1 | /* -*- C++ -*- |
---|
2 | * src/lemon/dijkstra.h - Part of LEMON, a generic C++ optimization library |
---|
3 | * |
---|
4 | * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
---|
5 | * (Egervary Combinatorial Optimization Research Group, 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_DIJKSTRA_H |
---|
18 | #define LEMON_DIJKSTRA_H |
---|
19 | |
---|
20 | ///\ingroup flowalgs |
---|
21 | ///\file |
---|
22 | ///\brief Dijkstra algorithm. |
---|
23 | |
---|
24 | #include <lemon/bin_heap.h> |
---|
25 | #include <lemon/invalid.h> |
---|
26 | |
---|
27 | namespace lemon { |
---|
28 | |
---|
29 | /// \addtogroup flowalgs |
---|
30 | /// @{ |
---|
31 | |
---|
32 | ///%Dijkstra algorithm class. |
---|
33 | |
---|
34 | ///This class provides an efficient implementation of %Dijkstra algorithm. |
---|
35 | ///The edge lengths are passed to the algorithm using a |
---|
36 | ///\ref concept::ReadMap "ReadMap", |
---|
37 | ///so it is easy to change it to any kind of length. |
---|
38 | /// |
---|
39 | ///The type of the length is determined by the |
---|
40 | ///\ref concept::ReadMap::ValueType "ValueType" of the length map. |
---|
41 | /// |
---|
42 | ///It is also possible to change the underlying priority heap. |
---|
43 | /// |
---|
44 | ///\param GR The graph type the algorithm runs on. |
---|
45 | ///\param LM This read-only |
---|
46 | ///EdgeMap |
---|
47 | ///determines the |
---|
48 | ///lengths of the edges. It is read once for each edge, so the map |
---|
49 | ///may involve in relatively time consuming process to compute the edge |
---|
50 | ///length if it is necessary. The default map type is |
---|
51 | ///\ref concept::StaticGraph::EdgeMap "Graph::EdgeMap<int>" |
---|
52 | ///\param Heap The heap type used by the %Dijkstra |
---|
53 | ///algorithm. The default |
---|
54 | ///is using \ref BinHeap "binary heap". |
---|
55 | /// |
---|
56 | ///\author Jacint Szabo and Alpar Juttner |
---|
57 | ///\todo We need a typedef-names should be standardized. (-: |
---|
58 | ///\todo Type of \c PredMap, \c PredNodeMap and \c DistMap |
---|
59 | ///should not be fixed. (Problematic to solve). |
---|
60 | |
---|
61 | #ifdef DOXYGEN |
---|
62 | template <typename GR, |
---|
63 | typename LM, |
---|
64 | typename Heap> |
---|
65 | #else |
---|
66 | template <typename GR, |
---|
67 | typename LM=typename GR::template EdgeMap<int>, |
---|
68 | template <class,class,class,class> class Heap = BinHeap > |
---|
69 | #endif |
---|
70 | class Dijkstra{ |
---|
71 | public: |
---|
72 | ///The type of the underlying graph. |
---|
73 | typedef GR Graph; |
---|
74 | ///\e |
---|
75 | typedef typename Graph::Node Node; |
---|
76 | ///\e |
---|
77 | typedef typename Graph::NodeIt NodeIt; |
---|
78 | ///\e |
---|
79 | typedef typename Graph::Edge Edge; |
---|
80 | ///\e |
---|
81 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
---|
82 | |
---|
83 | ///The type of the length of the edges. |
---|
84 | typedef typename LM::ValueType ValueType; |
---|
85 | ///The type of the map that stores the edge lengths. |
---|
86 | typedef LM LengthMap; |
---|
87 | ///\brief The type of the map that stores the last |
---|
88 | ///edges of the shortest paths. |
---|
89 | typedef typename Graph::template NodeMap<Edge> PredMap; |
---|
90 | ///\brief The type of the map that stores the last but one |
