[276] | 1 | // -*- c++ -*- |
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[306] | 2 | #ifndef HUGO_MINLENGTHPATHS_H |
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| 3 | #define HUGO_MINLENGTHPATHS_H |
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[276] | 4 | |
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[491] | 5 | ///\ingroup galgs |
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[294] | 6 | ///\file |
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[306] | 7 | ///\brief An algorithm for finding k paths of minimal total length. |
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[294] | 8 | |
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[276] | 9 | #include <iostream> |
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| 10 | #include <dijkstra.h> |
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| 11 | #include <graph_wrapper.h> |
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[306] | 12 | #include <maps.h> |
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[511] | 13 | #include <vector.h> |
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[322] | 14 | |
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[306] | 15 | |
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[276] | 16 | namespace hugo { |
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| 17 | |
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[430] | 18 | /// \addtogroup galgs |
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| 19 | /// @{ |
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[322] | 20 | |
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[310] | 21 | ///\brief Implementation of an algorithm for finding k paths between 2 nodes |
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[306] | 22 | /// of minimal total length |
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[310] | 23 | /// |
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| 24 | /// The class \ref hugo::MinLengthPaths "MinLengthPaths" implements |
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[513] | 25 | /// an algorithm for finding k edge-disjoint paths |
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[310] | 26 | /// from a given source node to a given target node in an |
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| 27 | /// edge-weighted directed graph having minimal total weigth (length). |
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[456] | 28 | /// |
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| 29 | ///\author Attila Bernath |
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[310] | 30 | template <typename Graph, typename LengthMap> |
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[306] | 31 | class MinLengthPaths { |
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[276] | 32 | |
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[310] | 33 | typedef typename LengthMap::ValueType Length; |
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[511] | 34 | |
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[276] | 35 | typedef typename Graph::Node Node; |
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| 36 | typedef typename Graph::NodeIt NodeIt; |
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| 37 | typedef typename Graph::Edge Edge; |
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| 38 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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[511] | 39 | typedef typename Graph::template EdgeMap<int> EdgeIntMap; |
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[306] | 40 | |
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| 41 | typedef ConstMap<Edge,int> ConstMap; |
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| 42 | |
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[330] | 43 | typedef ResGraphWrapper<const Graph,int,ConstMap,EdgeIntMap> ResGraphType; |
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[276] | 44 | |
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[306] | 45 | class ModLengthMap { |
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[511] | 46 | typedef typename ResGraphType::template NodeMap<Length> NodeMap; |
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[306] | 47 | const ResGraphType& G; |
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[310] | 48 | const EdgeIntMap& rev; |
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| 49 | const LengthMap &ol; |
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| 50 | const NodeMap &pot; |
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[306] | 51 | public : |
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| 52 | typedef typename LengthMap::KeyType KeyType; |
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| 53 | typedef typename LengthMap::ValueType ValueType; |
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[511] | 54 | |
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[306] | 55 | ValueType operator[](typename ResGraphType::Edge e) const { |
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[322] | 56 | //if ( (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)] ) <0 ){ |
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| 57 | // std::cout<<"Negative length!!"<<std::endl; |
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| 58 | //} |
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[306] | 59 | return (1-2*rev[e])*ol[e]-(pot[G.head(e)]-pot[G.tail(e)]); |
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| 60 | } |
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[511] | 61 | |
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[310] | 62 | ModLengthMap(const ResGraphType& _G, const EdgeIntMap& _rev, |
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| 63 | const LengthMap &o, const NodeMap &p) : |
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[306] | 64 | G(_G), rev(_rev), ol(o), pot(p){}; |
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[511] | 65 | };//ModLengthMap |
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| 66 | |
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| 67 | |
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[306] | 68 | |
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| 69 | |
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[276] | 70 | const Graph& G; |
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| 71 | const LengthMap& length; |
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| 72 | |
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[328] | 73 | //auxiliary variables |
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[322] | 74 | |
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[314] | 75 | //The value is 1 iff the edge is reversed. |
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| 76 | //If the algorithm has finished, the edges of the seeked paths are |
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| 77 | //exactly those that are reversed |
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[306] | 78 | EdgeIntMap reversed; |
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[276] | 79 | |
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[322] | 80 | //Container to store found paths |
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| 81 | std::vector< std::vector<Edge> > paths; |
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[511] | 82 | //typedef DirPath<Graph> DPath; |
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| 83 | //DPath paths; |
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| 84 | |
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| 85 | |
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| 86 | Length total_length; |
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[322] | 87 | |
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[276] | 88 | public : |
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[310] | 89 | |
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[276] | 90 | |
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[306] | 91 | MinLengthPaths(Graph& _G, LengthMap& _length) : G(_G), |
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| 92 | length(_length), reversed(_G)/*, dijkstra_dist(_G)*/{ } |
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[276] | 93 | |
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[294] | 94 | |
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[329] | 95 | ///Runs the algorithm. |
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| 96 | |
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| 97 | ///Runs the algorithm. |
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[306] | 98 | ///Returns k if there are at least k edge-disjoint paths from s to t. |
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[329] | 99 | ///Otherwise it returns the number of found edge-disjoint paths from s to t. |
