COIN-OR::LEMON - Graph Library

source: lemon/lemon/bfs.h @ 257:8d76a7bf9961

Last change on this file since 257:8d76a7bf9961 was 257:8d76a7bf9961, checked in by Peter Kovacs <kpeter@…>, 11 years ago

Rename Def* to Set* in Bfs, Dfs, Dijkstra (ticket #134)

File size: 53.0 KB
Line 
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) 2003-2008
6 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
7 * (Egervary Research Group on Combinatorial Optimization, EGRES).
8 *
9 * Permission to use, modify and distribute this software is granted
10 * provided that this copyright notice appears in all copies. For
11 * precise terms see the accompanying LICENSE file.
12 *
13 * This software is provided "AS IS" with no warranty of any kind,
14 * express or implied, and with no claim as to its suitability for any
15 * purpose.
16 *
17 */
18
19#ifndef LEMON_BFS_H
20#define LEMON_BFS_H
21
22///\ingroup search
23///\file
24///\brief BFS algorithm.
25
26#include <lemon/list_graph.h>
27#include <lemon/bits/path_dump.h>
28#include <lemon/core.h>
29#include <lemon/error.h>
30#include <lemon/maps.h>
31
32namespace lemon {
33
34  ///Default traits class of Bfs class.
35
36  ///Default traits class of Bfs class.
37  ///\tparam GR Digraph type.
38  template<class GR>
39  struct BfsDefaultTraits
40  {
41    ///The type of the digraph the algorithm runs on.
42    typedef GR Digraph;
43
44    ///\brief The type of the map that stores the predecessor
45    ///arcs of the shortest paths.
46    ///
47    ///The type of the map that stores the predecessor
48    ///arcs of the shortest paths.
49    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
50    typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap;
51    ///Instantiates a \ref PredMap.
52
53    ///This function instantiates a \ref PredMap.
54    ///\param g is the digraph, to which we would like to define the
55    ///\ref PredMap.
56    ///\todo The digraph alone may be insufficient to initialize
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    ///By default it is a NullMap.
67    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
68    ///Instantiates a \ref ProcessedMap.
69
70    ///This function instantiates a \ref ProcessedMap.
71    ///\param g is the digraph, to which
72    ///we would like to define the \ref ProcessedMap
73#ifdef DOXYGEN
74    static ProcessedMap *createProcessedMap(const Digraph &g)
75#else
76    static ProcessedMap *createProcessedMap(const Digraph &)
77#endif
78    {
79      return new ProcessedMap();
80    }
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::ReadWriteMap "ReadWriteMap" concept.
86    typedef typename Digraph::template NodeMap<bool> ReachedMap;
87    ///Instantiates a \ref ReachedMap.
88
89    ///This function instantiates a \ref ReachedMap.
90    ///\param g is the digraph, to which
91    ///we would like to define the \ref ReachedMap.
92    static ReachedMap *createReachedMap(const Digraph &g)
93    {
94      return new ReachedMap(g);
95    }
96
97    ///The type of the map that stores the distances of the nodes.
98
99    ///The type of the map that stores the distances of the nodes.
100    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
101    typedef typename Digraph::template NodeMap<int> DistMap;
102    ///Instantiates a \ref DistMap.
103
104    ///This function instantiates a \ref DistMap.
105    ///\param g is the digraph, to which we would like to define the
106    ///\ref DistMap.
107    static DistMap *createDistMap(const Digraph &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  ///There is also a \ref bfs() "function type interface" for the BFS
119  ///algorithm, which is convenient in the simplier cases and it can be
120  ///used easier.
121  ///
122  ///\tparam GR The type of the digraph the algorithm runs on.
123  ///The default value is \ref ListDigraph. The value of GR is not used
124  ///directly by \ref Bfs, it is only passed to \ref BfsDefaultTraits.
125  ///\tparam TR Traits class to set various data types used by the algorithm.
126  ///The default traits class is
127  ///\ref BfsDefaultTraits "BfsDefaultTraits<GR>".
128  ///See \ref BfsDefaultTraits for the documentation of
129  ///a Bfs traits class.
130#ifdef DOXYGEN
131  template <typename GR,
132            typename TR>
133#else
134  template <typename GR=ListDigraph,
135            typename TR=BfsDefaultTraits<GR> >
136#endif
137  class Bfs {
138  public:
139    ///\ref Exception for uninitialized parameters.
140
141    ///This error represents problems in the initialization of the
142    ///parameters of the algorithm.
143    class UninitializedParameter : public lemon::UninitializedParameter {
144    public:
145      virtual const char* what() const throw() {
146        return "lemon::Bfs::UninitializedParameter";
147      }
148    };
149
150    ///The type of the digraph the algorithm runs on.
151    typedef typename TR::Digraph Digraph;
152
153    ///\brief The type of the map that stores the predecessor arcs of the
154    ///shortest paths.
155    typedef typename TR::PredMap PredMap;
156    ///The type of the map that stores the distances of the nodes.
157    typedef typename TR::DistMap DistMap;
158    ///The type of the map that indicates which nodes are reached.
159    typedef typename TR::ReachedMap ReachedMap;
160    ///The type of the map that indicates which nodes are processed.
161    typedef typename TR::ProcessedMap ProcessedMap;
162    ///The type of the paths.
163    typedef PredMapPath<Digraph, PredMap> Path;
164
165    ///The traits class.
166    typedef TR Traits;
167
168  private:
169
170    typedef typename Digraph::Node Node;
171    typedef typename Digraph::NodeIt NodeIt;
172    typedef typename Digraph::Arc Arc;
173    typedef typename Digraph::OutArcIt OutArcIt;
174
175    //Pointer to the underlying digraph.
176    const Digraph *G;
177    //Pointer to the map of predecessor arcs.
178    PredMap *_pred;
179    //Indicates if _pred is locally allocated (true) or not.
180    bool local_pred;
181    //Pointer to the map of distances.
182    DistMap *_dist;
183    //Indicates if _dist is locally allocated (true) or not.
184    bool local_dist;
185    //Pointer to the map of reached status of the nodes.
186    ReachedMap *_reached;
187    //Indicates if _reached is locally allocated (true) or not.
188    bool local_reached;
189    //Pointer to the map of processed status of the nodes.
190    ProcessedMap *_processed;
191    //Indicates if _processed is locally allocated (true) or not.
192    bool local_processed;
193
194    std::vector<typename Digraph::Node> _queue;
195    int _queue_head,_queue_tail,_queue_next_dist;
196    int _curr_dist;
197
198    ///Creates the maps if necessary.
199    ///\todo Better memory allocation (instead of new).
200    void create_maps()
201    {
202      if(!_pred) {
203        local_pred = true;
204        _pred = Traits::createPredMap(*G);
205      }
206      if(!_dist) {
207        local_dist = true;
208        _dist = Traits::createDistMap(*G);
209      }
210      if(!_reached) {
211        local_reached = true;
212        _reached = Traits::createReachedMap(*G);
213      }
214      if(!_processed) {
215        local_processed = true;
216        _processed = Traits::createProcessedMap(*G);
217      }
218    }
219
220  protected:
221
222    Bfs() {}
223
224  public:
225
226    typedef Bfs Create;
227
228    ///\name Named template parameters
229
230    ///@{
231
232    template <class T>
233    struct SetPredMapTraits : public Traits {
234      typedef T PredMap;
235      static PredMap *createPredMap(const Digraph &)
236      {
237        throw UninitializedParameter();
238      }
239    };
240    ///\brief \ref named-templ-param "Named parameter" for setting
241    ///\ref PredMap type.
