# source:lemon-0.x/lemon/belmann_ford.h@1852:ffa7c6e96330

Last change on this file since 1852:ffa7c6e96330 was 1816:19ee9133a28c, checked in by Alpar Juttner, 14 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.
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::OutEdgeIt OutEdgeIt;
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    typedef typename Graph::template NodeMap<bool> MaskMap;
235
236    std::vector<Node> _process;
237
238    /// Creates the maps if necessary.
239    void create_maps() {
240      if(!_pred) {
241        local_pred = true;
242        _pred = Traits::createPredMap(*graph);
243      }
244      if(!_dist) {
245        local_dist = true;
246        _dist = Traits::createDistMap(*graph);
247      }
249    }
250
251  public :
252
253    typedef BelmannFord Create;
254
255    /// \name Named template parameters
256
257    ///@{
258
259    template <class T>
260    struct DefPredMapTraits : public Traits {
261      typedef T PredMap;
262      static PredMap *createPredMap(const Graph&) {
263        throw UninitializedParameter();
264      }
265    };
266
267    /// \brief \ref named-templ-param "Named parameter" for setting PredMap
268    /// type
269    /// \ref named-templ-param "Named parameter" for setting PredMap type
270    ///
271    template <class T>
272    struct DefPredMap {
273      typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create;
274    };
275
276    template <class T>
277    struct DefDistMapTraits : public Traits {
278      typedef T DistMap;
279      static DistMap *createDistMap(const Graph& graph) {
280        throw UninitializedParameter();
281      }
282    };
283
284    /// \brief \ref named-templ-param "Named parameter" for setting DistMap
285    /// type
286    ///
287    /// \ref named-templ-param "Named parameter" for setting DistMap type
288    ///
289    template <class T>
290    struct DefDistMap
291      : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > {
292      typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create;
293    };
294
295    template <class T>
296    struct DefOperationTraitsTraits : public Traits {
297      typedef T OperationTraits;
298    };
299
300    /// \brief \ref named-templ-param "Named parameter" for setting
301    /// OperationTraits type
302    ///
303    /// \ref named-templ-param "Named parameter" for setting OperationTraits
304    /// type
305    template <class T>
306    struct DefOperationTraits
307      : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
308      typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
309      Create;
310    };
311
312    ///@}
313
314  protected:
315
316    BelmannFord() {}
317
318  public:
319
320    /// \brief Constructor.
321    ///
322    /// \param _graph the graph the algorithm will run on.
323    /// \param _length the length map used by the algorithm.
324    BelmannFord(const Graph& _graph, const LengthMap& _length) :
325      graph(&_graph), length(&_length),
326      _pred(0), local_pred(false),
327      _dist(0), local_dist(false) {}
328
329    ///Destructor.
330    ~BelmannFord() {
331      if(local_pred) delete _pred;
332      if(local_dist) delete _dist;
334    }
335
336    /// \brief Sets the length map.
337    ///
338    /// Sets the length map.
339    /// \return \c (*this)
340    BelmannFord &lengthMap(const LengthMap &m) {
341      length = &m;
342      return *this;
343    }
344
345    /// \brief Sets the map storing the predecessor edges.
346    ///
347    /// Sets the map storing the predecessor edges.
348    /// If you don't use this function before calling \ref run(),
349    /// it will allocate one. The destuctor deallocates this
350    /// automatically allocated map, of course.
351    /// \return \c (*this)
352    BelmannFord &predMap(PredMap &m) {
353      if(local_pred) {
354        delete _pred;
355        local_pred=false;
356      }
357      _pred = &m;
358      return *this;
359    }
360
361    /// \brief Sets the map storing the distances calculated by the algorithm.
362    ///
363    /// Sets the map storing the distances calculated by the algorithm.
364    /// If you don't use this function before calling \ref run(),
365    /// it will allocate one. The destuctor deallocates this
366    /// automatically allocated map, of course.
367    /// \return \c (*this)
368    BelmannFord &distMap(DistMap &m) {
369      if(local_dist) {
370        delete _dist;
371        local_dist=false;
372      }
373      _dist = &m;
374      return *this;
375    }
376
377    /// \name Execution control
378    /// The simplest way to execute the algorithm is to use
379    /// one of the member functions called \c run(...).
380    /// \n
381    /// If you need more control on the execution,
382    /// first you must call \ref init(), then you can add several source nodes
384    /// Finally \ref start() will perform the actual path
385    /// computation.
386
387    ///@{
388
389    /// \brief Initializes the internal data structures.
