1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/lemon/bfs.h Wed Sep 29 15:30:04 2004 +0000
1.3 @@ -0,0 +1,286 @@
1.4 +/* -*- C++ -*-
1.5 + * src/lemon/bfs.h - Part of LEMON, a generic C++ optimization library
1.6 + *
1.7 + * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
1.8 + * (Egervary Combinatorial Optimization Research Group, EGRES).
1.9 + *
1.10 + * Permission to use, modify and distribute this software is granted
1.11 + * provided that this copyright notice appears in all copies. For
1.12 + * precise terms see the accompanying LICENSE file.
1.13 + *
1.14 + * This software is provided "AS IS" with no warranty of any kind,
1.15 + * express or implied, and with no claim as to its suitability for any
1.16 + * purpose.
1.17 + *
1.18 + */
1.19 +
1.20 +#ifndef LEMON_BFS_H
1.21 +#define LEMON_BFS_H
1.22 +
1.23 +///\ingroup flowalgs
1.24 +///\file
1.25 +///\brief Bfs algorithm.
1.26 +///
1.27 +///\todo Revise Manual.
1.28 +
1.29 +#include <lemon/bin_heap.h>
1.30 +#include <lemon/invalid.h>
1.31 +
1.32 +namespace lemon {
1.33 +
1.34 +/// \addtogroup flowalgs
1.35 +/// @{
1.36 +
1.37 + ///%BFS algorithm class.
1.38 +
1.39 + ///This class provides an efficient implementation of %BFS algorithm.
1.40 + ///\param GR The graph type the algorithm runs on.
1.41 + ///This class does the same as Dijkstra does with constant 1 edge length,
1.42 + ///but it is faster.
1.43 + ///
1.44 + ///\author Alpar Juttner
1.45 +
1.46 +#ifdef DOXYGEN
1.47 + template <typename GR>
1.48 +#else
1.49 + template <typename GR>
1.50 +#endif
1.51 + class Bfs{
1.52 + public:
1.53 + ///The type of the underlying graph.
1.54 + typedef GR Graph;
1.55 + ///\e
1.56 + typedef typename Graph::Node Node;
1.57 + ///\e
1.58 + typedef typename Graph::NodeIt NodeIt;
1.59 + ///\e
1.60 + typedef typename Graph::Edge Edge;
1.61 + ///\e
1.62 + typedef typename Graph::OutEdgeIt OutEdgeIt;
1.63 +
1.64 + ///\brief The type of the map that stores the last
1.65 + ///edges of the shortest paths.
1.66 + typedef typename Graph::template NodeMap<Edge> PredMap;
1.67 + ///\brief The type of the map that stores the last but one
1.68 + ///nodes of the shortest paths.
1.69 + typedef typename Graph::template NodeMap<Node> PredNodeMap;
1.70 + ///The type of the map that stores the dists of the nodes.
1.71 + typedef typename Graph::template NodeMap<int> DistMap;
1.72 +
1.73 + private:
1.74 + /// Pointer to the underlying graph.
1.75 + const Graph *G;
1.76 + ///Pointer to the map of predecessors edges.
1.77 + PredMap *predecessor;
1.78 + ///Indicates if \ref predecessor is locally allocated (\c true) or not.
1.79 + bool local_predecessor;
1.80 + ///Pointer to the map of predecessors nodes.
1.81 + PredNodeMap *pred_node;
1.82 + ///Indicates if \ref pred_node is locally allocated (\c true) or not.
1.83 + bool local_pred_node;
1.84 + ///Pointer to the map of distances.
1.85 + DistMap *distance;
1.86 + ///Indicates if \ref distance is locally allocated (\c true) or not.
1.87 + bool local_distance;
1.88 +
1.89 + ///The source node of the last execution.
1.90 + Node source;
1.91 +
1.92 +
1.93 + ///Initializes the maps.
