[743] | 1 | /* -*- C++ -*- |
---|
| 2 | * |
---|
| 3 | * This file is a part of LEMON, a generic C++ optimization library |
---|
| 4 | * |
---|
| 5 | * Copyright (C) 2003-2008 |
---|
| 6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
---|
| 7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
---|
| 8 | * |
---|
| 9 | * Permission to use, modify and distribute this software is granted |
---|
| 10 | * provided that this copyright notice appears in all copies. For |
---|
| 11 | * precise terms see the accompanying LICENSE file. |
---|
| 12 | * |
---|
| 13 | * This software is provided "AS IS" with no warranty of any kind, |
---|
| 14 | * express or implied, and with no claim as to its suitability for any |
---|
| 15 | * purpose. |
---|
| 16 | * |
---|
| 17 | */ |
---|
| 18 | |
---|
[744] | 19 | #ifndef LEMON_BELLMAN_FORD_H |
---|
| 20 | #define LEMON_BELLMAN_FORD_H |
---|
[743] | 21 | |
---|
| 22 | /// \ingroup shortest_path |
---|
| 23 | /// \file |
---|
| 24 | /// \brief Bellman-Ford algorithm. |
---|
| 25 | |
---|
| 26 | #include <lemon/bits/path_dump.h> |
---|
| 27 | #include <lemon/core.h> |
---|
| 28 | #include <lemon/error.h> |
---|
| 29 | #include <lemon/maps.h> |
---|
[744] | 30 | #include <lemon/path.h> |
---|
[743] | 31 | |
---|
| 32 | #include <limits> |
---|
| 33 | |
---|
| 34 | namespace lemon { |
---|
| 35 | |
---|
| 36 | /// \brief Default OperationTraits for the BellmanFord algorithm class. |
---|
| 37 | /// |
---|
[744] | 38 | /// This operation traits class defines all computational operations |
---|
| 39 | /// and constants that are used in the Bellman-Ford algorithm. |
---|
| 40 | /// The default implementation is based on the \c numeric_limits class. |
---|
| 41 | /// If the numeric type does not have infinity value, then the maximum |
---|
| 42 | /// value is used as extremal infinity value. |
---|
[743] | 43 | template < |
---|
[744] | 44 | typename V, |
---|
| 45 | bool has_inf = std::numeric_limits<V>::has_infinity> |
---|
[743] | 46 | struct BellmanFordDefaultOperationTraits { |
---|
[744] | 47 | /// \e |
---|
| 48 | typedef V Value; |
---|
[743] | 49 | /// \brief Gives back the zero value of the type. |
---|
| 50 | static Value zero() { |
---|
| 51 | return static_cast<Value>(0); |
---|
| 52 | } |
---|
| 53 | /// \brief Gives back the positive infinity value of the type. |
---|
| 54 | static Value infinity() { |
---|
| 55 | return std::numeric_limits<Value>::infinity(); |
---|
| 56 | } |
---|
| 57 | /// \brief Gives back the sum of the given two elements. |
---|
| 58 | static Value plus(const Value& left, const Value& right) { |
---|
| 59 | return left + right; |
---|
| 60 | } |
---|
[744] | 61 | /// \brief Gives back \c true only if the first value is less than |
---|
| 62 | /// the second. |
---|
[743] | 63 | static bool less(const Value& left, const Value& right) { |
---|
| 64 | return left < right; |
---|
| 65 | } |
---|
| 66 | }; |
---|
| 67 | |
---|
[744] | 68 | template <typename V> |
---|
| 69 | struct BellmanFordDefaultOperationTraits<V, false> { |
---|
| 70 | typedef V Value; |
---|
[743] | 71 | static Value zero() { |
---|
| 72 | return static_cast<Value>(0); |
---|
| 73 | } |
---|
| 74 | static Value infinity() { |
---|
| 75 | return std::numeric_limits<Value>::max(); |
---|
| 76 | } |
---|
| 77 | static Value plus(const Value& left, const Value& right) { |
---|
| 78 | if (left == infinity() || right == infinity()) return infinity(); |
---|
| 79 | return left + right; |
---|
| 80 | } |
---|
| 81 | static bool less(const Value& left, const Value& right) { |
---|
| 82 | return left < right; |
---|
| 83 | } |
---|
| 84 | }; |
---|
| 85 | |
---|
| 86 | /// \brief Default traits class of BellmanFord class. |
---|
| 87 | /// |
---|
| 88 | /// Default traits class of BellmanFord class. |
---|
[744] | 89 | /// \param GR The type of the digraph. |
---|
| 90 | /// \param LEN The type of the length map. |
---|
| 91 | template<typename GR, typename LEN> |
---|
[743] | 92 | struct BellmanFordDefaultTraits { |
---|
[744] | 93 | /// The type of the digraph the algorithm runs on. |
---|
| 94 | typedef GR Digraph; |
---|
[743] | 95 | |
---|
| 96 | /// \brief The type of the map that stores the arc lengths. |
---|
| 97 | /// |
---|
| 98 | /// The type of the map that stores the arc lengths. |
---|
[744] | 99 | /// It must conform to the \ref concepts::ReadMap "ReadMap" concept. |
---|
| 100 | typedef LEN LengthMap; |
---|
[743] | 101 | |
---|
[744] | 102 | /// The type of the arc lengths. |
---|
| 103 | typedef typename LEN::Value Value; |
---|
[743] | 104 | |
---|
| 105 | /// \brief Operation traits for Bellman-Ford algorithm. |
---|
| 106 | /// |
---|
[744] | 107 | /// It defines the used operations and the infinity value for the |
---|
| 108 | /// given \c Value type. |
---|
[743] | 109 | /// \see BellmanFordDefaultOperationTraits |
---|
| 110 | typedef BellmanFordDefaultOperationTraits<Value> OperationTraits; |
---|
| 111 | |
---|
| 112 | /// \brief The type of the map that stores the last arcs of the |
---|
| 113 | /// shortest paths. |
---|
| 114 | /// |
---|
| 115 | /// The type of the map that stores the last |
---|
| 116 | /// arcs of the shortest paths. |
---|
[744] | 117 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 118 | typedef typename GR::template NodeMap<typename GR::Arc> PredMap; |
---|
[743] | 119 | |
---|
[744] | 120 | /// \brief Instantiates a \c PredMap. |
---|
[743] | 121 | /// |
---|
| 122 | /// This function instantiates a \ref PredMap. |
---|
[744] | 123 | /// \param g is the digraph to which we would like to define the |
---|
| 124 | /// \ref PredMap. |
---|
| 125 | static PredMap *createPredMap(const GR& g) { |
---|
| 126 | return new PredMap(g); |
---|
[743] | 127 | } |
---|
| 128 | |
---|
[744] | 129 | /// \brief The type of the map that stores the distances of the nodes. |
---|
[743] | 130 | /// |
---|
[744] | 131 | /// The type of the map that stores the distances of the nodes. |
---|
| 132 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 133 | typedef typename GR::template NodeMap<typename LEN::Value> DistMap; |
---|
[743] | 134 | |
---|
[744] | 135 | /// \brief Instantiates a \c DistMap. |
---|
[743] | 136 | /// |
---|
| 137 | /// This function instantiates a \ref DistMap. |
---|
[744] | 138 | /// \param g is the digraph to which we would like to define the |
---|
| 139 | /// \ref DistMap. |
---|
