# source:lemon-0.x/lemon/belmann_ford.h@1723:fb4f801dd692

Last change on this file since 1723:fb4f801dd692 was 1723:fb4f801dd692, checked in by Balazs Dezso, 14 years ago

Really short description of these shortest path algorithms

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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/// \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 Belmann-Ford
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 Belmann-Ford algorithm solves the shortest path from one node
153  /// problem when the edges can have negative length but the graph should
154  /// not contain circle with negative sum of length. If we can assume
155  /// that all edge is non-negative in the graph then the dijkstra algorithm
156  /// should be used rather.
157  ///
158  /// The complexity of the algorithm is O(n * e).
159  ///
160  /// The type of the length is determined by the
161  /// \ref concept::ReadMap::Value "Value" of the length map.
162  ///
163  /// \param _Graph The graph type the algorithm runs on. The default value
164  /// is \ref ListGraph. The value of _Graph is not used directly by
165  /// BelmannFord, it is only passed to \ref BelmannFordDefaultTraits.
166  /// \param _LengthMap This read-only EdgeMap determines the lengths of the
167  /// edges. The default map type is \ref concept::StaticGraph::EdgeMap
168  /// "Graph::EdgeMap<int>".  The value of _LengthMap is not used directly
169  /// by BelmannFord, it is only passed to \ref BelmannFordDefaultTraits.
170  /// \param _Traits Traits class to set various data types used by the
171  /// algorithm.  The default traits class is \ref BelmannFordDefaultTraits
172  /// "BelmannFordDefaultTraits<_Graph,_LengthMap>".  See \ref
173  /// BelmannFordDefaultTraits for the documentation of a BelmannFord traits
174  /// class.
175  ///
176  /// \author Balazs Dezso
177
178#ifdef DOXYGEN
179  template <typename _Graph, typename _LengthMap, typename _Traits>
180#else
181  template <typename _Graph=ListGraph,
182            typename _LengthMap=typename _Graph::template EdgeMap<int>,
183            typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> >
184#endif
185  class BelmannFord {
186  public:
187
188    /// \brief \ref Exception for uninitialized parameters.
189    ///
190    /// This error represents problems in the initialization
191    /// of the parameters of the algorithms.
192
193    class UninitializedParameter : public lemon::UninitializedParameter {
194    public:
195      virtual const char* exceptionName() const {
196        return "lemon::BelmannFord::UninitializedParameter";
197      }
198    };
199
200    typedef _Traits Traits;
201    ///The type of the underlying graph.
202    typedef typename _Traits::Graph Graph;
203
204    typedef typename Graph::Node Node;
205    typedef typename Graph::NodeIt NodeIt;
206    typedef typename Graph::Edge Edge;
207    typedef typename Graph::EdgeIt EdgeIt;
208
209    /// \brief The type of the length of the edges.
210    typedef typename _Traits::LengthMap::Value Value;
211    /// \brief The type of the map that stores the edge lengths.
212    typedef typename _Traits::LengthMap LengthMap;
213    /// \brief The type of the map that stores the last
214    /// edges of the shortest paths.
215    typedef typename _Traits::PredMap PredMap;
216    /// \brief The type of the map that stores the dists of the nodes.
217    typedef typename _Traits::DistMap DistMap;
218    /// \brief The operation traits.
219    typedef typename _Traits::OperationTraits OperationTraits;
220  private:
221    /// Pointer to the underlying graph.
222    const Graph *graph;
223    /// Pointer to the length map
224    const LengthMap *length;
225    ///Pointer to the map of predecessors edges.
226    PredMap *_pred;
227    ///Indicates if \ref _pred is locally allocated (\c true) or not.
228    bool local_pred;
229    ///Pointer to the map of distances.
230    DistMap *_dist;
231    ///Indicates if \ref _dist is locally allocated (\c true) or not.
232    bool local_dist;
233
234    /// Creates the maps if necessary.
