Skeleton for paths.
2 #ifndef HUGO_DIJKSTRA_H
3 #define HUGO_DIJKSTRA_H
7 ///\brief Dijkstra algorithm.
9 #include <hugo/bin_heap.h>
10 #include <hugo/invalid.h>
17 ///%Dijkstra algorithm class.
19 ///This class provides an efficient implementation of %Dijkstra algorithm.
20 ///The edge lengths are passed to the algorithm using a
21 ///\ref ReadMapSkeleton "readable map",
22 ///so it is easy to change it to any kind of length.
24 ///The type of the length is determined by the \c ValueType of the length map.
26 ///It is also possible to change the underlying priority heap.
28 ///\param GR The graph type the algorithm runs on.
29 ///\param LM This read-only
32 ///lengths of the edges. It is read once for each edge, so the map
33 ///may involve in relatively time consuming process to compute the edge
34 ///length if it is necessary. The default map type is
35 ///\ref GraphSkeleton::EdgeMap "Graph::EdgeMap<int>"
36 ///\param Heap The heap type used by the %Dijkstra
37 ///algorithm. The default
38 ///is using \ref BinHeap "binary heap".
40 ///\author Jacint Szabo and Alpar Juttner
41 ///\todo We need a typedef-names should be standardized. (-:
44 template <typename GR,
48 template <typename GR,
49 typename LM=typename GR::template EdgeMap<int>,
50 template <class,class,class,class> class Heap = BinHeap >
54 ///The type of the underlying graph.
56 typedef typename Graph::Node Node;
57 typedef typename Graph::NodeIt NodeIt;
58 typedef typename Graph::Edge Edge;
59 typedef typename Graph::OutEdgeIt OutEdgeIt;
61 ///The type of the length of the edges.
62 typedef typename LM::ValueType ValueType;
63 ///The type of the map that stores the edge lengths.
65 ///\brief The type of the map that stores the last
66 ///edges of the shortest paths.
67 typedef typename Graph::template NodeMap<Edge> PredMap;
68 ///\brief The type of the map that stores the last but one
69 ///nodes of the shortest paths.
70 typedef typename Graph::template NodeMap<Node> PredNodeMap;
71 ///The type of the map that stores the dists of the nodes.
72 typedef typename Graph::template NodeMap<ValueType> DistMap;
79 bool local_predecessor;
80 PredNodeMap *pred_node;
87 ///\todo Error if \c G or are \c NULL. What about \c length?
88 ///\todo Better memory allocation (instead of new).
92 // local_length = true;
93 // length = new LM(G);
96 local_predecessor = true;
97 predecessor = new PredMap(*G);
100 local_pred_node = true;
101 pred_node = new PredNodeMap(*G);
104 local_distance = true;
105 distance = new DistMap(*G);
111 Dijkstra(const Graph& _G, const LM& _length) :
112 G(&_G), length(&_length),
113 predecessor(NULL), pred_node(NULL), distance(NULL),
114 local_predecessor(false), local_pred_node(false), local_distance(false)
119 // if(local_length) delete length;
120 if(local_predecessor) delete predecessor;
121 if(local_pred_node) delete pred_node;
122 if(local_distance) delete distance;
125 ///Sets the graph the algorithm will run on.
127 ///Sets the graph the algorithm will run on.
128 ///\return <tt> (*this) </tt>
129 Dijkstra &setGraph(const Graph &_G)
134 ///Sets the length map.
136 ///Sets the length map.
137 ///\return <tt> (*this) </tt>
138 Dijkstra &setLengthMap(const LM &m)
140 // if(local_length) {
142 // local_length=false;
148 ///Sets the map storing the predecessor edges.
150 ///Sets the map storing the predecessor edges.
151 ///If you don't use this function before calling \ref run(),
152 ///it will allocate one. The destuctor deallocates this
153 ///automatically allocated map, of course.
154 ///\return <tt> (*this) </tt>
155 Dijkstra &setPredMap(PredMap &m)
157 if(local_predecessor) {
159 local_predecessor=false;
165 ///Sets the map storing the predecessor nodes.
167 ///Sets the map storing the predecessor nodes.
168 ///If you don't use this function before calling \ref run(),
169 ///it will allocate one. The destuctor deallocates this
170 ///automatically allocated map, of course.