| 140 | static DistMap *createDistMap(const GR& g) { |
---|
| 141 | return new DistMap(g); |
---|
[743] | 142 | } |
---|
| 143 | |
---|
| 144 | }; |
---|
| 145 | |
---|
| 146 | /// \brief %BellmanFord algorithm class. |
---|
| 147 | /// |
---|
| 148 | /// \ingroup shortest_path |
---|
[744] | 149 | /// This class provides an efficient implementation of the Bellman-Ford |
---|
| 150 | /// algorithm. The maximum time complexity of the algorithm is |
---|
| 151 | /// <tt>O(ne)</tt>. |
---|
| 152 | /// |
---|
| 153 | /// The Bellman-Ford algorithm solves the single-source shortest path |
---|
| 154 | /// problem when the arcs can have negative lengths, but the digraph |
---|
| 155 | /// should not contain directed cycles with negative total length. |
---|
| 156 | /// If all arc costs are non-negative, consider to use the Dijkstra |
---|
| 157 | /// algorithm instead, since it is more efficient. |
---|
| 158 | /// |
---|
| 159 | /// The arc lengths are passed to the algorithm using a |
---|
[743] | 160 | /// \ref concepts::ReadMap "ReadMap", so it is easy to change it to any |
---|
[744] | 161 | /// kind of length. The type of the length values is determined by the |
---|
| 162 | /// \ref concepts::ReadMap::Value "Value" type of the length map. |
---|
[743] | 163 | /// |
---|
[744] | 164 | /// There is also a \ref bellmanFord() "function-type interface" for the |
---|
| 165 | /// Bellman-Ford algorithm, which is convenient in the simplier cases and |
---|
| 166 | /// it can be used easier. |
---|
[743] | 167 | /// |
---|
[744] | 168 | /// \tparam GR The type of the digraph the algorithm runs on. |
---|
| 169 | /// The default type is \ref ListDigraph. |
---|
| 170 | /// \tparam LEN A \ref concepts::ReadMap "readable" arc map that specifies |
---|
| 171 | /// the lengths of the arcs. The default map type is |
---|
| 172 | /// \ref concepts::Digraph::ArcMap "GR::ArcMap<int>". |
---|
[743] | 173 | #ifdef DOXYGEN |
---|
[744] | 174 | template <typename GR, typename LEN, typename TR> |
---|
[743] | 175 | #else |
---|
[744] | 176 | template <typename GR=ListDigraph, |
---|
| 177 | typename LEN=typename GR::template ArcMap<int>, |
---|
| 178 | typename TR=BellmanFordDefaultTraits<GR,LEN> > |
---|
[743] | 179 | #endif |
---|
| 180 | class BellmanFord { |
---|
| 181 | public: |
---|
| 182 | |
---|
| 183 | ///The type of the underlying digraph. |
---|
[744] | 184 | typedef typename TR::Digraph Digraph; |
---|
| 185 | |
---|
| 186 | /// \brief The type of the arc lengths. |
---|
| 187 | typedef typename TR::LengthMap::Value Value; |
---|
| 188 | /// \brief The type of the map that stores the arc lengths. |
---|
| 189 | typedef typename TR::LengthMap LengthMap; |
---|
| 190 | /// \brief The type of the map that stores the last |
---|
| 191 | /// arcs of the shortest paths. |
---|
| 192 | typedef typename TR::PredMap PredMap; |
---|
| 193 | /// \brief The type of the map that stores the distances of the nodes. |
---|
| 194 | typedef typename TR::DistMap DistMap; |
---|
| 195 | /// The type of the paths. |
---|
| 196 | typedef PredMapPath<Digraph, PredMap> Path; |
---|
| 197 | ///\brief The \ref BellmanFordDefaultOperationTraits |
---|
| 198 | /// "operation traits class" of the algorithm. |
---|
| 199 | typedef typename TR::OperationTraits OperationTraits; |
---|
| 200 | |
---|
| 201 | ///The \ref BellmanFordDefaultTraits "traits class" of the algorithm. |
---|
| 202 | typedef TR Traits; |
---|
| 203 | |
---|
| 204 | private: |
---|
[743] | 205 | |
---|
| 206 | typedef typename Digraph::Node Node; |
---|
| 207 | typedef typename Digraph::NodeIt NodeIt; |
---|
| 208 | typedef typename Digraph::Arc Arc; |
---|
| 209 | typedef typename Digraph::OutArcIt OutArcIt; |
---|
[744] | 210 | |
---|
| 211 | // Pointer to the underlying digraph. |
---|
| 212 | const Digraph *_gr; |
---|
| 213 | // Pointer to the length map |
---|
| 214 | const LengthMap *_length; |
---|
| 215 | // Pointer to the map of predecessors arcs. |
---|
[743] | 216 | PredMap *_pred; |
---|
[744] | 217 | // Indicates if _pred is locally allocated (true) or not. |
---|
| 218 | bool _local_pred; |
---|
| 219 | // Pointer to the map of distances. |
---|
[743] | 220 | DistMap *_dist; |
---|
[744] | 221 | // Indicates if _dist is locally allocated (true) or not. |
---|
| 222 | bool _local_dist; |
---|
[743] | 223 | |
---|
| 224 | typedef typename Digraph::template NodeMap<bool> MaskMap; |
---|
| 225 | MaskMap *_mask; |
---|
| 226 | |
---|
| 227 | std::vector<Node> _process; |
---|
| 228 | |
---|
[744] | 229 | // Creates the maps if necessary. |
---|
[743] | 230 | void create_maps() { |
---|
| 231 | if(!_pred) { |
---|
[744] | 232 | _local_pred = true; |
---|
| 233 | _pred = Traits::createPredMap(*_gr); |
---|
[743] | 234 | } |
---|
| 235 | if(!_dist) { |
---|
[744] | 236 | _local_dist = true; |
---|
| 237 | _dist = Traits::createDistMap(*_gr); |
---|
[743] | 238 | } |
---|
[744] | 239 | _mask = new MaskMap(*_gr, false); |
---|
[743] | 240 | } |
---|
| 241 | |
---|
| 242 | public : |
---|
| 243 | |
---|
| 244 | typedef BellmanFord Create; |
---|
| 245 | |
---|
[744] | 246 | /// \name Named Template Parameters |
---|
[743] | 247 | |
---|
| 248 | ///@{ |
---|
| 249 | |
---|
| 250 | template <class T> |
---|
[744] | 251 | struct SetPredMapTraits : public Traits { |
---|
[743] | 252 | typedef T PredMap; |
---|
| 253 | static PredMap *createPredMap(const Digraph&) { |
---|
| 254 | LEMON_ASSERT(false, "PredMap is not initialized"); |
---|
| 255 | return 0; // ignore warnings |
---|
| 256 | } |
---|
| 257 | }; |
---|
| 258 | |
---|
[744] | 259 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
| 260 | /// \c PredMap type. |
---|
[743] | 261 | /// |
---|
[744] | 262 | /// \ref named-templ-param "Named parameter" for setting |
---|
| 263 | /// \c PredMap type. |
---|
| 264 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
[743] | 265 | template <class T> |
---|
| 266 | struct SetPredMap |
---|
[744] | 267 | : public BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > { |
---|
| 268 | typedef BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > Create; |
---|
[743] | 269 | }; |
---|
| 270 | |
---|
| 271 | template <class T> |
---|
[744] | 272 | struct SetDistMapTraits : public Traits { |
---|
[743] | 273 | typedef T DistMap; |
---|
| 274 | static DistMap *createDistMap(const Digraph&) { |
---|
| 275 | LEMON_ASSERT(false, "DistMap is not initialized"); |
---|
