1 // -*- C++ -*- |
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2 #ifndef LEMON_DIJKSTRA_H |
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3 #define LEMON_DIJKSTRA_H |
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4 |
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5 ///\ingroup galgs |
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6 ///\file |
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7 ///\brief Dijkstra algorithm. |
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8 |
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9 #include <lemon/bin_heap.h> |
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10 #include <lemon/invalid.h> |
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11 |
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12 namespace lemon { |
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13 |
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14 /// \addtogroup galgs |
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15 /// @{ |
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16 |
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17 ///%Dijkstra algorithm class. |
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18 |
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19 ///This class provides an efficient implementation of %Dijkstra algorithm. |
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20 ///The edge lengths are passed to the algorithm using a |
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21 ///\ref ReadMap "readable map", |
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22 ///so it is easy to change it to any kind of length. |
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23 /// |
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24 ///The type of the length is determined by the \c Value of the length map. |
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25 /// |
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26 ///It is also possible to change the underlying priority heap. |
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27 /// |
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28 ///\param GR The graph type the algorithm runs on. |
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29 ///\param LM This read-only |
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30 ///EdgeMap |
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31 ///determines the |
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32 ///lengths of the edges. It is read once for each edge, so the map |
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33 ///may involve in relatively time consuming process to compute the edge |
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34 ///length if it is necessary. The default map type is |
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35 ///\ref Graph::EdgeMap "Graph::EdgeMap<int>" |
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36 ///\param Heap The heap type used by the %Dijkstra |
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37 ///algorithm. The default |
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38 ///is using \ref BinHeap "binary heap". |
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39 /// |
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40 ///\author Jacint Szabo and Alpar Juttner |
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41 ///\todo We need a typedef-names should be standardized. (-: |
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42 |
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43 #ifdef DOXYGEN |
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44 template <typename GR, |
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45 typename LM, |
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46 typename Heap> |
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47 #else |
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48 template <typename GR, |
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49 typename LM=typename GR::template EdgeMap<int>, |
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50 template <class,class,class,class> class Heap = BinHeap > |
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51 #endif |
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52 class Dijkstra{ |
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53 public: |
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54 ///The type of the underlying graph. |
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55 typedef GR Graph; |
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56 typedef typename Graph::Node Node; |
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57 typedef typename Graph::NodeIt NodeIt; |
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58 typedef typename Graph::Edge Edge; |
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59 typedef typename Graph::OutEdgeIt OutEdgeIt; |
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60 |
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61 ///The type of the length of the edges. |
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62 typedef typename LM::Value Value; |
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63 ///The type of the map that stores the edge lengths. |
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64 typedef LM LengthMap; |
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65 ///\brief The type of the map that stores the last |
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66 ///edges of the shortest paths. |
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67 typedef typename Graph::template NodeMap<Edge> PredMap; |
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68 ///\brief The type of the map that stores the last but one |
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69 ///nodes of the shortest paths. |
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70 typedef typename Graph::template NodeMap<Node> PredNodeMap; |
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71 ///The type of the map that stores the dists of the nodes. |
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72 typedef typename Graph::template NodeMap<Value> DistMap; |
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73 |
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74 private: |
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75 const Graph *G; |
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76 const LM *length; |
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77 // bool local_length; |
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78 PredMap *predecessor; |
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79 bool local_predecessor; |
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80 PredNodeMap *pred_node; |
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81 bool local_pred_node; |
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82 DistMap *distance; |
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83 bool local_distance; |
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84 |
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85 ///Initialize maps |
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86 |
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87 ///\todo Error if \c G or are \c NULL. What about \c length? |
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88 ///\todo Better memory allocation (instead of new). |
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89 void init_maps() |
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90 { |
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91 // if(!length) { |
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92 // local_length = true; |
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93 // length = new LM(G); |
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94 // } |
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95 if(!predecessor) { |
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96 local_predecessor = true; |
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97 predecessor = new PredMap(*G); |
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98 } |
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99 if(!pred_node) { |
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100 local_pred_node = true; |
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101 pred_node = new PredNodeMap(*G); |
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102 } |
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103 if(!distance) { |
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104 local_distance = true; |
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105 distance = new DistMap(*G); |
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106 } |
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107 } |
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108 |
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109 public : |
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110 |
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111 Dijkstra(const Graph& _G, const LM& _length) : |
