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// -*- C++ -*-
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#ifndef HUGO_BFS_H
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#define HUGO_BFS_H
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///\ingroup flowalgs
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///\file
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///\brief Bfs algorithm.
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///
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///\todo Revise Manual.
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#include <hugo/bin_heap.h>
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#include <hugo/invalid.h>
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namespace hugo {
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/// \addtogroup flowalgs
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/// @{
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///%Bfs algorithm class.
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///This class provides an efficient implementation of %Bfs algorithm.
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///The edge lengths are passed to the algorithm using a
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///\ref ReadMapSkeleton "readable map",
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///so it is easy to change it to any kind of length.
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///
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///The type of the length is determined by the \c ValueType of the length map.
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///
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///It is also possible to change the underlying priority heap.
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///
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///\param GR The graph type the algorithm runs on.
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///\param LM This read-only
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///EdgeMap
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///determines the
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///lengths of the edges. It is read once for each edge, so the map
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///may involve in relatively time consuming process to compute the edge
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///length if it is necessary. The default map type is
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///\ref GraphSkeleton::EdgeMap "Graph::EdgeMap<int>"
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///\param Heap The heap type used by the %Bfs
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///algorithm. The default
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///is using \ref BinHeap "binary heap".
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///
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///\author Jacint Szabo and Alpar Juttner
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///\todo We need a typedef-names should be standardized. (-:
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///\todo Type of \c PredMap, \c PredNodeMap and \c DistMap
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///should not be fixed. (Problematic to solve).
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#ifdef DOXYGEN
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template <typename GR>
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#else
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template <typename GR>
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#endif
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class Bfs{
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public:
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///The type of the underlying graph.
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typedef GR Graph;
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typedef typename Graph::Node Node;
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typedef typename Graph::NodeIt NodeIt;
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typedef typename Graph::Edge Edge;
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typedef typename Graph::OutEdgeIt OutEdgeIt;
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///\brief The type of the map that stores the last
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///edges of the shortest paths.
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typedef typename Graph::template NodeMap<Edge> PredMap;
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///\brief The type of the map that stores the last but one
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///nodes of the shortest paths.
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typedef typename Graph::template NodeMap<Node> PredNodeMap;
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///The type of the map that stores the dists of the nodes.
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typedef typename Graph::template NodeMap<int> DistMap;
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private:
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const Graph *G;
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PredMap *predecessor;
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bool local_predecessor;
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PredNodeMap *pred_node;
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bool local_pred_node;
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DistMap *distance;
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bool local_distance;
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//The source node of the last execution.
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Node source;
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///Initialize maps.
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///\todo Error if \c G or are \c NULL.
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///\todo Better memory allocation (instead of new).
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void init_maps()
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{
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// if(!length) {
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// local_length = true;
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// length = new LM(G);
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// }
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if(!predecessor) {
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local_predecessor = true;
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predecessor = new PredMap(*G);
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}
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if(!pred_node) {
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local_pred_node = true;
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pred_node = new PredNodeMap(*G);
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}
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if(!distance) {
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local_distance = true;
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distance = new DistMap(*G);
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}
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}
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public :
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Bfs(const Graph& _G) :
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G(&_G),
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predecessor(NULL), local_predecessor(false),
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pred_node(NULL), local_pred_node(false),
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distance(NULL), local_distance(false)
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{ }
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~Bfs()
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{
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// if(local_length) delete length;
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if(local_predecessor) delete predecessor;
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if(local_pred_node) delete pred_node;
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if(local_distance) delete distance;
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}
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///Sets the graph the algorithm will run on.
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///Sets the graph the algorithm will run on.
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///\return <tt> (*this) </tt>
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Bfs &setGraph(const Graph &_G)
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{
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G = &_G;
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return *this;
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}
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///Sets the length map.
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///Sets the map storing the predecessor edges.
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///Sets the map storing the predecessor edges.
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///If you don't use this function before calling \ref run(),
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///it will allocate one. The destuctor deallocates this
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///automatically allocated map, of course.
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///\return <tt> (*this) </tt>
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Bfs &setPredMap(PredMap &m)
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{
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if(local_predecessor) {
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delete predecessor;
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local_predecessor=false;
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}
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predecessor = &m;
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return *this;
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}
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///Sets the map storing the predecessor nodes.
