2 * lemon/belmann_ford.h - Part of LEMON, a generic C++ optimization library
4 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Research Group on Combinatorial Optimization, EGRES).
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.
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
17 #ifndef LEMON_BELMANN_FORD_H
18 #define LEMON_BELMANN_FORD_H
22 /// \brief BelmannFord algorithm.
25 #include <lemon/list_graph.h>
26 #include <lemon/invalid.h>
27 #include <lemon/error.h>
28 #include <lemon/maps.h>
34 /// \brief Default OperationTraits for the BelmannFord algorithm class.
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
43 bool has_infinity = std::numeric_limits<Value>::has_infinity>
44 struct BelmannFordDefaultOperationTraits {
45 /// \brief Gives back the zero value of the type.
47 return static_cast<Value>(0);
49 /// \brief Gives back the positive infinity value of the type.
50 static Value infinity() {
51 return std::numeric_limits<Value>::infinity();
53 /// \brief Gives back the sum of the given two elements.
54 static Value plus(const Value& left, const Value& right) {
57 /// \brief Gives back true only if the first value less than the second.
58 static bool less(const Value& left, const Value& right) {
63 template <typename Value>
64 struct BelmannFordDefaultOperationTraits<Value, false> {
66 return static_cast<Value>(0);
68 static Value infinity() {
69 return std::numeric_limits<Value>::max();
71 static Value plus(const Value& left, const Value& right) {
72 if (left == infinity() || right == infinity()) return infinity();
75 static bool less(const Value& left, const Value& right) {
80 /// \brief Default traits class of BelmannFord class.
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.
90 /// \brief The type of the map that stores the edge lengths.
92 /// The type of the map that stores the edge lengths.
93 /// It must meet the \ref concept::ReadMap "ReadMap" concept.
94 typedef _LengthMap LengthMap;
96 // The type of the length of the edges.
97 typedef typename _LengthMap::Value Value;
99 /// \brief Operation traits for belmann-ford algorithm.
101 /// It defines the infinity type on the given Value type
102 /// and the used operation.
103 /// \see BelmannFordDefaultOperationTraits
104 typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
106 /// \brief The type of the map that stores the last edges of the
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.
113 typedef typename Graph::template NodeMap<typename _Graph::Edge> PredMap;
115 /// \brief Instantiates a PredMap.
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);
124 /// \brief The type of the map that stores the dists of the nodes.
126 /// The type of the map that stores the dists of the nodes.
127 /// It must meet the \ref concept::WriteMap "WriteMap" concept.
129 typedef typename Graph::template NodeMap<typename _LengthMap::Value>
132 /// \brief Instantiates a DistMap.
134 /// This function instantiates a \ref DistMap.
135 /// \param G is the graph, to which we would like to define the
137 static DistMap *createDistMap(const _Graph& graph) {
138 return new DistMap(graph);
143 /// \brief %BelmannFord algorithm class.
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
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.
157 /// The complexity of the algorithm is O(n * e).
159 /// The type of the length is determined by the
160 /// \ref concept::ReadMap::Value "Value" of the length map.
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
175 /// \author Balazs Dezso
178 template <typename _Graph, typename _LengthMap, typename _Traits>
180 template <typename _Graph=ListGraph,
181 typename _LengthMap=typename _Graph::template EdgeMap<int>,
182 typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> >
187 /// \brief \ref Exception for uninitialized parameters.
189 /// This error represents problems in the initialization
190 /// of the parameters of the algorithms.
192 class UninitializedParameter : public lemon::UninitializedParameter {
194 virtual const char* exceptionName() const {
195 return "lemon::BelmannFord::UninitializedParameter";
199 typedef _Traits Traits;
200 ///The type of the underlying graph.
201 typedef typename _Traits::Graph Graph;
203 typedef typename Graph::Node Node;
204 typedef typename Graph::NodeIt NodeIt;
205 typedef typename Graph::Edge Edge;
206 typedef typename Graph::OutEdgeIt OutEdgeIt;
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;
220 /// Pointer to the underlying graph.
222 /// Pointer to the length map
223 const LengthMap *length;
224 ///Pointer to the map of predecessors edges.
226 ///Indicates if \ref _pred is locally allocated (\c true) or not.
228 ///Pointer to the map of distances.
230 ///Indicates if \ref _dist is locally allocated (\c true) or not.
233 typedef typename Graph::template NodeMap<bool> MaskMap;
236 std::vector<Node> _process;
238 /// Creates the maps if necessary.
