COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/belmann_ford.h @ 1699:29428f7b8b66

Last change on this file since 1699:29428f7b8b66 was 1699:29428f7b8b66, checked in by Balazs Dezso, 15 years ago

Some shortest path algorithms
All-pair-shortest path algorithms without function interface
we may need it

File size: 26.1 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.
94    /// It must meet the \ref concept::ReadMap "ReadMap" concept.
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  template <typename _Graph=ListGraph,
171            typename _LengthMap=typename _Graph::template EdgeMap<int>,
172            typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> >
173  class BelmannFord {
174  public:
175   
176    /// \brief \ref Exception for uninitialized parameters.
177    ///
178    /// This error represents problems in the initialization
179    /// of the parameters of the algorithms.
180
181    class UninitializedParameter : public lemon::UninitializedParameter {
182    public:
183      virtual const char* exceptionName() const {
184        return "lemon::BelmannFord::UninitializedParameter";
185      }
186    };
187
188    typedef _Traits Traits;
189    ///The type of the underlying graph.
190    typedef typename _Traits::Graph Graph;
191
192    typedef typename Graph::Node Node;
193    typedef typename Graph::NodeIt NodeIt;
194    typedef typename Graph::Edge Edge;
195    typedef typename Graph::EdgeIt EdgeIt;
196   
197    /// \brief The type of the length of the edges.
198    typedef typename _Traits::LengthMap::Value Value;
199    /// \brief The type of the map that stores the edge lengths.
200    typedef typename _Traits::LengthMap LengthMap;
201    /// \brief The type of the map that stores the last
202    /// edges of the shortest paths.
203    typedef typename _Traits::PredMap PredMap;
204    /// \brief The type of the map that stores the dists of the nodes.
205    typedef typename _Traits::DistMap DistMap;
206    /// \brief The operation traits.
207    typedef typename _Traits::OperationTraits OperationTraits;
208  private:
209    /// Pointer to the underlying graph.
210    const Graph *graph;
211    /// Pointer to the length map
212    const LengthMap *length;
213    ///Pointer to the map of predecessors edges.
214    PredMap *_pred;
215    ///Indicates if \ref _pred is locally allocated (\c true) or not.
216    bool local_pred;
217    ///Pointer to the map of distances.
218    DistMap *_dist;
219    ///Indicates if \ref _dist is locally allocated (\c true) or not.
220    bool local_dist;
221
222    /// Creates the maps if necessary.
223    void create_maps() {
224      if(!_pred) {
225        local_pred = true;
226        _pred = Traits::createPredMap(*graph);
227      }
228      if(!_dist) {
229        local_dist = true;
230        _dist = Traits::createDistMap(*graph);
231      }
232    }
233   
234  public :
235 
236    /// \name Named template parameters
237
238    ///@{
239
240    template <class T>
241    struct DefPredMapTraits : public Traits {
242      typedef T PredMap;
243      static PredMap *createPredMap(const Graph& graph) {
244        throw UninitializedParameter();
245      }
246    };
247
248    /// \brief \ref named-templ-param "Named parameter" for setting PredMap
249    /// type
250    /// \ref named-templ-param "Named parameter" for setting PredMap type
251    ///
252    template <class T>
253    class DefPredMap
254      : public BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > {};
255   
256    template <class T>
257    struct DefDistMapTraits : public Traits {
258      typedef T DistMap;
259      static DistMap *createDistMap(const Graph& graph) {
260        throw UninitializedParameter();
261      }
262    };
263
264    /// \brief \ref named-templ-param "Named parameter" for setting DistMap
265    /// type
266    ///
267    /// \ref named-templ-param "Named parameter" for setting DistMap type
268    ///
269    template <class T>
270    class DefDistMap
271      : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > {};
272   
273    template <class T>
274    struct DefOperationTraitsTraits : public Traits {
275      typedef T OperationTraits;
276    };
277   
278    /// \brief \ref named-templ-param "Named parameter" for setting
279    /// OperationTraits type
280    ///
281    /// \ref named-templ-param "Named parameter" for setting PredMap type
282    template <class T>
283    class DefOperationTraits
284      : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
285    public:
286      typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
287      BelmannFord;
288    };
289   
290    ///@}
291
292  public:     
293   
294    /// \brief Constructor.
