1 | /* -*- mode: C++; indent-tabs-mode: nil; -*- |
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2 | * |
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3 | * This file is a part of LEMON, a generic C++ optimization library. |
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4 | * |
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5 | * Copyright (C) 2003-2008 |
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6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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8 | * |
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9 | * Permission to use, modify and distribute this software is granted |
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10 | * provided that this copyright notice appears in all copies. For |
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11 | * precise terms see the accompanying LICENSE file. |
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12 | * |
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13 | * This software is provided "AS IS" with no warranty of any kind, |
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14 | * express or implied, and with no claim as to its suitability for any |
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15 | * purpose. |
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16 | * |
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17 | */ |
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18 | |
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19 | #ifndef LEMON_BFS_H |
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20 | #define LEMON_BFS_H |
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21 | |
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22 | ///\ingroup search |
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23 | ///\file |
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24 | ///\brief BFS algorithm. |
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25 | |
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26 | #include <lemon/list_graph.h> |
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27 | #include <lemon/bits/path_dump.h> |
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28 | #include <lemon/core.h> |
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29 | #include <lemon/error.h> |
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30 | #include <lemon/maps.h> |
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31 | |
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32 | namespace lemon { |
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33 | |
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34 | ///Default traits class of Bfs class. |
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35 | |
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36 | ///Default traits class of Bfs class. |
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37 | ///\tparam GR Digraph type. |
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38 | template<class GR> |
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39 | struct BfsDefaultTraits |
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40 | { |
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41 | ///The type of the digraph the algorithm runs on. |
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42 | typedef GR Digraph; |
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43 | |
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44 | ///\brief The type of the map that stores the predecessor |
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45 | ///arcs of the shortest paths. |
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46 | /// |
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47 | ///The type of the map that stores the predecessor |
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48 | ///arcs of the shortest paths. |
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49 | ///It must meet the \ref concepts::WriteMap "WriteMap" concept. |
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50 | typedef typename Digraph::template NodeMap<typename Digraph::Arc> PredMap; |
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51 | ///Instantiates a \ref PredMap. |
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52 | |
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53 | ///This function instantiates a \ref PredMap. |
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54 | ///\param g is the digraph, to which we would like to define the |
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55 | ///\ref PredMap. |
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56 | ///\todo The digraph alone may be insufficient to initialize |
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57 | static PredMap *createPredMap(const Digraph &g) |
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58 | { |
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59 | return new PredMap(g); |
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60 | } |
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61 | |
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62 | ///The type of the map that indicates which nodes are processed. |
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63 | |
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64 | ///The type of the map that indicates which nodes are processed. |
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65 | ///It must meet the \ref concepts::WriteMap "WriteMap" concept. |
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66 | ///By default it is a NullMap. |
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67 | typedef NullMap<typename Digraph::Node,bool> ProcessedMap; |
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68 | ///Instantiates a \ref ProcessedMap. |
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69 | |
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70 | ///This function instantiates a \ref ProcessedMap. |
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71 | ///\param g is the digraph, to which |
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72 | ///we would like to define the \ref ProcessedMap |
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73 | #ifdef DOXYGEN |
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74 | static ProcessedMap *createProcessedMap(const Digraph &g) |
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75 | #else |
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76 | static ProcessedMap *createProcessedMap(const Digraph &) |
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77 | #endif |
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78 | { |
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79 | return new ProcessedMap(); |
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80 | } |
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81 | |
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82 | ///The type of the map that indicates which nodes are reached. |
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83 | |
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84 | ///The type of the map that indicates which nodes are reached. |
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85 | ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept. |