242    ///
243    ///\ref named-templ-param "Named parameter" for setting
244    ///\ref PredMap type.
245    template <class T>
246    struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > {
247      typedef Bfs< Digraph, SetPredMapTraits<T> > Create;
248    };
249
250    template <class T>
251    struct SetDistMapTraits : public Traits {
252      typedef T DistMap;
253      static DistMap *createDistMap(const Digraph &)
254      {
255        throw UninitializedParameter();
256      }
257    };
258    ///\brief \ref named-templ-param "Named parameter" for setting
259    ///\ref DistMap type.
260    ///
261    ///\ref named-templ-param "Named parameter" for setting
262    ///\ref DistMap type.
263    template <class T>
264    struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > {
265      typedef Bfs< Digraph, SetDistMapTraits<T> > Create;
266    };
267
268    template <class T>
269    struct SetReachedMapTraits : public Traits {
270      typedef T ReachedMap;
271      static ReachedMap *createReachedMap(const Digraph &)
272      {
273        throw UninitializedParameter();
274      }
275    };
276    ///\brief \ref named-templ-param "Named parameter" for setting
277    ///\ref ReachedMap type.
278    ///
279    ///\ref named-templ-param "Named parameter" for setting
280    ///\ref ReachedMap type.
281    template <class T>
282    struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > {
283      typedef Bfs< Digraph, SetReachedMapTraits<T> > Create;
284    };
285
286    template <class T>
287    struct SetProcessedMapTraits : public Traits {
288      typedef T ProcessedMap;
289      static ProcessedMap *createProcessedMap(const Digraph &)
290      {
291        throw UninitializedParameter();
292      }
293    };
294    ///\brief \ref named-templ-param "Named parameter" for setting
295    ///\ref ProcessedMap type.
296    ///
297    ///\ref named-templ-param "Named parameter" for setting
298    ///\ref ProcessedMap type.
299    template <class T>
300    struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > {
301      typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create;
302    };
303
304    struct SetStandardProcessedMapTraits : public Traits {
305      typedef typename Digraph::template NodeMap<bool> ProcessedMap;
306      static ProcessedMap *createProcessedMap(const Digraph &g)
307      {
308        return new ProcessedMap(g);
309      }
310    };
311    ///\brief \ref named-templ-param "Named parameter" for setting
312    ///\ref ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
313    ///
314    ///\ref named-templ-param "Named parameter" for setting
315    ///\ref ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>.
316    ///If you don't set it explicitly, it will be automatically allocated.
317    struct SetStandardProcessedMap :
318      public Bfs< Digraph, SetStandardProcessedMapTraits > {
319      typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create;
320    };
321
322    ///@}
323
324  public:
325
326    ///Constructor.
327
328    ///Constructor.
329    ///\param g The digraph the algorithm runs on.
330    Bfs(const Digraph &g) :
331      G(&g),
332      _pred(NULL), local_pred(false),
333      _dist(NULL), local_dist(false),
334      _reached(NULL), local_reached(false),
335      _processed(NULL), local_processed(false)
336    { }
337
338    ///Destructor.
339    ~Bfs()
340    {
341      if(local_pred) delete _pred;
342      if(local_dist) delete _dist;
343      if(local_reached) delete _reached;
344      if(local_processed) delete _processed;
345    }
346
347    ///Sets the map that stores the predecessor arcs.
348
349    ///Sets the map that stores the predecessor arcs.
350    ///If you don't use this function before calling \ref run(),
351    ///it will allocate one. The destructor deallocates this
352    ///automatically allocated map, of course.
353    ///\return <tt> (*this) </tt>
354    Bfs &predMap(PredMap &m)
355    {
356      if(local_pred) {
357        delete _pred;
358        local_pred=false;
359      }
360      _pred = &m;
361      return *this;
362    }
363
364    ///Sets the map that indicates which nodes are reached.
365
366    ///Sets the map that indicates which nodes are reached.
367    ///If you don't use this function before calling \ref run(),
368    ///it will allocate one. The destructor deallocates this
369    ///automatically allocated map, of course.
370    ///\return <tt> (*this) </tt>
371    Bfs &reachedMap(ReachedMap &m)
372    {
373      if(local_reached) {
374        delete _reached;
375        local_reached=false;
376      }
377      _reached = &m;
378      return *this;
379    }
380
381    ///Sets the map that indicates which nodes are processed.
382
383    ///Sets the map that indicates which nodes are processed.
384    ///If you don't use this function before calling \ref run(),
385    ///it will allocate one. The destructor deallocates this
386    ///automatically allocated map, of course.
387    ///\return <tt> (*this) </tt>
388    Bfs &processedMap(ProcessedMap &m)
389    {
390      if(local_processed) {
391        delete _processed;
392        local_processed=false;
393      }
394      _processed = &m;
395      return *this;
396    }
397
398    ///Sets the map that stores the distances of the nodes.
399
400    ///Sets the map that stores the distances of the nodes calculated by
401    ///the algorithm.
402    ///If you don't use this function before calling \ref run(),
403    ///it will allocate one. The destructor deallocates this
404    ///automatically allocated map, of course.
405    ///\return <tt> (*this) </tt>
406    Bfs &distMap(DistMap &m)
407    {
408      if(local_dist) {
409        delete _dist;
410        local_dist=false;
411      }
412      _dist = &m;
413      return *this;
414    }
415
416  public:
417
418    ///\name Execution control
419    ///The simplest way to execute the algorithm is to use
420    ///one of the member functions called \ref lemon::Bfs::run() "run()".
421    ///\n
422    ///If you need more control on the execution, first you must call
423    ///\ref lemon::Bfs::init() "init()", then you can add several source
424    ///nodes with \ref lemon::Bfs::addSource() "addSource()".
425    ///Finally \ref lemon::Bfs::start() "start()" will perform the
426    ///actual path computation.
427
428    ///@{
429
430    ///Initializes the internal data structures.
431
432    ///Initializes the internal data structures.
433    ///
434    void init()
435    {
436      create_maps();
437      _queue.resize(countNodes(*G));
438      _queue_head=_queue_tail=0;
439      _curr_dist=1;
440      for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
441        _pred->set(u,INVALID);
442        _reached->set(u,false);
443        _processed->set(u,false);
444      }
445    }
446
447    ///Adds a new source node.
448
449    ///Adds a new source node to the set of nodes to be processed.
450    ///
451    void addSource(Node s)
452    {
453      if(!(*_reached)[s])
454        {
455          _reached->set(s,true);
456          _pred->set(s,INVALID);
457          _dist->set(s,0);
458          _queue[_queue_head++]=s;
459          _queue_next_dist=_queue_head;
460        }
461    }
462
463    ///Processes the next node.