| 276 | return 0; // ignore warnings |
---|
| 277 | } |
---|
| 278 | }; |
---|
| 279 | |
---|
[744] | 280 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
| 281 | /// \c DistMap type. |
---|
[743] | 282 | /// |
---|
[744] | 283 | /// \ref named-templ-param "Named parameter" for setting |
---|
| 284 | /// \c DistMap type. |
---|
| 285 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
[743] | 286 | template <class T> |
---|
| 287 | struct SetDistMap |
---|
[744] | 288 | : public BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > { |
---|
| 289 | typedef BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > Create; |
---|
[743] | 290 | }; |
---|
[744] | 291 | |
---|
[743] | 292 | template <class T> |
---|
[744] | 293 | struct SetOperationTraitsTraits : public Traits { |
---|
[743] | 294 | typedef T OperationTraits; |
---|
| 295 | }; |
---|
| 296 | |
---|
| 297 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
[744] | 298 | /// \c OperationTraits type. |
---|
[743] | 299 | /// |
---|
[744] | 300 | /// \ref named-templ-param "Named parameter" for setting |
---|
| 301 | /// \c OperationTraits type. |
---|
[833] | 302 | /// For more information, see \ref BellmanFordDefaultOperationTraits. |
---|
[743] | 303 | template <class T> |
---|
| 304 | struct SetOperationTraits |
---|
[744] | 305 | : public BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > { |
---|
| 306 | typedef BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > |
---|
[743] | 307 | Create; |
---|
| 308 | }; |
---|
| 309 | |
---|
| 310 | ///@} |
---|
| 311 | |
---|
| 312 | protected: |
---|
| 313 | |
---|
| 314 | BellmanFord() {} |
---|
| 315 | |
---|
| 316 | public: |
---|
| 317 | |
---|
| 318 | /// \brief Constructor. |
---|
| 319 | /// |
---|
[744] | 320 | /// Constructor. |
---|
| 321 | /// \param g The digraph the algorithm runs on. |
---|
| 322 | /// \param length The length map used by the algorithm. |
---|
| 323 | BellmanFord(const Digraph& g, const LengthMap& length) : |
---|
| 324 | _gr(&g), _length(&length), |
---|
| 325 | _pred(0), _local_pred(false), |
---|
| 326 | _dist(0), _local_dist(false), _mask(0) {} |
---|
[743] | 327 | |
---|
| 328 | ///Destructor. |
---|
| 329 | ~BellmanFord() { |
---|
[744] | 330 | if(_local_pred) delete _pred; |
---|
| 331 | if(_local_dist) delete _dist; |
---|
[743] | 332 | if(_mask) delete _mask; |
---|
| 333 | } |
---|
| 334 | |
---|
| 335 | /// \brief Sets the length map. |
---|
| 336 | /// |
---|
| 337 | /// Sets the length map. |
---|
[744] | 338 | /// \return <tt>(*this)</tt> |
---|
| 339 | BellmanFord &lengthMap(const LengthMap &map) { |
---|
| 340 | _length = ↦ |
---|
[743] | 341 | return *this; |
---|
| 342 | } |
---|
| 343 | |
---|
[744] | 344 | /// \brief Sets the map that stores the predecessor arcs. |
---|
[743] | 345 | /// |
---|
[744] | 346 | /// Sets the map that stores the predecessor arcs. |
---|
| 347 | /// If you don't use this function before calling \ref run() |
---|
| 348 | /// or \ref init(), an instance will be allocated automatically. |
---|
| 349 | /// The destructor deallocates this automatically allocated map, |
---|
| 350 | /// of course. |
---|
| 351 | /// \return <tt>(*this)</tt> |
---|
| 352 | BellmanFord &predMap(PredMap &map) { |
---|
| 353 | if(_local_pred) { |
---|
[743] | 354 | delete _pred; |
---|
[744] | 355 | _local_pred=false; |
---|
[743] | 356 | } |
---|
[744] | 357 | _pred = ↦ |
---|
[743] | 358 | return *this; |
---|
| 359 | } |
---|
| 360 | |
---|
[744] | 361 | /// \brief Sets the map that stores the distances of the nodes. |
---|
[743] | 362 | /// |
---|
[744] | 363 | /// Sets the map that stores the distances of the nodes calculated |
---|
| 364 | /// by the algorithm. |
---|
| 365 | /// If you don't use this function before calling \ref run() |
---|
| 366 | /// or \ref init(), an instance will be allocated automatically. |
---|
| 367 | /// The destructor deallocates this automatically allocated map, |
---|
| 368 | /// of course. |
---|
| 369 | /// \return <tt>(*this)</tt> |
---|
| 370 | BellmanFord &distMap(DistMap &map) { |
---|
| 371 | if(_local_dist) { |
---|
[743] | 372 | delete _dist; |
---|
[744] | 373 | _local_dist=false; |
---|
[743] | 374 | } |
---|
[744] | 375 | _dist = ↦ |
---|
[743] | 376 | return *this; |
---|
| 377 | } |
---|
| 378 | |
---|
[744] | 379 | /// \name Execution Control |
---|
| 380 | /// The simplest way to execute the Bellman-Ford algorithm is to use |
---|
| 381 | /// one of the member functions called \ref run().\n |
---|
| 382 | /// If you need better control on the execution, you have to call |
---|
| 383 | /// \ref init() first, then you can add several source nodes |
---|
| 384 | /// with \ref addSource(). Finally the actual path computation can be |
---|
| 385 | /// performed with \ref start(), \ref checkedStart() or |
---|
| 386 | /// \ref limitedStart(). |
---|
[743] | 387 | |
---|
| 388 | ///@{ |
---|
| 389 | |
---|
| 390 | /// \brief Initializes the internal data structures. |
---|
| 391 | /// |
---|
[744] | 392 | /// Initializes the internal data structures. The optional parameter |
---|
| 393 | /// is the initial distance of each node. |
---|
[743] | 394 | void init(const Value value = OperationTraits::infinity()) { |
---|
| 395 | create_maps(); |
---|
[744] | 396 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
---|
[743] | 397 | _pred->set(it, INVALID); |
---|
| 398 | _dist->set(it, value); |
---|
| 399 | } |
---|
| 400 | _process.clear(); |
---|
| 401 | if (OperationTraits::less(value, OperationTraits::infinity())) { |
---|
[744] | 402 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
---|
[743] | 403 | _process.push_back(it); |
---|
| 404 | _mask->set(it, true); |
---|
| 405 | } |
---|
| 406 | } |
---|
| 407 | } |
---|
| 408 | |
---|
| 409 | /// \brief Adds a new source node. |
---|
| 410 | /// |
---|
[744] | 411 | /// This function adds a new source node. The optional second parameter |
---|
| 412 | /// is the initial distance of the node. |
---|
[743] | 413 | void addSource(Node source, Value dst = OperationTraits::zero()) { |
---|
| 414 | _dist->set(source, dst); |
---|
| 415 | if (!(*_mask)[source]) { |
---|
| 416 | _process.push_back(source); |
---|
| 417 | _mask->set(source, true); |
---|
| 418 | } |
---|
| 419 | } |
---|
| 420 | |
---|
| 421 | /// \brief Executes one round from the Bellman-Ford algorithm. |
---|
| 422 | /// |
---|
