1 | // -*- C++ -*- |
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2 | |
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3 | /* |
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4 | *template <Graph, T, Heap=FibHeap, LengthMap=Graph::EdgeMap<T> > |
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5 | * |
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6 | *Constructor: |
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7 | * |
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8 | *Dijkstra(Graph G, LengthMap length) |
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9 | * |
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10 | * |
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11 | *Methods: |
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12 | * |
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13 | *void run(Node s) |
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14 | * |
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15 | *T dist(Node v) : After run(s) was run, it returns the distance from s to v. |
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16 | * Returns T() if v is not reachable from s. |
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17 | * |
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18 | *Edge pred(Node v) : After run(s) was run, it returns the last |
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19 | * edge of a shortest s-v path. It is INVALID for s and for |
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20 | * the nodes not reachable from s. |
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21 | * |
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22 | *bool reached(Node v) : After run(s) was run, it is true iff v is |
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23 | * reachable from s |
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24 | * |
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25 | */ |
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26 | |
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27 | #ifndef HUGO_DIJKSTRA_H |
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28 | #define HUGO_DIJKSTRA_H |
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29 | |
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30 | ///\file |
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31 | ///\brief Dijkstra algorithm. |
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32 | |
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33 | #include <fib_heap.h> |
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34 | #include <bin_heap.hh> |
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35 | #include <invalid.h> |
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36 | |
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37 | namespace hugo { |
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38 | |
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39 | //Alpar: Changed the order of the parameters |
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40 | |
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41 | ///%Dijkstra algorithm class. |
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42 | |
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43 | ///This class provides an efficient implementation of %Dijkstra algorithm. |
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44 | ///The edge lengths are passed to the algorithm using a |
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45 | ///\ref ReadMapSkeleton "readable map", |
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46 | ///so it is easy to change it to any kind of length. |
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47 | /// |
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48 | ///The type of the length is determined by the \c ValueType of the length map. |
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49 | /// |
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50 | ///It is also possible to change the underlying priority heap. |
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51 | /// |
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52 | ///\param Graph The graph type the algorithm runs on. |
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53 | ///\param LengthMap This read-only |
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54 | ///EdgeMap |
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55 | ///determines the |
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56 | ///lengths of the edges. It is read once for each edge, so the map |
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57 | ///may involve in relatively time consuming process to compute the edge |
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58 | ///length if it is necessary. The default map type is |
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59 | ///\ref GraphSkeleton::EdgeMap "Graph::EdgeMap<int>" |
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60 | ///\param Heap The heap type used by the %Dijkstra |
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61 | ///algorithm. The default |
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62 | ///is using \ref BinHeap "binary heap". |
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63 | |
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64 | #ifdef DOXYGEN |
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65 | template <typename Graph, |
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66 | typename LengthMap, |
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67 | typename Heap> |
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68 | #else |
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69 | template <typename Graph, |
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70 | typename LengthMap=typename Graph::EdgeMap<int>, |
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71 | typename Heap=BinHeap <typename Graph::Node, |
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72 | typename LengthMap::ValueType, |
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73 | typename Graph::NodeMap<int> > > |
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74 | #endif |
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75 | class Dijkstra{ |
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76 | public: |
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77 | typedef typename Graph::Node Node; |
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78 | typedef typename Graph::NodeIt NodeIt; |
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79 | typedef typename Graph::Edge Edge; |
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80 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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81 | |
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82 | typedef typename LengthMap::ValueType ValueType; |
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83 | typedef typename Graph::NodeMap<Edge> PredMap; |
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84 | typedef typename Graph::NodeMap<Node> PredNodeMap; |
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85 | typedef typename Graph::NodeMap<ValueType> DistMap; |
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86 | |
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87 | private: |
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88 | const Graph& G; |
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89 | const LengthMap& length; |
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90 | PredMap predecessor; |
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91 | //In place of reach: |
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92 | PredNodeMap pred_node; |
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93 | DistMap distance; |
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94 | //I don't like this: |
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95 | // //FIXME: |
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96 | // typename Graph::NodeMap<bool> reach; |
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97 | // //typename Graph::NodeMap<int> reach; |
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98 | |
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99 | public : |
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100 | |
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101 | /* |
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102 | The distance of the nodes is 0. |
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103 | */ |
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104 | Dijkstra(Graph& _G, LengthMap& _length) : |
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105 | G(_G), length(_length), predecessor(_G), pred_node(_G), distance(_G) { } |
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106 | |
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107 | |
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108 | void run(Node s); |
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109 | |
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110 | ///The distance of a node from the source. |
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111 | |
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112 | ///Returns the distance of a node from the source. |
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113 | ///\pre \ref run() must be called before using this function. |
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114 | ///\warning If node \c v in unreachable from the source the return value |
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115 | ///of this funcion is undefined. |
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116 | ValueType dist(Node v) const { return distance[v]; } |
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117 | ///Returns the edges of the shortest path tree. |
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118 | |
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119 | ///For a node \c v it returns the last edge of the shortest path |