242 _pred = Traits::createPredMap(*graph);
246 _dist = Traits::createDistMap(*graph);
248 _mask = new MaskMap(*graph, false);
253 typedef BelmannFord Create;
255 /// \name Named template parameters
260 struct DefPredMapTraits : public Traits {
262 static PredMap *createPredMap(const Graph&) {
263 throw UninitializedParameter();
267 /// \brief \ref named-templ-param "Named parameter" for setting PredMap
269 /// \ref named-templ-param "Named parameter" for setting PredMap type
273 typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create;
277 struct DefDistMapTraits : public Traits {
279 static DistMap *createDistMap(const Graph& graph) {
280 throw UninitializedParameter();
284 /// \brief \ref named-templ-param "Named parameter" for setting DistMap
287 /// \ref named-templ-param "Named parameter" for setting DistMap type
291 : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > {
292 typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create;
296 struct DefOperationTraitsTraits : public Traits {
297 typedef T OperationTraits;
300 /// \brief \ref named-templ-param "Named parameter" for setting
301 /// OperationTraits type
303 /// \ref named-templ-param "Named parameter" for setting OperationTraits
306 struct DefOperationTraits
307 : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
308 typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
320 /// \brief Constructor.
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) {}
331 if(local_pred) delete _pred;
332 if(local_dist) delete _dist;
336 /// \brief Sets the length map.
338 /// Sets the length map.
339 /// \return \c (*this)
340 BelmannFord &lengthMap(const LengthMap &m) {
345 /// \brief Sets the map storing the predecessor edges.
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) {
361 /// \brief Sets the map storing the distances calculated by the algorithm.
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) {
377 /// \name Execution control
378 /// The simplest way to execute the algorithm is to use
379 /// one of the member functions called \c run(...).
381 /// If you need more control on the execution,
382 /// first you must call \ref init(), then you can add several source nodes
383 /// with \ref addSource().
384 /// Finally \ref start() will perform the actual path
389 /// \brief Initializes the internal data structures.
391 /// Initializes the internal data structures.
392 void init(const Value value = OperationTraits::infinity()) {
394 for (NodeIt it(*graph); it != INVALID; ++it) {
395 _pred->set(it, INVALID);
396 _dist->set(it, value);
399 if (OperationTraits::less(value, OperationTraits::infinity())) {
400 for (NodeIt it(*graph); it != INVALID; ++it) {
401 _process.push_back(it);
406 /// \brief Adds a new source node.
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);
412 if (!(*_mask)[source]) {
413 _process.push_back(source);
414 _mask->set(source, true);
418 /// \brief Executes one round from the belmann ford algorithm.
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) {
426 _mask->set(_process[i], false);
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]];
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);
440 if (!(*_mask)[target]) {
441 _mask->set(target, true);
442 nextProcess.push_back(target);
447 _process.swap(nextProcess);
448 return _process.empty();
451 /// \brief Executes one weak round from the belmann ford algorithm.
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) {
460 _mask->set(_process[i], false);
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);
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);
471 if (!(*_mask)[target]) {
472 _mask->set(target, true);
473 nextProcess.push_back(target);
478 for (int i = 0; i < (int)nextProcess.size(); ++i) {
479 _mask->set(nextProcess[i], false);
481 _process.swap(nextProcess);
482 return _process.empty();
485 /// \brief Executes the algorithm.
487 /// \pre init() must be called and at least one node should be added
488 /// with addSource() before using this function.
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
493 /// - The shortest path tree.
494 /// - The distance of each node from the root(s).
496 int num = countNodes(*graph) - 1;
497 for (int i = 0; i < num; ++i) {
498 if (processNextWeakRound()) break;
502 /// \brief Executes the algorithm and checks the negative cycles.
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.
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
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;
521 /// \brief Executes the algorithm with path length limit.
523 /// \pre init() must be called and at least one node should be added
524 /// with addSource() before using this function.
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;
537 /// \brief Runs %BelmannFord algorithm from node \c s.
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
542 /// - The shortest path tree.
543 /// - The distance of each node from the root.
545 /// \note d.run(s) is just a shortcut of the following code.
559 /// \name Query Functions
560 /// The result of the %BelmannFord algorithm can be obtained using these
562 /// Before the use of these functions,
563 /// either run() or start() must be called.
567 /// \brief Copies the shortest path to \c t into \c p
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
573 /// \return Returns \c true if a path to \c t was actually copied to \c p,
574 /// \c false otherwise.
576 template <typename Path>
577 bool getPath(Path &p, Node t) {
580 typename Path::Builder b(p);
581 for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
582 b.pushFront(predEdge(t));
589 /// \brief The distance of a node from the root.
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]; }
597 /// \brief Returns the 'previous edge' of the shortest path tree.
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
606 Edge predEdge(Node v) const { return (*_pred)[v]; }
608 /// \brief Returns the 'previous node' of the shortest path tree.
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]);
620 /// \brief Returns a reference to the NodeMap of distances.
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;}
626 /// \brief Returns a reference to the shortest path tree map.
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; }
633 /// \brief Checks if a node is reachable from the root.
635 /// Returns \c true if \c v is reachable from the root.
636 /// \pre \ref run() must be called before using this function.
638 bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
643 /// \brief Default traits class of BelmannFord function.