295    ///
296    /// \param _graph the graph the algorithm will run on.
297    /// \param _length the length map used by the algorithm.
298    BelmannFord(const Graph& _graph, const LengthMap& _length) :
299      graph(&_graph), length(&_length),
300      _pred(0), local_pred(false),
301      _dist(0), local_dist(false) {}
302   
303    ///Destructor.
304    ~BelmannFord() {
305      if(local_pred) delete _pred;
306      if(local_dist) delete _dist;
307    }
308
309    /// \brief Sets the length map.
310    ///
311    /// Sets the length map.
312    /// \return \c (*this)
313    BelmannFord &lengthMap(const LengthMap &m) {
314      length = &m;
315      return *this;
316    }
317
318    /// \brief Sets the map storing the predecessor edges.
319    ///
320    /// Sets the map storing the predecessor edges.
321    /// If you don't use this function before calling \ref run(),
322    /// it will allocate one. The destuctor deallocates this
323    /// automatically allocated map, of course.
324    /// \return \c (*this)
325    BelmannFord &predMap(PredMap &m) {
326      if(local_pred) {
327        delete _pred;
328        local_pred=false;
329      }
330      _pred = &m;
331      return *this;
332    }
333
334    /// \brief Sets the map storing the distances calculated by the algorithm.
335    ///
336    /// Sets the map storing the distances calculated by the algorithm.
337    /// If you don't use this function before calling \ref run(),
338    /// it will allocate one. The destuctor deallocates this
339    /// automatically allocated map, of course.
340    /// \return \c (*this)
341    BelmannFord &distMap(DistMap &m) {
342      if(local_dist) {
343        delete _dist;
344        local_dist=false;
345      }
346      _dist = &m;
347      return *this;
348    }
349
350    /// \name Execution control
351    /// The simplest way to execute the algorithm is to use
352    /// one of the member functions called \c run(...).
353    /// \n
354    /// If you need more control on the execution,
355    /// first you must call \ref init(), then you can add several source nodes
356    /// with \ref addSource().
357    /// Finally \ref start() will perform the actual path
358    /// computation.
359
360    ///@{
361
362    /// \brief Initializes the internal data structures.
363    ///
364    /// Initializes the internal data structures.
365    void init() {
366      create_maps();
367      for (NodeIt it(*graph); it != INVALID; ++it) {
368        _pred->set(it, INVALID);
369        _dist->set(it, OperationTraits::infinity());
370      }
371    }
372   
373    /// \brief Adds a new source node.
374    ///
375    /// The optional second parameter is the initial distance of the node.
376    /// It just sets the distance of the node to the given value.
377    void addSource(Node source, Value dst = OperationTraits::zero()) {
378      _dist->set(source, dst);
379    }
380
381    /// \brief Executes the algorithm.
382    ///
383    /// \pre init() must be called and at least one node should be added
384    /// with addSource() before using this function.
385    ///
386    /// This method runs the %BelmannFord algorithm from the root node(s)
387    /// in order to compute the shortest path to each node. The algorithm
388    /// computes
389    /// - The shortest path tree.
390    /// - The distance of each node from the root(s).
391    void start() {
392      bool ready = false;
393      while (!ready) {
394        ready = true;
395        for (EdgeIt it(*graph); it != INVALID; ++it) {
396          Node source = graph->source(it);
397          Node target = graph->target(it);
398          Value relaxed =
399            OperationTraits::plus((*_dist)[source], (*length)[it]);
400          if (OperationTraits::less(relaxed, (*_dist)[target])) {
401            _pred->set(target, it);
402            _dist->set(target, relaxed);
403            ready = false;
404          }
405        }
406      }
407    }
408   
409    /// \brief Runs %BelmannFord algorithm from node \c s.
410    ///   
411    /// This method runs the %BelmannFord algorithm from a root node \c s
412    /// in order to compute the shortest path to each node. The algorithm
413    /// computes
414    /// - The shortest path tree.
415    /// - The distance of each node from the root.
416    ///
417    /// \note d.run(s) is just a shortcut of the following code.
