1 | /* -*- C++ -*- |
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2 | * src/lemon/dfs.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_DFS_H |
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18 | #define LEMON_DFS_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 %DFS algorithm. |
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23 | /// |
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24 | ///\todo Revise Manual. |
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25 | |
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26 | #include <lemon/bin_heap.h> |
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27 | #include <lemon/invalid.h> |
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28 | |
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29 | namespace lemon { |
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30 | |
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31 | /// \addtogroup flowalgs |
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32 | /// @{ |
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33 | |
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34 | ///%DFS algorithm class. |
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35 | |
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36 | ///This class provides an efficient implementation of %DFS algorithm. |
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37 | /// |
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38 | ///\param GR The graph type the algorithm runs on. |
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39 | /// |
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40 | ///\author Alpar Juttner |
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41 | |
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42 | #ifdef DOXYGEN |
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43 | template <typename GR> |
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44 | #else |
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45 | template <typename GR> |
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46 | #endif |
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47 | class Dfs{ |
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48 | public: |
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49 | ///The type of the underlying graph. |
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50 | typedef GR Graph; |
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51 | ///\e |
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52 | typedef typename Graph::Node Node; |
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53 | ///\e |
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54 | typedef typename Graph::NodeIt NodeIt; |
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55 | ///\e |
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56 | typedef typename Graph::Edge Edge; |
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57 | ///\e |
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58 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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59 | |
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60 | ///\brief The type of the map that stores the last |
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61 | ///edges of the paths on the %DFS tree. |
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62 | typedef typename Graph::template NodeMap<Edge> PredMap; |
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63 | ///\brief The type of the map that stores the last but one |
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64 | ///nodes of the paths on the %DFS tree. |
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65 | typedef typename Graph::template NodeMap<Node> PredNodeMap; |
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66 | ///The type of the map that stores the dists of the nodes on the %DFS tree. |
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67 | typedef typename Graph::template NodeMap<int> DistMap; |
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68 | |
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69 | private: |
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70 | /// Pointer to the underlying graph. |
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71 | const Graph *G; |
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72 | ///Pointer to the map of predecessors edges. |
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73 | PredMap *predecessor; |
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74 | ///Indicates if \ref predecessor is locally allocated (\c true) or not. |
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75 | bool local_predecessor; |
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76 | ///Pointer to the map of predecessors nodes. |
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77 | PredNodeMap *pred_node; |
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78 | ///Indicates if \ref pred_node is locally allocated (\c true) or not. |
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79 | bool local_pred_node; |
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80 | ///Pointer to the map of distances. |
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81 | DistMap *distance; |
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82 | ///Indicates if \ref distance is locally allocated (\c true) or not. |
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83 | bool local_distance; |
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84 | |
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85 | ///The source node of the last execution. |
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86 | Node source; |
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87 | |
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88 | |
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89 | ///Initializes the maps. |
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90 | void init_maps() |
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91 | { |
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92 | if(!predecessor) { |
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93 | local_predecessor = true; |
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94 | predecessor = new PredMap(*G); |
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95 | } |
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96 | if(!pred_node) { |
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97 | local_pred_node = true; |
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98 | pred_node = new PredNodeMap(*G); |
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99 | } |
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100 | if(!distance) { |
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101 | local_distance = true; |
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102 | distance = new DistMap(*G); |
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103 | } |
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104 | } |
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105 | |
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106 | public : |
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107 | ///Constructor. |
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108 | |
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109 | ///\param _G the graph the algorithm will run on. |
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110 | /// |
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111 | Dfs(const Graph& _G) : |
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112 | G(&_G), |
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113 | predecessor(NULL), local_predecessor(false), |
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114 | pred_node(NULL), local_pred_node(false), |
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115 | distance(NULL), local_distance(false) |
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116 | { } |
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117 | |
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118 | ///Destructor. |
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119 | ~Dfs() |
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120 | { |
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121 | if(local_predecessor) delete predecessor; |
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122 | if(local_pred_node) delete pred_node; |
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123 | if(local_distance) delete distance; |
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124 | } |
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125 | |
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126 | ///Sets the map storing the predecessor edges. |
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127 | |
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128 | ///Sets the map storing the predecessor edges. |
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129 | ///If you don't use this function before calling \ref run(), |
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130 | ///it will allocate one. The destuctor deallocates this |
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131 | ///automatically allocated map, of course. |
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132 | ///\return <tt> (*this) </tt> |
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133 | Dfs &setPredMap(PredMap &m) |
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134 | { |
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135 | if(local_predecessor) { |
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136 | delete predecessor; |
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137 | local_predecessor=false; |
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138 | } |
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139 | predecessor = &m; |
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140 | return *this; |
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141 | } |
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142 | |
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143 | ///Sets the map storing the predecessor nodes. |
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144 | |
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145 | ///Sets the map storing the predecessor nodes. |
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146 | ///If you don't use this function before calling \ref run(), |
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147 | ///it will allocate one. The destuctor deallocates this |
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148 | ///automatically allocated map, of course. |
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149 | ///\return <tt> (*this) </tt> |
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150 | Dfs &setPredNodeMap(PredNodeMap &m) |
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151 | { |
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152 | if(local_pred_node) { |
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153 | delete pred_node; |
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154 | local_pred_node=false; |
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155 | } |
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156 | pred_node = &m; |
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157 | return *this; |