| 423 | /// If the algoritm calculated the distances in the previous round |
---|
[744] | 424 | /// exactly for the paths of at most \c k arcs, then this function |
---|
| 425 | /// will calculate the distances exactly for the paths of at most |
---|
| 426 | /// <tt>k+1</tt> arcs. Performing \c k iterations using this function |
---|
| 427 | /// calculates the shortest path distances exactly for the paths |
---|
| 428 | /// consisting of at most \c k arcs. |
---|
[743] | 429 | /// |
---|
| 430 | /// \warning The paths with limited arc number cannot be retrieved |
---|
[744] | 431 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 432 | /// need the shortest paths and not only the distances, you should |
---|
| 433 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 434 | /// and build the path manually. |
---|
[743] | 435 | /// |
---|
| 436 | /// \return \c true when the algorithm have not found more shorter |
---|
| 437 | /// paths. |
---|
[744] | 438 | /// |
---|
| 439 | /// \see ActiveIt |
---|
[743] | 440 | bool processNextRound() { |
---|
| 441 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
| 442 | _mask->set(_process[i], false); |
---|
| 443 | } |
---|
| 444 | std::vector<Node> nextProcess; |
---|
| 445 | std::vector<Value> values(_process.size()); |
---|
| 446 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
| 447 | values[i] = (*_dist)[_process[i]]; |
---|
| 448 | } |
---|
| 449 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[744] | 450 | for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) { |
---|
| 451 | Node target = _gr->target(it); |
---|
| 452 | Value relaxed = OperationTraits::plus(values[i], (*_length)[it]); |
---|
[743] | 453 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 454 | _pred->set(target, it); |
---|
| 455 | _dist->set(target, relaxed); |
---|
| 456 | if (!(*_mask)[target]) { |
---|
| 457 | _mask->set(target, true); |
---|
| 458 | nextProcess.push_back(target); |
---|
| 459 | } |
---|
| 460 | } |
---|
| 461 | } |
---|
| 462 | } |
---|
| 463 | _process.swap(nextProcess); |
---|
| 464 | return _process.empty(); |
---|
| 465 | } |
---|
| 466 | |
---|
| 467 | /// \brief Executes one weak round from the Bellman-Ford algorithm. |
---|
| 468 | /// |
---|
[744] | 469 | /// If the algorithm calculated the distances in the previous round |
---|
| 470 | /// at least for the paths of at most \c k arcs, then this function |
---|
| 471 | /// will calculate the distances at least for the paths of at most |
---|
| 472 | /// <tt>k+1</tt> arcs. |
---|
| 473 | /// This function does not make it possible to calculate the shortest |
---|
| 474 | /// path distances exactly for paths consisting of at most \c k arcs, |
---|
| 475 | /// this is why it is called weak round. |
---|
| 476 | /// |
---|
| 477 | /// \return \c true when the algorithm have not found more shorter |
---|
| 478 | /// paths. |
---|
| 479 | /// |
---|
| 480 | /// \see ActiveIt |
---|
[743] | 481 | bool processNextWeakRound() { |
---|
| 482 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
| 483 | _mask->set(_process[i], false); |
---|
| 484 | } |
---|
| 485 | std::vector<Node> nextProcess; |
---|
| 486 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[744] | 487 | for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) { |
---|
| 488 | Node target = _gr->target(it); |
---|
[743] | 489 | Value relaxed = |
---|
[744] | 490 | OperationTraits::plus((*_dist)[_process[i]], (*_length)[it]); |
---|
[743] | 491 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 492 | _pred->set(target, it); |
---|
| 493 | _dist->set(target, relaxed); |
---|
| 494 | if (!(*_mask)[target]) { |
---|
| 495 | _mask->set(target, true); |
---|
| 496 | nextProcess.push_back(target); |
---|
| 497 | } |
---|
| 498 | } |
---|
| 499 | } |
---|
| 500 | } |
---|
| 501 | _process.swap(nextProcess); |
---|
| 502 | return _process.empty(); |
---|
| 503 | } |
---|
| 504 | |
---|
| 505 | /// \brief Executes the algorithm. |
---|
| 506 | /// |
---|
[744] | 507 | /// Executes the algorithm. |
---|
[743] | 508 | /// |
---|
[744] | 509 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 510 | /// in order to compute the shortest path to each node. |
---|
| 511 | /// |
---|
| 512 | /// The algorithm computes |
---|
| 513 | /// - the shortest path tree (forest), |
---|
| 514 | /// - the distance of each node from the root(s). |
---|
| 515 | /// |
---|
| 516 | /// \pre init() must be called and at least one root node should be |
---|
| 517 | /// added with addSource() before using this function. |
---|
[743] | 518 | void start() { |
---|
[744] | 519 | int num = countNodes(*_gr) - 1; |
---|
[743] | 520 | for (int i = 0; i < num; ++i) { |
---|
| 521 | if (processNextWeakRound()) break; |
---|
| 522 | } |
---|
| 523 | } |
---|
| 524 | |
---|
| 525 | /// \brief Executes the algorithm and checks the negative cycles. |
---|
| 526 | /// |
---|
[744] | 527 | /// Executes the algorithm and checks the negative cycles. |
---|
[743] | 528 | /// |
---|
[744] | 529 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 530 | /// in order to compute the shortest path to each node and also checks |
---|
| 531 | /// if the digraph contains cycles with negative total length. |
---|
| 532 | /// |
---|
| 533 | /// The algorithm computes |
---|
| 534 | /// - the shortest path tree (forest), |
---|
| 535 | /// - the distance of each node from the root(s). |
---|
[743] | 536 | /// |
---|
| 537 | /// \return \c false if there is a negative cycle in the digraph. |
---|
[744] | 538 | /// |
---|
| 539 | /// \pre init() must be called and at least one root node should be |
---|
| 540 | /// added with addSource() before using this function. |
---|
[743] | 541 | bool checkedStart() { |
---|
[744] | 542 | int num = countNodes(*_gr); |
---|
[743] | 543 | for (int i = 0; i < num; ++i) { |
---|
| 544 | if (processNextWeakRound()) return true; |
---|
| 545 | } |
---|
| 546 | return _process.empty(); |
---|
| 547 | } |
---|
| 548 | |
---|
[744] | 549 | /// \brief Executes the algorithm with arc number limit. |
---|
[743] | 550 | /// |
---|
[744] | 551 | /// Executes the algorithm with arc number limit. |
---|
[743] | 552 | /// |
---|
[744] | 553 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 554 | /// in order to compute the shortest path distance for each node |
---|
| 555 | /// using only the paths consisting of at most \c num arcs. |
---|
| 556 | /// |
---|