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112 G(&_G), length(&_length), |
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113 predecessor(NULL), pred_node(NULL), distance(NULL), |
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114 local_predecessor(false), local_pred_node(false), local_distance(false) |
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115 { } |
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116 |
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117 ~Dijkstra() |
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118 { |
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119 // if(local_length) delete length; |
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120 if(local_predecessor) delete predecessor; |
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121 if(local_pred_node) delete pred_node; |
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122 if(local_distance) delete distance; |
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123 } |
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124 |
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125 ///Sets the graph the algorithm will run on. |
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126 |
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127 ///Sets the graph the algorithm will run on. |
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128 ///\return <tt> (*this) </tt> |
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129 Dijkstra &setGraph(const Graph &_G) |
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130 { |
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131 G = &_G; |
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132 return *this; |
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133 } |
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134 ///Sets the length map. |
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135 |
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136 ///Sets the length map. |
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137 ///\return <tt> (*this) </tt> |
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138 Dijkstra &setLengthMap(const LM &m) |
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139 { |
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140 // if(local_length) { |
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141 // delete length; |
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142 // local_length=false; |
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143 // } |
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144 length = &m; |
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145 return *this; |
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146 } |
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147 |
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148 ///Sets the map storing the predecessor edges. |
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149 |
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150 ///Sets the map storing the predecessor edges. |
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151 ///If you don't use this function before calling \ref run(), |
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152 ///it will allocate one. The destuctor deallocates this |
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153 ///automatically allocated map, of course. |
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154 ///\return <tt> (*this) </tt> |
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155 Dijkstra &setPredMap(PredMap &m) |
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156 { |
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157 if(local_predecessor) { |
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158 delete predecessor; |
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159 local_predecessor=false; |
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160 } |
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161 predecessor = &m; |
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162 return *this; |
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163 } |
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164 |
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165 ///Sets the map storing the predecessor nodes. |
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166 |
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167 ///Sets the map storing the predecessor nodes. |
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168 ///If you don't use this function before calling \ref run(), |
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169 ///it will allocate one. The destuctor deallocates this |
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170 ///automatically allocated map, of course. |
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171 ///\return <tt> (*this) </tt> |
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172 Dijkstra &setPredNodeMap(PredNodeMap &m) |
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173 { |
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174 if(local_pred_node) { |
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175 delete pred_node; |
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176 local_pred_node=false; |
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177 } |
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178 pred_node = &m; |
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179 return *this; |
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180 } |
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181 |
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182 ///Sets the map storing the distances calculated by the algorithm. |
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183 |
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184 ///Sets the map storing the distances calculated by the algorithm. |
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185 ///If you don't use this function before calling \ref run(), |
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186 ///it will allocate one. The destuctor deallocates this |
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187 ///automatically allocated map, of course. |
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188 ///\return <tt> (*this) </tt> |
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189 Dijkstra &setDistMap(DistMap &m) |
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190 { |
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191 if(local_distance) { |
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192 delete distance; |
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193 local_distance=false; |
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194 } |
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195 distance = &m; |
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196 return *this; |
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197 } |
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198 |
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199 ///Runs %Dijkstra algorithm from node \c s. |
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200 |
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201 ///This method runs the %Dijkstra algorithm from a root node \c s |
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202 ///in order to |
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203 ///compute the |
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204 ///shortest path to each node. The algorithm computes |
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205 ///- The shortest path tree. |
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206 ///- The distance of each node from the root. |
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207 |
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208 void run(Node s) { |
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209 |
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210 init_maps(); |
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211 |
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212 for ( NodeIt u(*G) ; G->valid(u) ; G->next(u) ) { |
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213 predecessor->set(u,INVALID); |
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214 pred_node->set(u,INVALID); |
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215 } |
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216 |
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217 typename GR::template NodeMap<int> heap_map(*G,-1); |
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218 |
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219 typedef Heap<Node, Value, typename GR::template NodeMap<int>, |
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220 std::less<Value> > |
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221 HeapType; |
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222 |
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223 HeapType heap(heap_map); |
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224 |
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225 heap.push(s,0); |
