1 /* -*- C++ -*- |
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2 * src/lemon/dijkstra.h - Part of LEMON, a generic C++ optimization library |
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3 * |
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4 * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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5 * (Egervary Combinatorial Optimization Research Group, EGRES). |
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6 * |
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7 * Permission to use, modify and distribute this software is granted |
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8 * provided that this copyright notice appears in all copies. For |
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9 * precise terms see the accompanying LICENSE file. |
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10 * |
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11 * This software is provided "AS IS" with no warranty of any kind, |
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12 * express or implied, and with no claim as to its suitability for any |
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13 * purpose. |
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14 * |
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15 */ |
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16 |
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17 #ifndef LEMON_DIJKSTRA_H |
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18 #define LEMON_DIJKSTRA_H |
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19 |
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20 ///\ingroup flowalgs |
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21 ///\file |
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22 ///\brief Dijkstra algorithm. |
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23 |
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24 #include <lemon/bin_heap.h> |
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25 #include <lemon/invalid.h> |
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26 |
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27 namespace lemon { |
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28 |
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29 /// \addtogroup flowalgs |
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30 /// @{ |
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31 |
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32 ///%Dijkstra algorithm class. |
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33 |
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34 ///This class provides an efficient implementation of %Dijkstra algorithm. |
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35 ///The edge lengths are passed to the algorithm using a |
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36 ///\ref concept::ReadMap "ReadMap", |
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37 ///so it is easy to change it to any kind of length. |
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38 /// |
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39 ///The type of the length is determined by the |
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40 ///\ref concept::ReadMap::Value "Value" of the length map. |
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41 /// |
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42 ///It is also possible to change the underlying priority heap. |
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43 /// |
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44 ///\param GR The graph type the algorithm runs on. |
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45 ///\param LM This read-only |
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46 ///EdgeMap |
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47 ///determines the |
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48 ///lengths of the edges. It is read once for each edge, so the map |
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49 ///may involve in relatively time consuming process to compute the edge |
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50 ///length if it is necessary. The default map type is |
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51 ///\ref concept::StaticGraph::EdgeMap "Graph::EdgeMap<int>" |
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52 ///\param Heap The heap type used by the %Dijkstra |
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53 ///algorithm. The default |
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54 ///is using \ref BinHeap "binary heap". |
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55 /// |
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56 ///\author Jacint Szabo and Alpar Juttner |
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57 ///\todo We need a typedef-names should be standardized. (-: |
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58 ///\todo Type of \c PredMap, \c PredNodeMap and \c DistMap |
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59 ///should not be fixed. (Problematic to solve). |
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60 |
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61 #ifdef DOXYGEN |
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62 template <typename GR, |
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63 typename LM, |
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64 typename Heap> |
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65 #else |
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66 template <typename GR, |
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67 typename LM=typename GR::template EdgeMap<int>, |
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68 template <class,class,class,class> class Heap = BinHeap > |
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69 #endif |
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70 class Dijkstra{ |
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71 public: |
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72 ///The type of the underlying graph. |
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73 typedef GR Graph; |
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74 ///\e |
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75 typedef typename Graph::Node Node; |
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76 ///\e |
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77 typedef typename Graph::NodeIt NodeIt; |
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78 ///\e |
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79 typedef typename Graph::Edge Edge; |
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80 ///\e |
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81 typedef typename Graph::OutEdgeIt OutEdgeIt; |
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82 |
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83 ///The type of the length of the edges. |
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84 typedef typename LM::Value Value; |
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85 ///The type of the map that stores the edge lengths. |
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86 typedef LM LengthMap; |
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87 ///\brief The type of the map that stores the last |
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88 ///edges of the shortest paths. |
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89 typedef typename Graph::template NodeMap<Edge> PredMap; |
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90 ///\brief The type of the map that stores the last but one |
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91 ///nodes of the shortest paths. |
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92 typedef typename Graph::template NodeMap<Node> PredNodeMap; |
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93 ///The type of the map that stores the dists of the nodes. |
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94 typedef typename Graph::template NodeMap<Value> DistMap; |
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95 |
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96 private: |
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97 /// Pointer to the underlying graph. |
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98 const Graph *G; |
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99 /// Pointer to the length map |
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100 const LM *length; |
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101 ///Pointer to the map of predecessors edges. |
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102 PredMap *predecessor; |
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103 ///Indicates if \ref predecessor is locally allocated (\c true) or not. |
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104 bool local_predecessor; |
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105 ///Pointer to the map of predecessors nodes. |
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106 PredNodeMap *pred_node; |
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107 ///Indicates if \ref pred_node is locally allocated (\c true) or not. |
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108 bool local_pred_node; |
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109 ///Pointer to the map of distances. |
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110 DistMap *distance; |
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111 ///Indicates if \ref distance is locally allocated (\c true) or not. |
