# source:lemon-0.x/lemon/belmann_ford.h@1710:f531c16dd923

Last change on this file since 1710:f531c16dd923 was 1710:f531c16dd923, checked in by Balazs Dezso, 17 years ago

Bug solved in named parameters
Simplify my Johnson algorithm

File size: 26.9 KB
Line
1/* -*- C++ -*-
2 * lemon/belmann_ford.h - Part of LEMON, a generic C++ optimization library
3 *
4 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Research Group on Combinatorial Optimization, EGRES).
6 *
7 * Permission to use, modify and distribute this software is granted
8 * provided that this copyright notice appears in all copies. For
9 * precise terms see the accompanying LICENSE file.
10 *
11 * This software is provided "AS IS" with no warranty of any kind,
12 * express or implied, and with no claim as to its suitability for any
13 * purpose.
14 *
15 */
16
17#ifndef LEMON_BELMANN_FORD_H
18#define LEMON_BELMANN_FORD_H
19
20///\ingroup flowalgs
21/// \file
22/// \brief BelmannFord algorithm.
23///
24/// \todo getPath() should be implemented! (also for BFS and DFS)
25
26#include <lemon/list_graph.h>
27#include <lemon/invalid.h>
28#include <lemon/error.h>
29#include <lemon/maps.h>
30
31#include <limits>
32
33namespace lemon {
34
35  /// \brief Default OperationTraits for the BelmannFord algorithm class.
36  ///
37  /// It defines all computational operations and constants which are
38  /// used in the belmann ford algorithm. The default implementation
39  /// is based on the numeric_limits class. If the numeric type does not
40  /// have infinity value then the maximum value is used as extremal
41  /// infinity value.
42  template <
43    typename Value,
44    bool has_infinity = std::numeric_limits<Value>::has_infinity>
45  struct BelmannFordDefaultOperationTraits {
46    /// \brief Gives back the zero value of the type.
47    static Value zero() {
48      return static_cast<Value>(0);
49    }
50    /// \brief Gives back the positive infinity value of the type.
51    static Value infinity() {
52      return std::numeric_limits<Value>::infinity();
53    }
54    /// \brief Gives back the sum of the given two elements.
55    static Value plus(const Value& left, const Value& right) {
56      return left + right;
57    }
58    /// \brief Gives back true only if the first value less than the second.
59    static bool less(const Value& left, const Value& right) {
60      return left < right;
61    }
62  };
63
64  template <typename Value>
65  struct BelmannFordDefaultOperationTraits<Value, false> {
66    static Value zero() {
67      return static_cast<Value>(0);
68    }
69    static Value infinity() {
70      return std::numeric_limits<Value>::max();
71    }
72    static Value plus(const Value& left, const Value& right) {
73      if (left == infinity() || right == infinity()) return infinity();
74      return left + right;
75    }
76    static bool less(const Value& left, const Value& right) {
77      return left < right;
78    }
79  };
80
81  /// \brief Default traits class of BelmannFord class.
82  ///
83  /// Default traits class of BelmannFord class.
84  /// \param _Graph Graph type.
85  /// \param _LegthMap Type of length map.
86  template<class _Graph, class _LengthMap>
87  struct BelmannFordDefaultTraits {
88    /// The graph type the algorithm runs on.
89    typedef _Graph Graph;
90
91    /// \brief The type of the map that stores the edge lengths.
92    ///
93    /// The type of the map that stores the edge lengths.
95    typedef _LengthMap LengthMap;
96
97    // The type of the length of the edges.
98    typedef typename _LengthMap::Value Value;
99
100    /// \brief Operation traits for belmann-ford algorithm.
101    ///
102    /// It defines the infinity type on the given Value type
103    /// and the used operation.
104    /// \see BelmannFordDefaultOperationTraits
105    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
106
107    /// \brief The type of the map that stores the last edges of the
108    /// shortest paths.
109    ///
110    /// The type of the map that stores the last
111    /// edges of the shortest paths.
