# source:lemon-0.x/lemon/belmann_ford.h@1781:dca4c8a54e0a

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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);
402        }
403      }
404    }
405
406    /// \brief Adds a new source node.
407    ///
408    /// The optional second parameter is the initial distance of the node.
409    /// It just sets the distance of the node to the given value.
410    void addSource(Node source, Value dst = OperationTraits::zero()) {
411      _dist->set(source, dst);
413        _process.push_back(source);
415      }
416    }
417
418    /// \brief Executes one round from the belmann ford algorithm.
419    ///
420    /// If the algoritm calculated the distances in the previous round
421    /// strictly for all at most k length pathes then it will calculate the
422    /// distances strictly for all at most k + 1 length pathes. With k
423    /// iteration this function calculates the at most k length pathes.
424    bool processNextRound() {
425      for (int i = 0; i < (int)_process.size(); ++i) {
427      }
428      std::vector<Node> nextProcess;
429      std::vector<Value> values(_process.size());
430      for (int i = 0; i < (int)_process.size(); ++i) {
431        values[i] = _dist[_process[i]];
432      }
433      for (int i = 0; i < (int)_process.size(); ++i) {
434        for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
435          Node target = graph->target(it);
436          Value relaxed = OperationTraits::plus(values[i], (*length)[it]);
437          if (OperationTraits::less(relaxed, (*_dist)[target])) {
438            _pred->set(target, it);
439            _dist->set(target, relaxed);
442              nextProcess.push_back(target);
443            }
444          }
445        }
446      }
447      _process.swap(nextProcess);
448      return _process.empty();
449    }
450
451    /// \brief Executes one weak round from the belmann ford algorithm.
452    ///
453    /// If the algorithm calculated the distances in the
454    /// previous round at least for all at most k length pathes then it will
455    /// calculate the distances at least for all at most k + 1 length pathes.
456    /// This function does not make possible to calculate strictly the
457    /// at most k length minimal pathes, this way it called just weak round.
458    bool processNextWeakRound() {
459      for (int i = 0; i < (int)_process.size(); ++i) {
461      }
462      std::vector<Node> nextProcess;
463      for (int i = 0; i < (int)_process.size(); ++i) {
464        for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
465          Node target = graph->target(it);
466          Value relaxed =
467            OperationTraits::plus((*_dist)[_process[i]], (*length)[it]);
468          if (OperationTraits::less(relaxed, (*_dist)[target])) {
469            _pred->set(target, it);
470            _dist->set(target, relaxed);
473              nextProcess.push_back(target);
474            }
475          }
476        }
477      }
478      for (int i = 0; i < (int)nextProcess.size(); ++i) {
480      }
481      _process.swap(nextProcess);
482      return _process.empty();
483    }
484
485    /// \brief Executes the algorithm.
486    ///
487    /// \pre init() must be called and at least one node should be added
488    /// with addSource() before using this function.
489    ///
490    /// This method runs the %BelmannFord algorithm from the root node(s)
491    /// in order to compute the shortest path to each node. The algorithm
492    /// computes
493    /// - The shortest path tree.
494    /// - The distance of each node from the root(s).
495    void start() {
496      int num = countNodes(*graph) - 1;
497      for (int i = 0; i < num; ++i) {
498        if (processNextWeakRound()) break;
499      }
500    }
501
502    /// \brief Executes the algorithm and checks the negative cycles.
503    ///
504    /// \pre init() must be called and at least one node should be added
505    /// with addSource() before using this function. If there is
506    /// a negative cycles in the graph it gives back false.
507    ///
508    /// This method runs the %BelmannFord algorithm from the root node(s)
509    /// in order to compute the shortest path to each node. The algorithm
510    /// computes
511    /// - The shortest path tree.
512    /// - The distance of each node from the root(s).
513    bool checkedStart() {
514      int num = countNodes(*graph);
515      for (int i = 0; i < num; ++i) {
516        if (processNextWeakRound()) return true;
517      }
518      return false;
519    }
520
521    /// \brief Executes the algorithm with path length limit.
522    ///
523    /// \pre init() must be called and at least one node should be added
524    /// with addSource() before using this function.
525    ///
526    /// This method runs the %BelmannFord algorithm from the root node(s)
527    /// in order to compute the shortest path with at most \c length edge
528    /// long pathes to each node. The algorithm computes
529    /// - The shortest path tree.
530    /// - The limited distance of each node from the root(s).