1.94 + void init_maps()
1.95 + {
1.96 + if(!predecessor) {
1.97 + local_predecessor = true;
1.98 + predecessor = new PredMap(*G);
1.99 + }
1.100 + if(!pred_node) {
1.101 + local_pred_node = true;
1.102 + pred_node = new PredNodeMap(*G);
1.103 + }
1.104 + if(!distance) {
1.105 + local_distance = true;
1.106 + distance = new DistMap(*G);
1.107 + }
1.108 + }
1.109 +
1.110 + public :
1.111 + ///Constructor.
1.112 +
1.113 + ///\param _G the graph the algorithm will run on.
1.114 + ///
1.115 + Bfs(const Graph& _G) :
1.116 + G(&_G),
1.117 + predecessor(NULL), local_predecessor(false),
1.118 + pred_node(NULL), local_pred_node(false),
1.119 + distance(NULL), local_distance(false)
1.120 + { }
1.121 +
1.122 + ///Destructor.
1.123 + ~Bfs()
1.124 + {
1.125 + if(local_predecessor) delete predecessor;
1.126 + if(local_pred_node) delete pred_node;
1.127 + if(local_distance) delete distance;
1.128 + }
1.129 +
1.130 + ///Sets the map storing the predecessor edges.
1.131 +
1.132 + ///Sets the map storing the predecessor edges.
1.133 + ///If you don't use this function before calling \ref run(),
1.134 + ///it will allocate one. The destuctor deallocates this
1.135 + ///automatically allocated map, of course.
1.136 + ///\return <tt> (*this) </tt>
1.137 + Bfs &setPredMap(PredMap &m)
1.138 + {
1.139 + if(local_predecessor) {
1.140 + delete predecessor;
1.141 + local_predecessor=false;
1.142 + }
1.143 + predecessor = &m;
1.144 + return *this;
1.145 + }
1.146 +
1.147 + ///Sets the map storing the predecessor nodes.
1.148 +
1.149 + ///Sets the map storing the predecessor nodes.
1.150 + ///If you don't use this function before calling \ref run(),
1.151 + ///it will allocate one. The destuctor deallocates this
1.152 + ///automatically allocated map, of course.
1.153 + ///\return <tt> (*this) </tt>
1.154 + Bfs &setPredNodeMap(PredNodeMap &m)
1.155 + {
1.156 + if(local_pred_node) {
1.157 + delete pred_node;
1.158 + local_pred_node=false;
1.159 + }
1.160 + pred_node = &m;
1.161 + return *this;
1.162 + }
1.163 +
1.164 + ///Sets the map storing the distances calculated by the algorithm.
1.165 +
1.166 + ///Sets the map storing the distances calculated by the algorithm.
1.167 + ///If you don't use this function before calling \ref run(),
1.168 + ///it will allocate one. The destuctor deallocates this
1.169 + ///automatically allocated map, of course.
1.170 + ///\return <tt> (*this) </tt>
1.171 + Bfs &setDistMap(DistMap &m)
1.172 + {
1.173 + if(local_distance) {
1.174 + delete distance;
1.175 + local_distance=false;
1.176 + }
1.177 + distance = &m;
1.178 + return *this;
1.179 + }
1.180 +
1.181 + ///Runs %BFS algorithm from node \c s.
1.182 +
1.183 + ///This method runs the %BFS algorithm from a root node \c s
1.184 + ///in order to
1.185 + ///compute a
1.186 + ///shortest path to each node. The algorithm computes
1.187 + ///- The %BFS tree.
1.188 + ///- The distance of each node from the root.