112    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
113    ///
114    typedef typename Graph::template NodeMap<typename _Graph::Edge> PredMap;
115
116    /// \brief Instantiates a PredMap.
117    ///
118    /// This function instantiates a \ref PredMap.
119    /// \param G is the graph, to which we would like to define the PredMap.
120    /// \todo The graph alone may be insufficient for the initialization
121    static PredMap *createPredMap(const _Graph& graph) {
122      return new PredMap(graph);
123    }
124
125    /// \brief The type of the map that stores the dists of the nodes.
126    ///
127    /// The type of the map that stores the dists of the nodes.
128    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
129    ///
130    typedef typename Graph::template NodeMap<typename _LengthMap::Value>
131    DistMap;
132
133    /// \brief Instantiates a DistMap.
134    ///
135    /// This function instantiates a \ref DistMap.
136    /// \param G is the graph, to which we would like to define the
137    /// \ref DistMap
138    static DistMap *createDistMap(const _Graph& graph) {
139      return new DistMap(graph);
140    }
141
142  };
143
144  /// \brief BelmannFord algorithm class.
145  ///
146  /// \ingroup flowalgs
147  /// This class provides an efficient implementation of \c BelmannFord
148  /// algorithm. The edge lengths are passed to the algorithm using a
149  /// \ref concept::ReadMap "ReadMap", so it is easy to change it to any
150  /// kind of length.
151  ///
152  /// The type of the length is determined by the
153  /// \ref concept::ReadMap::Value "Value" of the length map.
154  ///
155  /// \param _Graph The graph type the algorithm runs on. The default value
156  /// is \ref ListGraph. The value of _Graph is not used directly by
157  /// BelmannFord, it is only passed to \ref BelmannFordDefaultTraits.
158  /// \param _LengthMap This read-only EdgeMap determines the lengths of the
159  /// edges. The default map type is \ref concept::StaticGraph::EdgeMap
160  /// "Graph::EdgeMap<int>".  The value of _LengthMap is not used directly
161  /// by BelmannFord, it is only passed to \ref BelmannFordDefaultTraits.
162  /// \param _Traits Traits class to set various data types used by the
163  /// algorithm.  The default traits class is \ref BelmannFordDefaultTraits
164  /// "BelmannFordDefaultTraits<_Graph,_LengthMap>".  See \ref
165  /// BelmannFordDefaultTraits for the documentation of a BelmannFord traits
166  /// class.
167  ///
168  /// \author Balazs Dezso
169
170#ifdef DOXYGEN
171  template <typename _Graph, typename _LengthMap, typename _Traits>
172#else
173  template <typename _Graph=ListGraph,
174            typename _LengthMap=typename _Graph::template EdgeMap<int>,
175            typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> >
176#endif
177  class BelmannFord {
178  public:
179
180    /// \brief \ref Exception for uninitialized parameters.
181    ///
182    /// This error represents problems in the initialization
183    /// of the parameters of the algorithms.
184
185    class UninitializedParameter : public lemon::UninitializedParameter {
186    public:
187      virtual const char* exceptionName() const {
188        return "lemon::BelmannFord::UninitializedParameter";
189      }
190    };
191
192    typedef _Traits Traits;
193    ///The type of the underlying graph.
194    typedef typename _Traits::Graph Graph;
195
196    typedef typename Graph::Node Node;
197    typedef typename Graph::NodeIt NodeIt;
198    typedef typename Graph::Edge Edge;
199    typedef typename Graph::EdgeIt EdgeIt;
200
201    /// \brief The type of the length of the edges.
202    typedef typename _Traits::LengthMap::Value Value;
203    /// \brief The type of the map that stores the edge lengths.
204    typedef typename _Traits::LengthMap LengthMap;
205    /// \brief The type of the map that stores the last
206    /// edges of the shortest paths.
207    typedef typename _Traits::PredMap PredMap;
208    /// \brief The type of the map that stores the dists of the nodes.
