athos@601: // -*- c++ -*- alpar@921: #ifndef LEMON_MINLENGTHPATHS_H alpar@921: #define LEMON_MINLENGTHPATHS_H athos@601: athos@601: ///\ingroup galgs athos@601: ///\file athos@601: ///\brief An algorithm for finding k paths of minimal total length. athos@601: athos@601: #include <iostream> alpar@921: #include <lemon/dijkstra.h> alpar@921: #include <lemon/graph_wrapper.h> alpar@921: #include <lemon/maps.h> athos@607: #include <vector> athos@601: athos@601: alpar@921: namespace lemon { athos@601: athos@601: /// \addtogroup galgs athos@601: /// @{ athos@601: athos@601: ///\brief Implementation of an algorithm for finding k paths between 2 nodes athos@601: /// of minimal total length athos@601: /// alpar@921: /// The class \ref lemon::MinLengthPaths "MinLengthPaths" implements athos@601: /// an algorithm for finding k edge-disjoint paths athos@601: /// from a given source node to a given target node in an athos@601: /// edge-weighted directed graph having minimal total weigth (length). athos@601: /// athos@601: ///\author Attila Bernath athos@601: template <typename Graph, typename LengthMap> athos@601: class MinLengthPaths { athos@601: alpar@987: typedef typename LengthMap::Value Length; athos@601: athos@601: typedef typename Graph::Node Node; athos@601: typedef typename Graph::NodeIt NodeIt; athos@601: typedef typename Graph::Edge Edge; athos@601: typedef typename Graph::OutEdgeIt OutEdgeIt; athos@601: typedef typename Graph::template EdgeMap<int> EdgeIntMap; athos@601: athos@601: typedef ConstMap<Edge,int> ConstMap; athos@601: athos@601: typedef ResGraphWrapper<const Graph,int,ConstMap,EdgeIntMap> ResGraphType; athos@601: athos@601: class ModLengthMap { athos@601: typedef typename ResGraphType::template NodeMap<Length> NodeMap; athos@601: const ResGraphType& G; athos@601: const EdgeIntMap& rev; athos@601: const LengthMap &ol; athos@601: const NodeMap &pot; athos@601: public : alpar@987: typedef typename LengthMap::Key Key; alpar@987: typedef typename LengthMap::Value Value; athos@601: alpar@987: Value operator[](typename ResGraphType::Edge e) const { alpar@986: //if ( (1-2*rev[e])*ol[e]-(pot[G.target(e)]-pot[G.source(e)] ) <0 ){ athos@601: // std::cout<<"Negative length!!"<<std::endl; athos@601: //} alpar@986: return (1-2*rev[e])*ol[e]-(pot[G.target(e)]-pot[G.source(e)]); athos@601: } athos@601: athos@601: ModLengthMap(const ResGraphType& _G, const EdgeIntMap& _rev, athos@601: const LengthMap &o, const NodeMap &p) : athos@601: G(_G), rev(_rev), ol(o), pot(p){}; athos@601: };//ModLengthMap athos@601: athos@601: athos@601: athos@601: athos@601: const Graph& G; athos@601: const LengthMap& length; athos@601: athos@601: //auxiliary variables athos@601: athos@601: //The value is 1 iff the edge is reversed. athos@601: //If the algorithm has finished, the edges of the seeked paths are athos@601: //exactly those that are reversed athos@601: EdgeIntMap reversed; athos@601: athos@601: //Container to store found paths athos@601: std::vector< std::vector<Edge> > paths; athos@601: //typedef DirPath<Graph> DPath; athos@601: //DPath paths; athos@601: athos@601: athos@601: Length total_length; athos@601: athos@601: public : athos@601: athos@601: athos@601: MinLengthPaths(Graph& _G, LengthMap& _length) : G(_G), athos@601: length(_length), reversed(_G)/*, dijkstra_dist(_G)*/{ } athos@601: athos@601: athos@601: ///Runs the algorithm. athos@601: athos@601: ///Runs the algorithm. athos@601: ///Returns k if there are at least k edge-disjoint