the predecessor
979    ///arcs of the shortest paths.
980    typedef typename TR::PredMap PredMap;
981    ///\brief The type of the map that stores the distances of the nodes.
982    typedef typename TR::DistMap DistMap;
983    ///\brief The type of the map that indicates which nodes are reached.
984    typedef typename TR::ReachedMap ReachedMap;
985    ///\brief The type of the map that indicates which nodes are processed.
986    typedef typename TR::ProcessedMap ProcessedMap;
987    ///The type of the shortest paths
988    typedef typename TR::Path Path;
989
990  public:
991
992    /// Constructor.
993    BfsWizard() : TR() {}
994
995    /// Constructor that requires parameters.
996
997    /// Constructor that requires parameters.
998    /// These parameters will be the default values for the traits class.
999    /// \param g The digraph the algorithm runs on.
1000    BfsWizard(const Digraph &g) :
1001      TR(g) {}
1002
1003    ///Copy constructor
1004    BfsWizard(const TR &b) : TR(b) {}
1005
1006    ~BfsWizard() {}
1007
1008    ///Runs BFS algorithm from the given source node.
1009
1010    ///This method runs BFS algorithm from node \c s
1011    ///in order to compute the shortest path to each node.
1012    void run(Node s)
1013    {
1014      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1015      if (Base::_pred)
1016        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1017      if (Base::_dist)
1018        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1019      if (Base::_reached)
1020        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1021      if (Base::_processed)
1022        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1023      if (s!=INVALID)
1024        alg.run(s);
1025      else
1026        alg.run();
1027    }
1028
1029    ///Finds the shortest path between \c s and \c t.
1030
1031    ///This method runs BFS algorithm from node \c s
1032    ///in order to compute the shortest path to node \c t
1033    ///(it stops searching when \c t is processed).
1034    ///
1035    ///\return \c true if \c t is reachable form \c s.
1036    bool run(Node s, Node t)
1037    {
1038      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1039      if (Base::_pred)
1040        alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred));
1041      if (Base::_dist)
1042        alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist));
1043      if (Base::_reached)
1044        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1045      if (Base::_processed)
1046        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
1047      alg.run(s,t);
1048      if (Base::_path)
1049        *reinterpret_cast<Path*>(Base::_path) = alg.path(t);
1050      if (Base::_di)
1051        *Base::_di = alg.dist(t);
1052      return alg.reached(t);
1053    }
1054
1055    ///Runs BFS algorithm to visit all nodes in the digraph.
1056
1057    ///This method runs BFS algorithm in order to compute
1058    ///the shortest path to each node.
1059    void run()
1060    {
1061      run(INVALID);
1062    }
1063
1064    template<class T>
1065    struct SetPredMapBase : public Base {
1066      typedef T PredMap;
1067      static PredMap *createPredMap(const Digraph &) { return 0; };
1068      SetPredMapBase(const TR &b) : TR(b) {}
1069    };
1070    ///\brief \ref named-func-param "Named parameter"
1071    ///for setting PredMap object.
1072    ///
1073    ///\ref named-func-param "Named parameter"
1074    ///for setting PredMap object.
1075    template<class T>
1076    BfsWizard<SetPredMapBase<T> > predMap(const T &t)
1077    {
1078      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1079      return BfsWizard<SetPredMapBase<T> >(*this);
1080    }
1081
1082    template<class T>
1083    struct SetReachedMapBase : public Base {
1084      typedef T ReachedMap;
1085      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
1086      SetReachedMapBase(const TR &b) : TR(b) {}
1087    };
1088    ///\brief \ref named-func-param "Named parameter"
1089    ///for setting ReachedMap object.
1090    ///
1091    /// \ref named-func-param "Named parameter"
1092    ///for setting ReachedMap object.
1093    template<class T>
1094    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)
1095    {
1096      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
1097      return BfsWizard<SetReachedMapBase<T> >(*this);
1098    }
1099
1100    template<class T>
1101    struct SetDistMapBase : public Base {
1102      typedef T DistMap;
1103      static DistMap *createDistMap(const Digraph &) { return 0; };
1104      SetDistMapBase(const TR &b) : TR(b) {}
1105    };
1106    ///\brief \ref named-func-param "Named parameter"
1107    ///for setting DistMap object.
1108    ///
1109    /// \ref named-func-param "Named parameter"
1110    ///for setting DistMap object.
