1 | /* -*- C++ -*- |
---|
2 | * src/lemon/bfs.h - Part of LEMON, a generic C++ optimization library |
---|
3 | * |
---|
4 | * Copyright (C) 2005 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_BFS_H |
---|
18 | #define LEMON_BFS_H |
---|
19 | |
---|
20 | ///\ingroup flowalgs |
---|
21 | ///\file |
---|
22 | ///\brief Bfs algorithm. |
---|
23 | /// |
---|
24 | ///\todo Revise Manual. |
---|
25 | |
---|
26 | #include <lemon/bin_heap.h> |
---|
27 | #include <lemon/invalid.h> |
---|
28 | #include <lemon/graph_utils.h> |
---|
29 | |
---|
30 | namespace lemon { |
---|
31 | |
---|
32 | /// \addtogroup flowalgs |
---|
33 | /// @{ |
---|
34 | |
---|
35 | ///%BFS algorithm class. |
---|
36 | |
---|
37 | ///This class provides an efficient implementation of %BFS algorithm. |
---|
38 | ///\param GR The graph type the algorithm runs on. |
---|
39 | ///This class does the same as Dijkstra does with constant 1 edge length, |
---|
40 | ///but it is faster. |
---|
41 | /// |
---|
42 | ///\author Alpar Juttner |
---|
43 | |
---|
44 | #ifdef DOXYGEN |
---|
45 | template <typename GR> |
---|
46 | #else |
---|
47 | template <typename GR> |
---|
48 | #endif |
---|
49 | class Bfs{ |
---|
50 | public: |
---|
51 | ///The type of the underlying graph. |
---|
52 | typedef GR Graph; |
---|
53 | ///\e |
---|
54 | typedef typename Graph::Node Node; |
---|
55 | ///\e |
---|
56 | typedef typename Graph::NodeIt NodeIt; |
---|
57 | ///\e |
---|
58 | typedef typename Graph::Edge Edge; |
---|
59 | ///\e |
---|
60 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
---|
61 | |
---|
62 | ///\brief The type of the map that stores the last |
---|
63 | ///edges of the shortest paths. |
---|
64 | typedef typename Graph::template NodeMap<Edge> PredMap; |
---|
65 | ///\brief The type of the map that stores the last but one |
---|
66 | ///nodes of the shortest paths. |
---|
67 | typedef typename Graph::template NodeMap<Node> PredNodeMap; |
---|
68 | ///The type of the map that stores the dists of the nodes. |
---|
69 | typedef typename Graph::template NodeMap<int> DistMap; |
---|
70 | |
---|
71 | private: |
---|
72 | /// Pointer to the underlying graph. |
---|
73 | const Graph *G; |
---|
74 | ///Pointer to the map of predecessors edges. |
---|
75 | PredMap *predecessor; |
---|
76 | ///Indicates if \ref predecessor is locally allocated (\c true) or not. |
---|
77 | bool local_predecessor; |
---|
78 | ///Pointer to the map of predecessors nodes. |
---|
79 | PredNodeMap *pred_node; |
---|
80 | ///Indicates if \ref pred_node is locally allocated (\c true) or not. |
---|
81 | bool local_pred_node; |
---|
82 | ///Pointer to the map of distances. |
---|
83 | DistMap *distance; |
---|
84 | ///Indicates if \ref distance is locally allocated (\c true) or not. |
---|
85 | bool local_distance; |
---|
86 | |
---|
87 | ///The source node of the last execution. |
---|
88 | Node source; |
---|
89 | |
---|
90 | |
---|
91 | ///Initializes the maps. |
---|
92 | void init_maps() |
---|
93 | { |
---|
94 | if(!predecessor) { |
---|
95 | local_predecessor = true; |
---|
96 | predecessor = new PredMap(*G); |
---|
97 | } |
---|
98 | if(!pred_node) { |
---|
99 | local_pred_node = true; |
---|
100 | pred_node = new PredNodeMap(*G); |
---|
101 | } |
---|
102 | if(!distance) { |
---|
103 | local_distance = true; |
---|
104 | distance = new DistMap(*G); |
---|
105 | } |
---|
106 | } |
---|
107 | |
---|
108 | public : |
---|
109 | ///Constructor. |
---|
110 | |
---|
111 | ///\param _G the graph the algorithm will run on. |