390    ///
391    /// Initializes the internal data structures.
392    void init(const Value value = OperationTraits::infinity()) {
393      create_maps();
394      for (NodeIt it(*graph); it != INVALID; ++it) {
395        _pred->set(it, INVALID);
396        _dist->set(it, value);
397      }
398      _process.clear();
399      if (OperationTraits::less(value, OperationTraits::infinity())) {
400        for (NodeIt it(*graph); it != INVALID; ++it) {
401          _process.push_back(it);
403        }
404      }
405    }
406
407    /// \brief Adds a new source node.
408    ///
409    /// The optional second parameter is the initial distance of the node.
410    /// It just sets the distance of the node to the given value.
411    void addSource(Node source, Value dst = OperationTraits::zero()) {
412      _dist->set(source, dst);
414        _process.push_back(source);
416      }
417    }
418
419    /// \brief Executes one round from the belmann ford algorithm.
420    ///
421    /// If the algoritm calculated the distances in the previous round
422    /// strictly for all at most k length paths then it will calculate the
423    /// distances strictly for all at most k + 1 length paths. With k
424    /// iteration this function calculates the at most k length paths.
425    ///\todo what is the return value?
426    bool processNextRound() {
427      for (int i = 0; i < (int)_process.size(); ++i) {
429      }
430      std::vector<Node> nextProcess;
431      std::vector<Value> values(_process.size());
432      for (int i = 0; i < (int)_process.size(); ++i) {
433        values[i] = _dist[_process[i]];
434      }
435      for (int i = 0; i < (int)_process.size(); ++i) {
436        for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
437          Node target = graph->target(it);
438          Value relaxed = OperationTraits::plus(values[i], (*length)[it]);
439          if (OperationTraits::less(relaxed, (*_dist)[target])) {
440            _pred->set(target, it);
441            _dist->set(target, relaxed);
444              nextProcess.push_back(target);
445            }
446          }
447        }
448      }
449      _process.swap(nextProcess);
450      return _process.empty();
451    }
452
453    /// \brief Executes one weak round from the belmann ford algorithm.
454    ///
455    /// If the algorithm calculated the distances in the
456    /// previous round at least for all at most k length paths then it will
457    /// calculate the distances at least for all at most k + 1 length paths.
458    /// This function does not make it possible to calculate strictly the
459    /// at most k length minimal paths, this is why it is
460    /// called just weak round.
461    ///\todo what is the return value?
462    bool processNextWeakRound() {
463      for (int i = 0; i < (int)_process.size(); ++i) {
465      }
466      std::vector<Node> nextProcess;
467      for (int i = 0; i < (int)_process.size(); ++i) {
468        for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
469          Node target = graph->target(it);
470          Value relaxed =
471            OperationTraits::plus((*_dist)[_process[i]], (*length)[it]);
472          if (OperationTraits::less(relaxed, (*_dist)[target])) {
473            _pred->set(target, it);
474            _dist->set(target, relaxed);
477              nextProcess.push_back(target);
478            }
479          }
480        }
481      }
482      _process.swap(nextProcess);
483      return _process.empty();
484    }
485
486    /// \brief Executes the algorithm.
487    ///
488    /// \pre init() must be called and at least one node should be added
489    /// with addSource() before using this function.
490    ///
491    /// This method runs the %BelmannFord algorithm from the root node(s)
492    /// in order to compute the shortest path to each node. The algorithm
493    /// computes
494    /// - The shortest path tree.
495    /// - The distance of each node from the root(s).
496    void start() {
497      int num = countNodes(*graph) - 1;
498      for (int i = 0; i < num; ++i) {
499        if (processNextWeakRound()) break;
500      }
501    }
502
503    /// \brief Executes the algorithm and checks the negative cycles.
504    ///
505    /// \pre init() must be called and at least one node should be added
506    /// with addSource() before using this function. If there is
507    /// a negative cycles in the graph it gives back false.
508    ///
509    /// This method runs the %BelmannFord algorithm from the root node(s)
510    /// in order to compute the shortest path to each node. The algorithm
511    /// computes
512    /// - The shortest path tree.
513    /// - The distance of each node from the root(s).
514    bool checkedStart() {
515      int num = countNodes(*graph);
516      for (int i = 0; i < num; ++i) {
517        if (processNextWeakRound()) return true;
518      }
519      return false;
520    }
521
522    /// \brief Executes the algorithm with path length limit.
523    ///
524    /// \pre init() must be called and at least one node should be added
525    /// with addSource() before using this function.