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86 | typedef typename Digraph::template NodeMap<bool> ReachedMap; |
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87 | ///Instantiates a \ref ReachedMap. |
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88 | |
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89 | ///This function instantiates a \ref ReachedMap. |
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90 | ///\param g is the digraph, to which |
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91 | ///we would like to define the \ref ReachedMap. |
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92 | static ReachedMap *createReachedMap(const Digraph &g) |
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93 | { |
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94 | return new ReachedMap(g); |
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95 | } |
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96 | |
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97 | ///The type of the map that stores the distances of the nodes. |
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98 | |
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99 | ///The type of the map that stores the distances of the nodes. |
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100 | ///It must meet the \ref concepts::WriteMap "WriteMap" concept. |
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101 | typedef typename Digraph::template NodeMap<int> DistMap; |
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102 | ///Instantiates a \ref DistMap. |
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103 | |
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104 | ///This function instantiates a \ref DistMap. |
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105 | ///\param g is the digraph, to which we would like to define the |
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106 | ///\ref DistMap. |
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107 | static DistMap *createDistMap(const Digraph &g) |
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108 | { |
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109 | return new DistMap(g); |
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110 | } |
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111 | }; |
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112 | |
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113 | ///%BFS algorithm class. |
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114 | |
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115 | ///\ingroup search |
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116 | ///This class provides an efficient implementation of the %BFS algorithm. |
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117 | /// |
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118 | ///There is also a \ref bfs() "function type interface" for the BFS |
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119 | ///algorithm, which is convenient in the simplier cases and it can be |
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120 | ///used easier. |
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121 | /// |
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122 | ///\tparam GR The type of the digraph the algorithm runs on. |
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123 | ///The default value is \ref ListDigraph. The value of GR is not used |
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124 | ///directly by \ref Bfs, it is only passed to \ref BfsDefaultTraits. |
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125 | ///\tparam TR Traits class to set various data types used by the algorithm. |
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126 | ///The default traits class is |
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127 | ///\ref BfsDefaultTraits "BfsDefaultTraits<GR>". |
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128 | ///See \ref BfsDefaultTraits for the documentation of |
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129 | ///a Bfs traits class. |
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130 | #ifdef DOXYGEN |
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131 | template <typename GR, |
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132 | typename TR> |
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133 | #else |
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134 | template <typename GR=ListDigraph, |
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135 | typename TR=BfsDefaultTraits<GR> > |
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136 | #endif |
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137 | class Bfs { |
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138 | public: |
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139 | ///\ref Exception for uninitialized parameters. |
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140 | |
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141 | ///This error represents problems in the initialization of the |
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142 | ///parameters of the algorithm. |
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143 | class UninitializedParameter : public lemon::UninitializedParameter { |
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144 | public: |
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145 | virtual const char* what() const throw() { |
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146 | return "lemon::Bfs::UninitializedParameter"; |
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147 | } |
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148 | }; |
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149 | |
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150 | ///The type of the digraph the algorithm runs on. |
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151 | typedef typename TR::Digraph Digraph; |
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152 | |
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153 | ///\brief The type of the map that stores the predecessor arcs of the |
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154 | ///shortest paths. |
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155 | typedef typename TR::PredMap PredMap; |
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156 | ///The type of the map that stores the distances of the nodes. |
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157 | typedef typename TR::DistMap DistMap; |
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158 | ///The type of the map that indicates which nodes are reached. |
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159 | typedef typename TR::ReachedMap ReachedMap; |
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160 | ///The type of the map that indicates which nodes are processed. |
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161 | typedef typename TR::ProcessedMap ProcessedMap; |
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162 | ///The type of the paths. |
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163 | typedef PredMapPath<Digraph, PredMap> Path; |
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164 | |
