COIN-OR::LEMON - Graph Library

source: lemon-0.x/lemon/belmann_ford.h @ 1765:f15b3c09481c

Last change on this file since 1765:f15b3c09481c was 1765:f15b3c09481c, checked in by Balazs Dezso, 16 years ago

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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
25#include <lemon/list_graph.h>
26#include <lemon/invalid.h>
27#include <lemon/error.h>
28#include <lemon/maps.h>
29
30#include <limits>
31
32namespace lemon {
33
34  /// \brief Default OperationTraits for the BelmannFord algorithm class.
35  /// 
36  /// It defines all computational operations and constants which are
37  /// used in the belmann ford algorithm. The default implementation
38  /// is based on the numeric_limits class. If the numeric type does not
39  /// have infinity value then the maximum value is used as extremal
40  /// infinity value.
41  template <
42    typename Value,
43    bool has_infinity = std::numeric_limits<Value>::has_infinity>
44  struct BelmannFordDefaultOperationTraits {
45    /// \brief Gives back the zero value of the type.
46    static Value zero() {
47      return static_cast<Value>(0);
48    }
49    /// \brief Gives back the positive infinity value of the type.
50    static Value infinity() {
51      return std::numeric_limits<Value>::infinity();
52    }
53    /// \brief Gives back the sum of the given two elements.
54    static Value plus(const Value& left, const Value& right) {
55      return left + right;
56    }
57    /// \brief Gives back true only if the first value less than the second.
58    static bool less(const Value& left, const Value& right) {
59      return left < right;
60    }
61  };
62
63  template <typename Value>
64  struct BelmannFordDefaultOperationTraits<Value, false> {
65    static Value zero() {
66      return static_cast<Value>(0);
67    }
68    static Value infinity() {
69      return std::numeric_limits<Value>::max();
70    }
71    static Value plus(const Value& left, const Value& right) {
72      if (left == infinity() || right == infinity()) return infinity();
73      return left + right;
74    }
75    static bool less(const Value& left, const Value& right) {
76      return left < right;
77    }
78  };
79 
80  /// \brief Default traits class of BelmannFord class.
81  ///
82  /// Default traits class of BelmannFord class.
83  /// \param _Graph Graph type.
84  /// \param _LegthMap Type of length map.
85  template<class _Graph, class _LengthMap>
86  struct BelmannFordDefaultTraits {
87    /// The graph type the algorithm runs on.
88    typedef _Graph Graph;
89
90    /// \brief The type of the map that stores the edge lengths.
91    ///
92    /// The type of the map that stores the edge lengths.
93    /// It must meet the \ref concept::ReadMap "ReadMap" concept.
94    typedef _LengthMap LengthMap;
95
96    // The type of the length of the edges.
97    typedef typename _LengthMap::Value Value;
98
99    /// \brief Operation traits for belmann-ford algorithm.
100    ///
101    /// It defines the infinity type on the given Value type
102    /// and the used operation.
103    /// \see BelmannFordDefaultOperationTraits
104    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
105 
106    /// \brief The type of the map that stores the last edges of the
107    /// shortest paths.
108    ///
109    /// The type of the map that stores the last
110    /// edges of the shortest paths.
111    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
112    ///
113    typedef typename Graph::template NodeMap<typename _Graph::Edge> PredMap;
114
115    /// \brief Instantiates a PredMap.
116    ///
117    /// This function instantiates a \ref PredMap.
118    /// \param G is the graph, to which we would like to define the PredMap.
119    /// \todo The graph alone may be insufficient for the initialization
120    static PredMap *createPredMap(const _Graph& graph) {
121      return new PredMap(graph);
122    }
123
124    /// \brief The type of the map that stores the dists of the nodes.
125    ///
126    /// The type of the map that stores the dists of the nodes.
127    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
128    ///
129    typedef typename Graph::template NodeMap<typename _LengthMap::Value>
130    DistMap;
131
132    /// \brief Instantiates a DistMap.
133    ///
134    /// This function instantiates a \ref DistMap.