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///Sets the map storing the predecessor nodes.
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///If you don't use this function before calling \ref run(),
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///it will allocate one. The destuctor deallocates this
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///automatically allocated map, of course.
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///\return <tt> (*this) </tt>
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Bfs &setPredNodeMap(PredNodeMap &m)
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{
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if(local_pred_node) {
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delete pred_node;
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local_pred_node=false;
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}
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pred_node = &m;
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return *this;
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}
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///Sets the map storing the distances calculated by the algorithm.
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///Sets the map storing the distances calculated by the algorithm.
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///If you don't use this function before calling \ref run(),
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///it will allocate one. The destuctor deallocates this
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///automatically allocated map, of course.
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///\return <tt> (*this) </tt>
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Bfs &setDistMap(DistMap &m)
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{
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if(local_distance) {
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delete distance;
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local_distance=false;
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}
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distance = &m;
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return *this;
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}
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///Runs %BFS algorithm from node \c s.
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///This method runs the %BFS algorithm from a root node \c s
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///in order to
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///compute the
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///shortest path to each node. The algorithm computes
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///- The shortest path tree.
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///- The distance of each node from the root.
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void run(Node s) {
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init_maps();
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source = s;
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for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
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predecessor->set(u,INVALID);
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pred_node->set(u,INVALID);
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}
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int N=G->nodeNum();
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std::vector<typename Graph::Node> Q(N);
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int Qh=0;
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int Qt=0;
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Q[Qh++]=source;
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distance->set(s, 0);
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do {
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Node m;
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Node n=Q[Qt++];
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int d= (*distance)[n]+1;
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for(OutEdgeIt e(*G,n);e!=INVALID;++e)
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if((m=G->head(e))!=s && (*predecessor)[m]==INVALID) {
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Q[Qh++]=m;
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predecessor->set(m,e);
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pred_node->set(m,n);
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distance->set(m,d);
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}
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} while(Qt!=Qh);
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}
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///The distance of a node from the root.
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///Returns the distance of a node from the root.
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///\pre \ref run() must be called before using this function.
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///\warning If node \c v in unreachable from the root the return value
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///of this funcion is undefined.
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int dist(Node v) const { return (*distance)[v]; }
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///Returns the 'previous edge' of the shortest path tree.
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///For a node \c v it returns the 'previous edge' of the shortest path tree,
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///i.e. it returns the last edge from a shortest path from the root to \c
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///v. It is \ref INVALID
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///if \c v is unreachable from the root or if \c v=s. The
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///shortest path tree used here is equal to the shortest path tree used in
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///\ref predNode(Node v). \pre \ref run() must be called before using
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///this function.
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Edge pred(Node v) const { return (*predecessor)[v]; }
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///Returns the 'previous node' of the shortest path tree.
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///For a node \c v it returns the 'previous node' of the shortest path tree,
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///i.e. it returns the last but one node from a shortest path from the
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///root to \c /v. It is INVALID if \c v is unreachable from the root or if
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///\c v=s. The shortest path tree used here is equal to the shortest path
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///tree used in \ref pred(Node v). \pre \ref run() must be called before
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///using this function.
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Node predNode(Node v) const { return (*pred_node)[v]; }
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///Returns a reference to the NodeMap of distances.
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///Returns a reference to the NodeMap of distances. \pre \ref run() must
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///be called before using this function.
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const DistMap &distMap() const { return *distance;}
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///Returns a reference to the shortest path tree map.
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///Returns a reference to the NodeMap of the edges of the
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///shortest path tree.
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///\pre \ref run() must be called before using this function.
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const PredMap &predMap() const { return *predecessor;}
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///Returns a reference to the map of nodes of shortest paths.
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///Returns a reference to the NodeMap of the last but one nodes of the
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///shortest path tree.
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///\pre \ref run() must be called before using this function.
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const PredNodeMap &predNodeMap() const { return *pred_node;}
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///Checks if a node is reachable from the root.
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///Returns \c true if \c v is reachable from the root.
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///\warning The root node is reported to be reached!
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///
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///\pre \ref run() must be called before using this function.
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///
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bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
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};
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// **********************************************************************
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// IMPLEMENTATIONS
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// **********************************************************************
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/// @}
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} //END OF NAMESPACE HUGO
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#endif
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