1111    template<class T>
1112    BfsWizard<SetDistMapBase<T> > distMap(const T &t)
1113    {
1114      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1115      return BfsWizard<SetDistMapBase<T> >(*this);
1116    }
1117
1118    template<class T>
1119    struct SetProcessedMapBase : public Base {
1120      typedef T ProcessedMap;
1121      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
1122      SetProcessedMapBase(const TR &b) : TR(b) {}
1123    };
1124    ///\brief \ref named-func-param "Named parameter"
1125    ///for setting ProcessedMap object.
1126    ///
1127    /// \ref named-func-param "Named parameter"
1128    ///for setting ProcessedMap object.
1129    template<class T>
1130    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)
1131    {
1132      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
1133      return BfsWizard<SetProcessedMapBase<T> >(*this);
1134    }
1135
1136    template<class T>
1137    struct SetPathBase : public Base {
1138      typedef T Path;
1139      SetPathBase(const TR &b) : TR(b) {}
1140    };
1141    ///\brief \ref named-func-param "Named parameter"
1142    ///for getting the shortest path to the target node.
1143    ///
1144    ///\ref named-func-param "Named parameter"
1145    ///for getting the shortest path to the target node.
1146    template<class T>
1147    BfsWizard<SetPathBase<T> > path(const T &t)
1148    {
1149      Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t));
1150      return BfsWizard<SetPathBase<T> >(*this);
1151    }
1152
1153    ///\brief \ref named-func-param "Named parameter"
1154    ///for getting the distance of the target node.
1155    ///
1156    ///\ref named-func-param "Named parameter"
1157    ///for getting the distance of the target node.
1158    BfsWizard dist(const int &d)
1159    {
1160      Base::_di=const_cast<int*>(&d);
1161      return *this;
1162    }
1163
1164  };
1165
1166  ///Function-type interface for BFS algorithm.
1167
1168  /// \ingroup search
1169  ///Function-type interface for BFS algorithm.
1170  ///
1171  ///This function also has several \ref named-func-param "named parameters",
1172  ///they are declared as the members of class \ref BfsWizard.
1173  ///The following examples show how to use these parameters.
1174  ///\code
1175  ///  // Compute shortest path from node s to each node
1176  ///  bfs(g).predMap(preds).distMap(dists).run(s);
1177  ///
1178  ///  // Compute shortest path from s to t
1179  ///  bool reached = bfs(g).path(p).dist(d).run(s,t);
1180  ///\endcode
1181  ///\warning Don't forget to put the \ref BfsWizard::run(Node) "run()"
1182  ///to the end of the parameter list.
1183  ///\sa BfsWizard
1184  ///\sa Bfs
1185  template<class GR>
1186  BfsWizard<BfsWizardBase<GR> >
1187  bfs(const GR &digraph)
1188  {
1189    return BfsWizard<BfsWizardBase<GR> >(digraph);
1190  }
1191
1192#ifdef DOXYGEN
1193  /// \brief Visitor class for BFS.
1194  ///
1195  /// This class defines the interface of the BfsVisit events, and
1196  /// it could be the base of a real visitor class.
1197  template <typename GR>
1198  struct BfsVisitor {
1199    typedef GR Digraph;
1200    typedef typename Digraph::Arc Arc;
1201    typedef typename Digraph::Node Node;
1202    /// \brief Called for the source node(s) of the BFS.
1203    ///
1204    /// This function is called for the source node(s) of the BFS.
1205    void start(const Node& node) {}
1206    /// \brief Called when a node is reached first time.
1207    ///
1208    /// This function is called when a node is reached first time.
1209    void reach(const Node& node) {}
1210    /// \brief Called when a node is processed.
1211    ///
1212    /// This function is called when a node is processed.
1213    void process(const Node& node) {}
1214    /// \brief Called when an arc reaches a new node.
1215    ///
1216    /// This function is called when the BFS finds an arc whose target node
1217    /// is not reached yet.
1218    void discover(const Arc& arc) {}
1219    /// \brief Called when an arc is examined but its target node is
1220    /// already discovered.
1221    ///
1222    /// This function is called when an arc is examined but its target node is
1223    /// already discovered.