235    void create_maps() {
236      if(!_pred) {
237        local_pred = true;
238        _pred = Traits::createPredMap(*graph);
239      }
240      if(!_dist) {
241        local_dist = true;
242        _dist = Traits::createDistMap(*graph);
243      }
244    }
245
246  public :
247
248    typedef BelmannFord Create;
249
250    /// \name Named template parameters
251
252    ///@{
253
254    template <class T>
255    struct DefPredMapTraits : public Traits {
256      typedef T PredMap;
257      static PredMap *createPredMap(const Graph&) {
258        throw UninitializedParameter();
259      }
260    };
261
262    /// \brief \ref named-templ-param "Named parameter" for setting PredMap
263    /// type
264    /// \ref named-templ-param "Named parameter" for setting PredMap type
265    ///
266    template <class T>
267    struct DefPredMap {
268      typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create;
269    };
270
271    template <class T>
272    struct DefDistMapTraits : public Traits {
273      typedef T DistMap;
274      static DistMap *createDistMap(const Graph& graph) {
275        throw UninitializedParameter();
276      }
277    };
278
279    /// \brief \ref named-templ-param "Named parameter" for setting DistMap
280    /// type
281    ///
282    /// \ref named-templ-param "Named parameter" for setting DistMap type
283    ///
284    template <class T>
285    struct DefDistMap
286      : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > {
287      typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create;
288    };
289
290    template <class T>
291    struct DefOperationTraitsTraits : public Traits {
292      typedef T OperationTraits;
293    };
294
295    /// \brief \ref named-templ-param "Named parameter" for setting
296    /// OperationTraits type
297    ///
298    /// \ref named-templ-param "Named parameter" for setting OperationTraits
299    /// type
300    template <class T>
301    struct DefOperationTraits
302      : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
303      typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
304      Create;
305    };
306
307    ///@}
308
309  protected:
310
311    BelmannFord() {}
312
313  public:
314
315    /// \brief Constructor.
316    ///
317    /// \param _graph the graph the algorithm will run on.
318    /// \param _length the length map used by the algorithm.
319    BelmannFord(const Graph& _graph, const LengthMap& _length) :
320      graph(&_graph), length(&_length),
321      _pred(0), local_pred(false),
322      _dist(0), local_dist(false) {}
323
324    ///Destructor.
325    ~BelmannFord() {
326      if(local_pred) delete _pred;
327      if(local_dist) delete _dist;
328    }
329
330    /// \brief Sets the length map.
331    ///
332    /// Sets the length map.
333    /// \return \c (*this)
334    BelmannFord &lengthMap(const LengthMap &m) {
335      length = &m;
336      return *this;
337    }
338
339    /// \brief Sets the map storing the predecessor edges.
340    ///
341    /// Sets the map storing the predecessor edges.
342    /// If you don't use this function before calling \ref run(),
343    /// it will allocate one. The destuctor deallocates this
344    /// automatically allocated map, of course.
345    /// \return \c (*this)
346    BelmannFord &predMap(PredMap &m) {
347      if(local_pred) {
348        delete _pred;
349        local_pred=false;
350      }
351      _pred = &m;
352      return *this;
353    }
354
355    /// \brief Sets the map storing the distances calculated by the algorithm.
356    ///
357    /// Sets the map storing the distances calculated by the algorithm.
358    /// If you don't use this function before calling \ref run(),
359    /// it will allocate one. The destuctor deallocates this
360    /// automatically allocated map, of course.
361    /// \return \c (*this)
362    BelmannFord &distMap(DistMap &m) {
363      if(local_dist) {
364        delete _dist;
365        local_dist=false;
366      }
367      _dist = &m;
368      return *this;
369    }
370
371    /// \name Execution control
372    /// The simplest way to execute the algorithm is to use
373    /// one of the member functions called \c run(...).
374    /// \n
375    /// If you need more control on the execution,
376    /// first you must call \ref init(), then you can add several source nodes
378    /// Finally \ref start() will perform the actual path
379    /// computation.
380
381    ///@{
382
383    /// \brief Initializes the internal data structures.