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165 | ///The traits class. |
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166 | typedef TR Traits; |
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167 | |
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168 | private: |
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169 | |
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170 | typedef typename Digraph::Node Node; |
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171 | typedef typename Digraph::NodeIt NodeIt; |
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172 | typedef typename Digraph::Arc Arc; |
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173 | typedef typename Digraph::OutArcIt OutArcIt; |
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174 | |
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175 | //Pointer to the underlying digraph. |
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176 | const Digraph *G; |
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177 | //Pointer to the map of predecessor arcs. |
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178 | PredMap *_pred; |
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179 | //Indicates if _pred is locally allocated (true) or not. |
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180 | bool local_pred; |
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181 | //Pointer to the map of distances. |
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182 | DistMap *_dist; |
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183 | //Indicates if _dist is locally allocated (true) or not. |
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184 | bool local_dist; |
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185 | //Pointer to the map of reached status of the nodes. |
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186 | ReachedMap *_reached; |
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187 | //Indicates if _reached is locally allocated (true) or not. |
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188 | bool local_reached; |
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189 | //Pointer to the map of processed status of the nodes. |
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190 | ProcessedMap *_processed; |
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191 | //Indicates if _processed is locally allocated (true) or not. |
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192 | bool local_processed; |
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193 | |
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194 | std::vector<typename Digraph::Node> _queue; |
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195 | int _queue_head,_queue_tail,_queue_next_dist; |
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196 | int _curr_dist; |
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197 | |
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198 | ///Creates the maps if necessary. |
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199 | ///\todo Better memory allocation (instead of new). |
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200 | void create_maps() |
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201 | { |
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202 | if(!_pred) { |
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203 | local_pred = true; |
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204 | _pred = Traits::createPredMap(*G); |
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205 | } |
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206 | if(!_dist) { |
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207 | local_dist = true; |
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208 | _dist = Traits::createDistMap(*G); |
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209 | } |
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210 | if(!_reached) { |
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211 | local_reached = true; |
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212 | _reached = Traits::createReachedMap(*G); |
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213 | } |
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214 | if(!_processed) { |
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215 | local_processed = true; |
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216 | _processed = Traits::createProcessedMap(*G); |
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217 | } |
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218 | } |
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219 | |
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220 | protected: |
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221 | |
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222 | Bfs() {} |
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223 | |
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224 | public: |
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225 | |
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226 | typedef Bfs Create; |
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227 | |
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228 | ///\name Named template parameters |
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229 | |
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230 | ///@{ |
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231 | |
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232 | template <class T> |
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233 | struct SetPredMapTraits : public Traits { |
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234 | typedef T PredMap; |
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235 | static PredMap *createPredMap(const Digraph &) |
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236 | { |
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237 | throw UninitializedParameter(); |
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238 | } |
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239 | }; |
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240 | ///\brief \ref named-templ-param "Named parameter" for setting |
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241 | ///\ref PredMap type. |
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242 | /// |
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243 | ///\ref named-templ-param "Named parameter" for setting |
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244 | ///\ref PredMap type. |
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245 | template <class T> |
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246 | struct SetPredMap : public Bfs< Digraph, SetPredMapTraits<T> > { |
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247 | typedef Bfs< Digraph, SetPredMapTraits<T> > Create; |
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248 | }; |
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249 | |
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250 | template <class T> |
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251 | struct SetDistMapTraits : public Traits { |
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252 | typedef T DistMap; |