1224    void examine(const Arc& arc) {}
1225  };
1226#else
1227  template <typename GR>
1228  struct BfsVisitor {
1229    typedef GR Digraph;
1230    typedef typename Digraph::Arc Arc;
1231    typedef typename Digraph::Node Node;
1232    void start(const Node&) {}
1233    void reach(const Node&) {}
1234    void process(const Node&) {}
1235    void discover(const Arc&) {}
1236    void examine(const Arc&) {}
1237
1238    template <typename _Visitor>
1239    struct Constraints {
1240      void constraints() {
1241        Arc arc;
1242        Node node;
1243        visitor.start(node);
1244        visitor.reach(node);
1245        visitor.process(node);
1246        visitor.discover(arc);
1247        visitor.examine(arc);
1248      }
1249      _Visitor& visitor;
1250      Constraints() {}
1251    };
1252  };
1253#endif
1254
1255  /// \brief Default traits class of BfsVisit class.
1256  ///
1257  /// Default traits class of BfsVisit class.
1258  /// \tparam GR The type of the digraph the algorithm runs on.
1259  template<class GR>
1260  struct BfsVisitDefaultTraits {
1261
1262    /// \brief The type of the digraph the algorithm runs on.
1263    typedef GR Digraph;
1264
1265    /// \brief The type of the map that indicates which nodes are reached.
1266    ///
1267    /// The type of the map that indicates which nodes are reached.
1268    /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
1269    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1270
1271    /// \brief Instantiates a ReachedMap.
1272    ///
1273    /// This function instantiates a ReachedMap.
1274    /// \param digraph is the digraph, to which
1275    /// we would like to define the ReachedMap.
1276    static ReachedMap *createReachedMap(const Digraph &digraph) {
1277      return new ReachedMap(digraph);
1278    }
1279
1280  };
1281
1282  /// \ingroup search
1283  ///
1284  /// \brief BFS algorithm class with visitor interface.
1285  ///
1286  /// This class provides an efficient implementation of the BFS algorithm
1287  /// with visitor interface.
1288  ///
1289  /// The BfsVisit class provides an alternative interface to the Bfs
1290  /// class. It works with callback mechanism, the BfsVisit object calls
1291  /// the member functions of the \c Visitor class on every BFS event.
1292  ///
1293  /// This interface of the BFS algorithm should be used in special cases
1294  /// when extra actions have to be performed in connection with certain
1295  /// events of the BFS algorithm. Otherwise consider to use Bfs or bfs()
1296  /// instead.
1297  ///
1298  /// \tparam GR The type of the digraph the algorithm runs on.
1299  /// The default type is \ref ListDigraph.
1300  /// The value of GR is not used directly by \ref BfsVisit,
1301  /// it is only passed to \ref BfsVisitDefaultTraits.
1302  /// \tparam VS The Visitor type that is used by the algorithm.
1303  /// \ref BfsVisitor "BfsVisitor<GR>" is an empty visitor, which
1304  /// does not observe the BFS events. If you want to observe the BFS
1305  /// events, you should implement your own visitor class.
1306  /// \tparam TR Traits class to set various data types used by the
1307  /// algorithm. The default traits class is
1308  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<GR>".
1309  /// See \ref BfsVisitDefaultTraits for the documentation of
1310  /// a BFS visit traits class.
1311#ifdef DOXYGEN
1312  template <typename GR, typename VS, typename TR>
1313#else
1314  template <typename GR = ListDigraph,
1315            typename VS = BfsVisitor<GR>,
1316            typename TR = BfsVisitDefaultTraits<GR> >
1317#endif
1318  class BfsVisit {
1319  public:
1320
1321    ///The traits class.
1322    typedef TR Traits;
1323
1324    ///The type of the digraph the algorithm runs on.
1325    typedef typename Traits::Digraph Digraph;
1326
1327    ///The visitor type used by the algorithm.
1328    typedef VS Visitor;
1329
1330    ///The type of the map that indicates which nodes are reached.
1331    typedef typename Traits::ReachedMap ReachedMap;
1332
1333  private:
1334
1335    typedef typename Digraph::Node Node;
1336    typedef typename Digraph::NodeIt NodeIt;
1337    typedef typename Digraph::Arc Arc;
1338    typedef typename Digraph::OutArcIt OutArcIt;
1339
1340    //Pointer to the underlying digraph.
1341    const Digraph *_digraph;
1342    //Pointer to the visitor object.
1343    Visitor *_visitor;
1344    //Pointer to the map of reached status of the nodes.
1345    ReachedMap *_reached;
1346    //Indicates if _reached is locally allocated (true) or not.
1347    bool local_reached;
1348
1349    std::vector<typename Digraph::Node> _list;
1350    int _list_front, _list_back;
1351
1352    //Creates the maps if necessary.