| 557 | /// The algorithm computes |
---|
| 558 | /// - the limited distance of each node from the root(s), |
---|
| 559 | /// - the predecessor arc for each node. |
---|
[743] | 560 | /// |
---|
| 561 | /// \warning The paths with limited arc number cannot be retrieved |
---|
[744] | 562 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 563 | /// need the shortest paths and not only the distances, you should |
---|
| 564 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 565 | /// and build the path manually. |
---|
[743] | 566 | /// |
---|
[744] | 567 | /// \pre init() must be called and at least one root node should be |
---|
| 568 | /// added with addSource() before using this function. |
---|
[743] | 569 | void limitedStart(int num) { |
---|
| 570 | for (int i = 0; i < num; ++i) { |
---|
| 571 | if (processNextRound()) break; |
---|
| 572 | } |
---|
| 573 | } |
---|
| 574 | |
---|
[744] | 575 | /// \brief Runs the algorithm from the given root node. |
---|
[743] | 576 | /// |
---|
[744] | 577 | /// This method runs the Bellman-Ford algorithm from the given root |
---|
| 578 | /// node \c s in order to compute the shortest path to each node. |
---|
[743] | 579 | /// |
---|
[744] | 580 | /// The algorithm computes |
---|
| 581 | /// - the shortest path tree (forest), |
---|
| 582 | /// - the distance of each node from the root(s). |
---|
| 583 | /// |
---|
| 584 | /// \note bf.run(s) is just a shortcut of the following code. |
---|
| 585 | /// \code |
---|
| 586 | /// bf.init(); |
---|
| 587 | /// bf.addSource(s); |
---|
| 588 | /// bf.start(); |
---|
| 589 | /// \endcode |
---|
[743] | 590 | void run(Node s) { |
---|
| 591 | init(); |
---|
| 592 | addSource(s); |
---|
| 593 | start(); |
---|
| 594 | } |
---|
| 595 | |
---|
[744] | 596 | /// \brief Runs the algorithm from the given root node with arc |
---|
| 597 | /// number limit. |
---|
[743] | 598 | /// |
---|
[744] | 599 | /// This method runs the Bellman-Ford algorithm from the given root |
---|
| 600 | /// node \c s in order to compute the shortest path distance for each |
---|
| 601 | /// node using only the paths consisting of at most \c num arcs. |
---|
[743] | 602 | /// |
---|
[744] | 603 | /// The algorithm computes |
---|
| 604 | /// - the limited distance of each node from the root(s), |
---|
| 605 | /// - the predecessor arc for each node. |
---|
| 606 | /// |
---|
| 607 | /// \warning The paths with limited arc number cannot be retrieved |
---|
| 608 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 609 | /// need the shortest paths and not only the distances, you should |
---|
| 610 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 611 | /// and build the path manually. |
---|
| 612 | /// |
---|
| 613 | /// \note bf.run(s, num) is just a shortcut of the following code. |
---|
| 614 | /// \code |
---|
| 615 | /// bf.init(); |
---|
| 616 | /// bf.addSource(s); |
---|
| 617 | /// bf.limitedStart(num); |
---|
| 618 | /// \endcode |
---|
[743] | 619 | void run(Node s, int num) { |
---|
| 620 | init(); |
---|
| 621 | addSource(s); |
---|
| 622 | limitedStart(num); |
---|
| 623 | } |
---|
| 624 | |
---|
| 625 | ///@} |
---|
| 626 | |
---|
[744] | 627 | /// \brief LEMON iterator for getting the active nodes. |
---|
[743] | 628 | /// |
---|
[744] | 629 | /// This class provides a common style LEMON iterator that traverses |
---|
| 630 | /// the active nodes of the Bellman-Ford algorithm after the last |
---|
| 631 | /// phase. These nodes should be checked in the next phase to |
---|
| 632 | /// find augmenting arcs outgoing from them. |
---|
[743] | 633 | class ActiveIt { |
---|
| 634 | public: |
---|
| 635 | |
---|
| 636 | /// \brief Constructor. |
---|
| 637 | /// |
---|
[744] | 638 | /// Constructor for getting the active nodes of the given BellmanFord |
---|
| 639 | /// instance. |
---|
[743] | 640 | ActiveIt(const BellmanFord& algorithm) : _algorithm(&algorithm) |
---|
| 641 | { |
---|
| 642 | _index = _algorithm->_process.size() - 1; |
---|
| 643 | } |
---|
| 644 | |
---|
| 645 | /// \brief Invalid constructor. |
---|
| 646 | /// |
---|
| 647 | /// Invalid constructor. |
---|
| 648 | ActiveIt(Invalid) : _algorithm(0), _index(-1) {} |
---|
| 649 | |
---|
[744] | 650 | /// \brief Conversion to \c Node. |
---|
[743] | 651 | /// |
---|
[744] | 652 | /// Conversion to \c Node. |
---|
[743] | 653 | operator Node() const { |
---|
| 654 | return _index >= 0 ? _algorithm->_process[_index] : INVALID; |
---|
| 655 | } |
---|
| 656 | |
---|
| 657 | /// \brief Increment operator. |
---|
| 658 | /// |
---|
| 659 | /// Increment operator. |
---|
| 660 | ActiveIt& operator++() { |
---|
| 661 | --_index; |
---|
| 662 | return *this; |
---|
| 663 | } |
---|
| 664 | |
---|
| 665 | bool operator==(const ActiveIt& it) const { |
---|
| 666 | return static_cast<Node>(*this) == static_cast<Node>(it); |
---|
| 667 | } |
---|
| 668 | bool operator!=(const ActiveIt& it) const { |
---|
| 669 | return static_cast<Node>(*this) != static_cast<Node>(it); |
---|
| 670 | } |
---|
| 671 | bool operator<(const ActiveIt& it) const { |
---|
| 672 | return static_cast<Node>(*this) < static_cast<Node>(it); |
---|
| 673 | } |
---|
| 674 | |
---|
| 675 | private: |
---|
| 676 | const BellmanFord* _algorithm; |
---|
| 677 | int _index; |
---|
| 678 | }; |
---|
[744] | 679 | |
---|
| 680 | /// \name Query Functions |
---|
| 681 | /// The result of the Bellman-Ford algorithm can be obtained using these |
---|
| 682 | /// functions.\n |
---|
| 683 | /// Either \ref run() or \ref init() should be called before using them. |
---|
| 684 | |
---|
| 685 | ///@{ |
---|
[743] | 686 | |
---|
[744] | 687 | /// \brief The shortest path to the given node. |
---|
| 688 | /// |
---|
| 689 | /// Gives back the shortest path to the given node from the root(s). |
---|
| 690 | /// |
---|
| 691 | /// \warning \c t should be reached from the root(s). |
---|
| 692 | /// |
---|
| 693 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 694 | /// using this function. |
---|
| 695 | Path path(Node t) const |
---|
| 696 | { |
---|
| 697 | return Path(*_gr, *_pred, t); |
---|
| 698 | } |
---|
| 699 | |
---|
| 700 | /// \brief The distance of the given node from the root(s). |
---|
| 701 | /// |
---|
| 702 | /// Returns the distance of the given node from the root(s). |
---|
| 703 | /// |
---|
| 704 | /// \warning If node \c v is not reached from the root(s), then |
---|