464
465    ///Processes the next node.
466    ///
467    ///\return The processed node.
468    ///
469    ///\pre The queue must not be empty.
470    Node processNextNode()
471    {
472      if(_queue_tail==_queue_next_dist) {
473        _curr_dist++;
474        _queue_next_dist=_queue_head;
475      }
476      Node n=_queue[_queue_tail++];
477      _processed->set(n,true);
478      Node m;
479      for(OutArcIt e(*G,n);e!=INVALID;++e)
480        if(!(*_reached)[m=G->target(e)]) {
481          _queue[_queue_head++]=m;
482          _reached->set(m,true);
483          _pred->set(m,e);
484          _dist->set(m,_curr_dist);
485        }
486      return n;
487    }
488
489    ///Processes the next node.
490
491    ///Processes the next node and checks if the given target node
492    ///is reached. If the target node is reachable from the processed
493    ///node, then the \c reach parameter will be set to \c true.
494    ///
495    ///\param target The target node.
496    ///\retval reach Indicates if the target node is reached.
497    ///It should be initially \c false.
498    ///
499    ///\return The processed node.
500    ///
501    ///\pre The queue must not be empty.
502    Node processNextNode(Node target, bool& reach)
503    {
504      if(_queue_tail==_queue_next_dist) {
505        _curr_dist++;
506        _queue_next_dist=_queue_head;
507      }
508      Node n=_queue[_queue_tail++];
509      _processed->set(n,true);
510      Node m;
511      for(OutArcIt e(*G,n);e!=INVALID;++e)
512        if(!(*_reached)[m=G->target(e)]) {
513          _queue[_queue_head++]=m;
514          _reached->set(m,true);
515          _pred->set(m,e);
516          _dist->set(m,_curr_dist);
517          reach = reach || (target == m);
518        }
519      return n;
520    }
521
522    ///Processes the next node.
523
524    ///Processes the next node and checks if at least one of reached
525    ///nodes has \c true value in the \c nm node map. If one node
526    ///with \c true value is reachable from the processed node, then the
527    ///\c rnode parameter will be set to the first of such nodes.
528    ///
529    ///\param nm A \c bool (or convertible) node map that indicates the
530    ///possible targets.
531    ///\retval rnode The reached target node.
532    ///It should be initially \c INVALID.
533    ///
534    ///\return The processed node.
535    ///
536    ///\pre The queue must not be empty.
537    template<class NM>
538    Node processNextNode(const NM& nm, Node& rnode)
539    {
540      if(_queue_tail==_queue_next_dist) {
541        _curr_dist++;
542        _queue_next_dist=_queue_head;
543      }
544      Node n=_queue[_queue_tail++];
545      _processed->set(n,true);
546      Node m;
547      for(OutArcIt e(*G,n);e!=INVALID;++e)
548        if(!(*_reached)[m=G->target(e)]) {
549          _queue[_queue_head++]=m;
550          _reached->set(m,true);
551          _pred->set(m,e);
552          _dist->set(m,_curr_dist);
553          if (nm[m] && rnode == INVALID) rnode = m;
554        }
555      return n;
556    }
557
558    ///The next node to be processed.
559
560    ///Returns the next node to be processed or \c INVALID if the queue
561    ///is empty.
562    Node nextNode() const
563    {
564      return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID;
565    }
566
567    ///\brief Returns \c false if there are nodes
568    ///to be processed.
569    ///
570    ///Returns \c false if there are nodes
571    ///to be processed in the queue.
572    bool emptyQueue() const { return _queue_tail==_queue_head; }
573
574    ///Returns the number of the nodes to be processed.
575
576    ///Returns the number of the nodes to be processed in the queue.
577    int queueSize() const { return _queue_head-_queue_tail; }
578
579    ///Executes the algorithm.
580
581    ///Executes the algorithm.
582    ///
583    ///This method runs the %BFS algorithm from the root node(s)
584    ///in order to compute the shortest path to each node.
585    ///
586    ///The algorithm computes
587    ///- the shortest path tree (forest),
588    ///- the distance of each node from the root(s).
589    ///
590    ///\pre init() must be called and at least one root node should be
591    ///added with addSource() before using this function.
592    ///
593    ///\note <tt>b.start()</tt> is just a shortcut of the following code.
594    ///\code
595    ///  while ( !b.emptyQueue() ) {
596    ///    b.processNextNode();
597    ///  }
598    ///\endcode
599    void start()
600    {
601      while ( !emptyQueue() ) processNextNode();
602    }
603
604    ///Executes the algorithm until the given target node is reached.
605
606    ///Executes the algorithm until the given target node is reached.
607    ///
608    ///This method runs the %BFS algorithm from the root node(s)
609    ///in order to compute the shortest path to \c dest.
610    ///
611    ///The algorithm computes
612    ///- the shortest path to \c dest,
613    ///- the distance of \c dest from the root(s).
614    ///
615    ///\pre init() must be called and at least one root node should be
616    ///added with addSource() before using this function.
617    ///
618    ///\note <tt>b.start(t)</tt> is just a shortcut of the following code.
619    ///\code
620    ///  bool reach = false;
621    ///  while ( !b.emptyQueue() && !reach ) {
622    ///    b.processNextNode(t, reach);
623    ///  }
624    ///\endcode
625    void start(Node dest)
626    {
627      bool reach = false;
628      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
629    }
630
631    ///Executes the algorithm until a condition is met.
632
633    ///Executes the algorithm until a condition is met.
634    ///
635    ///This method runs the %BFS algorithm from the root node(s) in
636    ///order to compute the shortest path to a node \c v with
637    /// <tt>nm[v]</tt> true, if such a node can be found.
638    ///
639    ///\param nm A \c bool (or convertible) node map. The algorithm
640    ///will stop when it reaches a node \c v with <tt>nm[v]</tt> true.
641    ///
642    ///\return The reached node \c v with <tt>nm[v]</tt> true or
643    ///\c INVALID if no such node was found.
644    ///
645    ///\pre init() must be called and at least one root node should be
646    ///added with addSource() before using this function.
647    ///
648    ///\note <tt>b.start(nm)</tt> is just a shortcut of the following code.
649    ///\code
650    ///  Node rnode = INVALID;
651    ///  while ( !b.emptyQueue() && rnode == INVALID ) {
652    ///    b.processNextNode(nm, rnode);
653    ///  }
654    ///  return rnode;
655    ///\endcode
656    template<class NodeBoolMap>
657    Node start(const NodeBoolMap &nm)
658    {
659      Node rnode = INVALID;
660      while ( !emptyQueue() && rnode == INVALID ) {
661        processNextNode(nm, rnode);
662      }
663      return rnode;
664    }
665
666    ///Runs the algorithm from the given node.
667
668    ///This method runs the %BFS algorithm from node \c s
669    ///in order to compute the shortest path to each node.
670    ///
671    ///The algorithm computes
672    ///- the shortest path tree,
673    ///- the distance of each node from the root.
674    ///
675    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
676    ///\code
677    ///  b.init();
678    ///  b.addSource(s);
679    ///  b.start();
680    ///\endcode
681    void run(Node s) {
682      init();
683      addSource(s);
684      start();
685    }
686
687    ///Finds the shortest path between \c s and \c t.