---|
91 | ///nodes of the shortest paths. |
---|
92 | typedef typename Graph::template NodeMap<Node> PredNodeMap; |
---|
93 | ///The type of the map that stores the dists of the nodes. |
---|
94 | typedef typename Graph::template NodeMap<ValueType> DistMap; |
---|
95 | |
---|
96 | private: |
---|
97 | /// Pointer to the underlying graph. |
---|
98 | const Graph *G; |
---|
99 | /// Pointer to the length map |
---|
100 | const LM *length; |
---|
101 | ///Pointer to the map of predecessors edges. |
---|
102 | PredMap *predecessor; |
---|
103 | ///Indicates if \ref predecessor is locally allocated (\c true) or not. |
---|
104 | bool local_predecessor; |
---|
105 | ///Pointer to the map of predecessors nodes. |
---|
106 | PredNodeMap *pred_node; |
---|
107 | ///Indicates if \ref pred_node is locally allocated (\c true) or not. |
---|
108 | bool local_pred_node; |
---|
109 | ///Pointer to the map of distances. |
---|
110 | DistMap *distance; |
---|
111 | ///Indicates if \ref distance is locally allocated (\c true) or not. |
---|
112 | bool local_distance; |
---|
113 | |
---|
114 | ///The source node of the last execution. |
---|
115 | Node source; |
---|
116 | |
---|
117 | ///Initializes the maps. |
---|
118 | |
---|
119 | ///\todo Error if \c G or are \c NULL. What about \c length? |
---|
120 | ///\todo Better memory allocation (instead of new). |
---|
121 | void init_maps() |
---|
122 | { |
---|
123 | if(!predecessor) { |
---|
124 | local_predecessor = true; |
---|
125 | predecessor = new PredMap(*G); |
---|
126 | } |
---|
127 | if(!pred_node) { |
---|
128 | local_pred_node = true; |
---|
129 | pred_node = new PredNodeMap(*G); |
---|
130 | } |
---|
131 | if(!distance) { |
---|
132 | local_distance = true; |
---|
133 | distance = new DistMap(*G); |
---|
134 | } |
---|
135 | } |
---|
136 | |
---|
137 | public : |
---|
138 | ///Constructor. |
---|
139 | |
---|
140 | ///\param _G the graph the algorithm will run on. |
---|
141 | ///\param _length the length map used by the algorithm. |
---|
142 | Dijkstra(const Graph& _G, const LM& _length) : |
---|
143 | G(&_G), length(&_length), |
---|
144 | predecessor(NULL), local_predecessor(false), |
---|
145 | pred_node(NULL), local_pred_node(false), |
---|
146 | distance(NULL), local_distance(false) |
---|
147 | { } |
---|
148 | |
---|
149 | ///Destructor. |
---|
150 | ~Dijkstra() |
---|
151 | { |
---|
152 | if(local_predecessor) delete predecessor; |
---|
153 | if(local_pred_node) delete pred_node; |
---|
154 | if(local_distance) delete distance; |
---|
155 | } |
---|
156 | |
---|
157 | ///Sets the length map. |
---|
158 | |
---|
159 | ///Sets the length map. |
---|
160 | ///\return <tt> (*this) </tt> |
---|
161 | Dijkstra &setLengthMap(const LM &m) |
---|
162 | { |
---|
163 | length = &m; |
---|
164 | return *this; |
---|
165 | } |
---|
166 | |
---|
167 | ///Sets the map storing the predecessor edges. |
---|
168 | |
---|
169 | ///Sets the map storing the predecessor edges. |
---|
170 | ///If you don't use this function before calling \ref run(), |
---|
171 | ///it will allocate one. The destuctor deallocates this |
---|
172 | ///automatically allocated map, of course. |
---|
173 | ///\return <tt> (*this) </tt> |
---|
174 | Dijkstra &setPredMap(PredMap &m) |
---|
175 | { |
---|
176 | if(local_predecessor) { |
---|
177 | delete predecessor; |