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;
653 /// \brief The type of the map that stores the edge lengths.
655 /// The type of the map that stores the edge lengths.
656 /// It must meet the \ref concept::ReadMap "ReadMap" concept.
657 typedef _LengthMap LengthMap;
659 /// \brief The value type of the length map.
660 typedef typename _LengthMap::Value Value;
662 /// \brief Operation traits for belmann-ford algorithm.
664 /// It defines the infinity type on the given Value type
665 /// and the used operation.
666 /// \see BelmannFordDefaultOperationTraits
667 typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
669 /// \brief The type of the map that stores the last
670 /// edges of the shortest paths.
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;
677 /// \brief Instantiates a PredMap.
679 /// This function instantiates a \ref PredMap.
680 static PredMap *createPredMap(const _Graph &) {
681 return new PredMap();
683 /// \brief The type of the map that stores the dists of the nodes.
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.
690 /// This function instantiates a \ref DistMap.
691 static DistMap *createDistMap(const _Graph &) {
692 return new DistMap();
696 /// \brief Default traits used by \ref BelmannFordWizard
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> {
709 typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
711 /// Type of the nodes in the graph.
712 typedef typename Base::Graph::Node Node;
714 /// Pointer to the underlying graph.
716 /// Pointer to the length map
718 ///Pointer to the map of predecessors edges.
720 ///Pointer to the map of distances.
722 ///Pointer to the source node.
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) {}
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) {}
749 /// A class to make the usage of BelmannFord algorithm easier
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.
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.
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;
772 ///The type of the underlying graph.
773 typedef typename _Traits::Graph Graph;
775 typedef typename Graph::Node Node;
776 typedef typename Graph::NodeIt NodeIt;
777 typedef typename Graph::Edge Edge;
778 typedef typename Graph::OutEdgeIt EdgeIt;
780 ///The type of the map that stores the edge lengths.
781 typedef typename _Traits::LengthMap LengthMap;
783 ///The type of the length of the edges.
784 typedef typename LengthMap::Value Value;
786 ///\brief The type of the map that stores the last
787 ///edges of the shortest paths.
788 typedef typename _Traits::PredMap PredMap;
790 ///The type of the map that stores the dists of the nodes.
791 typedef typename _Traits::DistMap DistMap;
795 BelmannFordWizard() : _Traits() {}
797 /// \brief Constructor that requires parameters.
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) {}
805 /// \brief Copy constructor
806 BelmannFordWizard(const _Traits &b) : _Traits(b) {}
808 ~BelmannFordWizard() {}
810 /// \brief Runs BelmannFord algorithm from a given node.
812 /// Runs BelmannFord algorithm from a given node.
813 /// The node can be given by the \ref source function.
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);
823 /// \brief Runs BelmannFord algorithm from the given node.
825 /// Runs BelmannFord algorithm from the given node.
826 /// \param s is the given source.
827 void run(Node source) {
828 Base::_source = source;
833 struct DefPredMapBase : public Base {
835 static PredMap *createPredMap(const Graph &) { return 0; };
836 DefPredMapBase(const _Traits &b) : _Traits(b) {}
839 ///\brief \ref named-templ-param "Named parameter"
840 ///function for setting PredMap type
842 /// \ref named-templ-param "Named parameter"
843 ///function for setting PredMap type
846 BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
848 Base::_pred=(void *)&t;
849 return BelmannFordWizard<DefPredMapBase<T> >(*this);
853 struct DefDistMapBase : public Base {
855 static DistMap *createDistMap(const Graph &) { return 0; };
856 DefDistMapBase(const _Traits &b) : _Traits(b) {}
859 ///\brief \ref named-templ-param "Named parameter"
860 ///function for setting DistMap type
862 /// \ref named-templ-param "Named parameter"
863 ///function for setting DistMap type
866 BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
867 Base::_dist=(void *)&t;
868 return BelmannFordWizard<DefDistMapBase<T> >(*this);
872 struct DefOperationTraitsBase : public Base {
873 typedef T OperationTraits;
874 DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
877 ///\brief \ref named-templ-param "Named parameter"
878 ///function for setting OperationTraits type
880 /// \ref named-templ-param "Named parameter"
881 ///function for setting OperationTraits type
884 BelmannFordWizard<DefOperationTraitsBase<T> > distMap() {
885 return BelmannFordWizard<DefDistMapBase<T> >(*this);
888 /// \brief Sets the source node, from which the BelmannFord algorithm runs.
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;
899 /// \brief Function type interface for BelmannFord algorithm.
901 /// \ingroup flowalgs
902 /// Function type interface for BelmannFord algorithm.
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.
908 /// example shows how to use these parameters.
910 /// belmannford(g,length,source).predMap(preds).run();
912 /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
913 /// to the end of the parameter list.
914 /// \sa BelmannFordWizard
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);
925 } //END OF NAMESPACE LEMON