688
689    ///This method runs the %BFS algorithm from node \c s
690    ///in order to compute the shortest path to \c t.
691    ///
692    ///\return The length of the shortest <tt>s</tt>--<tt>t</tt> path,
693    ///if \c t is reachable form \c s, \c 0 otherwise.
694    ///
695    ///\note Apart from the return value, <tt>b.run(s,t)</tt> is just a
696    ///shortcut of the following code.
697    ///\code
698    ///  b.init();
699    ///  b.addSource(s);
700    ///  b.start(t);
701    ///\endcode
702    int run(Node s,Node t) {
703      init();
704      addSource(s);
705      start(t);
706      return reached(t) ? _curr_dist : 0;
707    }
708
709    ///Runs the algorithm to visit all nodes in the digraph.
710
711    ///This method runs the %BFS algorithm in order to
712    ///compute the shortest path to each node.
713    ///
714    ///The algorithm computes
715    ///- the shortest path tree (forest),
716    ///- the distance of each node from the root(s).
717    ///
718    ///\note <tt>b.run(s)</tt> is just a shortcut of the following code.
719    ///\code
720    ///  b.init();
721    ///  for (NodeIt n(gr); n != INVALID; ++n) {
722    ///    if (!b.reached(n)) {
723    ///      b.addSource(n);
724    ///      b.start();
725    ///    }
726    ///  }
727    ///\endcode
728    void run() {
729      init();
730      for (NodeIt n(*G); n != INVALID; ++n) {
731        if (!reached(n)) {
732          addSource(n);
733          start();
734        }
735      }
736    }
737
738    ///@}
739
740    ///\name Query Functions
741    ///The result of the %BFS algorithm can be obtained using these
742    ///functions.\n
743    ///Either \ref lemon::Bfs::run() "run()" or \ref lemon::Bfs::start()
744    ///"start()" must be called before using them.
745
746    ///@{
747
748    ///The shortest path to a node.
749
750    ///Returns the shortest path to a node.
751    ///
752    ///\warning \c t should be reachable from the root(s).
753    ///
754    ///\pre Either \ref run() or \ref start() must be called before
755    ///using this function.
756    Path path(Node t) const { return Path(*G, *_pred, t); }
757
758    ///The distance of a node from the root(s).
759
760    ///Returns the distance of a node from the root(s).
761    ///
762    ///\warning If node \c v is not reachable from the root(s), then
763    ///the return value of this function is undefined.
764    ///
765    ///\pre Either \ref run() or \ref start() must be called before
766    ///using this function.
767    int dist(Node v) const { return (*_dist)[v]; }
768
769    ///Returns the 'previous arc' of the shortest path tree for a node.
770
771    ///This function returns the 'previous arc' of the shortest path
772    ///tree for the node \c v, i.e. it returns the last arc of a
773    ///shortest path from the root(s) to \c v. It is \c INVALID if \c v
774    ///is not reachable from the root(s) or if \c v is a root.
775    ///
776    ///The shortest path tree used here is equal to the shortest path
777    ///tree used in \ref predNode().
778    ///
779    ///\pre Either \ref run() or \ref start() must be called before
780    ///using this function.
781    Arc predArc(Node v) const { return (*_pred)[v];}
782
783    ///Returns the 'previous node' of the shortest path tree for a node.
784
785    ///This function returns the 'previous node' of the shortest path
786    ///tree for the node \c v, i.e. it returns the last but one node
787    ///from a shortest path from the root(s) to \c v. It is \c INVALID
788    ///if \c v is not reachable from the root(s) or if \c v is a root.
789    ///
790    ///The shortest path tree used here is equal to the shortest path
791    ///tree used in \ref predArc().
792    ///
793    ///\pre Either \ref run() or \ref start() must be called before
794    ///using this function.
795    Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID:
796                                  G->source((*_pred)[v]); }
797
798    ///\brief Returns a const reference to the node map that stores the
799    /// distances of the nodes.
800    ///
801    ///Returns a const reference to the node map that stores the distances
802    ///of the nodes calculated by the algorithm.
803    ///
804    ///\pre Either \ref run() or \ref init()
805    ///must be called before using this function.
806    const DistMap &distMap() const { return *_dist;}
807
808    ///\brief Returns a const reference to the node map that stores the
809    ///predecessor arcs.
810    ///
811    ///Returns a const reference to the node map that stores the predecessor
812    ///arcs, which form the shortest path tree.
813    ///
814    ///\pre Either \ref run() or \ref init()
815    ///must be called before using this function.
816    const PredMap &predMap() const { return *_pred;}
817
818    ///Checks if a node is reachable from the root(s).
819
820    ///Returns \c true if \c v is reachable from the root(s).
821    ///\pre Either \ref run() or \ref start()
822    ///must be called before using this function.
823    bool reached(Node v) const { return (*_reached)[v]; }
824
825    ///@}
826  };
827
828  ///Default traits class of bfs() function.
829
830  ///Default traits class of bfs() function.
831  ///\tparam GR Digraph type.
832  template<class GR>
833  struct BfsWizardDefaultTraits
834  {
835    ///The type of the digraph the algorithm runs on.
836    typedef GR Digraph;
837
838    ///\brief The type of the map that stores the predecessor
839    ///arcs of the shortest paths.
840    ///
841    ///The type of the map that stores the predecessor
842    ///arcs of the shortest paths.
843    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
844    typedef NullMap<typename Digraph::Node,typename Digraph::Arc> PredMap;
845    ///Instantiates a \ref PredMap.
846
847    ///This function instantiates a \ref PredMap.
848    ///\param g is the digraph, to which we would like to define the
849    ///\ref PredMap.
850    ///\todo The digraph alone may be insufficient to initialize
851#ifdef DOXYGEN
852    static PredMap *createPredMap(const Digraph &g)
853#else
854    static PredMap *createPredMap(const Digraph &)
855#endif
856    {
857      return new PredMap();
858    }
859
860    ///The type of the map that indicates which nodes are processed.
861
862    ///The type of the map that indicates which nodes are processed.
863    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
864    typedef NullMap<typename Digraph::Node,bool> ProcessedMap;
865    ///Instantiates a \ref ProcessedMap.
866
867    ///This function instantiates a \ref ProcessedMap.
868    ///\param g is the digraph, to which
869    ///we would like to define the \ref ProcessedMap.
870#ifdef DOXYGEN
871    static ProcessedMap *createProcessedMap(const Digraph &g)
872#else
873    static ProcessedMap *createProcessedMap(const Digraph &)
874#endif
875    {
876      return new ProcessedMap();
877    }
878
879    ///The type of the map that indicates which nodes are reached.
880
881    ///The type of the map that indicates which nodes are reached.
882    ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
883    typedef typename Digraph::template NodeMap<bool> ReachedMap;
884    ///Instantiates a \ref ReachedMap.
885
886    ///This function instantiates a \ref ReachedMap.
887    ///\param g is the digraph, to which
888    ///we would like to define the \ref ReachedMap.