418    /// \code
419    ///  d.init();
420    ///  d.addSource(s);
421    ///  d.start();
422    /// \endcode
423    void run(Node s) {
424      init();
425      addSource(s);
426      start();
427    }
428   
429    ///@}
430
431    /// \name Query Functions
432    /// The result of the %BelmannFord algorithm can be obtained using these
433    /// functions.\n
434    /// Before the use of these functions,
435    /// either run() or start() must be called.
436   
437    ///@{
438
439    /// \brief Copies the shortest path to \c t into \c p
440    ///   
441    /// This function copies the shortest path to \c t into \c p.
442    /// If it \c t is a source itself or unreachable, then it does not
443    /// alter \c p.
444    /// \todo Is it the right way to handle unreachable nodes?
445    /// \return Returns \c true if a path to \c t was actually copied to \c p,
446    /// \c false otherwise.
447    /// \sa DirPath
448    template <typename Path>
449    bool getPath(Path &p, Node t) {
450      if(reached(t)) {
451        p.clear();
452        typename Path::Builder b(p);
453        for(b.setStartNode(t);pred(t)!=INVALID;t=predNode(t))
454          b.pushFront(pred(t));
455        b.commit();
456        return true;
457      }
458      return false;
459    }
460         
461    /// \brief The distance of a node from the root.
462    ///
463    /// Returns the distance of a node from the root.
464    /// \pre \ref run() must be called before using this function.
465    /// \warning If node \c v in unreachable from the root the return value
466    /// of this funcion is undefined.
467    Value dist(Node v) const { return (*_dist)[v]; }
468
469    /// \brief Returns the 'previous edge' of the shortest path tree.
470    ///
471    /// For a node \c v it returns the 'previous edge' of the shortest path
472    /// tree, i.e. it returns the last edge of a shortest path from the root
473    /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
474    /// if \c v=s. The shortest path tree used here is equal to the shortest
475    /// path tree used in \ref predNode().
476    /// \pre \ref run() must be called before using
477    /// this function.
478    /// \todo predEdge could be a better name.
479    Edge pred(Node v) const { return (*_pred)[v]; }
480
481    /// \brief Returns the 'previous node' of the shortest path tree.
482    ///
483    /// For a node \c v it returns the 'previous node' of the shortest path
484    /// tree, i.e. it returns the last but one node from a shortest path from
485    /// the root to \c /v. It is INVALID if \c v is unreachable from the root
486    /// or if \c v=s. The shortest path tree used here is equal to the
487    /// shortest path tree used in \ref pred().  \pre \ref run() must be
488    /// called before using this function.
489    Node predNode(Node v) const {
490      return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
491    }
492   
493    /// \brief Returns a reference to the NodeMap of distances.
494    ///
495    /// Returns a reference to the NodeMap of distances. \pre \ref run() must
496    /// be called before using this function.
497    const DistMap &distMap() const { return *_dist;}
498 
499    /// \brief Returns a reference to the shortest path tree map.
500    ///
501    /// Returns a reference to the NodeMap of the edges of the
502    /// shortest path tree.
503    /// \pre \ref run() must be called before using this function.
504    const PredMap &predMap() const { return *_pred; }
505 
506    /// \brief Checks if a node is reachable from the root.
507    ///
508    /// Returns \c true if \c v is reachable from the root.
509    /// \pre \ref run() must be called before using this function.
510    ///
511    bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
512   
513    ///@}
514  };
515 
516  /// \brief Default traits class of BelmannFord function.
517  ///
518  /// Default traits class of BelmannFord function.
519  /// \param _Graph Graph type.
520  /// \param _LengthMap Type of length map.
521  template <typename _Graph, typename _LengthMap>
522  struct BelmannFordWizardDefaultTraits {
523    /// \brief The graph type the algorithm runs on.
524    typedef _Graph Graph;
525
526    /// \brief The type of the map that stores the edge lengths.
527    ///
528    /// The type of the map that stores the edge lengths.
529    /// It must meet the \ref concept::ReadMap "ReadMap" concept.
530    typedef _LengthMap LengthMap;
531
532    /// \brief The value type of the length map.
533    typedef typename _LengthMap::Value Value;
534
535    /// \brief Operation traits for belmann-ford algorithm.