531    void limitedStart(int length) {
532      for (int i = 0; i < length; ++i) {
533        if (processNextRound()) break;
534      }
535    }
536
537    /// \brief Runs %BelmannFord algorithm from node \c s.
538    ///
539    /// This method runs the %BelmannFord algorithm from a root node \c s
540    /// in order to compute the shortest path to each node. The algorithm
541    /// computes
542    /// - The shortest path tree.
543    /// - The distance of each node from the root.
544    ///
545    /// \note d.run(s) is just a shortcut of the following code.
546    /// \code
547    ///  d.init();
549    ///  d.start();
550    /// \endcode
551    void run(Node s) {
552      init();
554      start();
555    }
556
557    ///@}
558
559    /// \name Query Functions
560    /// The result of the %BelmannFord algorithm can be obtained using these
561    /// functions.\n
562    /// Before the use of these functions,
563    /// either run() or start() must be called.
564
565    ///@{
566
567    /// \brief Copies the shortest path to \c t into \c p
568    ///
569    /// This function copies the shortest path to \c t into \c p.
570    /// If it \c t is a source itself or unreachable, then it does not
571    /// alter \c p.
572    ///
573    /// \return Returns \c true if a path to \c t was actually copied to \c p,
574    /// \c false otherwise.
575    /// \sa DirPath
576    template <typename Path>
577    bool getPath(Path &p, Node t) {
578      if(reached(t)) {
579        p.clear();
580        typename Path::Builder b(p);
581        for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
582          b.pushFront(predEdge(t));
583        b.commit();
584        return true;
585      }
586      return false;
587    }
588
589    /// \brief The distance of a node from the root.
590    ///
591    /// Returns the distance of a node from the root.
592    /// \pre \ref run() must be called before using this function.
593    /// \warning If node \c v in unreachable from the root the return value
594    /// of this funcion is undefined.
595    Value dist(Node v) const { return (*_dist)[v]; }
596
597    /// \brief Returns the 'previous edge' of the shortest path tree.
598    ///
599    /// For a node \c v it returns the 'previous edge' of the shortest path
600    /// tree, i.e. it returns the last edge of a shortest path from the root
601    /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
602    /// if \c v=s. The shortest path tree used here is equal to the shortest
603    /// path tree used in \ref predNode().
604    /// \pre \ref run() must be called before using
605    /// this function.
606    Edge predEdge(Node v) const { return (*_pred)[v]; }
607
608    /// \brief Returns the 'previous node' of the shortest path tree.
609    ///
610    /// For a node \c v it returns the 'previous node' of the shortest path
611    /// tree, i.e. it returns the last but one node from a shortest path from
612    /// the root to \c /v. It is INVALID if \c v is unreachable from the root
613    /// or if \c v=s. The shortest path tree used here is equal to the
614    /// shortest path tree used in \ref predEdge().  \pre \ref run() must be
615    /// called before using this function.
616    Node predNode(Node v) const {
617      return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
618    }
619
620    /// \brief Returns a reference to the NodeMap of distances.
621    ///
622    /// Returns a reference to the NodeMap of distances. \pre \ref run() must
623    /// be called before using this function.
624    const DistMap &distMap() const { return *_dist;}
625
626    /// \brief Returns a reference to the shortest path tree map.
627    ///
628    /// Returns a reference to the NodeMap of the edges of the
629    /// shortest path tree.
630    /// \pre \ref run() must be called before using this function.
631    const PredMap &predMap() const { return *_pred; }
632
633    /// \brief Checks if a node is reachable from the root.
634    ///
635    /// Returns \c true if \c v is reachable from the root.
636    /// \pre \ref run() must be called before using this function.
637    ///
638    bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
639
640    ///@}
641  };
642
643  /// \brief Default traits class of BelmannFord function.
644  ///
645  /// Default traits class of BelmannFord function.
646  /// \param _Graph Graph type.
647  /// \param _LengthMap Type of length map.
648  template <typename _Graph, typename _LengthMap>
649  struct BelmannFordWizardDefaultTraits {
650    /// \brief The graph type the algorithm runs on.
651    typedef _Graph Graph;
652
653    /// \brief The type of the map that stores the edge lengths.
654    ///
655    /// The type of the map that stores the edge lengths.
657    typedef _LengthMap LengthMap;
658
659    /// \brief The value type of the length map.
660    typedef typename _LengthMap::Value Value;
661
662    /// \brief Operation traits for belmann-ford algorithm.
663    ///
664    /// It defines the infinity type on the given Value type
665    /// and the used operation.