| 705 | /// the return value of this function is undefined. |
---|
| 706 | /// |
---|
| 707 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 708 | /// using this function. |
---|
| 709 | Value dist(Node v) const { return (*_dist)[v]; } |
---|
[743] | 710 | |
---|
[744] | 711 | /// \brief Returns the 'previous arc' of the shortest path tree for |
---|
| 712 | /// the given node. |
---|
| 713 | /// |
---|
| 714 | /// This function returns the 'previous arc' of the shortest path |
---|
| 715 | /// tree for node \c v, i.e. it returns the last arc of a |
---|
| 716 | /// shortest path from a root to \c v. It is \c INVALID if \c v |
---|
| 717 | /// is not reached from the root(s) or if \c v is a root. |
---|
| 718 | /// |
---|
| 719 | /// The shortest path tree used here is equal to the shortest path |
---|
[833] | 720 | /// tree used in \ref predNode() and \ref predMap(). |
---|
[744] | 721 | /// |
---|
| 722 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 723 | /// using this function. |
---|
| 724 | Arc predArc(Node v) const { return (*_pred)[v]; } |
---|
| 725 | |
---|
| 726 | /// \brief Returns the 'previous node' of the shortest path tree for |
---|
| 727 | /// the given node. |
---|
| 728 | /// |
---|
| 729 | /// This function returns the 'previous node' of the shortest path |
---|
| 730 | /// tree for node \c v, i.e. it returns the last but one node of |
---|
| 731 | /// a shortest path from a root to \c v. It is \c INVALID if \c v |
---|
| 732 | /// is not reached from the root(s) or if \c v is a root. |
---|
| 733 | /// |
---|
| 734 | /// The shortest path tree used here is equal to the shortest path |
---|
[833] | 735 | /// tree used in \ref predArc() and \ref predMap(). |
---|
[744] | 736 | /// |
---|
| 737 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 738 | /// using this function. |
---|
| 739 | Node predNode(Node v) const { |
---|
| 740 | return (*_pred)[v] == INVALID ? INVALID : _gr->source((*_pred)[v]); |
---|
| 741 | } |
---|
| 742 | |
---|
| 743 | /// \brief Returns a const reference to the node map that stores the |
---|
| 744 | /// distances of the nodes. |
---|
| 745 | /// |
---|
| 746 | /// Returns a const reference to the node map that stores the distances |
---|
| 747 | /// of the nodes calculated by the algorithm. |
---|
| 748 | /// |
---|
| 749 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 750 | /// using this function. |
---|
| 751 | const DistMap &distMap() const { return *_dist;} |
---|
| 752 | |
---|
| 753 | /// \brief Returns a const reference to the node map that stores the |
---|
| 754 | /// predecessor arcs. |
---|
| 755 | /// |
---|
| 756 | /// Returns a const reference to the node map that stores the predecessor |
---|
| 757 | /// arcs, which form the shortest path tree (forest). |
---|
| 758 | /// |
---|
| 759 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 760 | /// using this function. |
---|
| 761 | const PredMap &predMap() const { return *_pred; } |
---|
| 762 | |
---|
| 763 | /// \brief Checks if a node is reached from the root(s). |
---|
| 764 | /// |
---|
| 765 | /// Returns \c true if \c v is reached from the root(s). |
---|
| 766 | /// |
---|
| 767 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 768 | /// using this function. |
---|
| 769 | bool reached(Node v) const { |
---|
| 770 | return (*_dist)[v] != OperationTraits::infinity(); |
---|
[743] | 771 | } |
---|
| 772 | |
---|
[746] | 773 | /// \brief Gives back a negative cycle. |
---|
| 774 | /// |
---|
| 775 | /// This function gives back a directed cycle with negative total |
---|
| 776 | /// length if the algorithm has already found one. |
---|
| 777 | /// Otherwise it gives back an empty path. |
---|
| 778 | lemon::Path<Digraph> negativeCycle() { |
---|
| 779 | typename Digraph::template NodeMap<int> state(*_gr, -1); |
---|
| 780 | lemon::Path<Digraph> cycle; |
---|
| 781 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
| 782 | if (state[_process[i]] != -1) continue; |
---|
| 783 | for (Node v = _process[i]; (*_pred)[v] != INVALID; |
---|
| 784 | v = _gr->source((*_pred)[v])) { |
---|
| 785 | if (state[v] == i) { |
---|
| 786 | cycle.addFront((*_pred)[v]); |
---|
| 787 | for (Node u = _gr->source((*_pred)[v]); u != v; |
---|
| 788 | u = _gr->source((*_pred)[u])) { |
---|
| 789 | cycle.addFront((*_pred)[u]); |
---|
| 790 | } |
---|
| 791 | return cycle; |
---|
| 792 | } |
---|
| 793 | else if (state[v] >= 0) { |
---|
| 794 | break; |
---|
| 795 | } |
---|
| 796 | state[v] = i; |
---|
| 797 | } |
---|
| 798 | } |
---|
| 799 | return cycle; |
---|
| 800 | } |
---|
[743] | 801 | |
---|
| 802 | ///@} |
---|
| 803 | }; |
---|
| 804 | |
---|
[744] | 805 | /// \brief Default traits class of bellmanFord() function. |
---|
[743] | 806 | /// |
---|
[744] | 807 | /// Default traits class of bellmanFord() function. |
---|
| 808 | /// \tparam GR The type of the digraph. |
---|
| 809 | /// \tparam LEN The type of the length map. |
---|
| 810 | template <typename GR, typename LEN> |
---|
[743] | 811 | struct BellmanFordWizardDefaultTraits { |
---|
[744] | 812 | /// The type of the digraph the algorithm runs on. |
---|
| 813 | typedef GR Digraph; |
---|
[743] | 814 | |
---|
| 815 | /// \brief The type of the map that stores the arc lengths. |
---|
| 816 | /// |
---|
| 817 | /// The type of the map that stores the arc lengths. |
---|
| 818 | /// It must meet the \ref concepts::ReadMap "ReadMap" concept. |
---|
[744] | 819 | typedef LEN LengthMap; |
---|
[743] | 820 | |
---|
[744] | 821 | /// The type of the arc lengths. |
---|
| 822 | typedef typename LEN::Value Value; |
---|
[743] | 823 | |
---|
| 824 | /// \brief Operation traits for Bellman-Ford algorithm. |
---|
| 825 | /// |
---|
[744] | 826 | /// It defines the used operations and the infinity value for the |
---|
| 827 | /// given \c Value type. |
---|
[743] | 828 | /// \see BellmanFordDefaultOperationTraits |
---|
| 829 | typedef BellmanFordDefaultOperationTraits<Value> OperationTraits; |
---|
| 830 | |
---|
| 831 | /// \brief The type of the map that stores the last |
---|
| 832 | /// arcs of the shortest paths. |
---|
| 833 | /// |
---|
[744] | 834 | /// The type of the map that stores the last arcs of the shortest paths. |
---|
| 835 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 836 | typedef typename GR::template NodeMap<typename GR::Arc> PredMap; |
---|
[743] | 837 | |
---|
