COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/work/deba/dijkstra.h @ 987:87f7c54892df

Last change on this file since 987:87f7c54892df was 987:87f7c54892df, checked in by Alpar Juttner, 15 years ago

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1// -*- C++ -*-
2#ifndef LEMON_DIJKSTRA_H
3#define LEMON_DIJKSTRA_H
4
5///\ingroup galgs
6///\file
7///\brief Dijkstra algorithm.
8
9#include <lemon/bin_heap.h>
10#include <lemon/invalid.h>
11
12namespace lemon {
13
14/// \addtogroup galgs
15/// @{
16
17  ///%Dijkstra algorithm class.
18
19  ///This class provides an efficient implementation of %Dijkstra algorithm.
20  ///The edge lengths are passed to the algorithm using a
21  ///\ref ReadMap "readable map",
22  ///so it is easy to change it to any kind of length.
23  ///
24  ///The type of the length is determined by the \c Value of the length map.
25  ///
26  ///It is also possible to change the underlying priority heap.
27  ///
28  ///\param GR The graph type the algorithm runs on.
29  ///\param LM This read-only
30  ///EdgeMap
31  ///determines the
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 Graph::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".
39  ///
40  ///\author Jacint Szabo and Alpar Juttner
41  ///\todo We need a typedef-names should be standardized. (-:
42
43#ifdef DOXYGEN
44  template <typename GR,
45            typename LM,
46            typename Heap>
47#else
48  template <typename GR,
49            typename LM=typename GR::template EdgeMap<int>,
50            template <class,class,class,class> class Heap = BinHeap >
51#endif
52  class Dijkstra{
53  public:
54    ///The type of the underlying graph.
55    typedef GR 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;
60   
61    ///The type of the length of the edges.
62    typedef typename LM::Value Value;
63    ///The type of the map that stores the edge lengths.
64    typedef LM LengthMap;
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<Value> DistMap;
73
74  private:
75    const Graph *G;
76    const LM *length;
77    //    bool local_length;
78    PredMap *predecessor;
79    bool local_predecessor;
80    PredNodeMap *pred_node;
81    bool local_pred_node;
82    DistMap *distance;
83    bool local_distance;
84
85    ///Initialize maps
86   
87    ///\todo Error if \c G or are \c NULL. What about \c length?
88    ///\todo Better memory allocation (instead of new).
89    void init_maps()
90    {
91//       if(!length) {
92//      local_length = true;
93//      length = new LM(G);
94//       }
95      if(!predecessor) {
96        local_predecessor = true;
97        predecessor = new PredMap(*G);
98      }
99      if(!pred_node) {
100        local_pred_node = true;
101        pred_node = new PredNodeMap(*G);
102      }
103      if(!distance) {
104        local_distance = true;
105        distance = new DistMap(*G);
106      }
107    }
108   
109  public :
110   
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)
115    { }
116   
117    ~Dijkstra()
118    {
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;
123    }
124
125    ///Sets the graph the algorithm will run on.
126
127    ///Sets the graph the algorithm will run on.
128    ///\return <tt> (*this) </tt>
129    Dijkstra &setGraph(const Graph &_G)
130    {
131      G = &_G;
132      return *this;
133    }
134    ///Sets the length map.
135
136    ///Sets the length map.
137    ///\return <tt> (*this) </tt>
138    Dijkstra &setLengthMap(const LM &m)
139    {
140//       if(local_length) {
141//      delete length;
142//      local_length=false;
143//       }
144      length = &m;
145      return *this;
146    }
147
148    ///Sets the map storing the predecessor edges.
149
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)
156    {
157      if(local_predecessor) {
158        delete predecessor;
159        local_predecessor=false;
160      }
161      predecessor = &m;
162      return *this;
163    }
164
165    ///Sets the map storing the predecessor nodes.
166
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)
173    {
174      if(local_pred_node) {
175        delete pred_node;
176        local_pred_node=false;
177      }
178      pred_node = &m;
179      return *this;
180    }
181
182    ///Sets the map storing the distances calculated by the algorithm.
183
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)
190    {
191      if(local_distance) {
192        delete distance;
193        local_distance=false;
194      }
195      distance = &m;
196      return *this;
197    }
198   
199  ///Runs %Dijkstra algorithm from node \c s.
200
201  ///This method runs the %Dijkstra algorithm from a root node \c s
202  ///in order to
203  ///compute the
204  ///shortest path to each node. The algorithm computes
205  ///- The shortest path tree.
206  ///- The distance of each node from the root.
207   
208    void run(Node s) {
209     
210      init_maps();
211     
212      for ( NodeIt u(*G) ; G->valid(u) ; G->next(u) ) {
213        predecessor->set(u,INVALID);
214        pred_node->set(u,INVALID);
215      }
216     
217      typename GR::template NodeMap<int> heap_map(*G,-1);
218     
219      typedef Heap<Node, Value, typename GR::template NodeMap<int>,
220      std::less<Value> >
221      HeapType;
222     
223      HeapType heap(heap_map);
224     
225      heap.push(s,0);
226     
227      while ( !heap.empty() ) {
228       
229        Node v=heap.top();
230        Value oldvalue=heap[v];
231        heap.pop();
232        distance->set(v, oldvalue);
233       
234       
235        for(OutEdgeIt e(*G,v); G->valid(e); G->next(e)) {
236          Node w=G->bNode(e);
237         
238          switch(heap.state(w)) {
239          case HeapType::PRE_HEAP:
240            heap.push(w,oldvalue+(*length)[e]);
241            predecessor->set(w,e);
242            pred_node->set(w,v);
243            break;
244          case HeapType::IN_HEAP:
245            if ( oldvalue+(*length)[e] < heap[w] ) {
246              heap.decrease(w, oldvalue+(*length)[e]);
247              predecessor->set(w,e);
248              pred_node->set(w,v);
249            }
250            break;
251          case HeapType::POST_HEAP:
252            break;
253          }
254        }
255      }
256    }
257   
258    ///The distance of a node from the root.
259
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    Value dist(Node v) const { return (*distance)[v]; }
265
266    ///Returns the 'previous edge' of the shortest path tree.
267
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
274    ///this function.
275    Edge pred(Node v) const { return (*predecessor)[v]; }
276
277    ///Returns the 'previous node' of the shortest path tree.
278
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]; }
286   
287    ///Returns a reference to the NodeMap of distances.
288
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;}
292 
293    ///Returns a reference to the shortest path tree map.
294
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;}
299 
300    ///Returns a reference to the map of nodes of shortest paths.
301
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;}
306
307    ///Checks if a node is reachable from the root.
308
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.
313    ///
314    bool reached(Node v) { return G->valid((*predecessor)[v]); }
315   
316  };
317 
318
319  // **********************************************************************
320  //  IMPLEMENTATIONS
321  // **********************************************************************
322
323/// @}
324 
325} //END OF NAMESPACE LEMON
326
327#endif
328
329
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