135    /// \param G is the graph, to which we would like to define the
136    /// \ref DistMap
137    static DistMap *createDistMap(const _Graph& graph) {
138      return new DistMap(graph);
139    }
140
141  };
142 
143  /// \brief %BelmannFord algorithm class.
144  ///
145  /// \ingroup flowalgs
146  /// This class provides an efficient implementation of \c Belmann-Ford
147  /// algorithm. The edge lengths are passed to the algorithm using a
148  /// \ref concept::ReadMap "ReadMap", so it is easy to change it to any
149  /// kind of length.
150  ///
151  /// The Belmann-Ford algorithm solves the shortest path from one node
152  /// problem when the edges can have negative length but the graph should
153  /// not contain cycles with negative sum of length. If we can assume
154  /// that all edge is non-negative in the graph then the dijkstra algorithm
155  /// should be used rather.
156  ///
157  /// The complexity of the algorithm is O(n * e).
158  ///
159  /// The type of the length is determined by the
160  /// \ref concept::ReadMap::Value "Value" of the length map.
161  ///
162  /// \param _Graph The graph type the algorithm runs on. The default value
163  /// is \ref ListGraph. The value of _Graph is not used directly by
164  /// BelmannFord, it is only passed to \ref BelmannFordDefaultTraits.
165  /// \param _LengthMap This read-only EdgeMap determines the lengths of the
166  /// edges. The default map type is \ref concept::StaticGraph::EdgeMap
167  /// "Graph::EdgeMap<int>".  The value of _LengthMap is not used directly
168  /// by BelmannFord, it is only passed to \ref BelmannFordDefaultTraits. 
169  /// \param _Traits Traits class to set various data types used by the
170  /// algorithm.  The default traits class is \ref BelmannFordDefaultTraits
171  /// "BelmannFordDefaultTraits<_Graph,_LengthMap>".  See \ref
172  /// BelmannFordDefaultTraits for the documentation of a BelmannFord traits
173  /// class.
174  ///
175  /// \author Balazs Dezso
176
177#ifdef DOXYGEN
178  template <typename _Graph, typename _LengthMap, typename _Traits>
179#else
180  template <typename _Graph=ListGraph,
181            typename _LengthMap=typename _Graph::template EdgeMap<int>,
182            typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> >
183#endif
184  class BelmannFord {
185  public:
186   
187    /// \brief \ref Exception for uninitialized parameters.
188    ///
189    /// This error represents problems in the initialization
190    /// of the parameters of the algorithms.
191
192    class UninitializedParameter : public lemon::UninitializedParameter {
193    public:
194      virtual const char* exceptionName() const {
195        return "lemon::BelmannFord::UninitializedParameter";
196      }
197    };
198
199    typedef _Traits Traits;
200    ///The type of the underlying graph.
201    typedef typename _Traits::Graph Graph;
202
203    typedef typename Graph::Node Node;
204    typedef typename Graph::NodeIt NodeIt;
205    typedef typename Graph::Edge Edge;
206    typedef typename Graph::EdgeIt EdgeIt;
207   
208    /// \brief The type of the length of the edges.
209    typedef typename _Traits::LengthMap::Value Value;
210    /// \brief The type of the map that stores the edge lengths.
211    typedef typename _Traits::LengthMap LengthMap;
212    /// \brief The type of the map that stores the last
213    /// edges of the shortest paths.
214    typedef typename _Traits::PredMap PredMap;
215    /// \brief The type of the map that stores the dists of the nodes.
216    typedef typename _Traits::DistMap DistMap;
217    /// \brief The operation traits.
218    typedef typename _Traits::OperationTraits OperationTraits;
219  private:
220    /// Pointer to the underlying graph.
221    const Graph *graph;
222    /// Pointer to the length map
223    const LengthMap *length;
224    ///Pointer to the map of predecessors edges.
225    PredMap *_pred;
226    ///Indicates if \ref _pred is locally allocated (\c true) or not.
227    bool local_pred;
228    ///Pointer to the map of distances.
229    DistMap *_dist;
230    ///Indicates if \ref _dist is locally allocated (\c true) or not.