666    /// \see BelmannFordDefaultOperationTraits
667    typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
668
669    /// \brief The type of the map that stores the last
670    /// edges of the shortest paths.
671    ///
672    /// The type of the map that stores the last
673    /// edges of the shortest paths.
674    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
675    typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
676
677    /// \brief Instantiates a PredMap.
678    ///
679    /// This function instantiates a \ref PredMap.
680    static PredMap *createPredMap(const _Graph &) {
681      return new PredMap();
682    }
683    /// \brief The type of the map that stores the dists of the nodes.
684    ///
685    /// The type of the map that stores the dists of the nodes.
686    /// It must meet the \ref concept::WriteMap "WriteMap" concept.
687    typedef NullMap<typename Graph::Node, Value> DistMap;
688    /// \brief Instantiates a DistMap.
689    ///
690    /// This function instantiates a \ref DistMap.
691    static DistMap *createDistMap(const _Graph &) {
692      return new DistMap();
693    }
694  };
695
696  /// \brief Default traits used by \ref BelmannFordWizard
697  ///
698  /// To make it easier to use BelmannFord algorithm
699  /// we have created a wizard class.
700  /// This \ref BelmannFordWizard class needs default traits,
701  /// as well as the \ref BelmannFord class.
702  /// The \ref BelmannFordWizardBase is a class to be the default traits of the
703  /// \ref BelmannFordWizard class.
704  /// \todo More named parameters are required...
705  template<class _Graph,class _LengthMap>
706  class BelmannFordWizardBase
707    : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> {
708
709    typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
710  protected:
711    /// Type of the nodes in the graph.
712    typedef typename Base::Graph::Node Node;
713
714    /// Pointer to the underlying graph.
715    void *_graph;
716    /// Pointer to the length map
717    void *_length;
718    ///Pointer to the map of predecessors edges.
719    void *_pred;
720    ///Pointer to the map of distances.
721    void *_dist;
722    ///Pointer to the source node.
723    Node _source;
724
725    public:
726    /// Constructor.
727
728    /// This constructor does not require parameters, therefore it initiates
729    /// all of the attributes to default values (0, INVALID).
730    BelmannFordWizardBase() : _graph(0), _length(0), _pred(0),
731                           _dist(0), _source(INVALID) {}
732
733    /// Constructor.
734
735    /// This constructor requires some parameters,
736    /// listed in the parameters list.
737    /// Others are initiated to 0.
738    /// \param graph is the initial value of  \ref _graph
739    /// \param length is the initial value of  \ref _length
740    /// \param source is the initial value of  \ref _source
741    BelmannFordWizardBase(const _Graph& graph,
742                          const _LengthMap& length,
743                          Node source = INVALID) :
744      _graph((void *)&graph), _length((void *)&length), _pred(0),
745      _dist(0), _source(source) {}
746
747  };
748
749  /// A class to make the usage of BelmannFord algorithm easier
750
751  /// This class is created to make it easier to use BelmannFord algorithm.
752  /// It uses the functions and features of the plain \ref BelmannFord,
753  /// but it is much simpler to use it.
754  ///
755  /// Simplicity means that the way to change the types defined
756  /// in the traits class is based on functions that returns the new class
757  /// and not on templatable built-in classes.
758  /// When using the plain \ref BelmannFord
759  /// the new class with the modified type comes from
760  /// the original class by using the ::
761  /// operator. In the case of \ref BelmannFordWizard only
762  /// a function have to be called and it will
763  /// return the needed class.
764  ///
765  /// It does not have own \ref run method. When its \ref run method is called
766  /// it initiates a plain \ref BelmannFord class, and calls the \ref
767  /// BelmannFord::run method of it.
768  template<class _Traits>
769  class BelmannFordWizard : public _Traits {
770    typedef _Traits Base;
771
772    ///The type of the underlying graph.
773    typedef typename _Traits::Graph Graph;
774
775    typedef typename Graph::Node Node;
776    typedef typename Graph::NodeIt NodeIt;
777    typedef typename Graph::Edge Edge;
778    typedef typename Graph::OutEdgeIt EdgeIt;
779
780    ///The type of the map that stores the edge lengths.
781    typedef typename _Traits::LengthMap LengthMap;
782
783    ///The type of the length of the edges.
784    typedef typename LengthMap::Value Value;
785
786    ///\brief The type of the map that stores the last
787    ///edges of the shortest paths.