171 ///\return <tt> (*this) </tt>
172 Dijkstra &setPredNodeMap(PredNodeMap &m)
174 if(local_pred_node) {
176 local_pred_node=false;
182 ///Sets the map storing the distances calculated by the algorithm.
184 ///Sets the map storing the distances calculated by the algorithm.
185 ///If you don't use this function before calling \ref run(),
186 ///it will allocate one. The destuctor deallocates this
187 ///automatically allocated map, of course.
188 ///\return <tt> (*this) </tt>
189 Dijkstra &setDistMap(DistMap &m)
193 local_distance=false;
199 ///Runs %Dijkstra algorithm from node \c s.
201 ///This method runs the %Dijkstra algorithm from a root node \c s
204 ///shortest path to each node. The algorithm computes
205 ///- The shortest path tree.
206 ///- The distance of each node from the root.
212 for ( NodeIt u(*G) ; G->valid(u) ; G->next(u) ) {
213 predecessor->set(u,INVALID);
214 pred_node->set(u,INVALID);
217 typename GR::template NodeMap<int> heap_map(*G,-1);
219 typedef Heap<Node, ValueType, typename GR::template NodeMap<int>,
220 std::less<ValueType> >
223 HeapType heap(heap_map);
227 while ( !heap.empty() ) {
230 ValueType oldvalue=heap[v];
232 distance->set(v, oldvalue);
235 for(OutEdgeIt e(*G,v); G->valid(e); G->next(e)) {
238 switch(heap.state(w)) {
239 case HeapType::PRE_HEAP:
240 heap.push(w,oldvalue+(*length)[e]);
241 predecessor->set(w,e);
244 case HeapType::IN_HEAP:
245 if ( oldvalue+(*length)[e] < heap[w] ) {
246 heap.decrease(w, oldvalue+(*length)[e]);
247 predecessor->set(w,e);
251 case HeapType::POST_HEAP:
258 ///The distance of a node from the root.
260 ///Returns the distance of a node from the root.
261 ///\pre \ref run() must be called before using this function.
262 ///\warning If node \c v in unreachable from the root the return value
263 ///of this funcion is undefined.
264 ValueType dist(Node v) const { return (*distance)[v]; }
266 ///Returns the 'previous edge' of the shortest path tree.
268 ///For a node \c v it returns the 'previous edge' of the shortest path tree,
269 ///i.e. it returns the last edge from a shortest path from the root to \c
270 ///v. It is \ref INVALID
271 ///if \c v is unreachable from the root or if \c v=s. The
272 ///shortest path tree used here is equal to the shortest path tree used in
273 ///\ref predNode(Node v). \pre \ref run() must be called before using
275 Edge pred(Node v) const { return (*predecessor)[v]; }
277 ///Returns the 'previous node' of the shortest path tree.
279 ///For a node \c v it returns the 'previous node' of the shortest path tree,
280 ///i.e. it returns the last but one node from a shortest path from the
281 ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
282 ///\c v=s. The shortest path tree used here is equal to the shortest path
283 ///tree used in \ref pred(Node v). \pre \ref run() must be called before
284 ///using this function.
285 Node predNode(Node v) const { return (*pred_node)[v]; }
287 ///Returns a reference to the NodeMap of distances.
289 ///Returns a reference to the NodeMap of distances. \pre \ref run() must
290 ///be called before using this function.
291 const DistMap &distMap() const { return *distance;}
293 ///Returns a reference to the shortest path tree map.
295 ///Returns a reference to the NodeMap of the edges of the
296 ///shortest path tree.
297 ///\pre \ref run() must be called before using this function.
298 const PredMap &predMap() const { return *predecessor;}
300 ///Returns a reference to the map of nodes of shortest paths.
302 ///Returns a reference to the NodeMap of the last but one nodes of the
303 ///shortest path tree.
304 ///\pre \ref run() must be called before using this function.
305 const PredNodeMap &predNodeMap() const { return *pred_node;}
307 ///Checks if a node is reachable from the root.
309 ///Returns \c true if \c v is reachable from the root.
310 ///\warning the root node is reported to be unreached!
311 ///\todo Is this what we want?
312 ///\pre \ref run() must be called before using this function.
314 bool reached(Node v) { return G->valid((*predecessor)[v]); }
319 // **********************************************************************
321 // **********************************************************************
325 } //END OF NAMESPACE HUGO