536    ///
537    /// It defines the infinity type on the given Value type
538    /// and the used operation.
539    /// \see BelmannFordDefaultOperationTraits
540    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
541
542    /// \brief The type of the map that stores the last
543    /// edges of the shortest paths.
544    ///
545    /// The type of the map that stores the last
546    /// edges of the shortest paths.
547    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
548    typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
549
550    /// \brief Instantiates a PredMap.
551    ///
552    /// This function instantiates a \ref PredMap.
553    static PredMap *createPredMap(const _Graph &) {
554      return new PredMap();
555    }
556    /// \brief The type of the map that stores the dists of the nodes.
557    ///
558    /// The type of the map that stores the dists of the nodes.
559    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
560    typedef NullMap<typename Graph::Node, Value> DistMap;
561    /// \brief Instantiates a DistMap.
562    ///
563    /// This function instantiates a \ref DistMap.
564    static DistMap *createDistMap(const _Graph &) {
565      return new DistMap();
566    }
567  };
568 
569  /// \brief Default traits used by \ref BelmannFordWizard
570  ///
571  /// To make it easier to use BelmannFord algorithm
572  /// we have created a wizard class.
573  /// This \ref BelmannFordWizard class needs default traits,
574  /// as well as the \ref BelmannFord class.
575  /// The \ref BelmannFordWizardBase is a class to be the default traits of the
576  /// \ref BelmannFordWizard class.
577  /// \todo More named parameters are required...
578  template<class _Graph,class _LengthMap>
579  class BelmannFordWizardBase
580    : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> {
581
582    typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
583  protected:
584    /// Type of the nodes in the graph.
585    typedef typename Base::Graph::Node Node;
586
587    /// Pointer to the underlying graph.
588    void *_graph;
589    /// Pointer to the length map
590    void *_length;
591    ///Pointer to the map of predecessors edges.
592    void *_pred;
593    ///Pointer to the map of distances.
594    void *_dist;
595    ///Pointer to the source node.
596    Node _source;
597
598    public:
599    /// Constructor.
600   
601    /// This constructor does not require parameters, therefore it initiates
602    /// all of the attributes to default values (0, INVALID).
603    BelmannFordWizardBase() : _graph(0), _length(0), _pred(0),
604                           _dist(0), _source(INVALID) {}
605
606    /// Constructor.
607   
608    /// This constructor requires some parameters,
609    /// listed in the parameters list.
610    /// Others are initiated to 0.
611    /// \param graph is the initial value of  \ref _graph
612    /// \param length is the initial value of  \ref _length
613    /// \param source is the initial value of  \ref _source
614    BelmannFordWizardBase(const _Graph& graph,
615                          const _LengthMap& length,
616                          Node source = INVALID) :
617      _graph((void *)&graph), _length((void *)&length), _pred(0),
618      _dist(0), _source(source) {}
619
620  };
621 
622  /// A class to make the usage of BelmannFord algorithm easier
623
624  /// This class is created to make it easier to use BelmannFord algorithm.
625  /// It uses the functions and features of the plain \ref BelmannFord,
626  /// but it is much simpler to use it.
627  ///
628  /// Simplicity means that the way to change the types defined
629  /// in the traits class is based on functions that returns the new class
630  /// and not on templatable built-in classes.
631  /// When using the plain \ref BelmannFord
632  /// the new class with the modified type comes from
633  /// the original class by using the ::
634  /// operator. In the case of \ref BelmannFordWizard only
635  /// a function have to be called and it will
636  /// return the needed class.
637  ///
638  /// It does not have own \ref run method. When its \ref run method is called
639  /// it initiates a plain \ref BelmannFord class, and calls the \ref
640  /// BelmannFord::run method of it.
641  template<class _Traits>
642  class BelmannFordWizard : public _Traits {
643    typedef _Traits Base;
644
645    ///The type of the underlying graph.
646    typedef typename _Traits::Graph Graph;
647
648    typedef typename Graph::Node Node;
649    typedef typename Graph::NodeIt NodeIt;
650    typedef typename Graph::Edge Edge;
651    typedef typename Graph::OutEdgeIt EdgeIt;
652   
653    ///The type of the map that stores the edge lengths.