889    static ReachedMap *createReachedMap(const Digraph &g)
890    {
891      return new ReachedMap(g);
892    }
893
894    ///The type of the map that stores the distances of the nodes.
895
896    ///The type of the map that stores the distances of the nodes.
897    ///It must meet the \ref concepts::WriteMap "WriteMap" concept.
898    ///
899    typedef NullMap<typename Digraph::Node,int> DistMap;
900    ///Instantiates a \ref DistMap.
901
902    ///This function instantiates a \ref DistMap.
903    ///\param g is the digraph, to which we would like to define
904    ///the \ref DistMap
905#ifdef DOXYGEN
906    static DistMap *createDistMap(const Digraph &g)
907#else
908    static DistMap *createDistMap(const Digraph &)
909#endif
910    {
911      return new DistMap();
912    }
913  };
914
915  /// Default traits class used by \ref BfsWizard
916
917  /// To make it easier to use Bfs algorithm
918  /// we have created a wizard class.
919  /// This \ref BfsWizard class needs default traits,
920  /// as well as the \ref Bfs class.
921  /// The \ref BfsWizardBase is a class to be the default traits of the
922  /// \ref BfsWizard class.
923  template<class GR>
924  class BfsWizardBase : public BfsWizardDefaultTraits<GR>
925  {
926
927    typedef BfsWizardDefaultTraits<GR> Base;
928  protected:
929    //The type of the nodes in the digraph.
930    typedef typename Base::Digraph::Node Node;
931
932    //Pointer to the digraph the algorithm runs on.
933    void *_g;
934    //Pointer to the map of reached nodes.
935    void *_reached;
936    //Pointer to the map of processed nodes.
937    void *_processed;
938    //Pointer to the map of predecessors arcs.
939    void *_pred;
940    //Pointer to the map of distances.
941    void *_dist;
942    //Pointer to the source node.
943    Node _source;
944
945    public:
946    /// Constructor.
947
948    /// This constructor does not require parameters, therefore it initiates
949    /// all of the attributes to default values (0, INVALID).
950    BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0),
951                      _dist(0), _source(INVALID) {}
952
953    /// Constructor.
954
955    /// This constructor requires some parameters,
956    /// listed in the parameters list.
957    /// Others are initiated to 0.
958    /// \param g The digraph the algorithm runs on.
959    /// \param s The source node.
960    BfsWizardBase(const GR &g, Node s=INVALID) :
961      _g(reinterpret_cast<void*>(const_cast<GR*>(&g))),
962      _reached(0), _processed(0), _pred(0), _dist(0), _source(s) {}
963
964  };
965
966  /// Auxiliary class for the function type interface of BFS algorithm.
967
968  /// This auxiliary class is created to implement the function type
969  /// interface of \ref Bfs algorithm. It uses the functions and features
970  /// of the plain \ref Bfs, but it is much simpler to use it.
971  /// It should only be used through the \ref bfs() function, which makes
972  /// it easier to use the algorithm.
973  ///
974  /// Simplicity means that the way to change the types defined
975  /// in the traits class is based on functions that returns the new class
976  /// and not on templatable built-in classes.
977  /// When using the plain \ref Bfs
978  /// the new class with the modified type comes from
979  /// the original class by using the ::
980  /// operator. In the case of \ref BfsWizard only
981  /// a function have to be called, and it will
982  /// return the needed class.
983  ///
984  /// It does not have own \ref run() method. When its \ref run() method
985  /// is called, it initiates a plain \ref Bfs object, and calls the
986  /// \ref Bfs::run() method of it.
987  template<class TR>
988  class BfsWizard : public TR
989  {
990    typedef TR Base;
991
992    ///The type of the digraph the algorithm runs on.
993    typedef typename TR::Digraph Digraph;
994
995    typedef typename Digraph::Node Node;
996    typedef typename Digraph::NodeIt NodeIt;
997    typedef typename Digraph::Arc Arc;
998    typedef typename Digraph::OutArcIt OutArcIt;
999
1000    ///\brief The type of the map that stores the predecessor
1001    ///arcs of the shortest paths.
1002    typedef typename TR::PredMap PredMap;
1003    ///\brief The type of the map that stores the distances of the nodes.
1004    typedef typename TR::DistMap DistMap;
1005    ///\brief The type of the map that indicates which nodes are reached.
1006    typedef typename TR::ReachedMap ReachedMap;
1007    ///\brief The type of the map that indicates which nodes are processed.
1008    typedef typename TR::ProcessedMap ProcessedMap;
1009
1010  public:
1011
1012    /// Constructor.
1013    BfsWizard() : TR() {}
1014
1015    /// Constructor that requires parameters.
1016
1017    /// Constructor that requires parameters.
1018    /// These parameters will be the default values for the traits class.
1019    BfsWizard(const Digraph &g, Node s=INVALID) :
1020      TR(g,s) {}
1021
1022    ///Copy constructor
1023    BfsWizard(const TR &b) : TR(b) {}
1024
1025    ~BfsWizard() {}
1026
1027    ///Runs BFS algorithm from a source node.
1028
1029    ///Runs BFS algorithm from a source node.
1030    ///The node can be given with the \ref source() function.
1031    void run()
1032    {
1033      if(Base::_source==INVALID) throw UninitializedParameter();
1034      Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g));
1035      if(Base::_reached)
1036        alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached));
1037      if(Base::_processed)
1038        alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed));
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      alg.run(Base::_source);
1044    }
1045
1046    ///Runs BFS algorithm from the given node.
1047
1048    ///Runs BFS algorithm from the given node.
1049    ///\param s is the given source.
1050    void run(Node s)
1051    {
1052      Base::_source=s;
1053      run();
1054    }
1055
1056    /// Sets the source node, from which the Bfs algorithm runs.
1057
1058    /// Sets the source node, from which the Bfs algorithm runs.
1059    /// \param s is the source node.
1060    BfsWizard<TR> &source(Node s)
1061    {
1062      Base::_source=s;
1063      return *this;
1064    }
1065
1066    template<class T>
1067    struct SetPredMapBase : public Base {
1068      typedef T PredMap;
1069      static PredMap *createPredMap(const Digraph &) { return 0; };
1070      SetPredMapBase(const TR &b) : TR(b) {}
1071    };
1072    ///\brief \ref named-templ-param "Named parameter"
1073    ///for setting \ref PredMap object.
1074    ///
1075    /// \ref named-templ-param "Named parameter"
1076    ///for setting \ref PredMap object.
1077    template<class T>
1078    BfsWizard<SetPredMapBase<T> > predMap(const T &t)
1079    {
1080      Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t));
1081      return BfsWizard<SetPredMapBase<T> >(*this);
1082    }
1083
1084    template<class T>
1085    struct SetReachedMapBase : public Base {
1086      typedef T ReachedMap;
1087      static ReachedMap *createReachedMap(const Digraph &) { return 0; };
1088      SetReachedMapBase(const TR &b) : TR(b) {}
1089    };
1090    ///\brief \ref named-templ-param "Named parameter"
1091    ///for setting \ref ReachedMap object.
1092    ///
1093    /// \ref named-templ-param "Named parameter"
1094    ///for setting \ref ReachedMap object.