231    bool local_dist;
232
233    /// Creates the maps if necessary.
234    void create_maps() {
235      if(!_pred) {
236        local_pred = true;
237        _pred = Traits::createPredMap(*graph);
238      }
239      if(!_dist) {
240        local_dist = true;
241        _dist = Traits::createDistMap(*graph);
242      }
243    }
244   
245  public :
246 
247    typedef BelmannFord Create;
248
249    /// \name Named template parameters
250
251    ///@{
252
253    template <class T>
254    struct DefPredMapTraits : public Traits {
255      typedef T PredMap;
256      static PredMap *createPredMap(const Graph&) {
257        throw UninitializedParameter();
258      }
259    };
260
261    /// \brief \ref named-templ-param "Named parameter" for setting PredMap
262    /// type
263    /// \ref named-templ-param "Named parameter" for setting PredMap type
264    ///
265    template <class T>
266    struct DefPredMap {
267      typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create;
268    };
269   
270    template <class T>
271    struct DefDistMapTraits : public Traits {
272      typedef T DistMap;
273      static DistMap *createDistMap(const Graph& graph) {
274        throw UninitializedParameter();
275      }
276    };
277
278    /// \brief \ref named-templ-param "Named parameter" for setting DistMap
279    /// type
280    ///
281    /// \ref named-templ-param "Named parameter" for setting DistMap type
282    ///
283    template <class T>
284    struct DefDistMap
285      : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > {
286      typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create;
287    };
288   
289    template <class T>
290    struct DefOperationTraitsTraits : public Traits {
291      typedef T OperationTraits;
292    };
293   
294    /// \brief \ref named-templ-param "Named parameter" for setting
295    /// OperationTraits type
296    ///
297    /// \ref named-templ-param "Named parameter" for setting OperationTraits
298    /// type
299    template <class T>
300    struct DefOperationTraits
301      : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
302      typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
303      Create;
304    };
305   
306    ///@}
307
308  protected:
309   
310    BelmannFord() {}
311
312  public:     
313   
314    /// \brief Constructor.
315    ///
316    /// \param _graph the graph the algorithm will run on.
317    /// \param _length the length map used by the algorithm.
318    BelmannFord(const Graph& _graph, const LengthMap& _length) :
319      graph(&_graph), length(&_length),
320      _pred(0), local_pred(false),
321      _dist(0), local_dist(false) {}
322   
323    ///Destructor.
324    ~BelmannFord() {
325      if(local_pred) delete _pred;
326      if(local_dist) delete _dist;
327    }
328
329    /// \brief Sets the length map.
330    ///
331    /// Sets the length map.
332    /// \return \c (*this)
333    BelmannFord &lengthMap(const LengthMap &m) {
334      length = &m;
335      return *this;
336    }
337
338    /// \brief Sets the map storing the predecessor edges.
339    ///
340    /// Sets the map storing the predecessor edges.
341    /// If you don't use this function before calling \ref run(),
342    /// it will allocate one. The destuctor deallocates this
343    /// automatically allocated map, of course.
344    /// \return \c (*this)
345    BelmannFord &predMap(PredMap &m) {
346      if(local_pred) {
347        delete _pred;
348        local_pred=false;
349      }
350      _pred = &m;
351      return *this;
352    }
353
354    /// \brief Sets the map storing the distances calculated by the algorithm.
355    ///
356    /// Sets the map storing the distances calculated by the algorithm.
357    /// If you don't use this function before calling \ref run(),
358    /// it will allocate one. The destuctor deallocates this
359    /// automatically allocated map, of course.
360    /// \return \c (*this)
361    BelmannFord &distMap(DistMap &m) {
362      if(local_dist) {
363        delete _dist;
364        local_dist=false;
365      }
366      _dist = &m;
367      return *this;
368    }
369
370    /// \name Execution control
371    /// The simplest way to execute the algorithm is to use
372    /// one of the member functions called \c run(...).
373    /// \n
374    /// If you need more control on the execution,
375    /// first you must call \ref init(), then you can add several source nodes
376    /// with \ref addSource().
