diff -r 2d6c8075d9d0 -r 818510fa3d99 src/lemon/dijkstra.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/lemon/dijkstra.h Wed Sep 29 15:30:04 2004 +0000 @@ -0,0 +1,344 @@ +/* -*- C++ -*- + * src/lemon/dijkstra.h - Part of LEMON, a generic C++ optimization library + * + * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport + * (Egervary Combinatorial Optimization Research Group, EGRES). + * + * Permission to use, modify and distribute this software is granted + * provided that this copyright notice appears in all copies. For + * precise terms see the accompanying LICENSE file. + * + * This software is provided "AS IS" with no warranty of any kind, + * express or implied, and with no claim as to its suitability for any + * purpose. + * + */ + +#ifndef LEMON_DIJKSTRA_H +#define LEMON_DIJKSTRA_H + +///\ingroup flowalgs +///\file +///\brief Dijkstra algorithm. + +#include +#include + +namespace lemon { + +/// \addtogroup flowalgs +/// @{ + + ///%Dijkstra algorithm class. + + ///This class provides an efficient implementation of %Dijkstra algorithm. + ///The edge lengths are passed to the algorithm using a + ///\ref skeleton::ReadMap "ReadMap", + ///so it is easy to change it to any kind of length. + /// + ///The type of the length is determined by the + ///\ref skeleton::ReadMap::ValueType "ValueType" of the length map. + /// + ///It is also possible to change the underlying priority heap. + /// + ///\param GR The graph type the algorithm runs on. + ///\param LM This read-only + ///EdgeMap + ///determines the + ///lengths of the edges. It is read once for each edge, so the map + ///may involve in relatively time consuming process to compute the edge + ///length if it is necessary. The default map type is + ///\ref skeleton::StaticGraph::EdgeMap "Graph::EdgeMap" + ///\param Heap The heap type used by the %Dijkstra + ///algorithm. The default + ///is using \ref BinHeap "binary heap". + /// + ///\author Jacint Szabo and Alpar Juttner + ///\todo We need a typedef-names should be standardized. (-: + ///\todo Type of \c PredMap, \c PredNodeMap and \c DistMap + ///should not be fixed. (Problematic to solve). + +#ifdef DOXYGEN + template +#else + template , + template class Heap = BinHeap > +#endif + class Dijkstra{ + public: + ///The type of the underlying graph. + typedef GR Graph; + ///\e + typedef typename Graph::Node Node; + ///\e + typedef typename Graph::NodeIt NodeIt; + ///\e + typedef typename Graph::Edge Edge; + ///\e + typedef typename Graph::OutEdgeIt OutEdgeIt; + + ///The type of the length of the edges. + typedef typename LM::ValueType ValueType; + ///The type of the map that stores the edge lengths. + typedef LM LengthMap; + ///\brief The type of the map that stores the last + ///edges of the shortest paths. + typedef typename Graph::template NodeMap PredMap; + ///\brief The type of the map that stores the last but one + ///nodes of the shortest paths. + typedef typename Graph::template NodeMap PredNodeMap; + ///The type of the map that stores the dists of the nodes. + typedef typename Graph::template NodeMap DistMap; + + private: + /// Pointer to the underlying graph. + const Graph *G; + /// Pointer to the length map + const LM *length; + ///Pointer to the map of predecessors edges. + PredMap *predecessor; + ///Indicates if \ref predecessor is locally allocated (\c true) or not. + bool local_predecessor; + ///Pointer to the map of predecessors nodes. + PredNodeMap *pred_node; + ///Indicates if \ref pred_node is locally allocated (\c true) or not. + bool local_pred_node; + ///Pointer to the map of distances. + DistMap *distance; + ///Indicates if \ref distance is locally allocated (\c true) or not. + bool local_distance; + + ///The source node of the last execution. + Node source; + + ///Initializes the maps. + + ///\todo Error if \c G or are \c NULL. What about \c length? + ///\todo Better memory allocation (instead of new). + void init_maps() + { + if(!predecessor) { + local_predecessor = true; + predecessor = new PredMap(*G); + } + if(!pred_node) { + local_pred_node = true; + pred_node = new PredNodeMap(*G); + } + if(!distance) { + local_distance = true; + distance = new DistMap(*G); + } + } + + public : + ///Constructor. + + ///\param _G the graph the algorithm will run on. + ///\param _length the length map used by the algorithm. + Dijkstra(const Graph& _G, const LM& _length) : + G(&_G), length(&_length), + predecessor(NULL), local_predecessor(false), + pred_node(NULL), local_pred_node(false), + distance(NULL), local_distance(false) + { } + + ///Destructor. + ~Dijkstra() + { + if(local_predecessor) delete predecessor; + if(local_pred_node) delete pred_node; + if(local_distance) delete distance; + } + + ///Sets the length map. + + ///Sets the length map. + ///\return (*this) + Dijkstra &setLengthMap(const LM &m) + { + length = &m; + return *this; + } + + ///Sets the map storing the predecessor edges. + + ///Sets the map storing the predecessor edges. + ///If you don't use