1095    template<class T>
1096    BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t)
1097    {
1098      Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t));
1099      return BfsWizard<SetReachedMapBase<T> >(*this);
1100    }
1101
1102    template<class T>
1103    struct SetProcessedMapBase : public Base {
1104      typedef T ProcessedMap;
1105      static ProcessedMap *createProcessedMap(const Digraph &) { return 0; };
1106      SetProcessedMapBase(const TR &b) : TR(b) {}
1107    };
1108    ///\brief \ref named-templ-param "Named parameter"
1109    ///for setting \ref ProcessedMap object.
1110    ///
1111    /// \ref named-templ-param "Named parameter"
1112    ///for setting \ref ProcessedMap object.
1113    template<class T>
1114    BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t)
1115    {
1116      Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t));
1117      return BfsWizard<SetProcessedMapBase<T> >(*this);
1118    }
1119
1120    template<class T>
1121    struct SetDistMapBase : public Base {
1122      typedef T DistMap;
1123      static DistMap *createDistMap(const Digraph &) { return 0; };
1124      SetDistMapBase(const TR &b) : TR(b) {}
1125    };
1126    ///\brief \ref named-templ-param "Named parameter"
1127    ///for setting \ref DistMap object.
1128    ///
1129    /// \ref named-templ-param "Named parameter"
1130    ///for setting \ref DistMap object.
1131    template<class T>
1132    BfsWizard<SetDistMapBase<T> > distMap(const T &t)
1133    {
1134      Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t));
1135      return BfsWizard<SetDistMapBase<T> >(*this);
1136    }
1137
1138  };
1139
1140  ///Function type interface for Bfs algorithm.
1141
1142  /// \ingroup search
1143  ///Function type interface for Bfs algorithm.
1144  ///
1145  ///This function also has several
1146  ///\ref named-templ-func-param "named parameters",
1147  ///they are declared as the members of class \ref BfsWizard.
1148  ///The following
1149  ///example shows how to use these parameters.
1150  ///\code
1151  ///  bfs(g,source).predMap(preds).run();
1152  ///\endcode
1153  ///\warning Don't forget to put the \ref BfsWizard::run() "run()"
1154  ///to the end of the parameter list.
1155  ///\sa BfsWizard
1156  ///\sa Bfs
1157  template<class GR>
1158  BfsWizard<BfsWizardBase<GR> >
1159  bfs(const GR &g,typename GR::Node s=INVALID)
1160  {
1161    return BfsWizard<BfsWizardBase<GR> >(g,s);
1162  }
1163
1164#ifdef DOXYGEN
1165  /// \brief Visitor class for BFS.
1166  ///
1167  /// This class defines the interface of the BfsVisit events, and
1168  /// it could be the base of a real visitor class.
1169  template <typename _Digraph>
1170  struct BfsVisitor {
1171    typedef _Digraph Digraph;
1172    typedef typename Digraph::Arc Arc;
1173    typedef typename Digraph::Node Node;
1174    /// \brief Called for the source node(s) of the BFS.
1175    ///
1176    /// This function is called for the source node(s) of the BFS.
1177    void start(const Node& node) {}
1178    /// \brief Called when a node is reached first time.
1179    ///
1180    /// This function is called when a node is reached first time.
1181    void reach(const Node& node) {}
1182    /// \brief Called when a node is processed.
1183    ///
1184    /// This function is called when a node is processed.
1185    void process(const Node& node) {}
1186    /// \brief Called when an arc reaches a new node.
1187    ///
1188    /// This function is called when the BFS finds an arc whose target node
1189    /// is not reached yet.
1190    void discover(const Arc& arc) {}
1191    /// \brief Called when an arc is examined but its target node is
1192    /// already discovered.
1193    ///
1194    /// This function is called when an arc is examined but its target node is
1195    /// already discovered.
1196    void examine(const Arc& arc) {}
1197  };
1198#else
1199  template <typename _Digraph>
1200  struct BfsVisitor {
1201    typedef _Digraph Digraph;
1202    typedef typename Digraph::Arc Arc;
1203    typedef typename Digraph::Node Node;
1204    void start(const Node&) {}
1205    void reach(const Node&) {}
1206    void process(const Node&) {}
1207    void discover(const Arc&) {}
1208    void examine(const Arc&) {}
1209
1210    template <typename _Visitor>
1211    struct Constraints {
1212      void constraints() {
1213        Arc arc;
1214        Node node;
1215        visitor.start(node);
1216        visitor.reach(node);
1217        visitor.process(node);
1218        visitor.discover(arc);
1219        visitor.examine(arc);
1220      }
1221      _Visitor& visitor;
1222    };
1223  };
1224#endif
1225
1226  /// \brief Default traits class of BfsVisit class.
1227  ///
1228  /// Default traits class of BfsVisit class.
1229  /// \tparam _Digraph The type of the digraph the algorithm runs on.
1230  template<class _Digraph>
1231  struct BfsVisitDefaultTraits {
1232
1233    /// \brief The type of the digraph the algorithm runs on.
1234    typedef _Digraph Digraph;
1235
1236    /// \brief The type of the map that indicates which nodes are reached.
1237    ///
1238    /// The type of the map that indicates which nodes are reached.
1239    /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept.
1240    typedef typename Digraph::template NodeMap<bool> ReachedMap;
1241
1242    /// \brief Instantiates a \ref ReachedMap.
1243    ///
1244    /// This function instantiates a \ref ReachedMap.
1245    /// \param digraph is the digraph, to which
1246    /// we would like to define the \ref ReachedMap.
1247    static ReachedMap *createReachedMap(const Digraph &digraph) {
1248      return new ReachedMap(digraph);
1249    }
1250
1251  };
1252
1253  /// \ingroup search
1254  ///
1255  /// \brief %BFS algorithm class with visitor interface.
1256  ///
1257  /// This class provides an efficient implementation of the %BFS algorithm
1258  /// with visitor interface.
1259  ///
1260  /// The %BfsVisit class provides an alternative interface to the Bfs
1261  /// class. It works with callback mechanism, the BfsVisit object calls
1262  /// the member functions of the \c Visitor class on every BFS event.
1263  ///
1264  /// \tparam _Digraph The type of the digraph the algorithm runs on.
1265  /// The default value is
1266  /// \ref ListDigraph. The value of _Digraph is not used directly by
1267  /// \ref BfsVisit, it is only passed to \ref BfsVisitDefaultTraits.
1268  /// \tparam _Visitor The Visitor type that is used by the algorithm.
1269  /// \ref BfsVisitor "BfsVisitor<_Digraph>" is an empty visitor, which
1270  /// does not observe the BFS events. If you want to observe the BFS
1271  /// events, you should implement your own visitor class.
1272  /// \tparam _Traits Traits class to set various data types used by the
1273  /// algorithm. The default traits class is
1274  /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<_Digraph>".
1275  /// See \ref BfsVisitDefaultTraits for the documentation of
1276  /// a BFS visit traits class.
