COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/lemon/dijkstra.h @ 947:93e9c45703ea

Last change on this file since 947:93e9c45703ea was 921:818510fa3d99, checked in by Alpar Juttner, 16 years ago

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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
27namespace 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 skeleton::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 skeleton::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 skeleton::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
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