377    /// Finally \ref start() will perform the actual path
378    /// computation.
379
380    ///@{
381
382    /// \brief Initializes the internal data structures.
383    ///
384    /// Initializes the internal data structures.
385    void init(const Value value = OperationTraits::infinity()) {
386      create_maps();
387      for (NodeIt it(*graph); it != INVALID; ++it) {
388        _pred->set(it, INVALID);
389        _dist->set(it, value);
390      }
391    }
392   
393    /// \brief Adds a new source node.
394    ///
395    /// The optional second parameter is the initial distance of the node.
396    /// It just sets the distance of the node to the given value.
397    void addSource(Node source, Value dst = OperationTraits::zero()) {
398      _dist->set(source, dst);
399    }
400
401    /// \brief Executes the algorithm.
402    ///
403    /// \pre init() must be called and at least one node should be added
404    /// with addSource() before using this function.
405    ///
406    /// This method runs the %BelmannFord algorithm from the root node(s)
407    /// in order to compute the shortest path to each node. The algorithm
408    /// computes
409    /// - The shortest path tree.
410    /// - The distance of each node from the root(s).
411    void start() {
412      int num = countNodes(*graph) - 1;
413      for (int i = 0; i < num; ++i) {
414        bool done = true;
415        for (EdgeIt it(*graph); it != INVALID; ++it) {
416          Node source = graph->source(it);
417          Node target = graph->target(it);
418          Value relaxed =
419            OperationTraits::plus((*_dist)[source], (*length)[it]);
420          if (OperationTraits::less(relaxed, (*_dist)[target])) {
421            _pred->set(target, it);
422            _dist->set(target, relaxed);
423            done = false;
424          }
425        }
426        if (done) return;
427      }
428    }
429
430    /// \brief Executes the algorithm and checks the negative cycles.
431    ///
432    /// \pre init() must be called and at least one node should be added
433    /// with addSource() before using this function. If there is
434    /// a negative cycles in the graph it gives back false.
435    ///
436    /// This method runs the %BelmannFord algorithm from the root node(s)
437    /// in order to compute the shortest path to each node. The algorithm
438    /// computes
439    /// - The shortest path tree.
440    /// - The distance of each node from the root(s).
441    bool checkedStart() {
442      int num = countNodes(*graph);
443      for (int i = 0; i < num; ++i) {
444        bool done = true;
445        for (EdgeIt it(*graph); it != INVALID; ++it) {
446          Node source = graph->source(it);
447          Node target = graph->target(it);
448          Value relaxed =
449            OperationTraits::plus((*_dist)[source], (*length)[it]);
450          if (OperationTraits::less(relaxed, (*_dist)[target])) {
451            _pred->set(target, it);
452            _dist->set(target, relaxed);
453            done = false;
454          }
455        }
456        if (done) return true;
457      }
458      return false;
459    }
460   
461    /// \brief Runs %BelmannFord algorithm from node \c s.
462    ///   
463    /// This method runs the %BelmannFord algorithm from a root node \c s
464    /// in order to compute the shortest path to each node. The algorithm
465    /// computes
466    /// - The shortest path tree.
467    /// - The distance of each node from the root.
468    ///
469    /// \note d.run(s) is just a shortcut of the following code.
470    /// \code
471    ///  d.init();
472    ///  d.addSource(s);
473    ///  d.start();
474    /// \endcode
475    void run(Node s) {
476      init();
477      addSource(s);
478      start();
479    }
480   
481    ///@}
482
483    /// \name Query Functions
484    /// The result of the %BelmannFord algorithm can be obtained using these
485    /// functions.\n
486    /// Before the use of these functions,
487    /// either run() or start() must be called.
488   
489    ///@{
490
491    /// \brief Copies the shortest path to \c t into \c p
492    ///   
493    /// This function copies the shortest path to \c t into \c p.
494    /// If it \c t is a source itself or unreachable, then it does not
495    /// alter \c p.
496    ///
497    /// \return Returns \c true if a path to \c t was actually copied to \c p,
498    /// \c false otherwise.