1277#ifdef DOXYGEN
1278  template <typename _Digraph, typename _Visitor, typename _Traits>
1279#else
1280  template <typename _Digraph = ListDigraph,
1281            typename _Visitor = BfsVisitor<_Digraph>,
1282            typename _Traits = BfsDefaultTraits<_Digraph> >
1283#endif
1284  class BfsVisit {
1285  public:
1286
1287    /// \brief \ref Exception for uninitialized parameters.
1288    ///
1289    /// This error represents problems in the initialization
1290    /// of the parameters of the algorithm.
1291    class UninitializedParameter : public lemon::UninitializedParameter {
1292    public:
1293      virtual const char* what() const throw()
1294      {
1295        return "lemon::BfsVisit::UninitializedParameter";
1296      }
1297    };
1298
1299    ///The traits class.
1300    typedef _Traits Traits;
1301
1302    ///The type of the digraph the algorithm runs on.
1303    typedef typename Traits::Digraph Digraph;
1304
1305    ///The visitor type used by the algorithm.
1306    typedef _Visitor Visitor;
1307
1308    ///The type of the map that indicates which nodes are reached.
1309    typedef typename Traits::ReachedMap ReachedMap;
1310
1311  private:
1312
1313    typedef typename Digraph::Node Node;
1314    typedef typename Digraph::NodeIt NodeIt;
1315    typedef typename Digraph::Arc Arc;
1316    typedef typename Digraph::OutArcIt OutArcIt;
1317
1318    //Pointer to the underlying digraph.
1319    const Digraph *_digraph;
1320    //Pointer to the visitor object.
1321    Visitor *_visitor;
1322    //Pointer to the map of reached status of the nodes.
1323    ReachedMap *_reached;
1324    //Indicates if _reached is locally allocated (true) or not.
1325    bool local_reached;
1326
1327    std::vector<typename Digraph::Node> _list;
1328    int _list_front, _list_back;
1329
1330    ///Creates the maps if necessary.
1331    ///\todo Better memory allocation (instead of new).
1332    void create_maps() {
1333      if(!_reached) {
1334        local_reached = true;
1335        _reached = Traits::createReachedMap(*_digraph);
1336      }
1337    }
1338
1339  protected:
1340
1341    BfsVisit() {}
1342
1343  public:
1344
1345    typedef BfsVisit Create;
1346
1347    /// \name Named template parameters
1348
1349    ///@{
1350    template <class T>
1351    struct SetReachedMapTraits : public Traits {
1352      typedef T ReachedMap;
1353      static ReachedMap *createReachedMap(const Digraph &digraph) {
1354        throw UninitializedParameter();
1355      }
1356    };
1357    /// \brief \ref named-templ-param "Named parameter" for setting
1358    /// ReachedMap type.
1359    ///
1360    /// \ref named-templ-param "Named parameter" for setting ReachedMap type.
1361    template <class T>
1362    struct SetReachedMap : public BfsVisit< Digraph, Visitor,
1363                                            SetReachedMapTraits<T> > {
1364      typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create;
1365    };
1366    ///@}
1367
1368  public:
1369
1370    /// \brief Constructor.
1371    ///
1372    /// Constructor.
1373    ///
1374    /// \param digraph The digraph the algorithm runs on.
1375    /// \param visitor The visitor object of the algorithm.
1376    BfsVisit(const Digraph& digraph, Visitor& visitor)
1377      : _digraph(&digraph), _visitor(&visitor),
1378        _reached(0), local_reached(false) {}
1379
1380    /// \brief Destructor.
1381    ~BfsVisit() {
1382      if(local_reached) delete _reached;
1383    }
1384
1385    /// \brief Sets the map that indicates which nodes are reached.
1386    ///
1387    /// Sets the map that indicates which nodes are reached.
1388    /// If you don't use this function before calling \ref run(),
1389    /// it will allocate one. The destructor deallocates this
1390    /// automatically allocated map, of course.
1391    /// \return <tt> (*this) </tt>
1392    BfsVisit &reachedMap(ReachedMap &m) {
1393      if(local_reached) {
1394        delete _reached;
1395        local_reached = false;
1396      }
1397      _reached = &m;
1398      return *this;
1399    }
1400
1401  public:
1402
1403    /// \name Execution control
1404    /// The simplest way to execute the algorithm is to use
1405    /// one of the member functions called \ref lemon::BfsVisit::run()
1406    /// "run()".
1407    /// \n
1408    /// If you need more control on the execution, first you must call
1409    /// \ref lemon::BfsVisit::init() "init()", then you can add several
1410    /// source nodes with \ref lemon::BfsVisit::addSource() "addSource()".
1411    /// Finally \ref lemon::BfsVisit::start() "start()" will perform the
1412    /// actual path computation.
1413
1414    /// @{
1415
1416    /// \brief Initializes the internal data structures.
1417    ///
1418    /// Initializes the internal data structures.
1419    void init() {
1420      create_maps();
1421      _list.resize(countNodes(*_digraph));
1422      _list_front = _list_back = -1;
1423      for (NodeIt u(*_digraph) ; u != INVALID ; ++u) {
1424        _reached->set(u, false);
1425      }
1426    }
1427
1428    /// \brief Adds a new source node.
1429    ///
1430    /// Adds a new source node to the set of nodes to be processed.
1431    void addSource(Node s) {
1432      if(!(*_reached)[s]) {
1433          _reached->set(s,true);
1434          _visitor->start(s);
1435          _visitor->reach(s);
1436          _list[++_list_back] = s;
1437        }
1438    }
1439
1440    /// \brief Processes the next node.
1441    ///
1442    /// Processes the next node.
1443    ///
1444    /// \return The processed node.
1445    ///
1446    /// \pre The queue must not be empty.
1447    Node processNextNode() {
1448      Node n = _list[++_list_front];
1449      _visitor->process(n);
1450      Arc e;
1451      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1452        Node m = _digraph->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        } else {
1459          _visitor->examine(e);
1460        }
1461      }
1462      return n;
1463    }
1464
1465    /// \brief Processes the next node.
1466    ///
1467    /// Processes the next node and checks if the given target node
1468    /// is reached. If the target node is reachable from the processed
1469    /// node, then the \c reach parameter will be set to \c true.
1470    ///
1471    /// \param target The target node.
1472    /// \retval reach Indicates if the target node is reached.
1473    /// It should be initially \c false.
1474    ///
1475    /// \return The processed node.
1476    ///
1477    /// \pre The queue must not be empty.
1478    Node processNextNode(Node target, bool& reach) {
1479      Node n = _list[++_list_front];
1480      _visitor->process(n);
1481      Arc e;
1482      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1483        Node m = _digraph->target(e);
1484        if (!(*_reached)[m]) {
1485          _visitor->discover(e);
1486          _visitor->reach(m);
1487          _reached->set(m, true);
1488          _list[++_list_back] = m;
1489          reach = reach || (target == m);
1490        } else {
1491          _visitor->examine(e);
1492        }
1493      }
1494      return n;
1495    }
1496
1497    /// \brief Processes the next node.
1498    ///
1499    /// Processes the next node and checks if at least one of reached
1500    /// nodes has \c true value in the \c nm node map. If one node
1501    /// with \c true value is reachable from the processed node, then the
1502    /// \c rnode parameter will be set to the first of such nodes.