---|
112 | /// |
---|
113 | Bfs(const Graph& _G) : |
---|
114 | G(&_G), |
---|
115 | predecessor(NULL), local_predecessor(false), |
---|
116 | pred_node(NULL), local_pred_node(false), |
---|
117 | distance(NULL), local_distance(false) |
---|
118 | { } |
---|
119 | |
---|
120 | ///Destructor. |
---|
121 | ~Bfs() |
---|
122 | { |
---|
123 | if(local_predecessor) delete predecessor; |
---|
124 | if(local_pred_node) delete pred_node; |
---|
125 | if(local_distance) delete distance; |
---|
126 | } |
---|
127 | |
---|
128 | ///Sets the map storing the predecessor edges. |
---|
129 | |
---|
130 | ///Sets the map storing the predecessor edges. |
---|
131 | ///If you don't use this function before calling \ref run(), |
---|
132 | ///it will allocate one. The destuctor deallocates this |
---|
133 | ///automatically allocated map, of course. |
---|
134 | ///\return <tt> (*this) </tt> |
---|
135 | Bfs &setPredMap(PredMap &m) |
---|
136 | { |
---|
137 | if(local_predecessor) { |
---|
138 | delete predecessor; |
---|
139 | local_predecessor=false; |
---|
140 | } |
---|
141 | predecessor = &m; |
---|
142 | return *this; |
---|
143 | } |
---|
144 | |
---|
145 | ///Sets the map storing the predecessor nodes. |
---|
146 | |
---|
147 | ///Sets the map storing the predecessor nodes. |
---|
148 | ///If you don't use this function before calling \ref run(), |
---|
149 | ///it will allocate one. The destuctor deallocates this |
---|
150 | ///automatically allocated map, of course. |
---|
151 | ///\return <tt> (*this) </tt> |
---|
152 | Bfs &setPredNodeMap(PredNodeMap &m) |
---|
153 | { |
---|
154 | if(local_pred_node) { |
---|
155 | delete pred_node; |
---|
156 | local_pred_node=false; |
---|
157 | } |
---|
158 | pred_node = &m; |
---|
159 | return *this; |
---|
160 | } |
---|
161 | |
---|
162 | ///Sets the map storing the distances calculated by the algorithm. |
---|
163 | |
---|
164 | ///Sets the map storing the distances calculated by the algorithm. |
---|
165 | ///If you don't use this function before calling \ref run(), |
---|
166 | ///it will allocate one. The destuctor deallocates this |
---|
167 | ///automatically allocated map, of course. |
---|
168 | ///\return <tt> (*this) </tt> |
---|
169 | Bfs &setDistMap(DistMap &m) |
---|
170 | { |
---|
171 | if(local_distance) { |
---|
172 | delete distance; |
---|
173 | local_distance=false; |
---|
174 | } |
---|
175 | distance = &m; |
---|
176 | return *this; |
---|
177 | } |
---|
178 | |
---|
179 | ///Runs %BFS algorithm from node \c s. |
---|
180 | |
---|
181 | ///This method runs the %BFS algorithm from a root node \c s |
---|
182 | ///in order to |
---|
183 | ///compute a |
---|
184 | ///shortest path to each node. The algorithm computes |
---|
185 | ///- The %BFS tree. |
---|
186 | ///- The distance of each node from the root. |
---|
187 | |
---|
188 | void run(Node s) { |
---|
189 | |
---|
190 | init_maps(); |
---|
191 | |
---|
192 | source = s; |
---|
193 | |
---|
194 | for ( NodeIt u(*G) ; u!=INVALID ; ++u ) { |
---|
195 | predecessor->set(u,INVALID); |
---|
196 | pred_node->set(u,INVALID); |
---|
197 | } |
---|
198 | |
---|
199 | int N = countNodes(*G); |
---|
200 | std::vector<typename Graph::Node> Q(N); |
---|
201 | int Qh=0; |
---|
202 | int Qt=0; |
---|
203 | |
---|
204 | Q[Qh++]=source; |
---|
205 | distance->set(s, 0); |
---|
206 | do { |
---|
207 | Node m; |
---|
208 | Node n=Q[Qt++]; |
---|
209 | int d= (*distance)[n]+1; |
---|
210 | |
---|