this function before calling \ref run(), + ///it will allocate one. The destuctor deallocates this + ///automatically allocated map, of course. + ///\return (*this) + Dijkstra &setPredMap(PredMap &m) + { + if(local_predecessor) { + delete predecessor; + local_predecessor=false; + } + predecessor = &m; + return *this; + } + + ///Sets the map storing the predecessor nodes. + + ///Sets the map storing the predecessor nodes. + ///If you don't use this function before calling \ref run(), + ///it will allocate one. The destuctor deallocates this + ///automatically allocated map, of course. + ///\return (*this) + Dijkstra &setPredNodeMap(PredNodeMap &m) + { + if(local_pred_node) { + delete pred_node; + local_pred_node=false; + } + pred_node = &m; + return *this; + } + + ///Sets the map storing the distances calculated by the algorithm. + + ///Sets the map storing the distances calculated by the algorithm. + ///If you don't use this function before calling \ref run(), + ///it will allocate one. The destuctor deallocates this + ///automatically allocated map, of course. + ///\return (*this) + Dijkstra &setDistMap(DistMap &m) + { + if(local_distance) { + delete distance; + local_distance=false; + } + distance = &m; + return *this; + } + + ///Runs %Dijkstra algorithm from node \c s. + + ///This method runs the %Dijkstra algorithm from a root node \c s + ///in order to + ///compute the + ///shortest path to each node. The algorithm computes + ///- The shortest path tree. + ///- The distance of each node from the root. + + void run(Node s) { + + init_maps(); + + source = s; + + for ( NodeIt u(*G) ; u!=INVALID ; ++u ) { + predecessor->set(u,INVALID); + pred_node->set(u,INVALID); + } + + typename GR::template NodeMap heap_map(*G,-1); + + typedef Heap, + std::less > + HeapType; + + HeapType heap(heap_map); + + heap.push(s,0); + + while ( !heap.empty() ) { + + Node v=heap.top(); + ValueType oldvalue=heap[v]; + heap.pop(); + distance->set(v, oldvalue); + + + for(OutEdgeIt e(*G,v); e!=INVALID; ++e) { + Node w=G->head(e); + switch(heap.state(w)) { + case HeapType::PRE_HEAP: + heap.push(w,oldvalue+(*length)[e]); + predecessor->set(w,e); + pred_node->set(w,v); + break; + case HeapType::IN_HEAP: + if ( oldvalue+(*length)[e] < heap[w] ) { + heap.decrease(w, oldvalue+(*length)[e]); + predecessor->set(w,e); + pred_node->set(w,v); + } + break; + case HeapType::POST_HEAP: + break; + } + } + } + } + + ///The distance of a node from the root. + + ///Returns the distance of a node from the root. + ///\pre \ref run() must be called before using this function. + ///\warning If node \c v in unreachable from the root the return value + ///of this funcion is undefined. + ValueType dist(Node v) const { return (*distance)[v]; } + + ///Returns the 'previous edge' of the shortest path tree. + + ///For a node \c v it returns the 'previous edge' of the shortest path tree, + ///i.e. it returns the last edge of a shortest path from the root to \c + ///v. It is \ref INVALID + ///if \c v is unreachable from the root or if \c v=s. The + ///shortest path tree used here is equal to the shortest path tree used in + ///\ref predNode(Node v). \pre \ref run() must be called before using + ///this function. + ///\todo predEdge could be a better name. + Edge pred(Node v) const { return (*predecessor)[v]; } + + ///Returns the 'previous node' of the shortest path tree. + + ///For a node \c v it returns the 'previous node' of the shortest path tree, + ///i.e. it returns the last but one node from a shortest path from the + ///root to \c /v. It is INVALID if \c v is unreachable from the root or if + ///\c v=s. The shortest path tree used here is equal to the shortest path + ///tree used in \ref pred(Node v). \pre \ref run() must be called before + ///using this function. + Node predNode(Node v) const { return (*pred_node)[v]; } + + ///Returns a reference to the NodeMap of distances. + + ///Returns a reference to the NodeMap of distances. \pre \ref run() must + ///be called before using this function. + const DistMap &distMap() const { return *distance;} + + ///Returns a reference to the shortest path tree map. + + ///Returns a reference to the NodeMap of the edges of the + ///shortest path tree. + ///\pre \ref run() must be called before using this function. + const PredMap &predMap() const { return *predecessor;} + + ///Returns a reference to the map of nodes of shortest paths. + + ///Returns a reference to the NodeMap of the last but one nodes of the + ///shortest path tree. + ///\pre \ref run() must be called before using this function. + const PredNodeMap &predNodeMap() const { return *pred_node;} + + ///Checks if a node is reachable from the root. + + ///Returns \c true if \c v is reachable from the root. + ///\note The root node is reported to be reached! + ///\pre \ref run() must be called before using this function. + /// + bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; } + + }; + +/// @} + +} //END OF NAMESPACE LEMON + +#endif + +