[744] | 838 | /// \brief Instantiates a \c PredMap. |
---|
[743] | 839 | /// |
---|
[744] | 840 | /// This function instantiates a \ref PredMap. |
---|
| 841 | /// \param g is the digraph to which we would like to define the |
---|
| 842 | /// \ref PredMap. |
---|
| 843 | static PredMap *createPredMap(const GR &g) { |
---|
| 844 | return new PredMap(g); |
---|
[743] | 845 | } |
---|
[744] | 846 | |
---|
| 847 | /// \brief The type of the map that stores the distances of the nodes. |
---|
[743] | 848 | /// |
---|
[744] | 849 | /// The type of the map that stores the distances of the nodes. |
---|
| 850 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 851 | typedef typename GR::template NodeMap<Value> DistMap; |
---|
| 852 | |
---|
| 853 | /// \brief Instantiates a \c DistMap. |
---|
[743] | 854 | /// |
---|
| 855 | /// This function instantiates a \ref DistMap. |
---|
[744] | 856 | /// \param g is the digraph to which we would like to define the |
---|
| 857 | /// \ref DistMap. |
---|
| 858 | static DistMap *createDistMap(const GR &g) { |
---|
| 859 | return new DistMap(g); |
---|
[743] | 860 | } |
---|
[744] | 861 | |
---|
| 862 | ///The type of the shortest paths. |
---|
| 863 | |
---|
| 864 | ///The type of the shortest paths. |
---|
| 865 | ///It must meet the \ref concepts::Path "Path" concept. |
---|
| 866 | typedef lemon::Path<Digraph> Path; |
---|
[743] | 867 | }; |
---|
| 868 | |
---|
[744] | 869 | /// \brief Default traits class used by BellmanFordWizard. |
---|
[743] | 870 | /// |
---|
[744] | 871 | /// Default traits class used by BellmanFordWizard. |
---|
| 872 | /// \tparam GR The type of the digraph. |
---|
| 873 | /// \tparam LEN The type of the length map. |
---|
| 874 | template <typename GR, typename LEN> |
---|
[743] | 875 | class BellmanFordWizardBase |
---|
[744] | 876 | : public BellmanFordWizardDefaultTraits<GR, LEN> { |
---|
[743] | 877 | |
---|
[744] | 878 | typedef BellmanFordWizardDefaultTraits<GR, LEN> Base; |
---|
[743] | 879 | protected: |
---|
[744] | 880 | // Type of the nodes in the digraph. |
---|
[743] | 881 | typedef typename Base::Digraph::Node Node; |
---|
| 882 | |
---|
[744] | 883 | // Pointer to the underlying digraph. |
---|
[743] | 884 | void *_graph; |
---|
[744] | 885 | // Pointer to the length map |
---|
[743] | 886 | void *_length; |
---|
[744] | 887 | // Pointer to the map of predecessors arcs. |
---|
[743] | 888 | void *_pred; |
---|
[744] | 889 | // Pointer to the map of distances. |
---|
[743] | 890 | void *_dist; |
---|
[744] | 891 | //Pointer to the shortest path to the target node. |
---|
| 892 | void *_path; |
---|
| 893 | //Pointer to the distance of the target node. |
---|
| 894 | void *_di; |
---|
[743] | 895 | |
---|
| 896 | public: |
---|
| 897 | /// Constructor. |
---|
| 898 | |
---|
[744] | 899 | /// This constructor does not require parameters, it initiates |
---|
| 900 | /// all of the attributes to default values \c 0. |
---|
| 901 | BellmanFordWizardBase() : |
---|
| 902 | _graph(0), _length(0), _pred(0), _dist(0), _path(0), _di(0) {} |
---|
[743] | 903 | |
---|
| 904 | /// Constructor. |
---|
| 905 | |
---|
[744] | 906 | /// This constructor requires two parameters, |
---|
| 907 | /// others are initiated to \c 0. |
---|
| 908 | /// \param gr The digraph the algorithm runs on. |
---|
| 909 | /// \param len The length map. |
---|
| 910 | BellmanFordWizardBase(const GR& gr, |
---|
| 911 | const LEN& len) : |
---|
| 912 | _graph(reinterpret_cast<void*>(const_cast<GR*>(&gr))), |
---|
| 913 | _length(reinterpret_cast<void*>(const_cast<LEN*>(&len))), |
---|
| 914 | _pred(0), _dist(0), _path(0), _di(0) {} |
---|
[743] | 915 | |
---|
| 916 | }; |
---|
| 917 | |
---|
[744] | 918 | /// \brief Auxiliary class for the function-type interface of the |
---|
| 919 | /// \ref BellmanFord "Bellman-Ford" algorithm. |
---|
| 920 | /// |
---|
| 921 | /// This auxiliary class is created to implement the |
---|
| 922 | /// \ref bellmanFord() "function-type interface" of the |
---|
| 923 | /// \ref BellmanFord "Bellman-Ford" algorithm. |
---|
| 924 | /// It does not have own \ref run() method, it uses the |
---|
| 925 | /// functions and features of the plain \ref BellmanFord. |
---|
| 926 | /// |
---|
| 927 | /// This class should only be used through the \ref bellmanFord() |
---|
| 928 | /// function, which makes it easier to use the algorithm. |
---|
| 929 | template<class TR> |
---|
| 930 | class BellmanFordWizard : public TR { |
---|
| 931 | typedef TR Base; |
---|
[743] | 932 | |
---|
[744] | 933 | typedef typename TR::Digraph Digraph; |
---|
[743] | 934 | |
---|
| 935 | typedef typename Digraph::Node Node; |
---|
| 936 | typedef typename Digraph::NodeIt NodeIt; |
---|
| 937 | typedef typename Digraph::Arc Arc; |
---|
| 938 | typedef typename Digraph::OutArcIt ArcIt; |
---|
| 939 | |
---|
[744] | 940 | typedef typename TR::LengthMap LengthMap; |
---|
[743] | 941 | typedef typename LengthMap::Value Value; |
---|
[744] | 942 | typedef typename TR::PredMap PredMap; |
---|
| 943 | typedef typename TR::DistMap DistMap; |
---|
| 944 | typedef typename TR::Path Path; |
---|
[743] | 945 | |
---|
| 946 | public: |
---|
| 947 | /// Constructor. |
---|
[744] | 948 | BellmanFordWizard() : TR() {} |
---|
[743] | 949 | |
---|
| 950 | /// \brief Constructor that requires parameters. |
---|
| 951 | /// |
---|
| 952 | /// Constructor that requires parameters. |
---|
| 953 | /// These parameters will be the default values for the traits class. |
---|
[744] | 954 | /// \param gr The digraph the algorithm runs on. |
---|
| 955 | /// \param len The length map. |
---|
| 956 | BellmanFordWizard(const Digraph& gr, const LengthMap& len) |
---|
| 957 | : TR(gr, len) {} |
---|
[743] | 958 | |
---|
| 959 | /// \brief Copy constructor |
---|
[744] | 960 | BellmanFordWizard(const TR &b) : TR(b) {} |
---|
[743] | 961 | |
---|
| 962 | ~BellmanFordWizard() {} |
---|
| 963 | |
---|
[744] | 964 | /// \brief Runs the Bellman-Ford algorithm from the given source node. |
---|
[743] | 965 | /// |
---|
[744] | 966 | /// This method runs the Bellman-Ford algorithm from the given source |
---|
| 967 | /// node in order to compute the shortest path to each node. |
---|
| 968 | void run(Node s) { |
---|
| 969 | BellmanFord<Digraph,LengthMap,TR> |
---|
[743] | 970 | bf(*reinterpret_cast<const Digraph*>(Base::_graph), |
---|
| 971 | *reinterpret_cast<const LengthMap*>(Base::_length)); |
---|