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253 | static DistMap *createDistMap(const Digraph &) |
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254 | { |
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255 | throw UninitializedParameter(); |
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256 | } |
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257 | }; |
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258 | ///\brief \ref named-templ-param "Named parameter" for setting |
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259 | ///\ref DistMap type. |
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260 | /// |
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261 | ///\ref named-templ-param "Named parameter" for setting |
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262 | ///\ref DistMap type. |
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263 | template <class T> |
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264 | struct SetDistMap : public Bfs< Digraph, SetDistMapTraits<T> > { |
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265 | typedef Bfs< Digraph, SetDistMapTraits<T> > Create; |
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266 | }; |
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267 | |
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268 | template <class T> |
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269 | struct SetReachedMapTraits : public Traits { |
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270 | typedef T ReachedMap; |
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271 | static ReachedMap *createReachedMap(const Digraph &) |
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272 | { |
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273 | throw UninitializedParameter(); |
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274 | } |
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275 | }; |
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276 | ///\brief \ref named-templ-param "Named parameter" for setting |
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277 | ///\ref ReachedMap type. |
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278 | /// |
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279 | ///\ref named-templ-param "Named parameter" for setting |
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280 | ///\ref ReachedMap type. |
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281 | template <class T> |
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282 | struct SetReachedMap : public Bfs< Digraph, SetReachedMapTraits<T> > { |
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283 | typedef Bfs< Digraph, SetReachedMapTraits<T> > Create; |
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284 | }; |
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285 | |
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286 | template <class T> |
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287 | struct SetProcessedMapTraits : public Traits { |
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288 | typedef T ProcessedMap; |
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289 | static ProcessedMap *createProcessedMap(const Digraph &) |
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290 | { |
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291 | throw UninitializedParameter(); |
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292 | } |
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293 | }; |
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294 | ///\brief \ref named-templ-param "Named parameter" for setting |
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295 | ///\ref ProcessedMap type. |
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296 | /// |
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297 | ///\ref named-templ-param "Named parameter" for setting |
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298 | ///\ref ProcessedMap type. |
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299 | template <class T> |
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300 | struct SetProcessedMap : public Bfs< Digraph, SetProcessedMapTraits<T> > { |
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301 | typedef Bfs< Digraph, SetProcessedMapTraits<T> > Create; |
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302 | }; |
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303 | |
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304 | struct SetStandardProcessedMapTraits : public Traits { |
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305 | typedef typename Digraph::template NodeMap<bool> ProcessedMap; |
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306 | static ProcessedMap *createProcessedMap(const Digraph &g) |
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307 | { |
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308 | return new ProcessedMap(g); |
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309 | } |
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310 | }; |
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311 | ///\brief \ref named-templ-param "Named parameter" for setting |
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312 | ///\ref ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>. |
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313 | /// |
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314 | ///\ref named-templ-param "Named parameter" for setting |
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315 | ///\ref ProcessedMap type to be <tt>Digraph::NodeMap<bool></tt>. |
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316 | ///If you don't set it explicitly, it will be automatically allocated. |
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317 | struct SetStandardProcessedMap : |
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318 | public Bfs< Digraph, SetStandardProcessedMapTraits > { |
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319 | typedef Bfs< Digraph, SetStandardProcessedMapTraits > Create; |
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320 | }; |
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321 | |
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322 | ///@} |
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323 | |
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324 | public: |
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325 | |
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326 | ///Constructor. |
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327 | |
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328 | ///Constructor. |
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329 | ///\param g The digraph the algorithm runs on. |
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330 | Bfs(const Digraph &g) : |
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331 | G(&g), |
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332 | _pred(NULL), local_pred(false), |
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333 | _dist(NULL), local_dist(false), |
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334 | _reached(NULL), local_reached(false), |
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335 | _processed(NULL), local_processed(false) |