209    typedef typename _Traits::DistMap DistMap;
210    /// \brief The operation traits.
211    typedef typename _Traits::OperationTraits OperationTraits;
212  private:
213    /// Pointer to the underlying graph.
214    const Graph *graph;
215    /// Pointer to the length map
216    const LengthMap *length;
217    ///Pointer to the map of predecessors edges.
218    PredMap *_pred;
219    ///Indicates if \ref _pred is locally allocated (\c true) or not.
220    bool local_pred;
221    ///Pointer to the map of distances.
222    DistMap *_dist;
223    ///Indicates if \ref _dist is locally allocated (\c true) or not.
224    bool local_dist;
225
226    /// Creates the maps if necessary.
227    void create_maps() {
228      if(!_pred) {
229        local_pred = true;
230        _pred = Traits::createPredMap(*graph);
231      }
232      if(!_dist) {
233        local_dist = true;
234        _dist = Traits::createDistMap(*graph);
235      }
236    }
237
238  public :
239
240    typedef BelmannFord Create;
241
242    /// \name Named template parameters
243
244    ///@{
245
246    template <class T>
247    struct DefPredMapTraits : public Traits {
248      typedef T PredMap;
249      static PredMap *createPredMap(const Graph&) {
250        throw UninitializedParameter();
251      }
252    };
253
254    /// \brief \ref named-templ-param "Named parameter" for setting PredMap
255    /// type
256    /// \ref named-templ-param "Named parameter" for setting PredMap type
257    ///
258    template <class T>
259    struct DefPredMap {
260      typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create;
261    };
262
263    template <class T>
264    struct DefDistMapTraits : public Traits {
265      typedef T DistMap;
266      static DistMap *createDistMap(const Graph& graph) {
267        throw UninitializedParameter();
268      }
269    };
270
271    /// \brief \ref named-templ-param "Named parameter" for setting DistMap
272    /// type
273    ///
274    /// \ref named-templ-param "Named parameter" for setting DistMap type
275    ///
276    template <class T>
277    struct DefDistMap
278      : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > {
279      typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create;
280    };
281
282    template <class T>
283    struct DefOperationTraitsTraits : public Traits {
284      typedef T OperationTraits;
285    };
286
287    /// \brief \ref named-templ-param "Named parameter" for setting
288    /// OperationTraits type
289    ///
290    /// \ref named-templ-param "Named parameter" for setting OperationTraits
291    /// type
292    template <class T>
293    struct DefOperationTraits
294      : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
295      typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
296      Create;
297    };
298
299    ///@}
300
301  protected:
302
303    BelmannFord() {}
304
305  public:
306
307    /// \brief Constructor.
308    ///
309    /// \param _graph the graph the algorithm will run on.
310    /// \param _length the length map used by the algorithm.
311    BelmannFord(const Graph& _graph, const LengthMap& _length) :
312      graph(&_graph), length(&_length),
313      _pred(0), local_pred(false),
314      _dist(0), local_dist(false) {}
315
316    ///Destructor.
317    ~BelmannFord() {
318      if(local_pred) delete _pred;
319      if(local_dist) delete _dist;
320    }
321
322    /// \brief Sets the length map.
323    ///
324    /// Sets the length map.
325    /// \return \c (*this)
326    BelmannFord &lengthMap(const LengthMap &m) {
327      length = &m;
328      return *this;
329    }
330
331    /// \brief Sets the map storing the predecessor edges.
332    ///
333    /// Sets the map storing the predecessor edges.
334    /// If you don't use this function before calling \ref run(),
335    /// it will allocate one. The destuctor deallocates this
336    /// automatically allocated map, of course.
337    /// \return \c (*this)
338    BelmannFord &predMap(PredMap &m) {
339      if(local_pred) {
340        delete _pred;
341        local_pred=false;
342      }
343      _pred = &m;
344      return *this;
345    }
346
347    /// \brief Sets the map storing the distances calculated by the algorithm.