526    ///
527    /// This method runs the %BelmannFord algorithm from the root node(s)
528    /// in order to compute the shortest path with at most \c length edge
529    /// long paths to each node. The algorithm computes
530    /// - The shortest path tree.
531    /// - The limited distance of each node from the root(s).
532    void limitedStart(int length) {
533      for (int i = 0; i < length; ++i) {
534        if (processNextRound()) break;
535      }
536    }
537
538    /// \brief Runs %BelmannFord algorithm from node \c s.
539    ///
540    /// This method runs the %BelmannFord algorithm from a root node \c s
541    /// in order to compute the shortest path to each node. The algorithm
542    /// computes
543    /// - The shortest path tree.
544    /// - The distance of each node from the root.
545    ///
546    /// \note d.run(s) is just a shortcut of the following code.
547    /// \code
548    ///  d.init();
550    ///  d.start();
551    /// \endcode
552    void run(Node s) {
553      init();
555      start();
556    }
557
558    ///@}
559
560    /// \name Query Functions
561    /// The result of the %BelmannFord algorithm can be obtained using these
562    /// functions.\n
563    /// Before the use of these functions,
564    /// either run() or start() must be called.
565
566    ///@{
567
568    /// \brief Copies the shortest path to \c t into \c p
569    ///
570    /// This function copies the shortest path to \c t into \c p.
571    /// If it \c t is a source itself or unreachable, then it does not
572    /// alter \c p.
573    ///
574    /// \return Returns \c true if a path to \c t was actually copied to \c p,
575    /// \c false otherwise.
576    /// \sa DirPath
577    template <typename Path>
578    bool getPath(Path &p, Node t) {
579      if(reached(t)) {
580        p.clear();
581        typename Path::Builder b(p);
582        for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
583          b.pushFront(predEdge(t));
584        b.commit();
585        return true;
586      }
587      return false;
588    }
589
590    /// \brief The distance of a node from the root.
591    ///
592    /// Returns the distance of a node from the root.
593    /// \pre \ref run() must be called before using this function.
594    /// \warning If node \c v in unreachable from the root the return value
595    /// of this funcion is undefined.
596    Value dist(Node v) const { return (*_dist)[v]; }
597
598    /// \brief Returns the 'previous edge' of the shortest path tree.
599    ///
600    /// For a node \c v it returns the 'previous edge' of the shortest path
601    /// tree, i.e. it returns the last edge of a shortest path from the root
602    /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
603    /// if \c v=s. The shortest path tree used here is equal to the shortest
604    /// path tree used in \ref predNode().
605    /// \pre \ref run() must be called before using
606    /// this function.
607    Edge predEdge(Node v) const { return (*_pred)[v]; }
608
609    /// \brief Returns the 'previous node' of the shortest path tree.
610    ///
611    /// For a node \c v it returns the 'previous node' of the shortest path
612    /// tree, i.e. it returns the last but one node from a shortest path from
613    /// the root to \c /v. It is INVALID if \c v is unreachable from the root
614    /// or if \c v=s. The shortest path tree used here is equal to the
615    /// shortest path tree used in \ref predEdge().  \pre \ref run() must be
616    /// called before using this function.
617    Node predNode(Node v) const {
618      return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
619    }
620
621    /// \brief Returns a reference to the NodeMap of distances.
622    ///
623    /// Returns a reference to the NodeMap of distances. \pre \ref run() must
624    /// be called before using this function.
625    const DistMap &distMap() const { return *_dist;}
626
627    /// \brief Returns a reference to the shortest path tree map.
628    ///
629    /// Returns a reference to the NodeMap of the edges of the
630    /// shortest path tree.
631    /// \pre \ref run() must be called before using this function.
632    const PredMap &predMap() const { return *_pred; }
633
634    /// \brief Checks if a node is reachable from the root.
635    ///
636    /// Returns \c true if \c v is reachable from the root.
637    /// \pre \ref run() must be called before using this function.
638    ///
639    bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
640
641    ///@}
642  };
643
644  /// \brief Default traits class of BelmannFord function.
645  ///
646  /// Default traits class of BelmannFord function.
647  /// \param _Graph Graph type.
648  /// \param _LengthMap Type of length map.
649  template <typename _Graph, typename _LengthMap>
650  struct BelmannFordWizardDefaultTraits {
651    /// \brief The graph type the algorithm runs on.
652    typedef _Graph Graph;
653
654    /// \brief The type of the map that stores the edge lengths.
655    ///
656    /// The type of the map that stores the edge lengths.
658    typedef _LengthMap LengthMap;
659
660    /// \brief The value type of the length map.