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112 bool local_distance; |
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113 |
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114 ///The source node of the last execution. |
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115 Node source; |
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116 |
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117 ///Initializes the maps. |
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118 |
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119 ///\todo Error if \c G or are \c NULL. What about \c length? |
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120 ///\todo Better memory allocation (instead of new). |
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121 void init_maps() |
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122 { |
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123 if(!predecessor) { |
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124 local_predecessor = true; |
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125 predecessor = new PredMap(*G); |
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126 } |
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127 if(!pred_node) { |
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128 local_pred_node = true; |
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129 pred_node = new PredNodeMap(*G); |
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130 } |
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131 if(!distance) { |
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132 local_distance = true; |
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133 distance = new DistMap(*G); |
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134 } |
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135 } |
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136 |
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137 public : |
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138 ///Constructor. |
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139 |
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140 ///\param _G the graph the algorithm will run on. |
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141 ///\param _length the length map used by the algorithm. |
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142 Dijkstra(const Graph& _G, const LM& _length) : |
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143 G(&_G), length(&_length), |
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144 predecessor(NULL), local_predecessor(false), |
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145 pred_node(NULL), local_pred_node(false), |
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146 distance(NULL), local_distance(false) |
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147 { } |
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148 |
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149 ///Destructor. |
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150 ~Dijkstra() |
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151 { |
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152 if(local_predecessor) delete predecessor; |
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153 if(local_pred_node) delete pred_node; |
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154 if(local_distance) delete distance; |
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155 } |
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156 |
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157 ///Sets the length map. |
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158 |
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159 ///Sets the length map. |
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160 ///\return <tt> (*this) </tt> |
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161 Dijkstra &setLengthMap(const LM &m) |
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162 { |
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163 length = &m; |
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164 return *this; |
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165 } |
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166 |
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167 ///Sets the map storing the predecessor edges. |
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168 |
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169 ///Sets the map storing the predecessor edges. |
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170 ///If you don't use this function before calling \ref run(), |
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171 ///it will allocate one. The destuctor deallocates this |
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172 ///automatically allocated map, of course. |
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173 ///\return <tt> (*this) </tt> |
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174 Dijkstra &setPredMap(PredMap &m) |
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175 { |
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176 if(local_predecessor) { |
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177 delete predecessor; |
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178 local_predecessor=false; |
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179 } |
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180 predecessor = &m; |
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181 return *this; |
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182 } |
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183 |
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184 ///Sets the map storing the predecessor nodes. |
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185 |
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186 ///Sets the map storing the predecessor nodes. |
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187 ///If you don't use this function before calling \ref run(), |
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188 ///it will allocate one. The destuctor deallocates this |
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189 ///automatically allocated map, of course. |
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190 ///\return <tt> (*this) </tt> |
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191 Dijkstra &setPredNodeMap(PredNodeMap &m) |
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192 { |
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193 if(local_pred_node) { |
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194 delete pred_node; |
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195 local_pred_node=false; |
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196 } |
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197 pred_node = &m; |
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198 return *this; |
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199 } |
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200 |
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201 ///Sets the map storing the distances calculated by the algorithm. |
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202 |
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203 ///Sets the map storing the distances calculated by the algorithm. |
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204 ///If you don't use this function before calling \ref run(), |
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205 ///it will allocate one. The destuctor deallocates this |
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206 ///automatically allocated map, of course. |
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207 ///\return <tt> (*this) </tt> |
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208 Dijkstra &setDistMap(DistMap &m) |
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209 { |
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210 if(local_distance) { |
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211 delete distance; |
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212 local_distance=false; |
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213 } |
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214 distance = &m; |
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215 return *this; |
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216 } |
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217 |
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218 ///Runs %Dijkstra algorithm from node \c s. |
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219 |
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220 ///This method runs the %Dijkstra algorithm from a root node \c s |
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221 ///in order to |
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222 ///compute the |
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223 ///shortest path to each node. The algorithm computes |
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224 ///- The shortest path tree. |
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225 ///- The distance of each node from the root. |
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226 |
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227 void run(Node s) { |
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228 |
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229 init_maps(); |
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230 |
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231 source = s; |
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232 |