348    ///
349    /// Sets the map storing the distances calculated by the algorithm.
350    /// If you don't use this function before calling \ref run(),
351    /// it will allocate one. The destuctor deallocates this
352    /// automatically allocated map, of course.
353    /// \return \c (*this)
354    BelmannFord &distMap(DistMap &m) {
355      if(local_dist) {
356        delete _dist;
357        local_dist=false;
358      }
359      _dist = &m;
360      return *this;
361    }
362
363    /// \name Execution control
364    /// The simplest way to execute the algorithm is to use
365    /// one of the member functions called \c run(...).
366    /// \n
367    /// If you need more control on the execution,
368    /// first you must call \ref init(), then you can add several source nodes
370    /// Finally \ref start() will perform the actual path
371    /// computation.
372
373    ///@{
374
375    /// \brief Initializes the internal data structures.
376    ///
377    /// Initializes the internal data structures.
378    void init(const Value value = OperationTraits::infinity()) {
379      create_maps();
380      for (NodeIt it(*graph); it != INVALID; ++it) {
381        _pred->set(it, INVALID);
382        _dist->set(it, value);
383      }
384    }
385
386    /// \brief Adds a new source node.
387    ///
388    /// The optional second parameter is the initial distance of the node.
389    /// It just sets the distance of the node to the given value.
390    void addSource(Node source, Value dst = OperationTraits::zero()) {
391      _dist->set(source, dst);
392    }
393
394    /// \brief Executes the algorithm.
395    ///
396    /// \pre init() must be called and at least one node should be added
397    /// with addSource() before using this function.
398    ///
399    /// This method runs the %BelmannFord algorithm from the root node(s)
400    /// in order to compute the shortest path to each node. The algorithm
401    /// computes
402    /// - The shortest path tree.
403    /// - The distance of each node from the root(s).
404    void start() {
408        for (EdgeIt it(*graph); it != INVALID; ++it) {
409          Node source = graph->source(it);
410          Node target = graph->target(it);
411          Value relaxed =
412            OperationTraits::plus((*_dist)[source], (*length)[it]);
413          if (OperationTraits::less(relaxed, (*_dist)[target])) {
414            _pred->set(target, it);
415            _dist->set(target, relaxed);
417          }
418        }
419      }
420    }
421
422    /// \brief Runs %BelmannFord algorithm from node \c s.
423    ///
424    /// This method runs the %BelmannFord algorithm from a root node \c s
425    /// in order to compute the shortest path to each node. The algorithm
426    /// computes
427    /// - The shortest path tree.
428    /// - The distance of each node from the root.
429    ///
430    /// \note d.run(s) is just a shortcut of the following code.
431    /// \code
432    ///  d.init();
434    ///  d.start();
435    /// \endcode
436    void run(Node s) {
437      init();
439      start();
440    }
441
442    ///@}
443
444    /// \name Query Functions
445    /// The result of the %BelmannFord algorithm can be obtained using these
446    /// functions.\n
447    /// Before the use of these functions,
448    /// either run() or start() must be called.
449
450    ///@{
451
452    /// \brief Copies the shortest path to \c t into \c p
453    ///
454    /// This function copies the shortest path to \c t into \c p.
455    /// If it \c t is a source itself or unreachable, then it does not
456    /// alter \c p.
457    /// \todo Is it the right way to handle unreachable nodes?
458    /// \return Returns \c true if a path to \c t was actually copied to \c p,
459    /// \c false otherwise.
460    /// \sa DirPath
461    template <typename Path>
462    bool getPath(Path &p, Node t) {
463      if(reached(t)) {
464        p.clear();
465        typename Path::Builder b(p);
466        for(b.setStartNode(t);pred(t)!=INVALID;t=predNode(t))
467          b.pushFront(pred(t));
468        b.commit();
469        return true;
470      }
471      return false;
472    }
473
474    /// \brief The distance of a node from the root.