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120 | ///from the source to \c v or INVALID if \c v is unreachable |
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121 | ///from the source. |
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122 | ///\pre \ref run() must be called before using this function. |
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123 | Edge pred(Node v) const { return predecessor[v]; } |
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124 | ///Returns the nodes of the shortest paths. |
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125 | |
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126 | ///For a node \c v it returns the last but one node of the shortest path |
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127 | ///from the source to \c v or INVALID if \c v is unreachable |
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128 | ///from the source. |
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129 | ///\pre \ref run() must be called before using this function. |
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130 | Node predNode(Node v) const { return pred_node[v]; } |
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131 | |
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132 | ///Returns a reference to the NodeMap of distances. |
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133 | |
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134 | ///\pre \ref run() must be called before using this function. |
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135 | /// |
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136 | const DistMap &distMap() const { return distance;} |
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137 | ///Returns a reference to the shortest path tree map. |
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138 | |
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139 | ///Returns a reference to the NodeMap of the edges of the |
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140 | ///shortest path tree. |
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141 | ///\pre \ref run() must be called before using this function. |
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142 | const PredMap &predMap() const { return predecessor;} |
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143 | ///Returns a reference to the map of nodes of shortest paths. |
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144 | |
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145 | ///Returns a reference to the NodeMap of the last but one nodes of the |
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146 | ///shortest paths. |
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147 | ///\pre \ref run() must be called before using this function. |
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148 | const PredNodeMap &predNodeMap() const { return pred_node;} |
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149 | |
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150 | // bool reached(Node v) { return reach[v]; } |
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151 | |
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152 | ///Checks if a node is reachable from the source. |
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153 | |
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154 | ///Returns \c true if \c v is reachable from the source. |
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155 | ///\warning the source node is reported to be unreached! |
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156 | ///\todo Is this what we want? |
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157 | ///\pre \ref run() must be called before using this function. |
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158 | /// |
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159 | bool reached(Node v) { return G.valid(predecessor[v]); } |
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160 | |
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161 | }; |
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162 | |
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163 | |
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164 | // ********************************************************************** |
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165 | // IMPLEMENTATIONS |
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166 | // ********************************************************************** |
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167 | |
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168 | ///Runs %Dijkstra algorithm from node the source. |
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169 | |
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170 | ///This method runs the %Dijkstra algorithm from a source node \c s |
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171 | ///in order to |
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172 | ///compute the |
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173 | ///shortest path to each node. The algorithm computes |
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174 | ///- The shortest path tree. |
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175 | ///- The distance of each node from the source. |
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176 | template <typename Graph, typename LengthMap, typename Heap > |
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177 | void Dijkstra<Graph,LengthMap,Heap>::run(Node s) { |
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178 | |
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179 | NodeIt u; |
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180 | for ( G.first(u) ; G.valid(u) ; G.next(u) ) { |
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181 | predecessor.set(u,INVALID); |
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182 | pred_node.set(u,INVALID); |
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183 | // If a node is unreacheable, then why should be the dist=0? |
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184 | // distance.set(u,0); |
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185 | // reach.set(u,false); |
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186 | } |
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187 | |
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188 | //We don't need it at all. |
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189 | // //FIXME: |
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190 | // typename Graph::NodeMap<bool> scanned(G,false); |
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191 | // //typename Graph::NodeMap<int> scanned(G,false); |
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192 | typename Graph::NodeMap<int> heap_map(G,-1); |
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193 | |
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194 | Heap heap(heap_map); |
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195 | |
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196 | heap.push(s,0); |
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197 | // reach.set(s, true); |
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198 | |
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199 | while ( !heap.empty() ) { |
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200 | |
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201 | Node v=heap.top(); |
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202 | ValueType oldvalue=heap[v]; |
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203 | heap.pop(); |
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204 | distance.set(v, oldvalue); |
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205 | |
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206 | for(OutEdgeIt e(G,v); G.valid(e); G.next(e)) { |
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207 | Node w=G.head(e); |
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208 | |
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209 | switch(heap.state(w)) { |
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210 | case Heap::PRE_HEAP: |
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211 | // reach.set(w,true); |
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212 | heap.push(w,oldvalue+length[e]); |
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213 | predecessor.set(w,e); |
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214 | pred_node.set(w,v); |
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215 | break; |
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216 | case Heap::IN_HEAP: |
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217 | if ( oldvalue+length[e] < heap[w] ) { |
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218 | heap.decrease(w, oldvalue+length[e]); |
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219 | predecessor.set(w,e); |
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220 | pred_node.set(w,v); |
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221 | } |
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222 | break; |
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223 | case Heap::POST_HEAP: |
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224 | break; |
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225 | } |
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226 | } |
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227 | } |
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228 | } |
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229 | |
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230 | } //END OF NAMESPACE HUGO |
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231 | |
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232 | #endif |
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233 | |
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234 | |
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