1353    void create_maps() {
1354      if(!_reached) {
1355        local_reached = true;
1356        _reached = Traits::createReachedMap(*_digraph);
1357      }
1358    }
1359
1360  protected:
1361
1362    BfsVisit() {}
1363
1364  public:
1365
1366    typedef BfsVisit Create;
1367
1368    /// \name Named Template Parameters
1369
1370    ///@{
1371    template <class T>
1372    struct SetReachedMapTraits : public Traits {
1373      typedef T ReachedMap;
1374      static ReachedMap *createReachedMap(const Digraph &digraph) {
1375        LEMON_ASSERT(false, "ReachedMap is not initialized");
1376        return 0; // ignore warnings
1377      }
1378    };
1379    /// \brief \ref named-templ-param "Named parameter" for setting
1380    /// ReachedMap type.
1381    ///
1382    /// \ref named-templ-param "Named parameter" for setting ReachedMap type.
1383    template <class T>
1384    struct SetReachedMap : public BfsVisit< Digraph, Visitor,
1385                                            SetReachedMapTraits<T> > {
1386      typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create;
1387    };
1388    ///@}
1389
1390  public:
1391
1392    /// \brief Constructor.
1393    ///
1394    /// Constructor.
1395    ///
1396    /// \param digraph The digraph the algorithm runs on.
1397    /// \param visitor The visitor object of the algorithm.
1398    BfsVisit(const Digraph& digraph, Visitor& visitor)
1399      : _digraph(&digraph), _visitor(&visitor),
1400        _reached(0), local_reached(false) {}
1401
1402    /// \brief Destructor.
1403    ~BfsVisit() {
1404      if(local_reached) delete _reached;
1405    }
1406
1407    /// \brief Sets the map that indicates which nodes are reached.
1408    ///
1409    /// Sets the map that indicates which nodes are reached.
1410    /// If you don't use this function before calling \ref run(Node) "run()"
1411    /// or \ref init(), an instance will be allocated automatically.
1412    /// The destructor deallocates this automatically allocated map,
1413    /// of course.
1414    /// \return <tt> (*this) </tt>
1415    BfsVisit &reachedMap(ReachedMap &m) {
1416      if(local_reached) {
1417        delete _reached;
1418        local_reached = false;
1419      }
1420      _reached = &m;
1421      return *this;
1422    }
1423
1424  public:
1425
1426    /// \name Execution Control
1427    /// The simplest way to execute the BFS algorithm is to use one of the
1428    /// member functions called \ref run(Node) "run()".\n
1429    /// If you need more control on the execution, first you have to call
1430    /// \ref init(), then you can add several source nodes with
1431    /// \ref addSource(). Finally the actual path computation can be
1432    /// performed with one of the \ref start() functions.
1433
1434    /// @{
1435
1436    /// \brief Initializes the internal data structures.
1437    ///
1438    /// Initializes the internal data structures.
1439    void init() {
1440      create_maps();
1441      _list.resize(countNodes(*_digraph));
1442      _list_front = _list_back = -1;
1443      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
1444        _reached->set(u, false);
1445      }
1446    }
1447
1448    /// \brief Adds a new source node.
1449    ///
1450    /// Adds a new source node to the set of nodes to be processed.
1451    void addSource(Node s) {
1452      if(!(*_reached)[s]) {
1453          _reached->set(s,true);
1454          _visitor->start(s);
1455          _visitor->reach(s);
1456          _list[++_list_back] = s;
1457        }
1458    }
1459
1460    /// \brief Processes the next node.
1461    ///
1462    /// Processes the next node.
1463    ///
1464    /// \return The processed node.
1465    ///
1466    /// \pre The queue must not be empty.
1467    Node processNextNode() {
1468      Node n = _list[++_list_front];
1469      _visitor->process(n);
1470      Arc e;
1471      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1472        Node m = _digraph->target(e);
1473        if (!(*_reached)[m]) {
1474          _visitor->discover(e);
1475          _visitor->reach(m);
1476          _reached->set(m, true);
1477          _list[++_list_back] = m;
1478        } else {
1479          _visitor->examine(e);
1480        }
1481      }
1482      return n;
1483    }
1484
1485    /// \brief Processes the next node.
1486    ///
1487    /// Processes the next node and checks if the given target node
1488    /// is reached. If the target node is reachable from the processed
1489    /// node, then the \c reach parameter will be set to \c true.