1.189 +
1.190 + void run(Node s) {
1.191 +
1.192 + init_maps();
1.193 +
1.194 + source = s;
1.195 +
1.196 + for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
1.197 + predecessor->set(u,INVALID);
1.198 + pred_node->set(u,INVALID);
1.199 + }
1.200 +
1.201 + int N=G->nodeNum();
1.202 + std::vector<typename Graph::Node> Q(N);
1.203 + int Qh=0;
1.204 + int Qt=0;
1.205 +
1.206 + Q[Qh++]=source;
1.207 + distance->set(s, 0);
1.208 + do {
1.209 + Node m;
1.210 + Node n=Q[Qt++];
1.211 + int d= (*distance)[n]+1;
1.212 +
1.213 + for(OutEdgeIt e(*G,n);e!=INVALID;++e)
1.214 + if((m=G->head(e))!=s && (*predecessor)[m]==INVALID) {
1.215 + Q[Qh++]=m;
1.216 + predecessor->set(m,e);
1.217 + pred_node->set(m,n);
1.218 + distance->set(m,d);
1.219 + }
1.220 + } while(Qt!=Qh);
1.221 + }
1.222 +
1.223 + ///The distance of a node from the root.
1.224 +
1.225 + ///Returns the distance of a node from the root.
1.226 + ///\pre \ref run() must be called before using this function.
1.227 + ///\warning If node \c v in unreachable from the root the return value
1.228 + ///of this funcion is undefined.
1.229 + int dist(Node v) const { return (*distance)[v]; }
1.230 +
1.231 + ///Returns the 'previous edge' of the %BFS path tree.
1.232 +
1.233 + ///For a node \c v it returns the 'previous edge' of the %BFS tree,
1.234 + ///i.e. it returns the last edge of a shortest path from the root to \c
1.235 + ///v. It is \ref INVALID
1.236 + ///if \c v is unreachable from the root or if \c v=s. The
1.237 + ///%BFS tree used here is equal to the %BFS tree used in
1.238 + ///\ref predNode(Node v). \pre \ref run() must be called before using
1.239 + ///this function.
1.240 + Edge pred(Node v) const { return (*predecessor)[v]; }
1.241 +
1.242 + ///Returns the 'previous node' of the %BFS tree.
1.243 +
1.244 + ///For a node \c v it returns the 'previous node' on the %BFS tree,
1.245 + ///i.e. it returns the last but one node from a shortest path from the
1.246 + ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
1.247 + ///\c v=s. The shortest path tree used here is equal to the %BFS
1.248 + ///tree used in \ref pred(Node v). \pre \ref run() must be called before
1.249 + ///using this function.
1.250 + Node predNode(Node v) const { return (*pred_node)[v]; }
1.251 +
1.252 + ///Returns a reference to the NodeMap of distances.
1.253 +
1.254 + ///Returns a reference to the NodeMap of distances. \pre \ref run() must
1.255 + ///be called before using this function.
1.256 + const DistMap &distMap() const { return *distance;}
1.257 +
1.258 + ///Returns a reference to the %BFS tree map.
1.259 +
1.260 + ///Returns a reference to the NodeMap of the edges of the
1.261 + ///%BFS tree.
1.262 + ///\pre \ref run() must be called before using this function.
1.263 + const PredMap &predMap() const { return *predecessor;}
1.264 +
1.265 + ///Returns a reference to the map of last but one nodes of shortest paths.
1.266 +
1.267 + ///Returns a reference to the NodeMap of the last but one nodes on the
1.268 + ///%BFS tree.
1.269 + ///\pre \ref run() must be called before using this function.
1.270 + const PredNodeMap &predNodeMap() const { return *pred_node;}
1.271 +
1.272 + ///Checks if a node is reachable from the root.
1.273 +
1.274 + ///Returns \c true if \c v is reachable from the root.
1.275 + ///\note The root node is reported to be reached!
1.276 + ///
1.277 + ///\pre \ref run() must be called before using this function.
1.278 + ///
1.279 + bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
1.280 +
1.281 + };
1.282 +
1.283 +/// @}
1.284 +
1.285 +} //END OF NAMESPACE LEMON
1.286 +
1.287 +#endif
1.288 +
1.289 +