384    ///
385    /// Initializes the internal data structures.
386    void init(const Value value = OperationTraits::infinity()) {
387      create_maps();
388      for (NodeIt it(*graph); it != INVALID; ++it) {
389        _pred->set(it, INVALID);
390        _dist->set(it, value);
391      }
392    }
393
394    /// \brief Adds a new source node.
395    ///
396    /// The optional second parameter is the initial distance of the node.
397    /// It just sets the distance of the node to the given value.
398    void addSource(Node source, Value dst = OperationTraits::zero()) {
399      _dist->set(source, dst);
400    }
401
402    /// \brief Executes the algorithm.
403    ///
404    /// \pre init() must be called and at least one node should be added
405    /// with addSource() before using this function.
406    ///
407    /// This method runs the %BelmannFord algorithm from the root node(s)
408    /// in order to compute the shortest path to each node. The algorithm
409    /// computes
410    /// - The shortest path tree.
411    /// - The distance of each node from the root(s).
412    void start() {
413      int num = countNodes(*graph) - 1;
414      for (int i = 0; i < num; ++i) {
416        for (EdgeIt it(*graph); it != INVALID; ++it) {
417          Node source = graph->source(it);
418          Node target = graph->target(it);
419          Value relaxed =
420            OperationTraits::plus((*_dist)[source], (*length)[it]);
421          if (OperationTraits::less(relaxed, (*_dist)[target])) {
422            _pred->set(target, it);
423            _dist->set(target, relaxed);
425          }
426        }
428      }
429    }
430
431    /// \brief Executes the algorithm and check the negative circles.
432    ///
433    /// \pre init() must be called and at least one node should be added
434    /// with addSource() before using this function. If there is
435    /// a negative circle in the graph it gives back false.
436    ///
437    /// This method runs the %BelmannFord algorithm from the root node(s)
438    /// in order to compute the shortest path to each node. The algorithm
439    /// computes
440    /// - The shortest path tree.
441    /// - The distance of each node from the root(s).
442    bool checkedStart() {
443      int num = countNodes(*graph);
444      for (int i = 0; i < num; ++i) {
446        for (EdgeIt it(*graph); it != INVALID; ++it) {
447          Node source = graph->source(it);
448          Node target = graph->target(it);
449          Value relaxed =
450            OperationTraits::plus((*_dist)[source], (*length)[it]);
451          if (OperationTraits::less(relaxed, (*_dist)[target])) {
452            _pred->set(target, it);
453            _dist->set(target, relaxed);
455          }
456        }
458      }
459      return false;
460    }
461
462    /// \brief Runs %BelmannFord algorithm from node \c s.
463    ///
464    /// This method runs the %BelmannFord algorithm from a root node \c s
465    /// in order to compute the shortest path to each node. The algorithm
466    /// computes
467    /// - The shortest path tree.
468    /// - The distance of each node from the root.
469    ///
470    /// \note d.run(s) is just a shortcut of the following code.
471    /// \code
472    ///  d.init();
474    ///  d.start();
475    /// \endcode
476    void run(Node s) {
477      init();
479      start();
480    }
481
482    ///@}
483
484    /// \name Query Functions
485    /// The result of the %BelmannFord algorithm can be obtained using these
486    /// functions.\n
487    /// Before the use of these functions,
488    /// either run() or start() must be called.
489
490    ///@{
491
492    /// \brief Copies the shortest path to \c t into \c p
493    ///
494    /// This function copies the shortest path to \c t into \c p.
495    /// If it \c t is a source itself or unreachable, then it does not
496    /// alter \c p.
497    /// \todo Is it the right way to handle unreachable nodes?
498    /// \return Returns \c true if a path to \c t was actually copied to \c p,
499    /// \c false otherwise.
500    /// \sa DirPath
501    template <typename Path>
502    bool getPath(Path &p, Node t) {
503      if(reached(t)) {
504        p.clear();
505        typename Path::Builder b(p);
506        for(b.setStartNode(t);pred(t)!=INVALID;t=predNode(t))
507          b.pushFront(pred(t));
508        b.commit();
509        return true;
510      }
511      return false;
512    }
513
514    /// \brief The distance of a node from the root.
