The graph_factory branch (@ 1321) has been merged to trunk.
2 * src/lemon/bfs.h - Part of LEMON, a generic C++ optimization library
4 * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
5 * (Egervary Combinatorial Optimization Research Group, EGRES).
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.
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
22 ///\brief Bfs algorithm.
24 ///\todo Revise Manual.
26 #include <lemon/bin_heap.h>
27 #include <lemon/invalid.h>
31 /// \addtogroup flowalgs
34 ///%BFS algorithm class.
36 ///This class provides an efficient implementation of %BFS algorithm.
37 ///\param GR The graph type the algorithm runs on.
38 ///This class does the same as Dijkstra does with constant 1 edge length,
41 ///\author Alpar Juttner
44 template <typename GR>
46 template <typename GR>
50 ///The type of the underlying graph.
53 typedef typename Graph::Node Node;
55 typedef typename Graph::NodeIt NodeIt;
57 typedef typename Graph::Edge Edge;
59 typedef typename Graph::OutEdgeIt OutEdgeIt;
61 ///\brief The type of the map that stores the last
62 ///edges of the shortest paths.
63 typedef typename Graph::template NodeMap<Edge> PredMap;
64 ///\brief The type of the map that stores the last but one
65 ///nodes of the shortest paths.
66 typedef typename Graph::template NodeMap<Node> PredNodeMap;
67 ///The type of the map that stores the dists of the nodes.
68 typedef typename Graph::template NodeMap<int> DistMap;
71 /// Pointer to the underlying graph.
73 ///Pointer to the map of predecessors edges.
75 ///Indicates if \ref predecessor is locally allocated (\c true) or not.
76 bool local_predecessor;
77 ///Pointer to the map of predecessors nodes.
78 PredNodeMap *pred_node;
79 ///Indicates if \ref pred_node is locally allocated (\c true) or not.
81 ///Pointer to the map of distances.
83 ///Indicates if \ref distance is locally allocated (\c true) or not.
86 ///The source node of the last execution.
90 ///Initializes the maps.
94 local_predecessor = true;
95 predecessor = new PredMap(*G);
98 local_pred_node = true;
99 pred_node = new PredNodeMap(*G);
102 local_distance = true;
103 distance = new DistMap(*G);
110 ///\param _G the graph the algorithm will run on.
112 Bfs(const Graph& _G) :
114 predecessor(NULL), local_predecessor(false),
115 pred_node(NULL), local_pred_node(false),
116 distance(NULL), local_distance(false)
122 if(local_predecessor) delete predecessor;
123 if(local_pred_node) delete pred_node;
124 if(local_distance) delete distance;
127 ///Sets the map storing the predecessor edges.
129 ///Sets the map storing the predecessor edges.
130 ///If you don't use this function before calling \ref run(),
131 ///it will allocate one. The destuctor deallocates this
132 ///automatically allocated map, of course.
133 ///\return <tt> (*this) </tt>
134 Bfs &setPredMap(PredMap &m)
136 if(local_predecessor) {
138 local_predecessor=false;
144 ///Sets the map storing the predecessor nodes.
146 ///Sets the map storing the predecessor nodes.
147 ///If you don't use this function before calling \ref run(),
148 ///it will allocate one. The destuctor deallocates this
149 ///automatically allocated map, of course.
150 ///\return <tt> (*this) </tt>
151 Bfs &setPredNodeMap(PredNodeMap &m)
153 if(local_pred_node) {
155 local_pred_node=false;
161 ///Sets the map storing the distances calculated by the algorithm.
163 ///Sets the map storing the distances calculated by the algorithm.
164 ///If you don't use this function before calling \ref run(),
165 ///it will allocate one. The destuctor deallocates this
166 ///automatically allocated map, of course.
167 ///\return <tt> (*this) </tt>
168 Bfs &setDistMap(DistMap &m)
172 local_distance=false;
178 ///Runs %BFS algorithm from node \c s.
180 ///This method runs the %BFS algorithm from a root node \c s
183 ///shortest path to each node. The algorithm computes
185 ///- The distance of each node from the root.
193 for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
194 predecessor->set(u,INVALID);
195 pred_node->set(u,INVALID);
198 int N = countNodes(*G);
199 std::vector<typename Graph::Node> Q(N);
208 int d= (*distance)[n]+1;
210 for(OutEdgeIt e(*G,n);e!=INVALID;++e)
211 if((m=G->head(e))!=s && (*predecessor)[m]==INVALID) {
213 predecessor->set(m,e);
220 ///The distance of a node from the root.
222 ///Returns the distance of a node from the root.
223 ///\pre \ref run() must be called before using this function.
224 ///\warning If node \c v in unreachable from the root the return value
225 ///of this funcion is undefined.
226 int dist(Node v) const { return (*distance)[v]; }
228 ///Returns the 'previous edge' of the %BFS path tree.
230 ///For a node \c v it returns the 'previous edge' of the %BFS tree,
231 ///i.e. it returns the last edge of a shortest path from the root to \c
232 ///v. It is \ref INVALID
233 ///if \c v is unreachable from the root or if \c v=s. The
234 ///%BFS tree used here is equal to the %BFS tree used in
235 ///\ref predNode(Node v). \pre \ref run() must be called before using
237 Edge pred(Node v) const { return (*predecessor)[v]; }
239 ///Returns the 'previous node' of the %BFS tree.
241 ///For a node \c v it returns the 'previous node' on the %BFS tree,
242 ///i.e. it returns the last but one node from a shortest path from the
243 ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
244 ///\c v=s. The shortest path tree used here is equal to the %BFS
245 ///tree used in \ref pred(Node v). \pre \ref run() must be called before
246 ///using this function.
247 Node predNode(Node v) const { return (*pred_node)[v]; }
249 ///Returns a reference to the NodeMap of distances.
251 ///Returns a reference to the NodeMap of distances. \pre \ref run() must
252 ///be called before using this function.
253 const DistMap &distMap() const { return *distance;}
255 ///Returns a reference to the %BFS tree map.
257 ///Returns a reference to the NodeMap of the edges of the
259 ///\pre \ref run() must be called before using this function.
260 const PredMap &predMap() const { return *predecessor;}
262 ///Returns a reference to the map of last but one nodes of shortest paths.
264 ///Returns a reference to the NodeMap of the last but one nodes on the
266 ///\pre \ref run() must be called before using this function.
267 const PredNodeMap &predNodeMap() const { return *pred_node;}
269 ///Checks if a node is reachable from the root.
271 ///Returns \c true if \c v is reachable from the root.
272 ///\note The root node is reported to be reached!
274 ///\pre \ref run() must be called before using this function.
276 bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
282 } //END OF NAMESPACE LEMON