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336 | { } |
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337 | |
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338 | ///Destructor. |
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339 | ~Bfs() |
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340 | { |
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341 | if(local_pred) delete _pred; |
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342 | if(local_dist) delete _dist; |
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343 | if(local_reached) delete _reached; |
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344 | if(local_processed) delete _processed; |
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345 | } |
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346 | |
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347 | ///Sets the map that stores the predecessor arcs. |
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348 | |
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349 | ///Sets the map that stores the predecessor arcs. |
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350 | ///If you don't use this function before calling \ref run(), |
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351 | ///it will allocate one. The destructor deallocates this |
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352 | ///automatically allocated map, of course. |
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353 | ///\return <tt> (*this) </tt> |
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354 | Bfs &predMap(PredMap &m) |
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355 | { |
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356 | if(local_pred) { |
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357 | delete _pred; |
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358 | local_pred=false; |
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359 | } |
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360 | _pred = &m; |
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361 | return *this; |
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362 | } |
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363 | |
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364 | ///Sets the map that indicates which nodes are reached. |
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365 | |
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366 | ///Sets the map that indicates which nodes are reached. |
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367 | ///If you don't use this function before calling \ref run(), |
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368 | ///it will allocate one. The destructor deallocates this |
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369 | ///automatically allocated map, of course. |
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370 | ///\return <tt> (*this) </tt> |
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371 | Bfs &reachedMap(ReachedMap &m) |
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372 | { |
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373 | if(local_reached) { |
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374 | delete _reached; |
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375 | local_reached=false; |
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376 | } |
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377 | _reached = &m; |
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378 | return *this; |
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379 | } |
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380 | |
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381 | ///Sets the map that indicates which nodes are processed. |
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382 | |
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383 | ///Sets the map that indicates which nodes are processed. |
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384 | ///If you don't use this function before calling \ref run(), |
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385 | ///it will allocate one. The destructor deallocates this |
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386 | ///automatically allocated map, of course. |
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387 | ///\return <tt> (*this) </tt> |
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388 | Bfs &processedMap(ProcessedMap &m) |
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389 | { |
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390 | if(local_processed) { |
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391 | delete _processed; |
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392 | local_processed=false; |
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393 | } |
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394 | _processed = &m; |
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395 | return *this; |
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396 | } |
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397 | |
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398 | ///Sets the map that stores the distances of the nodes. |
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399 | |
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400 | ///Sets the map that stores the distances of the nodes calculated by |
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401 | ///the algorithm. |
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402 | ///If you don't use this function before calling \ref run(), |
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403 | ///it will allocate one. The destructor deallocates this |
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404 | ///automatically allocated map, of course. |
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405 | ///\return <tt> (*this) </tt> |
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406 | Bfs &distMap(DistMap &m) |
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407 | { |
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408 | if(local_dist) { |
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409 | delete _dist; |
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410 | local_dist=false; |
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411 | } |
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412 | _dist = &m; |
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413 | return *this; |
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414 | } |
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415 | |
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416 | public: |
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417 | |
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418 | ///\name Execution control |
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419 | ///The simplest way to execute the algorithm is to use |
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420 | ///one of the member functions called \ref lemon::Bfs::run() "run()". |
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421 | ///\n |
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422 | ///If you need more control on the execution, first you must call |