499    /// \sa DirPath
500    template <typename Path>
501    bool getPath(Path &p, Node t) {
502      if(reached(t)) {
503        p.clear();
504        typename Path::Builder b(p);
505        for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
506          b.pushFront(predEdge(t));
507        b.commit();
508        return true;
509      }
510      return false;
511    }
512         
513    /// \brief The distance of a node from the root.
514    ///
515    /// Returns the distance of a node from the root.
516    /// \pre \ref run() must be called before using this function.
517    /// \warning If node \c v in unreachable from the root the return value
518    /// of this funcion is undefined.
519    Value dist(Node v) const { return (*_dist)[v]; }
520
521    /// \brief Returns the 'previous edge' of the shortest path tree.
522    ///
523    /// For a node \c v it returns the 'previous edge' of the shortest path
524    /// tree, i.e. it returns the last edge of a shortest path from the root
525    /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
526    /// if \c v=s. The shortest path tree used here is equal to the shortest
527    /// path tree used in \ref predNode().
528    /// \pre \ref run() must be called before using
529    /// this function.
530    Edge predEdge(Node v) const { return (*_pred)[v]; }
531
532    /// \brief Returns the 'previous node' of the shortest path tree.
533    ///
534    /// For a node \c v it returns the 'previous node' of the shortest path
535    /// tree, i.e. it returns the last but one node from a shortest path from
536    /// the root to \c /v. It is INVALID if \c v is unreachable from the root
537    /// or if \c v=s. The shortest path tree used here is equal to the
538    /// shortest path tree used in \ref predEdge().  \pre \ref run() must be
539    /// called before using this function.
540    Node predNode(Node v) const {
541      return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
542    }
543   
544    /// \brief Returns a reference to the NodeMap of distances.
545    ///
546    /// Returns a reference to the NodeMap of distances. \pre \ref run() must
547    /// be called before using this function.
548    const DistMap &distMap() const { return *_dist;}
549 
550    /// \brief Returns a reference to the shortest path tree map.
551    ///
552    /// Returns a reference to the NodeMap of the edges of the
553    /// shortest path tree.
554    /// \pre \ref run() must be called before using this function.
555    const PredMap &predMap() const { return *_pred; }
556 
557    /// \brief Checks if a node is reachable from the root.
558    ///
559    /// Returns \c true if \c v is reachable from the root.
560    /// \pre \ref run() must be called before using this function.
561    ///
562    bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
563   
564    ///@}
565  };
566 
567  /// \brief Default traits class of BelmannFord function.
568  ///
569  /// Default traits class of BelmannFord function.
570  /// \param _Graph Graph type.
571  /// \param _LengthMap Type of length map.
572  template <typename _Graph, typename _LengthMap>
573  struct BelmannFordWizardDefaultTraits {
574    /// \brief The graph type the algorithm runs on.
575    typedef _Graph Graph;
576
577    /// \brief The type of the map that stores the edge lengths.
578    ///
579    /// The type of the map that stores the edge lengths.
580    /// It must meet the \ref concept::ReadMap "ReadMap" concept.
581    typedef _LengthMap LengthMap;
582
583    /// \brief The value type of the length map.
584    typedef typename _LengthMap::Value Value;
585
586    /// \brief Operation traits for belmann-ford algorithm.
587    ///
588    /// It defines the infinity type on the given Value type
589    /// and the used operation.
590    /// \see BelmannFordDefaultOperationTraits
591    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
592
593    /// \brief The type of the map that stores the last
594    /// edges of the shortest paths.
595    ///
596    /// The type of the map that stores the last
597    /// edges of the shortest paths.
598    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
599    typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
600
601    /// \brief Instantiates a PredMap.
602    ///
603    /// This function instantiates a \ref PredMap.
604    static PredMap *createPredMap(const _Graph &) {
605      return new PredMap();
606    }
607    /// \brief The type of the map that stores the dists of the nodes.
608    ///
609    /// The type of the map that stores the dists of the nodes.
610    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
611    typedef NullMap<typename Graph::Node, Value> DistMap;
612    /// \brief Instantiates a DistMap.