---|
178 | local_predecessor=false; |
---|
179 | } |
---|
180 | predecessor = &m; |
---|
181 | return *this; |
---|
182 | } |
---|
183 | |
---|
184 | ///Sets the map storing the predecessor nodes. |
---|
185 | |
---|
186 | ///Sets the map storing the predecessor nodes. |
---|
187 | ///If you don't use this function before calling \ref run(), |
---|
188 | ///it will allocate one. The destuctor deallocates this |
---|
189 | ///automatically allocated map, of course. |
---|
190 | ///\return <tt> (*this) </tt> |
---|
191 | Dijkstra &setPredNodeMap(PredNodeMap &m) |
---|
192 | { |
---|
193 | if(local_pred_node) { |
---|
194 | delete pred_node; |
---|
195 | local_pred_node=false; |
---|
196 | } |
---|
197 | pred_node = &m; |
---|
198 | return *this; |
---|
199 | } |
---|
200 | |
---|
201 | ///Sets the map storing the distances calculated by the algorithm. |
---|
202 | |
---|
203 | ///Sets the map storing the distances calculated by the algorithm. |
---|
204 | ///If you don't use this function before calling \ref run(), |
---|
205 | ///it will allocate one. The destuctor deallocates this |
---|
206 | ///automatically allocated map, of course. |
---|
207 | ///\return <tt> (*this) </tt> |
---|
208 | Dijkstra &setDistMap(DistMap &m) |
---|
209 | { |
---|
210 | if(local_distance) { |
---|
211 | delete distance; |
---|
212 | local_distance=false; |
---|
213 | } |
---|
214 | distance = &m; |
---|
215 | return *this; |
---|
216 | } |
---|
217 | |
---|
218 | ///Runs %Dijkstra algorithm from node \c s. |
---|
219 | |
---|
220 | ///This method runs the %Dijkstra algorithm from a root node \c s |
---|
221 | ///in order to |
---|
222 | ///compute the |
---|
223 | ///shortest path to each node. The algorithm computes |
---|
224 | ///- The shortest path tree. |
---|
225 | ///- The distance of each node from the root. |
---|
226 | |
---|
227 | void run(Node s) { |
---|
228 | |
---|
229 | init_maps(); |
---|
230 | |
---|
231 | source = s; |
---|
232 | |
---|
233 | for ( NodeIt u(*G) ; u!=INVALID ; ++u ) { |
---|
234 | predecessor->set(u,INVALID); |
---|
235 | pred_node->set(u,INVALID); |
---|
236 | } |
---|
237 | |
---|
238 | typename GR::template NodeMap<int> heap_map(*G,-1); |
---|
239 | |
---|
240 | typedef Heap<Node, ValueType, typename GR::template NodeMap<int>, |
---|
241 | std::less<ValueType> > |
---|
242 | HeapType; |
---|
243 | |
---|
244 | HeapType heap(heap_map); |
---|
245 | |
---|
246 | heap.push(s,0); |
---|
247 | |
---|
248 | while ( !heap.empty() ) { |
---|
249 | |
---|
250 | Node v=heap.top(); |
---|
251 | ValueType oldvalue=heap[v]; |
---|
252 | heap.pop(); |
---|
253 | distance->set(v, oldvalue); |
---|
254 | |
---|
255 | |
---|
256 | for(OutEdgeIt e(*G,v); e!=INVALID; ++e) { |
---|
257 | Node w=G->head(e); |
---|
258 | switch(heap.state(w)) { |
---|
259 | case HeapType::PRE_HEAP: |
---|
260 | heap.push(w,oldvalue+(*length)[e]); |
---|
261 | predecessor->set(w,e); |
---|
262 | pred_node->set(w,v); |
---|
263 | break; |
---|
264 | case HeapType::IN_HEAP: |
---|
265 | if ( oldvalue+(*length)[e] < heap[w] ) { |
---|
266 | heap.decrease(w, oldvalue+(*length)[e]); |
---|
267 | predecessor->set(w,e); |
---|
268 | pred_node->set(w,v); |
---|
269 | } |
---|
270 | break; |
---|
271 | case HeapType::POST_HEAP: |
---|
272 | break; |
---|
273 | } |
---|
274 | } |
---|
275 | } |
---|