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423 | ///\ref lemon::Bfs::init() "init()", then you can add several source |
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424 | ///nodes with \ref lemon::Bfs::addSource() "addSource()". |
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425 | ///Finally \ref lemon::Bfs::start() "start()" will perform the |
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426 | ///actual path computation. |
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427 | |
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428 | ///@{ |
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429 | |
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430 | ///Initializes the internal data structures. |
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431 | |
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432 | ///Initializes the internal data structures. |
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433 | /// |
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434 | void init() |
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435 | { |
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436 | create_maps(); |
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437 | _queue.resize(countNodes(*G)); |
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438 | _queue_head=_queue_tail=0; |
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439 | _curr_dist=1; |
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440 | for ( NodeIt u(*G) ; u!=INVALID ; ++u ) { |
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441 | _pred->set(u,INVALID); |
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442 | _reached->set(u,false); |
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443 | _processed->set(u,false); |
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444 | } |
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445 | } |
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446 | |
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447 | ///Adds a new source node. |
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448 | |
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449 | ///Adds a new source node to the set of nodes to be processed. |
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450 | /// |
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451 | void addSource(Node s) |
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452 | { |
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453 | if(!(*_reached)[s]) |
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454 | { |
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455 | _reached->set(s,true); |
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456 | _pred->set(s,INVALID); |
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457 | _dist->set(s,0); |
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458 | _queue[_queue_head++]=s; |
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459 | _queue_next_dist=_queue_head; |
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460 | } |
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461 | } |
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462 | |
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463 | ///Processes the next node. |
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464 | |
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465 | ///Processes the next node. |
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466 | /// |
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467 | ///\return The processed node. |
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468 | /// |
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469 | ///\pre The queue must not be empty. |
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470 | Node processNextNode() |
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471 | { |
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472 | if(_queue_tail==_queue_next_dist) { |
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473 | _curr_dist++; |
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474 | _queue_next_dist=_queue_head; |
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475 | } |
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476 | Node n=_queue[_queue_tail++]; |
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477 | _processed->set(n,true); |
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478 | Node m; |
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479 | for(OutArcIt e(*G,n);e!=INVALID;++e) |
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480 | if(!(*_reached)[m=G->target(e)]) { |
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481 | _queue[_queue_head++]=m; |
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482 | _reached->set(m,true); |
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483 | _pred->set(m,e); |
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484 | _dist->set(m,_curr_dist); |
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485 | } |
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486 | return n; |
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487 | } |
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488 | |
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489 | ///Processes the next node. |
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490 | |
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491 | ///Processes the next node and checks if the given target node |
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492 | ///is reached. If the target node is reachable from the processed |
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493 | ///node, then the \c reach parameter will be set to \c true. |
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494 | /// |
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495 | ///\param target The target node. |
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496 | ///\retval reach Indicates if the target node is reached. |
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497 | ///It should be initially \c false. |
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498 | /// |
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499 | ///\return The processed node. |
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500 | /// |
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501 | ///\pre The queue must not be empty. |
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502 | Node processNextNode(Node target, bool& reach) |
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503 | { |
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504 | if(_queue_tail==_queue_next_dist) { |
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505 | _curr_dist++; |
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506 | _queue_next_dist=_queue_head; |
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507 | } |
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508 | Node n=_queue[_queue_tail++]; |
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509 | _processed->set(n,true); |
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510 | Node m; |
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511 | for(OutArcIt e(*G,n);e!=INVALID;++e) |