211 | for(OutEdgeIt e(*G,n);e!=INVALID;++e) |
---|
212 | if((m=G->target(e))!=s && (*predecessor)[m]==INVALID) { |
---|
213 | Q[Qh++]=m; |
---|
214 | predecessor->set(m,e); |
---|
215 | pred_node->set(m,n); |
---|
216 | distance->set(m,d); |
---|
217 | } |
---|
218 | } while(Qt!=Qh); |
---|
219 | } |
---|
220 | |
---|
221 | ///The distance of a node from the root. |
---|
222 | |
---|
223 | ///Returns the distance of a node from the root. |
---|
224 | ///\pre \ref run() must be called before using this function. |
---|
225 | ///\warning If node \c v in unreachable from the root the return value |
---|
226 | ///of this funcion is undefined. |
---|
227 | int dist(Node v) const { return (*distance)[v]; } |
---|
228 | |
---|
229 | ///Returns the 'previous edge' of the %BFS path tree. |
---|
230 | |
---|
231 | ///For a node \c v it returns the 'previous edge' of the %BFS tree, |
---|
232 | ///i.e. it returns the last edge of a shortest path from the root to \c |
---|
233 | ///v. It is \ref INVALID |
---|
234 | ///if \c v is unreachable from the root or if \c v=s. The |
---|
235 | ///%BFS tree used here is equal to the %BFS tree used in |
---|
236 | ///\ref predNode(Node v). \pre \ref run() must be called before using |
---|
237 | ///this function. |
---|
238 | Edge pred(Node v) const { return (*predecessor)[v]; } |
---|
239 | |
---|
240 | ///Returns the 'previous node' of the %BFS tree. |
---|
241 | |
---|
242 | ///For a node \c v it returns the 'previous node' on the %BFS tree, |
---|
243 | ///i.e. it returns the last but one node from a shortest path from the |
---|
244 | ///root to \c /v. It is INVALID if \c v is unreachable from the root or if |
---|
245 | ///\c v=s. The shortest path tree used here is equal to the %BFS |
---|
246 | ///tree used in \ref pred(Node v). \pre \ref run() must be called before |
---|
247 | ///using this function. |
---|
248 | Node predNode(Node v) const { return (*pred_node)[v]; } |
---|
249 | |
---|
250 | ///Returns a reference to the NodeMap of distances. |
---|
251 | |
---|
252 | ///Returns a reference to the NodeMap of distances. \pre \ref run() must |
---|
253 | ///be called before using this function. |
---|
254 | const DistMap &distMap() const { return *distance;} |
---|
255 | |
---|
256 | ///Returns a reference to the %BFS tree map. |
---|
257 | |
---|
258 | ///Returns a reference to the NodeMap of the edges of the |
---|
259 | ///%BFS tree. |
---|
260 | ///\pre \ref run() must be called before using this function. |
---|
261 | const PredMap &predMap() const { return *predecessor;} |
---|
262 | |
---|
263 | ///Returns a reference to the map of last but one nodes of shortest paths. |
---|
264 | |
---|
265 | ///Returns a reference to the NodeMap of the last but one nodes on the |
---|
266 | ///%BFS tree. |
---|
267 | ///\pre \ref run() must be called before using this function. |
---|
268 | const PredNodeMap &predNodeMap() const { return *pred_node;} |
---|
269 | |
---|
270 | ///Checks if a node is reachable from the root. |
---|
271 | |
---|
272 | ///Returns \c true if \c v is reachable from the root. |
---|
273 | ///\note The root node is reported to be reached! |
---|
274 | /// |
---|
275 | ///\pre \ref run() must be called before using this function. |
---|
276 | /// |
---|
277 | bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; } |
---|
278 | |
---|
279 | }; |
---|
280 | |
---|
281 | /// @} |
---|
282 | |
---|
283 | } //END OF NAMESPACE LEMON |
---|
284 | |
---|
285 | #endif |
---|
286 | |
---|
287 | |
---|