661    typedef typename _LengthMap::Value Value;
662
663    /// \brief Operation traits for belmann-ford algorithm.
664    ///
665    /// It defines the infinity type on the given Value type
666    /// and the used operation.
667    /// \see BelmannFordDefaultOperationTraits
668    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
669
670    /// \brief The type of the map that stores the last
671    /// edges of the shortest paths.
672    ///
673    /// The type of the map that stores the last
674    /// edges of the shortest paths.
675    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
676    typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
677
678    /// \brief Instantiates a PredMap.
679    ///
680    /// This function instantiates a \ref PredMap.
681    static PredMap *createPredMap(const _Graph &) {
682      return new PredMap();
683    }
684    /// \brief The type of the map that stores the dists of the nodes.
685    ///
686    /// The type of the map that stores the dists of the nodes.
687    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
688    typedef NullMap<typename Graph::Node, Value> DistMap;
689    /// \brief Instantiates a DistMap.
690    ///
691    /// This function instantiates a \ref DistMap.
692    static DistMap *createDistMap(const _Graph &) {
693      return new DistMap();
694    }
695  };
696
697  /// \brief Default traits used by \ref BelmannFordWizard
698  ///
699  /// To make it easier to use BelmannFord algorithm
700  /// we have created a wizard class.
701  /// This \ref BelmannFordWizard class needs default traits,
702  /// as well as the \ref BelmannFord class.
703  /// The \ref BelmannFordWizardBase is a class to be the default traits of the
704  /// \ref BelmannFordWizard class.
705  /// \todo More named parameters are required...
706  template<class _Graph,class _LengthMap>
707  class BelmannFordWizardBase
708    : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> {
709
710    typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
711  protected:
712    /// Type of the nodes in the graph.
713    typedef typename Base::Graph::Node Node;
714
715    /// Pointer to the underlying graph.
716    void *_graph;
717    /// Pointer to the length map
718    void *_length;
719    ///Pointer to the map of predecessors edges.
720    void *_pred;
721    ///Pointer to the map of distances.
722    void *_dist;
723    ///Pointer to the source node.
724    Node _source;
725
726    public:
727    /// Constructor.
728
729    /// This constructor does not require parameters, therefore it initiates
730    /// all of the attributes to default values (0, INVALID).
731    BelmannFordWizardBase() : _graph(0), _length(0), _pred(0),
732                           _dist(0), _source(INVALID) {}
733
734    /// Constructor.
735
736    /// This constructor requires some parameters,
737    /// listed in the parameters list.
738    /// Others are initiated to 0.
739    /// \param graph is the initial value of  \ref _graph
740    /// \param length is the initial value of  \ref _length
741    /// \param source is the initial value of  \ref _source
742    BelmannFordWizardBase(const _Graph& graph,
743                          const _LengthMap& length,
744                          Node source = INVALID) :
745      _graph((void *)&graph), _length((void *)&length), _pred(0),
746      _dist(0), _source(source) {}
747
748  };
749
750  /// A class to make the usage of BelmannFord algorithm easier
751
752  /// This class is created to make it easier to use BelmannFord algorithm.
753  /// It uses the functions and features of the plain \ref BelmannFord,
754  /// but it is much simpler to use it.
755  ///
756  /// Simplicity means that the way to change the types defined
757  /// in the traits class is based on functions that returns the new class
758  /// and not on templatable built-in classes.
759  /// When using the plain \ref BelmannFord
760  /// the new class with the modified type comes from
761  /// the original class by using the ::
762  /// operator. In the case of \ref BelmannFordWizard only
763  /// a function have to be called and it will
764  /// return the needed class.
765  ///
766  /// It does not have own \ref run method. When its \ref run method is called
767  /// it initiates a plain \ref BelmannFord class, and calls the \ref
768  /// BelmannFord::run method of it.
769  template<class _Traits>
770  class BelmannFordWizard : public _Traits {
771    typedef _Traits Base;
772
773    ///The type of the underlying graph.
774    typedef typename _Traits::Graph Graph;
775
776    typedef typename Graph::Node Node;
777    typedef typename Graph::NodeIt NodeIt;
778    typedef typename Graph::Edge Edge;
779    typedef typename Graph::OutEdgeIt EdgeIt;
780
781    ///The type of the map that stores the edge lengths.
782    typedef typename _Traits::LengthMap LengthMap;
783
784    ///The type of the length of the edges.
785    typedef typename LengthMap::Value Value;
786
787    ///\brief The type of the map that stores the last
788    ///edges of the shortest paths.