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[306] | 100 | int run(Node s, Node t, int k) { |
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| 101 | ConstMap const1map(1); |
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[276] | 102 | |
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[511] | 103 | |
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[314] | 104 | //We need a residual graph, in which some of the edges are reversed |
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[330] | 105 | ResGraphType res_graph(G, const1map, reversed); |
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[306] | 106 | |
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| 107 | //Initialize the copy of the Dijkstra potential to zero |
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[511] | 108 | typename ResGraphType::template NodeMap<Length> dijkstra_dist(res_graph); |
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[310] | 109 | ModLengthMap mod_length(res_graph, reversed, length, dijkstra_dist); |
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[306] | 110 | |
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| 111 | Dijkstra<ResGraphType, ModLengthMap> dijkstra(res_graph, mod_length); |
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[322] | 112 | |
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| 113 | int i; |
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| 114 | for (i=0; i<k; ++i){ |
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[276] | 115 | dijkstra.run(s); |
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| 116 | if (!dijkstra.reached(t)){ |
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[314] | 117 | //There are no k paths from s to t |
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[322] | 118 | break; |
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[276] | 119 | }; |
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[306] | 120 | |
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| 121 | { |
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| 122 | //We have to copy the potential |
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| 123 | typename ResGraphType::NodeIt n; |
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| 124 | for ( res_graph.first(n) ; res_graph.valid(n) ; res_graph.next(n) ) { |
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| 125 | dijkstra_dist[n] += dijkstra.distMap()[n]; |
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| 126 | } |
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| 127 | } |
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| 128 | |
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| 129 | |
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[276] | 130 | //Reversing the sortest path |
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| 131 | Node n=t; |
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| 132 | Edge e; |
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| 133 | while (n!=s){ |
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[291] | 134 | e = dijkstra.pred(n); |
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| 135 | n = dijkstra.predNode(n); |
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[276] | 136 | reversed[e] = 1-reversed[e]; |
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| 137 | } |
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| 138 | |
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| 139 | |
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| 140 | } |
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[322] | 141 | |
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| 142 | //Let's find the paths |
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[511] | 143 | //We put the paths into stl vectors (as an inner representation). |
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| 144 | //In the meantime we lose the information stored in 'reversed'. |
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[322] | 145 | //We suppose the lengths to be positive now. |
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[511] | 146 | |
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| 147 | //Meanwhile we put the total length of the found paths |
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| 148 | //in the member variable total_length |
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[322] | 149 | paths.clear(); |
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[511] | 150 | total_length=0; |
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[322] | 151 | paths.resize(k); |
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| 152 | for (int j=0; j<i; ++j){ |
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| 153 | Node n=s; |
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| 154 | OutEdgeIt e; |
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| 155 | |
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| 156 | while (n!=t){ |
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| 157 | |
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| 158 | |
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| 159 | G.first(e,n); |
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| 160 | |
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| 161 | while (!reversed[e]){ |
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| 162 | G.next(e); |
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| 163 | } |
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| 164 | n = G.head(e); |
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| 165 | paths[j].push_back(e); |
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[511] | 166 | total_length += length[e]; |
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[322] | 167 | reversed[e] = 1-reversed[e]; |
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| 168 | } |
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| 169 | |
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| 170 | } |
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| 171 | |
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| 172 | return i; |
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[276] | 173 | } |
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| 174 | |
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[511] | 175 | ///This function gives back the total length of the found paths. |
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| 176 | ///Assumes that \c run() has been run and nothing changed since then. |
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| 177 | Length totalLength(){ |
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| 178 | return total_length; |
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| 179 | } |
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| 180 | |
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| 181 | ///This function gives back the \c j-th path in argument p. |
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| 182 | ///Assumes that \c run() has been run and nothing changed since then. |
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[519] | 183 | /// \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. |
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[511] | 184 | template<typename DirPath> |
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| 185 | void getPath(DirPath& p, int j){ |
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| 186 | p.clear(); |
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| 187 | typename DirPath::Builder B(p); |
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| 188 | for(typename std::vector<Edge>::iterator i=paths[j].begin(); |
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| 189 | i!=paths[j].end(); ++i ){ |
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[520] | 190 | B.pushBack(*i); |
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[511] | 191 | } |
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| 192 | |
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| 193 | B.commit(); |
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| 194 | } |
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[276] | 195 | |
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[310] | 196 | }; //class MinLengthPaths |
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[276] | 197 | |
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[430] | 198 | ///@} |
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[276] | 199 | |
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| 200 | } //namespace hugo |
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| 201 | |
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[306] | 202 | #endif //HUGO_MINLENGTHPATHS_H |
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