613    ///
614    /// This function instantiates a \ref DistMap.
615    static DistMap *createDistMap(const _Graph &) {
616      return new DistMap();
617    }
618  };
619 
620  /// \brief Default traits used by \ref BelmannFordWizard
621  ///
622  /// To make it easier to use BelmannFord algorithm
623  /// we have created a wizard class.
624  /// This \ref BelmannFordWizard class needs default traits,
625  /// as well as the \ref BelmannFord class.
626  /// The \ref BelmannFordWizardBase is a class to be the default traits of the
627  /// \ref BelmannFordWizard class.
628  /// \todo More named parameters are required...
629  template<class _Graph,class _LengthMap>
630  class BelmannFordWizardBase
631    : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> {
632
633    typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
634  protected:
635    /// Type of the nodes in the graph.
636    typedef typename Base::Graph::Node Node;
637
638    /// Pointer to the underlying graph.
639    void *_graph;
640    /// Pointer to the length map
641    void *_length;
642    ///Pointer to the map of predecessors edges.
643    void *_pred;
644    ///Pointer to the map of distances.
645    void *_dist;
646    ///Pointer to the source node.
647    Node _source;
648
649    public:
650    /// Constructor.
651   
652    /// This constructor does not require parameters, therefore it initiates
653    /// all of the attributes to default values (0, INVALID).
654    BelmannFordWizardBase() : _graph(0), _length(0), _pred(0),
655                           _dist(0), _source(INVALID) {}
656
657    /// Constructor.
658   
659    /// This constructor requires some parameters,
660    /// listed in the parameters list.
661    /// Others are initiated to 0.
662    /// \param graph is the initial value of  \ref _graph
663    /// \param length is the initial value of  \ref _length
664    /// \param source is the initial value of  \ref _source
665    BelmannFordWizardBase(const _Graph& graph,
666                          const _LengthMap& length,
667                          Node source = INVALID) :
668      _graph((void *)&graph), _length((void *)&length), _pred(0),
669      _dist(0), _source(source) {}
670
671  };
672 
673  /// A class to make the usage of BelmannFord algorithm easier
674
675  /// This class is created to make it easier to use BelmannFord algorithm.
676  /// It uses the functions and features of the plain \ref BelmannFord,
677  /// but it is much simpler to use it.
678  ///
679  /// Simplicity means that the way to change the types defined
680  /// in the traits class is based on functions that returns the new class
681  /// and not on templatable built-in classes.
682  /// When using the plain \ref BelmannFord
683  /// the new class with the modified type comes from
684  /// the original class by using the ::
685  /// operator. In the case of \ref BelmannFordWizard only
686  /// a function have to be called and it will
687  /// return the needed class.
688  ///
689  /// It does not have own \ref run method. When its \ref run method is called
690  /// it initiates a plain \ref BelmannFord class, and calls the \ref
691  /// BelmannFord::run method of it.
692  template<class _Traits>
693  class BelmannFordWizard : public _Traits {
694    typedef _Traits Base;
695
696    ///The type of the underlying graph.
697    typedef typename _Traits::Graph Graph;
698
699    typedef typename Graph::Node Node;
700    typedef typename Graph::NodeIt NodeIt;
701    typedef typename Graph::Edge Edge;
702    typedef typename Graph::OutEdgeIt EdgeIt;
703   
704    ///The type of the map that stores the edge lengths.
705    typedef typename _Traits::LengthMap LengthMap;
706
707    ///The type of the length of the edges.
708    typedef typename LengthMap::Value Value;
709
710    ///\brief The type of the map that stores the last
711    ///edges of the shortest paths.
712    typedef typename _Traits::PredMap PredMap;
713
714    ///The type of the map that stores the dists of the nodes.
715    typedef typename _Traits::DistMap DistMap;
716
717  public:
718    /// Constructor.
719    BelmannFordWizard() : _Traits() {}
720
721    /// \brief Constructor that requires parameters.
722    ///
723    /// Constructor that requires parameters.
724    /// These parameters will be the default values for the traits class.