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226 |
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227 while ( !heap.empty() ) { |
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228 |
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229 Node v=heap.top(); |
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230 Value oldvalue=heap[v]; |
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231 heap.pop(); |
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232 distance->set(v, oldvalue); |
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233 |
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234 |
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235 for(OutEdgeIt e(*G,v); G->valid(e); G->next(e)) { |
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236 Node w=G->bNode(e); |
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237 |
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238 switch(heap.state(w)) { |
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239 case HeapType::PRE_HEAP: |
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240 heap.push(w,oldvalue+(*length)[e]); |
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241 predecessor->set(w,e); |
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242 pred_node->set(w,v); |
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243 break; |
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244 case HeapType::IN_HEAP: |
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245 if ( oldvalue+(*length)[e] < heap[w] ) { |
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246 heap.decrease(w, oldvalue+(*length)[e]); |
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247 predecessor->set(w,e); |
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248 pred_node->set(w,v); |
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249 } |
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250 break; |
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251 case HeapType::POST_HEAP: |
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252 break; |
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253 } |
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254 } |
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255 } |
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256 } |
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257 |
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258 ///The distance of a node from the root. |
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259 |
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260 ///Returns the distance of a node from the root. |
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261 ///\pre \ref run() must be called before using this function. |
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262 ///\warning If node \c v in unreachable from the root the return value |
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263 ///of this funcion is undefined. |
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264 Value dist(Node v) const { return (*distance)[v]; } |
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265 |
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266 ///Returns the 'previous edge' of the shortest path tree. |
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267 |
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268 ///For a node \c v it returns the 'previous edge' of the shortest path tree, |
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269 ///i.e. it returns the last edge from a shortest path from the root to \c |
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270 ///v. It is \ref INVALID |
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271 ///if \c v is unreachable from the root or if \c v=s. The |
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272 ///shortest path tree used here is equal to the shortest path tree used in |
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273 ///\ref predNode(Node v). \pre \ref run() must be called before using |
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274 ///this function. |
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275 Edge pred(Node v) const { return (*predecessor)[v]; } |
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276 |
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277 ///Returns the 'previous node' of the shortest path tree. |
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278 |
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279 ///For a node \c v it returns the 'previous node' of the shortest path tree, |
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280 ///i.e. it returns the last but one node from a shortest path from the |
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281 ///root to \c /v. It is INVALID if \c v is unreachable from the root or if |
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282 ///\c v=s. The shortest path tree used here is equal to the shortest path |
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283 ///tree used in \ref pred(Node v). \pre \ref run() must be called before |
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284 ///using this function. |
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285 Node predNode(Node v) const { return (*pred_node)[v]; } |
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286 |
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287 ///Returns a reference to the NodeMap of distances. |
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288 |
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289 ///Returns a reference to the NodeMap of distances. \pre \ref run() must |
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290 ///be called before using this function. |
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291 const DistMap &distMap() const { return *distance;} |
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292 |
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293 ///Returns a reference to the shortest path tree map. |
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294 |
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295 ///Returns a reference to the NodeMap of the edges of the |
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296 ///shortest path tree. |
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297 ///\pre \ref run() must be called before using this function. |
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298 const PredMap &predMap() const { return *predecessor;} |
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299 |
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300 ///Returns a reference to the map of nodes of shortest paths. |
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301 |
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302 ///Returns a reference to the NodeMap of the last but one nodes of the |
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303 ///shortest path tree. |
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304 ///\pre \ref run() must be called before using this function. |
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305 const PredNodeMap &predNodeMap() const { return *pred_node;} |
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306 |
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307 ///Checks if a node is reachable from the root. |
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308 |
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309 ///Returns \c true if \c v is reachable from the root. |
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310 ///\warning the root node is reported to be unreached! |
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311 ///\todo Is this what we want? |
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312 ///\pre \ref run() must be called before using this function. |
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313 /// |
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314 bool reached(Node v) { return G->valid((*predecessor)[v]); } |
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315 |
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316 }; |
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317 |
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318 |
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319 // ********************************************************************** |
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320 // IMPLEMENTATIONS |
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321 // ********************************************************************** |
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322 |
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323 /// @} |
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324 |
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325 } //END OF NAMESPACE LEMON |
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326 |
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327 #endif |
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328 |
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329 |
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