475    ///
476    /// Returns the distance of a node from the root.
477    /// \pre \ref run() must be called before using this function.
478    /// \warning If node \c v in unreachable from the root the return value
479    /// of this funcion is undefined.
480    Value dist(Node v) const { return (*_dist)[v]; }
481
482    /// \brief Returns the 'previous edge' of the shortest path tree.
483    ///
484    /// For a node \c v it returns the 'previous edge' of the shortest path
485    /// tree, i.e. it returns the last edge of a shortest path from the root
486    /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
487    /// if \c v=s. The shortest path tree used here is equal to the shortest
488    /// path tree used in \ref predNode().
489    /// \pre \ref run() must be called before using
490    /// this function.
491    /// \todo predEdge could be a better name.
492    Edge pred(Node v) const { return (*_pred)[v]; }
493
494    /// \brief Returns the 'previous node' of the shortest path tree.
495    ///
496    /// For a node \c v it returns the 'previous node' of the shortest path
497    /// tree, i.e. it returns the last but one node from a shortest path from
498    /// the root to \c /v. It is INVALID if \c v is unreachable from the root
499    /// or if \c v=s. The shortest path tree used here is equal to the
500    /// shortest path tree used in \ref pred().  \pre \ref run() must be
501    /// called before using this function.
502    Node predNode(Node v) const {
503      return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
504    }
505
506    /// \brief Returns a reference to the NodeMap of distances.
507    ///
508    /// Returns a reference to the NodeMap of distances. \pre \ref run() must
509    /// be called before using this function.
510    const DistMap &distMap() const { return *_dist;}
511
512    /// \brief Returns a reference to the shortest path tree map.
513    ///
514    /// Returns a reference to the NodeMap of the edges of the
515    /// shortest path tree.
516    /// \pre \ref run() must be called before using this function.
517    const PredMap &predMap() const { return *_pred; }
518
519    /// \brief Checks if a node is reachable from the root.
520    ///
521    /// Returns \c true if \c v is reachable from the root.
522    /// \pre \ref run() must be called before using this function.
523    ///
524    bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
525
526    ///@}
527  };
528
529  /// \brief Default traits class of BelmannFord function.
530  ///
531  /// Default traits class of BelmannFord function.
532  /// \param _Graph Graph type.
533  /// \param _LengthMap Type of length map.
534  template <typename _Graph, typename _LengthMap>
535  struct BelmannFordWizardDefaultTraits {
536    /// \brief The graph type the algorithm runs on.
537    typedef _Graph Graph;
538
539    /// \brief The type of the map that stores the edge lengths.
540    ///
541    /// The type of the map that stores the edge lengths.
543    typedef _LengthMap LengthMap;
544
545    /// \brief The value type of the length map.
546    typedef typename _LengthMap::Value Value;
547
548    /// \brief Operation traits for belmann-ford algorithm.
549    ///
550    /// It defines the infinity type on the given Value type
551    /// and the used operation.
552    /// \see BelmannFordDefaultOperationTraits
553    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
554
555    /// \brief The type of the map that stores the last
556    /// edges of the shortest paths.
557    ///
558    /// The type of the map that stores the last
559    /// edges of the shortest paths.
560    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
561    typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
562
563    /// \brief Instantiates a PredMap.
564    ///
565    /// This function instantiates a \ref PredMap.
566    static PredMap *createPredMap(const _Graph &) {
567      return new PredMap();
568    }
569    /// \brief The type of the map that stores the dists of the nodes.
570    ///
571    /// The type of the map that stores the dists of the nodes.
572    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
573    typedef NullMap<typename Graph::Node, Value> DistMap;
574    /// \brief Instantiates a DistMap.
575    ///
576    /// This function instantiates a \ref DistMap.
577    static DistMap *createDistMap(const _Graph &) {
578      return new DistMap();
579    }
580  };
581
582  /// \brief Default traits used by \ref BelmannFordWizard
583  ///
584  /// To make it easier to use BelmannFord algorithm
585  /// we have created a wizard class.