515    ///
516    /// Returns the distance of a node from the root.
517    /// \pre \ref run() must be called before using this function.
518    /// \warning If node \c v in unreachable from the root the return value
519    /// of this funcion is undefined.
520    Value dist(Node v) const { return (*_dist)[v]; }
521
522    /// \brief Returns the 'previous edge' of the shortest path tree.
523    ///
524    /// For a node \c v it returns the 'previous edge' of the shortest path
525    /// tree, i.e. it returns the last edge of a shortest path from the root
526    /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
527    /// if \c v=s. The shortest path tree used here is equal to the shortest
528    /// path tree used in \ref predNode().
529    /// \pre \ref run() must be called before using
530    /// this function.
531    /// \todo predEdge could be a better name.
532    Edge pred(Node v) const { return (*_pred)[v]; }
533
534    /// \brief Returns the 'previous node' of the shortest path tree.
535    ///
536    /// For a node \c v it returns the 'previous node' of the shortest path
537    /// tree, i.e. it returns the last but one node from a shortest path from
538    /// the root to \c /v. It is INVALID if \c v is unreachable from the root
539    /// or if \c v=s. The shortest path tree used here is equal to the
540    /// shortest path tree used in \ref pred().  \pre \ref run() must be
541    /// called before using this function.
542    Node predNode(Node v) const {
543      return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
544    }
545
546    /// \brief Returns a reference to the NodeMap of distances.
547    ///
548    /// Returns a reference to the NodeMap of distances. \pre \ref run() must
549    /// be called before using this function.
550    const DistMap &distMap() const { return *_dist;}
551
552    /// \brief Returns a reference to the shortest path tree map.
553    ///
554    /// Returns a reference to the NodeMap of the edges of the
555    /// shortest path tree.
556    /// \pre \ref run() must be called before using this function.
557    const PredMap &predMap() const { return *_pred; }
558
559    /// \brief Checks if a node is reachable from the root.
560    ///
561    /// Returns \c true if \c v is reachable from the root.
562    /// \pre \ref run() must be called before using this function.
563    ///
564    bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
565
566    ///@}
567  };
568
569  /// \brief Default traits class of BelmannFord function.
570  ///
571  /// Default traits class of BelmannFord function.
572  /// \param _Graph Graph type.
573  /// \param _LengthMap Type of length map.
574  template <typename _Graph, typename _LengthMap>
575  struct BelmannFordWizardDefaultTraits {
576    /// \brief The graph type the algorithm runs on.
577    typedef _Graph Graph;
578
579    /// \brief The type of the map that stores the edge lengths.
580    ///
581    /// The type of the map that stores the edge lengths.
583    typedef _LengthMap LengthMap;
584
585    /// \brief The value type of the length map.
586    typedef typename _LengthMap::Value Value;
587
588    /// \brief Operation traits for belmann-ford algorithm.
589    ///
590    /// It defines the infinity type on the given Value type
591    /// and the used operation.
592    /// \see BelmannFordDefaultOperationTraits
593    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
594
595    /// \brief The type of the map that stores the last
596    /// edges of the shortest paths.
597    ///
598    /// The type of the map that stores the last
599    /// edges of the shortest paths.
600    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
601    typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
602
603    /// \brief Instantiates a PredMap.
604    ///
605    /// This function instantiates a \ref PredMap.
606    static PredMap *createPredMap(const _Graph &) {
607      return new PredMap();
608    }
609    /// \brief The type of the map that stores the dists of the nodes.
610    ///
611    /// The type of the map that stores the dists of the nodes.
612    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
613    typedef NullMap<typename Graph::Node, Value> DistMap;
614    /// \brief Instantiates a DistMap.
615    ///
616    /// This function instantiates a \ref DistMap.