654    typedef typename _Traits::LengthMap LengthMap;
655
656    ///The type of the length of the edges.
657    typedef typename LengthMap::Value Value;
658
659    ///\brief The type of the map that stores the last
660    ///edges of the shortest paths.
661    typedef typename _Traits::PredMap PredMap;
662
663    ///The type of the map that stores the dists of the nodes.
664    typedef typename _Traits::DistMap DistMap;
665
666  public:
667    /// Constructor.
668    BelmannFordWizard() : _Traits() {}
669
670    /// \brief Constructor that requires parameters.
671    ///
672    /// Constructor that requires parameters.
673    /// These parameters will be the default values for the traits class.
674    BelmannFordWizard(const Graph& graph, const LengthMap& length,
675                      Node source = INVALID)
676      : _Traits(graph, length, source) {}
677
678    /// \brief Copy constructor
679    BelmannFordWizard(const _Traits &b) : _Traits(b) {}
680
681    ~BelmannFordWizard() {}
682
683    /// \brief Runs BelmannFord algorithm from a given node.
684    ///   
685    /// Runs BelmannFord algorithm from a given node.
686    /// The node can be given by the \ref source function.
687    void run() {
688      if(Base::_source == INVALID) throw UninitializedParameter();
689      BelmannFord<Graph,LengthMap,_Traits>
690        bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
691      if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
692      if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
693      bf.run(Base::_source);
694    }
695
696    /// \brief Runs BelmannFord algorithm from the given node.
697    ///
698    /// Runs BelmannFord algorithm from the given node.
699    /// \param s is the given source.
700    void run(Node source) {
701      Base::_source = source;
702      run();
703    }
704
705    template<class T>
706    struct DefPredMapBase : public Base {
707      typedef T PredMap;
708      static PredMap *createPredMap(const Graph &) { return 0; };
709      DefPredMapBase(const _Traits &b) : _Traits(b) {}
710    };
711   
712    ///\brief \ref named-templ-param "Named parameter"
713    ///function for setting PredMap type
714    ///
715    /// \ref named-templ-param "Named parameter"
716    ///function for setting PredMap type
717    ///
718    template<class T>
719    BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
720    {
721      Base::_pred=(void *)&t;
722      return BelmannFordWizard<DefPredMapBase<T> >(*this);
723    }
724   
725    template<class T>
726    struct DefDistMapBase : public Base {
727      typedef T DistMap;
728      static DistMap *createDistMap(const Graph &) { return 0; };
729      DefDistMapBase(const _Traits &b) : _Traits(b) {}
730    };
731   
732    ///\brief \ref named-templ-param "Named parameter"
733    ///function for setting DistMap type
734    ///
735    /// \ref named-templ-param "Named parameter"
736    ///function for setting DistMap type
737    ///
738    template<class T>
739    BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
740      Base::_dist=(void *)&t;
741      return BelmannFordWizard<DefDistMapBase<T> >(*this);
742    }
743   
744    /// \brief Sets the source node, from which the BelmannFord algorithm runs.
745    ///
746    /// Sets the source node, from which the BelmannFord algorithm runs.
747    /// \param s is the source node.
748    BelmannFordWizard<_Traits>& source(Node source) {
749      Base::_source = source;
750      return *this;
751    }
752   
753  };
754 
755  /// \brief Function type interface for BelmannFord algorithm.
756  ///
757  /// \ingroup flowalgs
758  /// Function type interface for BelmannFord algorithm.
759  ///
760  /// This function also has several \ref named-templ-func-param
761  /// "named parameters", they are declared as the members of class
762  /// \ref BelmannFordWizard.
763  /// The following
764  /// example shows how to use these parameters.
765  /// \code
766  /// belmannford(g,length,source).predMap(preds).run();
767  /// \endcode
768  /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
769  /// to the end of the parameter list.
770  /// \sa BelmannFordWizard
771  /// \sa BelmannFord
772  template<class _Graph, class _LengthMap>
773  BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
774  belmannFord(const _Graph& graph,
775              const _LengthMap& length,
776              typename _Graph::Node source = INVALID) {
777    return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
778      (graph, length, source);
779  }
780
781} //END OF NAMESPACE LEMON
782
783#endif
784
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