276 | } |
---|
277 | |
---|
278 | ///The distance of a node from the root. |
---|
279 | |
---|
280 | ///Returns the distance of a node from the root. |
---|
281 | ///\pre \ref run() must be called before using this function. |
---|
282 | ///\warning If node \c v in unreachable from the root the return value |
---|
283 | ///of this funcion is undefined. |
---|
284 | ValueType dist(Node v) const { return (*distance)[v]; } |
---|
285 | |
---|
286 | ///Returns the 'previous edge' of the shortest path tree. |
---|
287 | |
---|
288 | ///For a node \c v it returns the 'previous edge' of the shortest path tree, |
---|
289 | ///i.e. it returns the last edge of a shortest path from the root to \c |
---|
290 | ///v. It is \ref INVALID |
---|
291 | ///if \c v is unreachable from the root or if \c v=s. The |
---|
292 | ///shortest path tree used here is equal to the shortest path tree used in |
---|
293 | ///\ref predNode(Node v). \pre \ref run() must be called before using |
---|
294 | ///this function. |
---|
295 | ///\todo predEdge could be a better name. |
---|
296 | Edge pred(Node v) const { return (*predecessor)[v]; } |
---|
297 | |
---|
298 | ///Returns the 'previous node' of the shortest path tree. |
---|
299 | |
---|
300 | ///For a node \c v it returns the 'previous node' of the shortest path tree, |
---|
301 | ///i.e. it returns the last but one node from a shortest path from the |
---|
302 | ///root to \c /v. It is INVALID if \c v is unreachable from the root or if |
---|
303 | ///\c v=s. The shortest path tree used here is equal to the shortest path |
---|
304 | ///tree used in \ref pred(Node v). \pre \ref run() must be called before |
---|
305 | ///using this function. |
---|
306 | Node predNode(Node v) const { return (*pred_node)[v]; } |
---|
307 | |
---|
308 | ///Returns a reference to the NodeMap of distances. |
---|
309 | |
---|
310 | ///Returns a reference to the NodeMap of distances. \pre \ref run() must |
---|
311 | ///be called before using this function. |
---|
312 | const DistMap &distMap() const { return *distance;} |
---|
313 | |
---|
314 | ///Returns a reference to the shortest path tree map. |
---|
315 | |
---|
316 | ///Returns a reference to the NodeMap of the edges of the |
---|
317 | ///shortest path tree. |
---|
318 | ///\pre \ref run() must be called before using this function. |
---|
319 | const PredMap &predMap() const { return *predecessor;} |
---|
320 | |
---|
321 | ///Returns a reference to the map of nodes of shortest paths. |
---|
322 | |
---|
323 | ///Returns a reference to the NodeMap of the last but one nodes of the |
---|
324 | ///shortest path tree. |
---|
325 | ///\pre \ref run() must be called before using this function. |
---|
326 | const PredNodeMap &predNodeMap() const { return *pred_node;} |
---|
327 | |
---|
328 | ///Checks if a node is reachable from the root. |
---|
329 | |
---|
330 | ///Returns \c true if \c v is reachable from the root. |
---|
331 | ///\note The root node is reported to be reached! |
---|
332 | ///\pre \ref run() must be called before using this function. |
---|
333 | /// |
---|
334 | bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; } |
---|
335 | |
---|
336 | }; |
---|
337 | |
---|
338 | /// @} |
---|
339 | |
---|
340 | } //END OF NAMESPACE LEMON |
---|
341 | |
---|
342 | #endif |
---|
343 | |
---|
344 | |
---|