1490    ///
1491    /// \param target The target node.
1492    /// \retval reach Indicates if the target node is reached.
1493    /// It should be initially \c false.
1494    ///
1495    /// \return The processed node.
1496    ///
1497    /// \pre The queue must not be empty.
1498    Node processNextNode(Node target, bool& reach) {
1499      Node n = _list[++_list_front];
1500      _visitor->process(n);
1501      Arc e;
1502      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1503        Node m = _digraph->target(e);
1504        if (!(*_reached)[m]) {
1505          _visitor->discover(e);
1506          _visitor->reach(m);
1507          _reached->set(m, true);
1508          _list[++_list_back] = m;
1509          reach = reach || (target == m);
1510        } else {
1511          _visitor->examine(e);
1512        }
1513      }
1514      return n;
1515    }
1516
1517    /// \brief Processes the next node.
1518    ///
1519    /// Processes the next node and checks if at least one of reached
1520    /// nodes has \c true value in the \c nm node map. If one node
1521    /// with \c true value is reachable from the processed node, then the
1522    /// \c rnode parameter will be set to the first of such nodes.
1523    ///
1524    /// \param nm A \c bool (or convertible) node map that indicates the
1525    /// possible targets.
1526    /// \retval rnode The reached target node.
1527    /// It should be initially \c INVALID.
1528    ///
1529    /// \return The processed node.
1530    ///
1531    /// \pre The queue must not be empty.
1532    template <typename NM>
1533    Node processNextNode(const NM& nm, Node& rnode) {
1534      Node n = _list[++_list_front];
1535      _visitor->process(n);
1536      Arc e;
1537      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1538        Node m = _digraph->target(e);
1539        if (!(*_reached)[m]) {
1540          _visitor->discover(e);
1541          _visitor->reach(m);
1542          _reached->set(m, true);
1543          _list[++_list_back] = m;
1544          if (nm[m] && rnode == INVALID) rnode = m;
1545        } else {
1546          _visitor->examine(e);
1547        }
1548      }
1549      return n;
1550    }
1551
1552    /// \brief The next node to be processed.
1553    ///
1554    /// Returns the next node to be processed or \c INVALID if the queue
1555    /// is empty.
1556    Node nextNode() const {
1557      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1558    }
1559
1560    /// \brief Returns \c false if there are nodes
1561    /// to be processed.
1562    ///
1563    /// Returns \c false if there are nodes
1564    /// to be processed in the queue.
1565    bool emptyQueue() const { return _list_front == _list_back; }
1566
1567    /// \brief Returns the number of the nodes to be processed.
1568    ///
1569    /// Returns the number of the nodes to be processed in the queue.
1570    int queueSize() const { return _list_back - _list_front; }
1571
1572    /// \brief Executes the algorithm.
1573    ///
1574    /// Executes the algorithm.
1575    ///
1576    /// This method runs the %BFS algorithm from the root node(s)
1577    /// in order to compute the shortest path to each node.
1578    ///
1579    /// The algorithm computes
1580    /// - the shortest path tree (forest),
1581    /// - the distance of each node from the root(s).
1582    ///
1583    /// \pre init() must be called and at least one root node should be added
1584    /// with addSource() before using this function.
1585    ///
1586    /// \note <tt>b.start()</tt> is just a shortcut of the following code.
1587    /// \code
1588    ///   while ( !b.emptyQueue() ) {
1589    ///     b.processNextNode();
1590    ///   }
1591    /// \endcode
1592    void start() {
1593      while ( !emptyQueue() ) processNextNode();
1594    }
1595
1596    /// \brief Executes the algorithm until the given target node is reached.
1597    ///
1598    /// Executes the algorithm until the given target node is reached.
1599    ///
1600    /// This method runs the %BFS algorithm from the root node(s)
1601    /// in order to compute the shortest path to \c t.
1602    ///
1603    /// The algorithm computes
1604    /// - the shortest path to \c t,
1605    /// - the distance of \c t from the root(s).
1606    ///
1607    /// \pre init() must be called and at least one root node should be
1608    /// added with addSource() before using this function.
1609    ///
1610    /// \note <tt>b.start(t)</tt> is just a shortcut of the following code.
1611    /// \code
1612    ///   bool reach = false;
1613    ///   while ( !b.emptyQueue() && !reach ) {
1614    ///     b.processNextNode(t, reach);
1615    ///   }
1616    /// \endcode
1617    void start(Node t) {
1618      bool reach = false;
1619      while ( !emptyQueue() && !reach ) processNextNode(t, reach);
1620    }
1621
1622    /// \brief Executes the algorithm until a condition is met.