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512 | if(!(*_reached)[m=G->target(e)]) { |
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513 | _queue[_queue_head++]=m; |
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514 | _reached->set(m,true); |
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515 | _pred->set(m,e); |
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516 | _dist->set(m,_curr_dist); |
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517 | reach = reach || (target == m); |
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518 | } |
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519 | return n; |
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520 | } |
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521 | |
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522 | ///Processes the next node. |
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523 | |
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524 | ///Processes the next node and checks if at least one of reached |
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525 | ///nodes has \c true value in the \c nm node map. If one node |
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526 | ///with \c true value is reachable from the processed node, then the |
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527 | ///\c rnode parameter will be set to the first of such nodes. |
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528 | /// |
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529 | ///\param nm A \c bool (or convertible) node map that indicates the |
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530 | ///possible targets. |
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531 | ///\retval rnode The reached target node. |
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532 | ///It should be initially \c INVALID. |
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533 | /// |
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534 | ///\return The processed node. |
---|
535 | /// |
---|
536 | ///\pre The queue must not be empty. |
---|
537 | template<class NM> |
---|
538 | Node processNextNode(const NM& nm, Node& rnode) |
---|
539 | { |
---|
540 | if(_queue_tail==_queue_next_dist) { |
---|
541 | _curr_dist++; |
---|
542 | _queue_next_dist=_queue_head; |
---|
543 | } |
---|
544 | Node n=_queue[_queue_tail++]; |
---|
545 | _processed->set(n,true); |
---|
546 | Node m; |
---|
547 | for(OutArcIt e(*G,n);e!=INVALID;++e) |
---|
548 | if(!(*_reached)[m=G->target(e)]) { |
---|
549 | _queue[_queue_head++]=m; |
---|
550 | _reached->set(m,true); |
---|
551 | _pred->set(m,e); |
---|
552 | _dist->set(m,_curr_dist); |
---|
553 | if (nm[m] && rnode == INVALID) rnode = m; |
---|
554 | } |
---|
555 | return n; |
---|
556 | } |
---|
557 | |
---|
558 | ///The next node to be processed. |
---|
559 | |
---|
560 | ///Returns the next node to be processed or \c INVALID if the queue |
---|
561 | ///is empty. |
---|
562 | Node nextNode() const |
---|
563 | { |
---|
564 | return _queue_tail<_queue_head?_queue[_queue_tail]:INVALID; |
---|
565 | } |
---|
566 | |
---|
567 | ///\brief Returns \c false if there are nodes |
---|
568 | ///to be processed. |
---|
569 | /// |
---|
570 | ///Returns \c false if there are nodes |
---|
571 | ///to be processed in the queue. |
---|
572 | bool emptyQueue() const { return _queue_tail==_queue_head; } |
---|
573 | |
---|
574 | ///Returns the number of the nodes to be processed. |
---|
575 | |
---|
576 | ///Returns the number of the nodes to be processed in the queue. |
---|
577 | int queueSize() const { return _queue_head-_queue_tail; } |
---|
578 | |
---|
579 | ///Executes the algorithm. |
---|
580 | |
---|
581 | ///Executes the algorithm. |
---|
582 | /// |
---|
583 | ///This method runs the %BFS algorithm from the root node(s) |
---|
584 | ///in order to compute the shortest path to each node. |
---|
585 | /// |
---|
586 | ///The algorithm computes |
---|
587 | ///- the shortest path tree (forest), |
---|
588 | ///- the distance of each node from the root(s). |
---|
589 | /// |
---|
590 | ///\pre init() must be called and at least one root node should be |
---|
591 | ///added with addSource() before using this function. |
---|
592 | /// |
---|
593 | ///\note <tt>b.start()</tt> is just a shortcut of the following code. |
---|
594 | ///\code |
---|
595 | /// while ( !b.emptyQueue() ) { |
---|
596 | /// b.processNextNode(); |
---|
597 | /// } |
---|
598 | ///\endcode |
---|
599 | void start() |
---|
600 | { |
---|
601 | while ( !emptyQueue() ) processNextNode(); |
---|
602 | } |
---|
603 | |
---|
604 | ///Executes the algorithm until the given target node is reached. |
---|
605 | |
---|
606 | ///Executes the algorithm until the given target node is reached. |
---|
607 | /// |
---|
608 | ///This method runs the %BFS algorithm from the root node(s) |
---|
609 | ///in order to compute the shortest path to \c dest. |
---|
610 | /// |
---|
611 | ///The algorithm computes |
---|
612 | ///- the shortest path to \c dest, |
---|
613 | ///- the distance of \c dest from the root(s). |
---|
614 | /// |
---|
615 | ///\pre init() must be called and at least one root node should be |
---|
616 | ///added with addSource() before using this function. |
---|
617 | /// |
---|
618 | ///\note <tt>b.start(t)</tt> is just a shortcut of the following code. |
---|
619 | ///\code |
---|
620 | /// bool reach = false; |
---|
621 | /// while ( !b.emptyQueue() && !reach ) { |
---|
622 | /// b.processNextNode(t, reach); |
---|
623 | /// } |
---|
624 | ///\endcode |
---|
625 | void start(Node dest) |
---|
626 | { |
---|
627 | bool reach = false; |
---|
628 | while ( !emptyQueue() && !reach ) processNextNode(dest, reach); |
---|
629 | } |
---|
630 | |
---|
631 | ///Executes the algorithm until a condition is met. |
---|
632 | |
---|
633 | ///Executes the algorithm until a condition is met. |
---|
634 | /// |
---|
635 | ///This method runs the %BFS algorithm from the root node(s) in |
---|
636 | ///order to compute the shortest path to a node \c v with |
---|
637 | /// <tt>nm[v]</tt> true, if such a node can be found. |
---|
638 | /// |
---|
639 | ///\param nm A \c bool (or convertible) node map. The algorithm |
---|
640 | ///will stop when it reaches a node \c v with <tt>nm[v]</tt> true. |
---|
641 | /// |
---|
642 | ///\return The reached node \c v with <tt>nm[v]</tt> true or |
---|
643 | ///\c INVALID if no such node was found. |
---|
644 | /// |
---|
645 | ///\pre init() must be called and at least one root node should be |
---|
646 | ///added with addSource() before using this function. |
---|
647 | /// |
---|
648 | ///\note <tt>b.start(nm)</tt> is just a shortcut of the following code. |
---|
649 | ///\code |
---|
650 | /// Node rnode = INVALID; |
---|
651 | /// while ( !b.emptyQueue() && rnode == INVALID ) { |
---|
652 | /// b.processNextNode(nm, rnode); |
---|
653 | /// } |
---|
654 | /// return rnode; |
---|
655 | ///\endcode |
---|
656 | template<class NodeBoolMap> |
---|
657 | Node start(const NodeBoolMap &nm) |
---|
658 | { |
---|
659 | Node rnode = INVALID; |
---|
660 | while ( !emptyQueue() && rnode == INVALID ) { |
---|
661 | processNextNode(nm, rnode); |
---|
662 | } |
---|
663 | return rnode; |
---|
664 | } |
---|
665 | |
---|
666 | ///Runs the algorithm from the given node. |
---|
667 | |
---|