paths from s to t. athos@601: ///Otherwise it returns the number of found edge-disjoint paths from s to t. athos@601: int run(Node s, Node t, int k) { athos@601: ConstMap const1map(1); athos@601: athos@601: athos@601: //We need a residual graph, in which some of the edges are reversed athos@601: ResGraphType res_graph(G, const1map, reversed); athos@601: athos@601: //Initialize the copy of the Dijkstra potential to zero athos@601: typename ResGraphType::template NodeMap<Length> dijkstra_dist(res_graph); athos@601: ModLengthMap mod_length(res_graph, reversed, length, dijkstra_dist); athos@601: athos@601: Dijkstra<ResGraphType, ModLengthMap> dijkstra(res_graph, mod_length); athos@601: athos@601: int i; athos@601: for (i=0; i<k; ++i){ athos@601: dijkstra.run(s); athos@601: if (!dijkstra.reached(t)){ athos@601: //There are no k paths from s to t athos@601: break; athos@601: }; athos@601: athos@601: { athos@601: //We have to copy the potential athos@601: typename ResGraphType::NodeIt n; athos@601: for ( res_graph.first(n) ; res_graph.valid(n) ; res_graph.next(n) ) { athos@601: dijkstra_dist[n] += dijkstra.distMap()[n]; athos@601: } athos@601: } athos@601: athos@601: athos@601: //Reversing the sortest path athos@601: Node n=t; athos@601: Edge e; athos@601: while (n!=s){ athos@601: e = dijkstra.pred(n); athos@601: n = dijkstra.predNode(n); athos@601: reversed[e] = 1-reversed[e]; athos@601: } athos@601: athos@601: athos@601: } athos@601: athos@601: //Let's find the paths athos@601: //We put the paths into stl vectors (as an inner representation). athos@601: //In the meantime we lose the information stored in 'reversed'. athos@601: //We suppose the lengths to be positive now. athos@601: athos@601: //Meanwhile we put the total length of the found paths athos@601: //in the member variable total_length athos@601: paths.clear(); athos@601: total_length=0; athos@601: paths.resize(k); athos@601: for (int j=0; j<i; ++j){ athos@601: Node n=s; athos@601: OutEdgeIt e; athos@601: athos@601: while (n!=t){ athos@601: athos@601: athos@601: G.first(e,n); athos@601: athos@601: while (!reversed[e]){ athos@601: G.next(e); athos@601: } alpar@986: n = G.target(e); athos@601: paths[j].push_back(e); athos@601: total_length += length[e]; athos@601: reversed[e] = 1-reversed[e]; athos@601: } athos@601: athos@601: } athos@601: athos@601: return i; athos@601: } athos@601: athos@601: ///This function gives back the total length of the found paths. athos@601: ///Assumes that \c run() has been run and nothing changed since then. athos@601: Length totalLength(){ athos@601: return total_length; athos@601: } athos@601: athos@601: ///This function gives back the \c j-th path in argument p. athos@601: ///Assumes that \c run() has been run and nothing changed since then. athos@601: /// \warning It is assumed that \c p is constructed to be a path of graph \c G. If \c j is greater than the result of previous \c run, then the result here will be an empty path. athos@601: template<typename DirPath> athos@601: void getPath(DirPath& p, int j){ athos@601: p.clear(); athos@601: typename DirPath::Builder B(p); athos@601: for(typename std::vector<Edge>::iterator i=paths[j].begin(); athos@601: i!=paths[j].end(); ++i ){ athos@601: B.pushBack(*i); athos@601: } athos@601: athos@601: B.commit(); athos@601: } athos@601: athos@601: }; //class MinLengthPaths athos@601: athos@601: ///@} athos@601: alpar@921: } //namespace lemon athos@601: alpar@921: #endif //LEMON_MINLENGTHPATHS_H