1503    ///
1504    /// \param nm A \c bool (or convertible) node map that indicates the
1505    /// possible targets.
1506    /// \retval rnode The reached target node.
1507    /// It should be initially \c INVALID.
1508    ///
1509    /// \return The processed node.
1510    ///
1511    /// \pre The queue must not be empty.
1512    template <typename NM>
1513    Node processNextNode(const NM& nm, Node& rnode) {
1514      Node n = _list[++_list_front];
1515      _visitor->process(n);
1516      Arc e;
1517      for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) {
1518        Node m = _digraph->target(e);
1519        if (!(*_reached)[m]) {
1520          _visitor->discover(e);
1521          _visitor->reach(m);
1522          _reached->set(m, true);
1523          _list[++_list_back] = m;
1524          if (nm[m] && rnode == INVALID) rnode = m;
1525        } else {
1526          _visitor->examine(e);
1527        }
1528      }
1529      return n;
1530    }
1531
1532    /// \brief The next node to be processed.
1533    ///
1534    /// Returns the next node to be processed or \c INVALID if the queue
1535    /// is empty.
1536    Node nextNode() const {
1537      return _list_front != _list_back ? _list[_list_front + 1] : INVALID;
1538    }
1539
1540    /// \brief Returns \c false if there are nodes
1541    /// to be processed.
1542    ///
1543    /// Returns \c false if there are nodes
1544    /// to be processed in the queue.
1545    bool emptyQueue() const { return _list_front == _list_back; }
1546
1547    /// \brief Returns the number of the nodes to be processed.
1548    ///
1549    /// Returns the number of the nodes to be processed in the queue.
1550    int queueSize() const { return _list_back - _list_front; }
1551
1552    /// \brief Executes the algorithm.
1553    ///
1554    /// Executes the algorithm.
1555    ///
1556    /// This method runs the %BFS algorithm from the root node(s)
1557    /// in order to compute the shortest path to each node.
1558    ///
1559    /// The algorithm computes
1560    /// - the shortest path tree (forest),
1561    /// - the distance of each node from the root(s).
1562    ///
1563    /// \pre init() must be called and at least one root node should be added
1564    /// with addSource() before using this function.
1565    ///
1566    /// \note <tt>b.start()</tt> is just a shortcut of the following code.
1567    /// \code
1568    ///   while ( !b.emptyQueue() ) {
1569    ///     b.processNextNode();
1570    ///   }
1571    /// \endcode
1572    void start() {
1573      while ( !emptyQueue() ) processNextNode();
1574    }
1575
1576    /// \brief Executes the algorithm until the given target node is reached.
1577    ///
1578    /// Executes the algorithm until the given target node is reached.
1579    ///
1580    /// This method runs the %BFS algorithm from the root node(s)
1581    /// in order to compute the shortest path to \c dest.
1582    ///
1583    /// The algorithm computes
1584    /// - the shortest path to \c dest,
1585    /// - the distance of \c dest from the root(s).
1586    ///
1587    /// \pre init() must be called and at least one root node should be
1588    /// added with addSource() before using this function.
1589    ///
1590    /// \note <tt>b.start(t)</tt> is just a shortcut of the following code.
1591    /// \code
1592    ///   bool reach = false;
1593    ///   while ( !b.emptyQueue() && !reach ) {
1594    ///     b.processNextNode(t, reach);
1595    ///   }
1596    /// \endcode
1597    void start(Node dest) {
1598      bool reach = false;
1599      while ( !emptyQueue() && !reach ) processNextNode(dest, reach);
1600    }
1601
1602    /// \brief Executes the algorithm until a condition is met.
1603    ///
1604    /// Executes the algorithm until a condition is met.
1605    ///
1606    /// This method runs the %BFS algorithm from the root node(s) in
1607    /// order to compute the shortest path to a node \c v with
1608    /// <tt>nm[v]</tt> true, if such a node can be found.
1609    ///
1610    /// \param nm must be a bool (or convertible) node map. The
1611    /// algorithm will stop when it reaches a node \c v with
1612    /// <tt>nm[v]</tt> true.
1613    ///
1614    /// \return The reached node \c v with <tt>nm[v]</tt> true or
1615    /// \c INVALID if no such node was found.
1616    ///
1617    /// \pre init() must be called and at least one root node should be
1618    /// added with addSource() before using this function.
1619    ///
1620    /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code.
1621    /// \code
1622    ///   Node rnode = INVALID;
1623    ///   while ( !b.emptyQueue() && rnode == INVALID ) {
1624    ///     b.processNextNode(nm, rnode);
1625    ///   }
1626    ///   return rnode;
1627    /// \endcode
1628    template <typename NM>
1629    Node start(const NM &nm) {
1630      Node rnode = INVALID;
1631      while ( !emptyQueue() && rnode == INVALID ) {
1632        processNextNode(nm, rnode);
1633      }
1634      return rnode;
1635    }
1636
1637    /// \brief Runs the algorithm from the given node.
1638    ///
1639    /// This method runs the %BFS algorithm from node \c s
1640    /// in order to compute the shortest path to each node.
1641    ///
1642    /// The algorithm computes
1643    /// - the shortest path tree,
1644    /// - the distance of each node from the root.
1645    ///
1646    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1647    ///\code
1648    ///   b.init();
1649    ///   b.addSource(s);
1650    ///   b.start();
1651    ///\endcode
1652    void run(Node s) {
1653      init();
1654      addSource(s);
1655      start();
1656    }
1657
1658    /// \brief Runs the algorithm to visit all nodes in the digraph.
1659    ///
1660    /// This method runs the %BFS algorithm in order to
1661    /// compute the shortest path to each node.
1662    ///
1663    /// The algorithm computes
1664    /// - the shortest path tree (forest),
1665    /// - the distance of each node from the root(s).
1666    ///
1667    /// \note <tt>b.run(s)</tt> is just a shortcut of the following code.
1668    ///\code
1669    ///  b.init();
1670    ///  for (NodeIt n(gr); n != INVALID; ++n) {
1671    ///    if (!b.reached(n)) {
1672    ///      b.addSource(n);
1673    ///      b.start();
1674    ///    }
1675    ///  }
1676    ///\endcode
1677    void run() {
1678      init();
1679      for (NodeIt it(*_digraph); it != INVALID; ++it) {
1680        if (!reached(it)) {
1681          addSource(it);
1682          start();
1683        }
1684      }
1685    }
1686
1687    ///@}
1688
1689    /// \name Query Functions
1690    /// The result of the %BFS algorithm can be obtained using these
1691    /// functions.\n
1692    /// Either \ref lemon::BfsVisit::run() "run()" or
1693    /// \ref lemon::BfsVisit::start() "start()" must be called before
1694    /// using them.
1695    ///@{
1696
1697    /// \brief Checks if a node is reachable from the root(s).
1698    ///
1699    /// Returns \c true if \c v is reachable from the root(s).
1700    /// \pre Either \ref run() or \ref start()
1701    /// must be called before using this function.
1702    bool reached(Node v) { return (*_reached)[v]; }
1703
1704    ///@}
1705
1706  };
1707
1708} //END OF NAMESPACE LEMON
1709
1710#endif
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