| 972 | if (Base::_pred) bf.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
---|
| 973 | if (Base::_dist) bf.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
---|
[744] | 974 | bf.run(s); |
---|
[743] | 975 | } |
---|
| 976 | |
---|
[744] | 977 | /// \brief Runs the Bellman-Ford algorithm to find the shortest path |
---|
| 978 | /// between \c s and \c t. |
---|
[743] | 979 | /// |
---|
[744] | 980 | /// This method runs the Bellman-Ford algorithm from node \c s |
---|
| 981 | /// in order to compute the shortest path to node \c t. |
---|
| 982 | /// Actually, it computes the shortest path to each node, but using |
---|
| 983 | /// this function you can retrieve the distance and the shortest path |
---|
| 984 | /// for a single target node easier. |
---|
| 985 | /// |
---|
| 986 | /// \return \c true if \c t is reachable form \c s. |
---|
| 987 | bool run(Node s, Node t) { |
---|
| 988 | BellmanFord<Digraph,LengthMap,TR> |
---|
| 989 | bf(*reinterpret_cast<const Digraph*>(Base::_graph), |
---|
| 990 | *reinterpret_cast<const LengthMap*>(Base::_length)); |
---|
| 991 | if (Base::_pred) bf.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
---|
| 992 | if (Base::_dist) bf.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
---|
| 993 | bf.run(s); |
---|
| 994 | if (Base::_path) *reinterpret_cast<Path*>(Base::_path) = bf.path(t); |
---|
| 995 | if (Base::_di) *reinterpret_cast<Value*>(Base::_di) = bf.dist(t); |
---|
| 996 | return bf.reached(t); |
---|
[743] | 997 | } |
---|
| 998 | |
---|
| 999 | template<class T> |
---|
[744] | 1000 | struct SetPredMapBase : public Base { |
---|
[743] | 1001 | typedef T PredMap; |
---|
| 1002 | static PredMap *createPredMap(const Digraph &) { return 0; }; |
---|
[744] | 1003 | SetPredMapBase(const TR &b) : TR(b) {} |
---|
[743] | 1004 | }; |
---|
| 1005 | |
---|
[744] | 1006 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
| 1007 | /// the predecessor map. |
---|
[743] | 1008 | /// |
---|
[744] | 1009 | /// \ref named-templ-param "Named parameter" for setting |
---|
| 1010 | /// the map that stores the predecessor arcs of the nodes. |
---|
[743] | 1011 | template<class T> |
---|
[744] | 1012 | BellmanFordWizard<SetPredMapBase<T> > predMap(const T &t) { |
---|
[743] | 1013 | Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
[744] | 1014 | return BellmanFordWizard<SetPredMapBase<T> >(*this); |
---|
[743] | 1015 | } |
---|
| 1016 | |
---|
| 1017 | template<class T> |
---|
[744] | 1018 | struct SetDistMapBase : public Base { |
---|
[743] | 1019 | typedef T DistMap; |
---|
| 1020 | static DistMap *createDistMap(const Digraph &) { return 0; }; |
---|
[744] | 1021 | SetDistMapBase(const TR &b) : TR(b) {} |
---|
[743] | 1022 | }; |
---|
| 1023 | |
---|
[744] | 1024 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
| 1025 | /// the distance map. |
---|
[743] | 1026 | /// |
---|
[744] | 1027 | /// \ref named-templ-param "Named parameter" for setting |
---|
| 1028 | /// the map that stores the distances of the nodes calculated |
---|
| 1029 | /// by the algorithm. |
---|
[743] | 1030 | template<class T> |
---|
[744] | 1031 | BellmanFordWizard<SetDistMapBase<T> > distMap(const T &t) { |
---|
[743] | 1032 | Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
[744] | 1033 | return BellmanFordWizard<SetDistMapBase<T> >(*this); |
---|
[743] | 1034 | } |
---|
| 1035 | |
---|
| 1036 | template<class T> |
---|
[744] | 1037 | struct SetPathBase : public Base { |
---|
| 1038 | typedef T Path; |
---|
| 1039 | SetPathBase(const TR &b) : TR(b) {} |
---|
[743] | 1040 | }; |
---|
[744] | 1041 | |
---|
| 1042 | /// \brief \ref named-func-param "Named parameter" for getting |
---|
| 1043 | /// the shortest path to the target node. |
---|
[743] | 1044 | /// |
---|
[744] | 1045 | /// \ref named-func-param "Named parameter" for getting |
---|
| 1046 | /// the shortest path to the target node. |
---|
| 1047 | template<class T> |
---|
| 1048 | BellmanFordWizard<SetPathBase<T> > path(const T &t) |
---|
| 1049 | { |
---|
| 1050 | Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
| 1051 | return BellmanFordWizard<SetPathBase<T> >(*this); |
---|
| 1052 | } |
---|
| 1053 | |
---|
| 1054 | /// \brief \ref named-func-param "Named parameter" for getting |
---|
| 1055 | /// the distance of the target node. |
---|
[743] | 1056 | /// |
---|
[744] | 1057 | /// \ref named-func-param "Named parameter" for getting |
---|
| 1058 | /// the distance of the target node. |
---|
| 1059 | BellmanFordWizard dist(const Value &d) |
---|
| 1060 | { |
---|
| 1061 | Base::_di=reinterpret_cast<void*>(const_cast<Value*>(&d)); |
---|
[743] | 1062 | return *this; |
---|
| 1063 | } |
---|
| 1064 | |
---|
| 1065 | }; |
---|
| 1066 | |
---|
[744] | 1067 | /// \brief Function type interface for the \ref BellmanFord "Bellman-Ford" |
---|
| 1068 | /// algorithm. |
---|
[743] | 1069 | /// |
---|
| 1070 | /// \ingroup shortest_path |
---|
[744] | 1071 | /// Function type interface for the \ref BellmanFord "Bellman-Ford" |
---|
| 1072 | /// algorithm. |
---|
[743] | 1073 | /// |
---|
| 1074 | /// This function also has several \ref named-templ-func-param |
---|
| 1075 | /// "named parameters", they are declared as the members of class |
---|
| 1076 | /// \ref BellmanFordWizard. |
---|
[744] | 1077 | /// The following examples show how to use these parameters. |
---|
| 1078 | /// \code |
---|
| 1079 | /// // Compute shortest path from node s to each node |
---|
| 1080 | /// bellmanFord(g,length).predMap(preds).distMap(dists).run(s); |
---|
| 1081 | /// |
---|
| 1082 | /// // Compute shortest path from s to t |
---|
| 1083 | /// bool reached = bellmanFord(g,length).path(p).dist(d).run(s,t); |
---|
| 1084 | /// \endcode |
---|
[743] | 1085 | /// \warning Don't forget to put the \ref BellmanFordWizard::run() "run()" |
---|
| 1086 | /// to the end of the parameter list. |
---|
| 1087 | /// \sa BellmanFordWizard |
---|
| 1088 | /// \sa BellmanFord |
---|
[744] | 1089 | template<typename GR, typename LEN> |
---|
| 1090 | BellmanFordWizard<BellmanFordWizardBase<GR,LEN> > |
---|
| 1091 | bellmanFord(const GR& digraph, |
---|
| 1092 | const LEN& length) |
---|
| 1093 | { |
---|
| 1094 | return BellmanFordWizard<BellmanFordWizardBase<GR,LEN> >(digraph, length); |
---|
[743] | 1095 | } |
---|
| 1096 | |
---|
| 1097 | } //END OF NAMESPACE LEMON |
---|
| 1098 | |
---|
| 1099 | #endif |
---|
| 1100 | |
---|