617    static DistMap *createDistMap(const _Graph &) {
618      return new DistMap();
619    }
620  };
621
622  /// \brief Default traits used by \ref BelmannFordWizard
623  ///
624  /// To make it easier to use BelmannFord algorithm
625  /// we have created a wizard class.
626  /// This \ref BelmannFordWizard class needs default traits,
627  /// as well as the \ref BelmannFord class.
628  /// The \ref BelmannFordWizardBase is a class to be the default traits of the
629  /// \ref BelmannFordWizard class.
630  /// \todo More named parameters are required...
631  template<class _Graph,class _LengthMap>
632  class BelmannFordWizardBase
633    : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> {
634
635    typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
636  protected:
637    /// Type of the nodes in the graph.
638    typedef typename Base::Graph::Node Node;
639
640    /// Pointer to the underlying graph.
641    void *_graph;
642    /// Pointer to the length map
643    void *_length;
644    ///Pointer to the map of predecessors edges.
645    void *_pred;
646    ///Pointer to the map of distances.
647    void *_dist;
648    ///Pointer to the source node.
649    Node _source;
650
651    public:
652    /// Constructor.
653
654    /// This constructor does not require parameters, therefore it initiates
655    /// all of the attributes to default values (0, INVALID).
656    BelmannFordWizardBase() : _graph(0), _length(0), _pred(0),
657                           _dist(0), _source(INVALID) {}
658
659    /// Constructor.
660
661    /// This constructor requires some parameters,
662    /// listed in the parameters list.
663    /// Others are initiated to 0.
664    /// \param graph is the initial value of  \ref _graph
665    /// \param length is the initial value of  \ref _length
666    /// \param source is the initial value of  \ref _source
667    BelmannFordWizardBase(const _Graph& graph,
668                          const _LengthMap& length,
669                          Node source = INVALID) :
670      _graph((void *)&graph), _length((void *)&length), _pred(0),
671      _dist(0), _source(source) {}
672
673  };
674
675  /// A class to make the usage of BelmannFord algorithm easier
676
677  /// This class is created to make it easier to use BelmannFord algorithm.
678  /// It uses the functions and features of the plain \ref BelmannFord,
679  /// but it is much simpler to use it.
680  ///
681  /// Simplicity means that the way to change the types defined
682  /// in the traits class is based on functions that returns the new class
683  /// and not on templatable built-in classes.
684  /// When using the plain \ref BelmannFord
685  /// the new class with the modified type comes from
686  /// the original class by using the ::
687  /// operator. In the case of \ref BelmannFordWizard only
688  /// a function have to be called and it will
689  /// return the needed class.
690  ///
691  /// It does not have own \ref run method. When its \ref run method is called
692  /// it initiates a plain \ref BelmannFord class, and calls the \ref
693  /// BelmannFord::run method of it.
694  template<class _Traits>
695  class BelmannFordWizard : public _Traits {
696    typedef _Traits Base;
697
698    ///The type of the underlying graph.
699    typedef typename _Traits::Graph Graph;
700
701    typedef typename Graph::Node Node;
702    typedef typename Graph::NodeIt NodeIt;
703    typedef typename Graph::Edge Edge;
704    typedef typename Graph::OutEdgeIt EdgeIt;
705
706    ///The type of the map that stores the edge lengths.
707    typedef typename _Traits::LengthMap LengthMap;
708
709    ///The type of the length of the edges.
710    typedef typename LengthMap::Value Value;
711
712    ///\brief The type of the map that stores the last
713    ///edges of the shortest paths.
714    typedef typename _Traits::PredMap PredMap;
715
716    ///The type of the map that stores the dists of the nodes.
717    typedef typename _Traits::DistMap DistMap;
718
719  public:
720    /// Constructor.
721    BelmannFordWizard() : _Traits() {}
722
723    /// \brief Constructor that requires parameters.
724    ///
725    /// Constructor that requires parameters.
726    /// These parameters will be the default values for the traits class.