586  /// This \ref BelmannFordWizard class needs default traits,
587  /// as well as the \ref BelmannFord class.
588  /// The \ref BelmannFordWizardBase is a class to be the default traits of the
589  /// \ref BelmannFordWizard class.
590  /// \todo More named parameters are required...
591  template<class _Graph,class _LengthMap>
592  class BelmannFordWizardBase
593    : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> {
594
595    typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
596  protected:
597    /// Type of the nodes in the graph.
598    typedef typename Base::Graph::Node Node;
599
600    /// Pointer to the underlying graph.
601    void *_graph;
602    /// Pointer to the length map
603    void *_length;
604    ///Pointer to the map of predecessors edges.
605    void *_pred;
606    ///Pointer to the map of distances.
607    void *_dist;
608    ///Pointer to the source node.
609    Node _source;
610
611    public:
612    /// Constructor.
613
614    /// This constructor does not require parameters, therefore it initiates
615    /// all of the attributes to default values (0, INVALID).
616    BelmannFordWizardBase() : _graph(0), _length(0), _pred(0),
617                           _dist(0), _source(INVALID) {}
618
619    /// Constructor.
620
621    /// This constructor requires some parameters,
622    /// listed in the parameters list.
623    /// Others are initiated to 0.
624    /// \param graph is the initial value of  \ref _graph
625    /// \param length is the initial value of  \ref _length
626    /// \param source is the initial value of  \ref _source
627    BelmannFordWizardBase(const _Graph& graph,
628                          const _LengthMap& length,
629                          Node source = INVALID) :
630      _graph((void *)&graph), _length((void *)&length), _pred(0),
631      _dist(0), _source(source) {}
632
633  };
634
635  /// A class to make the usage of BelmannFord algorithm easier
636
637  /// This class is created to make it easier to use BelmannFord algorithm.
638  /// It uses the functions and features of the plain \ref BelmannFord,
639  /// but it is much simpler to use it.
640  ///
641  /// Simplicity means that the way to change the types defined
642  /// in the traits class is based on functions that returns the new class
643  /// and not on templatable built-in classes.
644  /// When using the plain \ref BelmannFord
645  /// the new class with the modified type comes from
646  /// the original class by using the ::
647  /// operator. In the case of \ref BelmannFordWizard only
648  /// a function have to be called and it will
649  /// return the needed class.
650  ///
651  /// It does not have own \ref run method. When its \ref run method is called
652  /// it initiates a plain \ref BelmannFord class, and calls the \ref
653  /// BelmannFord::run method of it.
654  template<class _Traits>
655  class BelmannFordWizard : public _Traits {
656    typedef _Traits Base;
657
658    ///The type of the underlying graph.
659    typedef typename _Traits::Graph Graph;
660
661    typedef typename Graph::Node Node;
662    typedef typename Graph::NodeIt NodeIt;
663    typedef typename Graph::Edge Edge;
664    typedef typename Graph::OutEdgeIt EdgeIt;
665
666    ///The type of the map that stores the edge lengths.
667    typedef typename _Traits::LengthMap LengthMap;
668
669    ///The type of the length of the edges.
670    typedef typename LengthMap::Value Value;
671
672    ///\brief The type of the map that stores the last
673    ///edges of the shortest paths.
674    typedef typename _Traits::PredMap PredMap;
675
676    ///The type of the map that stores the dists of the nodes.
677    typedef typename _Traits::DistMap DistMap;
678
679  public:
680    /// Constructor.
681    BelmannFordWizard() : _Traits() {}
682
683    /// \brief Constructor that requires parameters.
684    ///
685    /// Constructor that requires parameters.
686    /// These parameters will be the default values for the traits class.