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158 | } |
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159 | |
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160 | ///Sets the map storing the distances calculated by the algorithm. |
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161 | |
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162 | ///Sets the map storing the distances calculated by the algorithm. |
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163 | ///If you don't use this function before calling \ref run(), |
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164 | ///it will allocate one. The destuctor deallocates this |
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165 | ///automatically allocated map, of course. |
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166 | ///\return <tt> (*this) </tt> |
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167 | Dfs &setDistMap(DistMap &m) |
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168 | { |
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169 | if(local_distance) { |
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170 | delete distance; |
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171 | local_distance=false; |
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172 | } |
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173 | distance = &m; |
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174 | return *this; |
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175 | } |
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176 | |
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177 | ///Runs %DFS algorithm from node \c s. |
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178 | |
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179 | ///This method runs the %DFS algorithm from a root node \c s |
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180 | ///in order to |
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181 | ///compute |
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182 | ///- a %DFS tree and |
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183 | ///- the distance of each node from the root on this tree. |
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184 | |
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185 | void run(Node s) { |
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186 | |
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187 | init_maps(); |
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188 | |
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189 | source = s; |
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190 | |
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191 | for ( NodeIt u(*G) ; u!=INVALID ; ++u ) { |
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192 | predecessor->set(u,INVALID); |
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193 | pred_node->set(u,INVALID); |
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194 | } |
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195 | |
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196 | int N=G->nodeNum(); |
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197 | std::vector<typename Graph::OutEdgeIt> Q(N); |
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198 | |
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199 | int Qh=0; |
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200 | |
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201 | G->first(Q[Qh],s); |
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202 | distance->set(s, 0); |
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203 | |
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204 | Node n=s; |
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205 | Node m; |
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206 | OutEdgeIt e; |
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207 | do { |
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208 | if((e=Q[Qh])!=INVALID) |
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209 | if((m=G->head(e))!=s && (*predecessor)[m=G->head(e)]==INVALID) { |
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210 | predecessor->set(m,e); |
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211 | pred_node->set(m,n); |
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212 | G->first(Q[++Qh],m); |
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213 | distance->set(m,Qh); |
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214 | n=m; |
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215 | } |
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216 | else ++Q[Qh]; |
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217 | else if(--Qh>=0) n=G->tail(Q[Qh]); |
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218 | } while(Qh>=0); |
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219 | } |
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220 | |
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221 | ///The distance of a node from the root on the %DFS tree. |
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222 | |
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223 | ///Returns the distance of a node from the root on the %DFS tree. |
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224 | ///\pre \ref run() must be called before using this function. |
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225 | ///\warning If node \c v in unreachable from the root the return value |
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226 | ///of this funcion is undefined. |
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227 | int dist(Node v) const { return (*distance)[v]; } |
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228 | |
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229 | ///Returns the 'previous edge' of the %DFS path tree. |
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230 | |
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231 | ///For a node \c v it returns the last edge of the path on the %DFS tree |
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232 | ///from the root to \c |
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233 | ///v. It is \ref INVALID |
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234 | ///if \c v is unreachable from the root or if \c v=s. The |
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235 | ///%DFS tree used here is equal to the %DFS tree used in |
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236 | ///\ref predNode(Node v). \pre \ref run() must be called before using |
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237 | ///this function. |
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238 | Edge pred(Node v) const { return (*predecessor)[v]; } |
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239 | |
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240 | ///Returns the 'previous node' of the %DFS tree. |
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241 | |
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242 | ///For a node \c v it returns the 'previous node' on the %DFS tree, |
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243 | ///i.e. it returns the last but one node of the path from the |
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244 | ///root to \c /v on the %DFS tree. |
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245 | ///It is INVALID if \c v is unreachable from the root or if |
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246 | ///\c v=s. |
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247 | ///\pre \ref run() must be called before |
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248 | ///using this function. |
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249 | Node predNode(Node v) const { return (*pred_node)[v]; } |
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250 | |
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251 | ///Returns a reference to the NodeMap of distances on the %DFS tree. |
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252 | |
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253 | ///Returns a reference to the NodeMap of distances on the %DFS tree. |
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254 | ///\pre \ref run() must |
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255 | ///be called before using this function. |
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256 | const DistMap &distMap() const { return *distance;} |
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257 | |
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258 | ///Returns a reference to the %DFS tree map. |
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259 | |
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260 | ///Returns a reference to the NodeMap of the edges of the |
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261 | ///%DFS tree. |
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262 | ///\pre \ref run() must be called before using this function. |
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263 | const PredMap &predMap() const { return *predecessor;} |
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264 | |
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265 | ///Returns a reference to the map of last but one nodes of the %DFS tree. |
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266 | |
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267 | ///Returns a reference to the NodeMap of the last but one nodes of the paths |
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268 | ///on the |
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269 | ///%DFS tree. |
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270 | ///\pre \ref run() must be called before using this function. |
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271 | const PredNodeMap &predNodeMap() const { return *pred_node;} |
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272 | |
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273 | ///Checks if a node is reachable from the root. |
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274 | |
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275 | ///Returns \c true if \c v is reachable from the root. |
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276 | ///\note The root node is reported to be reached! |
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277 | /// |
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278 | ///\pre \ref run() must be called before using this function. |
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279 | /// |
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280 | bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; } |
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281 | |
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282 | }; |
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283 | |
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284 | /// @} |
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285 | |
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286 | } //END OF NAMESPACE LEMON |
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287 | |
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288 | #endif |
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289 | |
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290 | |
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