725    BelmannFordWizard(const Graph& graph, const LengthMap& length,
726                      Node source = INVALID)
727      : _Traits(graph, length, source) {}
728
729    /// \brief Copy constructor
730    BelmannFordWizard(const _Traits &b) : _Traits(b) {}
731
732    ~BelmannFordWizard() {}
733
734    /// \brief Runs BelmannFord algorithm from a given node.
735    ///   
736    /// Runs BelmannFord algorithm from a given node.
737    /// The node can be given by the \ref source function.
738    void run() {
739      if(Base::_source == INVALID) throw UninitializedParameter();
740      BelmannFord<Graph,LengthMap,_Traits>
741        bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
742      if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
743      if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
744      bf.run(Base::_source);
745    }
746
747    /// \brief Runs BelmannFord algorithm from the given node.
748    ///
749    /// Runs BelmannFord algorithm from the given node.
750    /// \param s is the given source.
751    void run(Node source) {
752      Base::_source = source;
753      run();
754    }
755
756    template<class T>
757    struct DefPredMapBase : public Base {
758      typedef T PredMap;
759      static PredMap *createPredMap(const Graph &) { return 0; };
760      DefPredMapBase(const _Traits &b) : _Traits(b) {}
761    };
762   
763    ///\brief \ref named-templ-param "Named parameter"
764    ///function for setting PredMap type
765    ///
766    /// \ref named-templ-param "Named parameter"
767    ///function for setting PredMap type
768    ///
769    template<class T>
770    BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
771    {
772      Base::_pred=(void *)&t;
773      return BelmannFordWizard<DefPredMapBase<T> >(*this);
774    }
775   
776    template<class T>
777    struct DefDistMapBase : public Base {
778      typedef T DistMap;
779      static DistMap *createDistMap(const Graph &) { return 0; };
780      DefDistMapBase(const _Traits &b) : _Traits(b) {}
781    };
782   
783    ///\brief \ref named-templ-param "Named parameter"
784    ///function for setting DistMap type
785    ///
786    /// \ref named-templ-param "Named parameter"
787    ///function for setting DistMap type
788    ///
789    template<class T>
790    BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
791      Base::_dist=(void *)&t;
792      return BelmannFordWizard<DefDistMapBase<T> >(*this);
793    }
794
795    template<class T>
796    struct DefOperationTraitsBase : public Base {
797      typedef T OperationTraits;
798      DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
799    };
800   
801    ///\brief \ref named-templ-param "Named parameter"
802    ///function for setting OperationTraits type
803    ///
804    /// \ref named-templ-param "Named parameter"
805    ///function for setting OperationTraits type
806    ///
807    template<class T>
808    BelmannFordWizard<DefOperationTraitsBase<T> > distMap() {
809      return BelmannFordWizard<DefDistMapBase<T> >(*this);
810    }
811   
812    /// \brief Sets the source node, from which the BelmannFord algorithm runs.
813    ///
814    /// Sets the source node, from which the BelmannFord algorithm runs.
815    /// \param s is the source node.
816    BelmannFordWizard<_Traits>& source(Node source) {
817      Base::_source = source;
818      return *this;
819    }
820   
821  };
822 
823  /// \brief Function type interface for BelmannFord algorithm.
824  ///
825  /// \ingroup flowalgs
826  /// Function type interface for BelmannFord algorithm.
827  ///
828  /// This function also has several \ref named-templ-func-param
829  /// "named parameters", they are declared as the members of class
830  /// \ref BelmannFordWizard.
831  /// The following
832  /// example shows how to use these parameters.
833  /// \code
834  /// belmannford(g,length,source).predMap(preds).run();
835  /// \endcode
836  /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
837  /// to the end of the parameter list.
838  /// \sa BelmannFordWizard
839  /// \sa BelmannFord
840  template<class _Graph, class _LengthMap>
841  BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
842  belmannFord(const _Graph& graph,
843              const _LengthMap& length,
844              typename _Graph::Node source = INVALID) {
845    return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
846      (graph, length, source);
847  }
848
849} //END OF NAMESPACE LEMON
850
851#endif
852
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