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 skeleton::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 skeleton::ReadMap::ValueType "ValueType" 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 skeleton::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::ValueType ValueType; |
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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<ValueType> 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, ValueType, typename GR::template NodeMap<int>, |
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241 | std::less<ValueType> > |
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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 | ValueType 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->head(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 | ValueType 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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