789    typedef typename _Traits::PredMap PredMap;
790
791    ///The type of the map that stores the dists of the nodes.
792    typedef typename _Traits::DistMap DistMap;
793
794  public:
795    /// Constructor.
796    BelmannFordWizard() : _Traits() {}
797
798    /// \brief Constructor that requires parameters.
799    ///
800    /// Constructor that requires parameters.
801    /// These parameters will be the default values for the traits class.
802    BelmannFordWizard(const Graph& graph, const LengthMap& length,
803                      Node source = INVALID)
804      : _Traits(graph, length, source) {}
805
806    /// \brief Copy constructor
807    BelmannFordWizard(const _Traits &b) : _Traits(b) {}
808
809    ~BelmannFordWizard() {}
810
811    /// \brief Runs BelmannFord algorithm from a given node.
812    ///
813    /// Runs BelmannFord algorithm from a given node.
814    /// The node can be given by the \ref source function.
815    void run() {
816      if(Base::_source == INVALID) throw UninitializedParameter();
817      BelmannFord<Graph,LengthMap,_Traits>
818        bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
819      if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
820      if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
821      bf.run(Base::_source);
822    }
823
824    /// \brief Runs BelmannFord algorithm from the given node.
825    ///
826    /// Runs BelmannFord algorithm from the given node.
827    /// \param s is the given source.
828    void run(Node source) {
829      Base::_source = source;
830      run();
831    }
832
833    template<class T>
834    struct DefPredMapBase : public Base {
835      typedef T PredMap;
836      static PredMap *createPredMap(const Graph &) { return 0; };
837      DefPredMapBase(const _Traits &b) : _Traits(b) {}
838    };
839
840    ///\brief \ref named-templ-param "Named parameter"
841    ///function for setting PredMap type
842    ///
843    /// \ref named-templ-param "Named parameter"
844    ///function for setting PredMap type
845    ///
846    template<class T>
847    BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
848    {
849      Base::_pred=(void *)&t;
850      return BelmannFordWizard<DefPredMapBase<T> >(*this);
851    }
852
853    template<class T>
854    struct DefDistMapBase : public Base {
855      typedef T DistMap;
856      static DistMap *createDistMap(const Graph &) { return 0; };
857      DefDistMapBase(const _Traits &b) : _Traits(b) {}
858    };
859
860    ///\brief \ref named-templ-param "Named parameter"
861    ///function for setting DistMap type
862    ///
863    /// \ref named-templ-param "Named parameter"
864    ///function for setting DistMap type
865    ///
866    template<class T>
867    BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
868      Base::_dist=(void *)&t;
869      return BelmannFordWizard<DefDistMapBase<T> >(*this);
870    }
871
872    template<class T>
873    struct DefOperationTraitsBase : public Base {
874      typedef T OperationTraits;
875      DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
876    };
877
878    ///\brief \ref named-templ-param "Named parameter"
879    ///function for setting OperationTraits type
880    ///
881    /// \ref named-templ-param "Named parameter"
882    ///function for setting OperationTraits type
883    ///
884    template<class T>
885    BelmannFordWizard<DefOperationTraitsBase<T> > distMap() {
886      return BelmannFordWizard<DefDistMapBase<T> >(*this);
887    }
888
889    /// \brief Sets the source node, from which the BelmannFord algorithm runs.
890    ///
891    /// Sets the source node, from which the BelmannFord algorithm runs.
892    /// \param s is the source node.
893    BelmannFordWizard<_Traits>& source(Node source) {
894      Base::_source = source;
895      return *this;
896    }
897
898  };
899
900  /// \brief Function type interface for BelmannFord algorithm.
901  ///
902  /// \ingroup flowalgs
903  /// Function type interface for BelmannFord algorithm.
904  ///
905  /// This function also has several \ref named-templ-func-param
906  /// "named parameters", they are declared as the members of class
907  /// \ref BelmannFordWizard.
908  /// The following
909  /// example shows how to use these parameters.
910  /// \code
911  /// belmannford(g,length,source).predMap(preds).run();
912  /// \endcode
913  /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
914  /// to the end of the parameter list.
915  /// \sa BelmannFordWizard
916  /// \sa BelmannFord
917  template<class _Graph, class _LengthMap>
918  BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
919  belmannFord(const _Graph& graph,
920              const _LengthMap& length,
921              typename _Graph::Node source = INVALID) {
922    return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
923      (graph, length, source);
924  }
925
926} //END OF NAMESPACE LEMON
927
928#endif
929
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