687    BelmannFordWizard(const Graph& graph, const LengthMap& length,
688                      Node source = INVALID)
689      : _Traits(graph, length, source) {}
690
691    /// \brief Copy constructor
692    BelmannFordWizard(const _Traits &b) : _Traits(b) {}
693
694    ~BelmannFordWizard() {}
695
696    /// \brief Runs BelmannFord algorithm from a given node.
697    ///
698    /// Runs BelmannFord algorithm from a given node.
699    /// The node can be given by the \ref source function.
700    void run() {
701      if(Base::_source == INVALID) throw UninitializedParameter();
702      BelmannFord<Graph,LengthMap,_Traits>
703        bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
704      if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
705      if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
706      bf.run(Base::_source);
707    }
708
709    /// \brief Runs BelmannFord algorithm from the given node.
710    ///
711    /// Runs BelmannFord algorithm from the given node.
712    /// \param s is the given source.
713    void run(Node source) {
714      Base::_source = source;
715      run();
716    }
717
718    template<class T>
719    struct DefPredMapBase : public Base {
720      typedef T PredMap;
721      static PredMap *createPredMap(const Graph &) { return 0; };
722      DefPredMapBase(const _Traits &b) : _Traits(b) {}
723    };
724
725    ///\brief \ref named-templ-param "Named parameter"
726    ///function for setting PredMap type
727    ///
728    /// \ref named-templ-param "Named parameter"
729    ///function for setting PredMap type
730    ///
731    template<class T>
732    BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
733    {
734      Base::_pred=(void *)&t;
735      return BelmannFordWizard<DefPredMapBase<T> >(*this);
736    }
737
738    template<class T>
739    struct DefDistMapBase : public Base {
740      typedef T DistMap;
741      static DistMap *createDistMap(const Graph &) { return 0; };
742      DefDistMapBase(const _Traits &b) : _Traits(b) {}
743    };
744
745    ///\brief \ref named-templ-param "Named parameter"
746    ///function for setting DistMap type
747    ///
748    /// \ref named-templ-param "Named parameter"
749    ///function for setting DistMap type
750    ///
751    template<class T>
752    BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
753      Base::_dist=(void *)&t;
754      return BelmannFordWizard<DefDistMapBase<T> >(*this);
755    }
756
757    template<class T>
758    struct DefOperationTraitsBase : public Base {
759      typedef T OperationTraits;
760      DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
761    };
762
763    ///\brief \ref named-templ-param "Named parameter"
764    ///function for setting OperationTraits type
765    ///
766    /// \ref named-templ-param "Named parameter"
767    ///function for setting OperationTraits type
768    ///
769    template<class T>
770    BelmannFordWizard<DefOperationTraitsBase<T> > distMap() {
771      return BelmannFordWizard<DefDistMapBase<T> >(*this);
772    }
773
774    /// \brief Sets the source node, from which the BelmannFord algorithm runs.
775    ///
776    /// Sets the source node, from which the BelmannFord algorithm runs.
777    /// \param s is the source node.
778    BelmannFordWizard<_Traits>& source(Node source) {
779      Base::_source = source;
780      return *this;
781    }
782
783  };
784
785  /// \brief Function type interface for BelmannFord algorithm.
786  ///
787  /// \ingroup flowalgs
788  /// Function type interface for BelmannFord algorithm.
789  ///
790  /// This function also has several \ref named-templ-func-param
791  /// "named parameters", they are declared as the members of class
792  /// \ref BelmannFordWizard.
793  /// The following
794  /// example shows how to use these parameters.
795  /// \code
796  /// belmannford(g,length,source).predMap(preds).run();
797  /// \endcode
798  /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
799  /// to the end of the parameter list.
800  /// \sa BelmannFordWizard
801  /// \sa BelmannFord
802  template<class _Graph, class _LengthMap>
803  BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
804  belmannFord(const _Graph& graph,
805              const _LengthMap& length,
806              typename _Graph::Node source = INVALID) {
807    return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
808      (graph, length, source);
809  }
810
811} //END OF NAMESPACE LEMON
812
813#endif
814
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