788    typedef typename _Traits::PredMap PredMap;
789
790    ///The type of the map that stores the dists of the nodes.
791    typedef typename _Traits::DistMap DistMap;
792
793  public:
794    /// Constructor.
795    BelmannFordWizard() : _Traits() {}
796
797    /// \brief Constructor that requires parameters.
798    ///
799    /// Constructor that requires parameters.
800    /// These parameters will be the default values for the traits class.
801    BelmannFordWizard(const Graph& graph, const LengthMap& length,
802                      Node source = INVALID)
803      : _Traits(graph, length, source) {}
804
805    /// \brief Copy constructor
806    BelmannFordWizard(const _Traits &b) : _Traits(b) {}
807
808    ~BelmannFordWizard() {}
809
810    /// \brief Runs BelmannFord algorithm from a given node.
811    ///
812    /// Runs BelmannFord algorithm from a given node.
813    /// The node can be given by the \ref source function.
814    void run() {
815      if(Base::_source == INVALID) throw UninitializedParameter();
816      BelmannFord<Graph,LengthMap,_Traits>
817        bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
818      if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
819      if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
820      bf.run(Base::_source);
821    }
822
823    /// \brief Runs BelmannFord algorithm from the given node.
824    ///
825    /// Runs BelmannFord algorithm from the given node.
826    /// \param s is the given source.
827    void run(Node source) {
828      Base::_source = source;
829      run();
830    }
831
832    template<class T>
833    struct DefPredMapBase : public Base {
834      typedef T PredMap;
835      static PredMap *createPredMap(const Graph &) { return 0; };
836      DefPredMapBase(const _Traits &b) : _Traits(b) {}
837    };
838
839    ///\brief \ref named-templ-param "Named parameter"
840    ///function for setting PredMap type
841    ///
842    /// \ref named-templ-param "Named parameter"
843    ///function for setting PredMap type
844    ///
845    template<class T>
846    BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
847    {
848      Base::_pred=(void *)&t;
849      return BelmannFordWizard<DefPredMapBase<T> >(*this);
850    }
851
852    template<class T>
853    struct DefDistMapBase : public Base {
854      typedef T DistMap;
855      static DistMap *createDistMap(const Graph &) { return 0; };
856      DefDistMapBase(const _Traits &b) : _Traits(b) {}
857    };
858
859    ///\brief \ref named-templ-param "Named parameter"
860    ///function for setting DistMap type
861    ///
862    /// \ref named-templ-param "Named parameter"
863    ///function for setting DistMap type
864    ///
865    template<class T>
866    BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
867      Base::_dist=(void *)&t;
868      return BelmannFordWizard<DefDistMapBase<T> >(*this);
869    }
870
871    template<class T>
872    struct DefOperationTraitsBase : public Base {
873      typedef T OperationTraits;
874      DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
875    };
876
877    ///\brief \ref named-templ-param "Named parameter"
878    ///function for setting OperationTraits type
879    ///
880    /// \ref named-templ-param "Named parameter"
881    ///function for setting OperationTraits type
882    ///
883    template<class T>
884    BelmannFordWizard<DefOperationTraitsBase<T> > distMap() {
885      return BelmannFordWizard<DefDistMapBase<T> >(*this);
886    }
887
888    /// \brief Sets the source node, from which the BelmannFord algorithm runs.
889    ///
890    /// Sets the source node, from which the BelmannFord algorithm runs.
891    /// \param s is the source node.
892    BelmannFordWizard<_Traits>& source(Node source) {
893      Base::_source = source;
894      return *this;
895    }
896
897  };
898
899  /// \brief Function type interface for BelmannFord algorithm.
900  ///
901  /// \ingroup flowalgs
902  /// Function type interface for BelmannFord algorithm.
903  ///
904  /// This function also has several \ref named-templ-func-param
905  /// "named parameters", they are declared as the members of class
906  /// \ref BelmannFordWizard.
907  /// The following
908  /// example shows how to use these parameters.
909  /// \code
910  /// belmannford(g,length,source).predMap(preds).run();
911  /// \endcode
912  /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
913  /// to the end of the parameter list.
914  /// \sa BelmannFordWizard
915  /// \sa BelmannFord
916  template<class _Graph, class _LengthMap>
917  BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
918  belmannFord(const _Graph& graph,
919              const _LengthMap& length,
920              typename _Graph::Node source = INVALID) {
921    return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
922      (graph, length, source);
923  }
924
925} //END OF NAMESPACE LEMON
926
927#endif
928
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