727    BelmannFordWizard(const Graph& graph, const LengthMap& length,
728                      Node source = INVALID)
729      : _Traits(graph, length, source) {}
730
731    /// \brief Copy constructor
732    BelmannFordWizard(const _Traits &b) : _Traits(b) {}
733
734    ~BelmannFordWizard() {}
735
736    /// \brief Runs BelmannFord algorithm from a given node.
737    ///
738    /// Runs BelmannFord algorithm from a given node.
739    /// The node can be given by the \ref source function.
740    void run() {
741      if(Base::_source == INVALID) throw UninitializedParameter();
742      BelmannFord<Graph,LengthMap,_Traits>
743        bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
744      if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
745      if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
746      bf.run(Base::_source);
747    }
748
749    /// \brief Runs BelmannFord algorithm from the given node.
750    ///
751    /// Runs BelmannFord algorithm from the given node.
752    /// \param s is the given source.
753    void run(Node source) {
754      Base::_source = source;
755      run();
756    }
757
758    template<class T>
759    struct DefPredMapBase : public Base {
760      typedef T PredMap;
761      static PredMap *createPredMap(const Graph &) { return 0; };
762      DefPredMapBase(const _Traits &b) : _Traits(b) {}
763    };
764
765    ///\brief \ref named-templ-param "Named parameter"
766    ///function for setting PredMap type
767    ///
768    /// \ref named-templ-param "Named parameter"
769    ///function for setting PredMap type
770    ///
771    template<class T>
772    BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
773    {
774      Base::_pred=(void *)&t;
775      return BelmannFordWizard<DefPredMapBase<T> >(*this);
776    }
777
778    template<class T>
779    struct DefDistMapBase : public Base {
780      typedef T DistMap;
781      static DistMap *createDistMap(const Graph &) { return 0; };
782      DefDistMapBase(const _Traits &b) : _Traits(b) {}
783    };
784
785    ///\brief \ref named-templ-param "Named parameter"
786    ///function for setting DistMap type
787    ///
788    /// \ref named-templ-param "Named parameter"
789    ///function for setting DistMap type
790    ///
791    template<class T>
792    BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
793      Base::_dist=(void *)&t;
794      return BelmannFordWizard<DefDistMapBase<T> >(*this);
795    }
796
797    template<class T>
798    struct DefOperationTraitsBase : public Base {
799      typedef T OperationTraits;
800      DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
801    };
802
803    ///\brief \ref named-templ-param "Named parameter"
804    ///function for setting OperationTraits type
805    ///
806    /// \ref named-templ-param "Named parameter"
807    ///function for setting OperationTraits type
808    ///
809    template<class T>
810    BelmannFordWizard<DefOperationTraitsBase<T> > distMap() {
811      return BelmannFordWizard<DefDistMapBase<T> >(*this);
812    }
813
814    /// \brief Sets the source node, from which the BelmannFord algorithm runs.
815    ///
816    /// Sets the source node, from which the BelmannFord algorithm runs.
817    /// \param s is the source node.
818    BelmannFordWizard<_Traits>& source(Node source) {
819      Base::_source = source;
820      return *this;
821    }
822
823  };
824
825  /// \brief Function type interface for BelmannFord algorithm.
826  ///
827  /// \ingroup flowalgs
828  /// Function type interface for BelmannFord algorithm.
829  ///
830  /// This function also has several \ref named-templ-func-param
831  /// "named parameters", they are declared as the members of class
832  /// \ref BelmannFordWizard.
833  /// The following
834  /// example shows how to use these parameters.
835  /// \code
836  /// belmannford(g,length,source).predMap(preds).run();
837  /// \endcode
838  /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
839  /// to the end of the parameter list.
840  /// \sa BelmannFordWizard
841  /// \sa BelmannFord
842  template<class _Graph, class _LengthMap>
843  BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
844  belmannFord(const _Graph& graph,
845              const _LengthMap& length,
846              typename _Graph::Node source = INVALID) {
847    return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
848      (graph, length, source);
849  }
850
851} //END OF NAMESPACE LEMON
852
853#endif
854
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