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233 for ( NodeIt u(*G) ; u!=INVALID ; ++u ) { |
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234 predecessor->set(u,INVALID); |
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235 pred_node->set(u,INVALID); |
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236 } |
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237 |
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238 typename GR::template NodeMap<int> heap_map(*G,-1); |
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239 |
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240 typedef Heap<Node, Value, typename GR::template NodeMap<int>, |
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241 std::less<Value> > |
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242 HeapType; |
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243 |
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244 HeapType heap(heap_map); |
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245 |
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246 heap.push(s,0); |
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247 |
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248 while ( !heap.empty() ) { |
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249 |
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250 Node v=heap.top(); |
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251 Value oldvalue=heap[v]; |
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252 heap.pop(); |
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253 distance->set(v, oldvalue); |
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254 |
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255 |
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256 for(OutEdgeIt e(*G,v); e!=INVALID; ++e) { |
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257 Node w=G->target(e); |
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258 switch(heap.state(w)) { |
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259 case HeapType::PRE_HEAP: |
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260 heap.push(w,oldvalue+(*length)[e]); |
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261 predecessor->set(w,e); |
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262 pred_node->set(w,v); |
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263 break; |
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264 case HeapType::IN_HEAP: |
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265 if ( oldvalue+(*length)[e] < heap[w] ) { |
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266 heap.decrease(w, oldvalue+(*length)[e]); |
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267 predecessor->set(w,e); |
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268 pred_node->set(w,v); |
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269 } |
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270 break; |
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271 case HeapType::POST_HEAP: |
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272 break; |
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273 } |
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274 } |
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275 } |
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276 } |
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277 |
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278 ///The distance of a node from the root. |
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279 |
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280 ///Returns the distance of a node from the root. |
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281 ///\pre \ref run() must be called before using this function. |
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282 ///\warning If node \c v in unreachable from the root the return value |
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283 ///of this funcion is undefined. |
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284 Value dist(Node v) const { return (*distance)[v]; } |
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285 |
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286 ///Returns the 'previous edge' of the shortest path tree. |
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287 |
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288 ///For a node \c v it returns the 'previous edge' of the shortest path tree, |
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289 ///i.e. it returns the last edge of a shortest path from the root to \c |
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290 ///v. It is \ref INVALID |
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291 ///if \c v is unreachable from the root or if \c v=s. The |
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292 ///shortest path tree used here is equal to the shortest path tree used in |
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293 ///\ref predNode(Node v). \pre \ref run() must be called before using |
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294 ///this function. |
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295 ///\todo predEdge could be a better name. |
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296 Edge pred(Node v) const { return (*predecessor)[v]; } |
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297 |
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298 ///Returns the 'previous node' of the shortest path tree. |
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299 |
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300 ///For a node \c v it returns the 'previous node' of the shortest path tree, |
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301 ///i.e. it returns the last but one node from a shortest path from the |
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302 ///root to \c /v. It is INVALID if \c v is unreachable from the root or if |
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303 ///\c v=s. The shortest path tree used here is equal to the shortest path |
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304 ///tree used in \ref pred(Node v). \pre \ref run() must be called before |
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305 ///using this function. |
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306 Node predNode(Node v) const { return (*pred_node)[v]; } |
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307 |
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308 ///Returns a reference to the NodeMap of distances. |
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309 |
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310 ///Returns a reference to the NodeMap of distances. \pre \ref run() must |
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311 ///be called before using this function. |
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312 const DistMap &distMap() const { return *distance;} |
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313 |
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314 ///Returns a reference to the shortest path tree map. |
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315 |
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316 ///Returns a reference to the NodeMap of the edges of the |
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317 ///shortest path tree. |
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318 ///\pre \ref run() must be called before using this function. |
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319 const PredMap &predMap() const { return *predecessor;} |
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320 |
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321 ///Returns a reference to the map of nodes of shortest paths. |
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322 |
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323 ///Returns a reference to the NodeMap of the last but one nodes of the |
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324 ///shortest path tree. |
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325 ///\pre \ref run() must be called before using this function. |
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326 const PredNodeMap &predNodeMap() const { return *pred_node;} |
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327 |
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328 ///Checks if a node is reachable from the root. |
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329 |
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330 ///Returns \c true if \c v is reachable from the root. |
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331 ///\note The root node is reported to be reached! |
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332 ///\pre \ref run() must be called before using this function. |
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333 /// |
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334 bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; } |
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335 |
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336 }; |
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337 |
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338 /// @} |
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339 |
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340 } //END OF NAMESPACE LEMON |
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341 |
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342 #endif |
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343 |
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344 |
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