1623    ///
1624    /// Executes the algorithm until a condition is met.
1625    ///
1626    /// This method runs the %BFS algorithm from the root node(s) in
1627    /// order to compute the shortest path to a node \c v with
1628    /// <tt>nm[v]</tt> true, if such a node can be found.
1629    ///
1630    /// \param nm must be a bool (or convertible) node map. The
1631    /// algorithm will stop when it reaches a node \c v with
1632    /// <tt>nm[v]</tt> true.
1633    ///
1634    /// \return The reached node \c v with <tt>nm[v]</tt> true or
1635    /// \c INVALID if no such node was found.
1636    ///
1637    /// \pre init() must be called and at least one root node should be
1638    /// added with addSource() before using this function.
1639    ///
1640    /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code.
1641    /// \code
1642    ///   Node rnode = INVALID;
1643    ///   while ( !b.emptyQueue() && rnode == INVALID ) {
1644    ///     b.processNextNode(nm, rnode);
1645    ///   }
1646    ///   return rnode;
1647    /// \endcode
1648    template <typename NM>
1649    Node start(const NM &nm) {
1650      Node rnode = INVALID;
1651      while ( !emptyQueue() && rnode == INVALID ) {
1652        processNextNode(nm, rnode);
1653      }
1654      return rnode;
1655    }
1656
1657    /// \brief Runs the algorithm from the given source node.
1658    ///
1659    /// This method runs the %BFS algorithm from node \c s
1660    /// in order to compute the shortest path to each node.
1661    ///
1662    /// The algorithm computes
1663    /// - the shortest path tree,
1664    /// - the distance of each node from the root.
1665    ///
1666    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1667    ///\code
1668    ///   b.init();
1669    ///   b.addSource(s);
1670    ///   b.start();
1671    ///\endcode
1672    void run(Node s) {
1673      init();
1674      addSource(s);
1675      start();
1676    }
1677
1678    /// \brief Finds the shortest path between \c s and \c t.
1679    ///
1680    /// This method runs the %BFS algorithm from node \c s
1681    /// in order to compute the shortest path to node \c t
1682    /// (it stops searching when \c t is processed).
1683    ///
1684    /// \return \c true if \c t is reachable form \c s.
1685    ///
1686    /// \note Apart from the return value, <tt>b.run(s,t)</tt> is just a
1687    /// shortcut of the following code.
1688    ///\code
1689    ///   b.init();
1690    ///   b.addSource(s);
1691    ///   b.start(t);
1692    ///\endcode
1693    bool run(Node s,Node t) {
1694      init();
1695      addSource(s);
1696      start(t);
1697      return reached(t);
1698    }
1699
1700    /// \brief Runs the algorithm to visit all nodes in the digraph.
1701    ///
1702    /// This method runs the %BFS algorithm in order to
1703    /// compute the shortest path to each node.
1704    ///
1705    /// The algorithm computes
1706    /// - the shortest path tree (forest),
1707    /// - the distance of each node from the root(s).
1708    ///
1709    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1710    ///\code
1711    ///  b.init();
1712    ///  for (NodeIt n(gr); n != INVALID; ++n) {
1713    ///    if (!b.reached(n)) {
1714    ///      b.addSource(n);
1715    ///      b.start();
1716    ///    }
1717    ///  }
1718    ///\endcode
1719    void run() {
1720      init();
1721      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1722        if (!reached(it)) {
1723          addSource(it);
1724          start();
1725        }
1726      }
1727    }
1728
1729    ///@}
1730
1731    /// \name Query Functions
1732    /// The results of the BFS algorithm can be obtained using these
1733    /// functions.\n
1734    /// Either \ref run(Node) "run()" or \ref start() should be called
1735    /// before using them.
1736
1737    ///@{
1738
1739    /// \brief Checks if a node is reached from the root(s).
1740    ///
1741    /// Returns \c true if \c v is reached from the root(s).
1742    ///
1743    /// \pre Either \ref run(Node) "run()" or \ref init()
1744    /// must be called before using this function.
1745    bool reached(Node v) const { return (*_reached)[v]; }
1746
1747    ///@}
1748
1749  };
1750
1751} //END OF NAMESPACE LEMON
1752
1753#endif
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