668 | ///This method runs the %BFS algorithm from node \c s |
---|
669 | ///in order to compute the shortest path to each node. |
---|
670 | /// |
---|
671 | ///The algorithm computes |
---|
672 | ///- the shortest path tree, |
---|
673 | ///- the distance of each node from the root. |
---|
674 | /// |
---|
675 | ///\note <tt>b.run(s)</tt> is just a shortcut of the following code. |
---|
676 | ///\code |
---|
677 | /// b.init(); |
---|
678 | /// b.addSource(s); |
---|
679 | /// b.start(); |
---|
680 | ///\endcode |
---|
681 | void run(Node s) { |
---|
682 | init(); |
---|
683 | addSource(s); |
---|
684 | start(); |
---|
685 | } |
---|
686 | |
---|
687 | ///Finds the shortest path between \c s and \c t. |
---|
688 | |
---|
689 | ///This method runs the %BFS algorithm from node \c s |
---|
690 | ///in order to compute the shortest path to \c t. |
---|
691 | /// |
---|
692 | ///\return The length of the shortest <tt>s</tt>--<tt>t</tt> path, |
---|
693 | ///if \c t is reachable form \c s, \c 0 otherwise. |
---|
694 | /// |
---|
695 | ///\note Apart from the return value, <tt>b.run(s,t)</tt> is just a |
---|
696 | ///shortcut of the following code. |
---|
697 | ///\code |
---|
698 | /// b.init(); |
---|
699 | /// b.addSource(s); |
---|
700 | /// b.start(t); |
---|
701 | ///\endcode |
---|
702 | int run(Node s,Node t) { |
---|
703 | init(); |
---|
704 | addSource(s); |
---|
705 | start(t); |
---|
706 | return reached(t) ? _curr_dist : 0; |
---|
707 | } |
---|
708 | |
---|
709 | ///Runs the algorithm to visit all nodes in the digraph. |
---|
710 | |
---|
711 | ///This method runs the %BFS algorithm in order to |
---|
712 | ///compute the shortest path to each node. |
---|
713 | /// |
---|
714 | ///The algorithm computes |
---|
715 | ///- the shortest path tree (forest), |
---|
716 | ///- the distance of each node from the root(s). |
---|
717 | /// |
---|
718 | ///\note <tt>b.run(s)</tt> is just a shortcut of the following code. |
---|
719 | ///\code |
---|
720 | /// b.init(); |
---|
721 | /// for (NodeIt n(gr); n != INVALID; ++n) { |
---|
722 | /// if (!b.reached(n)) { |
---|
723 | /// b.addSource(n); |
---|
724 | /// b.start(); |
---|
725 | /// } |
---|
726 | /// } |
---|
727 | ///\endcode |
---|
728 | void run() { |
---|
729 | init(); |
---|
730 | for (NodeIt n(*G); n != INVALID; ++n) { |
---|
731 | if (!reached(n)) { |
---|
732 | addSource(n); |
---|
733 | start(); |
---|
734 | } |
---|
735 | } |
---|
736 | } |
---|
737 | |
---|
738 | ///@} |
---|
739 | |
---|
740 | ///\name Query Functions |
---|
741 | ///The result of the %BFS algorithm can be obtained using these |
---|
742 | ///functions.\n |
---|
743 | ///Either \ref lemon::Bfs::run() "run()" or \ref lemon::Bfs::start() |
---|
744 | ///"start()" must be called before using them. |
---|
745 | |
---|
746 | ///@{ |
---|
747 | |
---|
748 | ///The shortest path to a node. |
---|
749 | |
---|
750 | ///Returns the shortest path to a node. |
---|
751 | /// |
---|
752 | ///\warning \c t should be reachable from the root(s). |
---|
753 | /// |
---|
754 | ///\pre Either \ref run() or \ref start() must be called before |
---|
755 | ///using this function. |
---|
756 | Path path(Node t) const { return Path(*G, *_pred, t); } |
---|
757 | |
---|
758 | ///The distance of a node from the root(s). |
---|
759 | |
---|
760 | ///Returns the distance of a node from the root(s). |
---|
761 | /// |
---|
762 | ///\warning If node \c v is not reachable from the root(s), then |
---|
763 | ///the return value of this function is undefined. |
---|
764 | /// |
---|
765 | ///\pre Either \ref run() or \ref start() must be called before |
---|
766 | ///using this function. |
---|
767 | int dist(Node v) const { return (*_dist)[v]; } |
---|
768 | |
---|
769 | ///Returns the 'previous arc' of the shortest path tree for a node. |
---|
770 | |
---|
771 | ///This function returns the 'previous arc' of the shortest path |
---|
772 | ///tree for the node \c v, i.e. it returns the last arc of a |
---|
773 | ///shortest path from the root(s) to \c v. It is \c INVALID if \c v |
---|
774 | ///is not reachable from the root(s) or if \c v is a root. |
---|
775 | /// |
---|
776 | ///The shortest path tree used here is equal to the shortest path |
---|
777 | ///tree used in \ref predNode(). |
---|
778 | /// |
---|
779 | ///\pre Either \ref run() or \ref start() must be called before |
---|
780 | ///using this function. |
---|
781 | Arc predArc(Node v) const { return (*_pred)[v];} |
---|
782 | |
---|
783 | ///Returns the 'previous node' of the shortest path tree for a node. |
---|
784 | |
---|
785 | ///This function returns the 'previous node' of the shortest path |
---|
786 | ///tree for the node \c v, i.e. it returns the last but one node |
---|
787 | ///from a shortest path from the root(s) to \c v. It is \c INVALID |
---|
788 | ///if \c v is not reachable from the root(s) or if \c v is a root. |
---|
789 | /// |
---|
790 | ///The shortest path tree used here is equal to the shortest path |
---|
791 | ///tree used in \ref predArc(). |
---|
792 | /// |
---|
793 | ///\pre Either \ref run() or \ref start() must be called before |
---|
794 | ///using this function. |
---|
795 | Node predNode(Node v) const { return (*_pred)[v]==INVALID ? INVALID: |
---|
796 | G->source((*_pred)[v]); } |
---|
797 | |
---|
798 | ///\brief Returns a const reference to the node map that stores the |
---|
799 | /// distances of the nodes. |
---|
800 | /// |
---|
801 | ///Returns a const reference to the node map that stores the distances |
---|
802 | ///of the nodes calculated by the algorithm. |
---|
803 | /// |
---|
804 | ///\pre Either \ref run() or \ref init() |
---|
805 | ///must be called before using this function. |
---|
806 | const DistMap &distMap() const { return *_dist;} |
---|
807 | |
---|
808 | ///\brief Returns a const reference to the node map that stores the |
---|
809 | ///predecessor arcs. |
---|
810 | /// |
---|
811 | ///Returns a const reference to the node map that stores the predecessor |
---|
812 | ///arcs, which form the shortest path tree. |
---|
813 | /// |
---|
814 | ///\pre Either \ref run() or \ref init() |
---|
815 | ///must be called before using this function. |
---|
816 | const PredMap &predMap() const { return *_pred;} |
---|
817 | |
---|
818 | ///Checks if a node is reachable from the root(s). |
---|
819 | |
---|
820 | ///Returns \c true if \c v is reachable from the root(s). |
---|
821 | ///\pre Either \ref run() or \ref start() |
---|
822 | ///must be called before using this function. |
---|
823 | bool reached(Node v) const { return (*_reached)[v]; } |
---|
824 | |
---|
825 | ///@} |
---|
826 | }; |
---|
827 | |
---|
828 | ///Default traits class of bfs() function. |
---|
829 | |
---|
830 | ///Default traits class of bfs() function. |
---|
831 | ///\tparam GR Digraph type. |
---|
832 | template<class GR> |
---|
833 | struct BfsWizardDefaultTraits |
---|
834 | { |
---|
835 | ///The type of the digraph the algorithm runs on. |
---|
836 | typedef GR Digraph; |
---|
837 | |
---|
838 | ///\brief The type of the map that stores the predecessor |
---|
839 | ///arcs of the shortest paths. |
---|
840 | /// |
---|
841 | ///The type of the map that stores the predecessor |
---|
842 | ///arcs of the shortest paths. |
---|
843 | ///It must meet the \ref concepts::WriteMap "WriteMap" concept. |
---|
844 | typedef NullMap<typename Digraph::Node,typename Digraph::Arc> PredMap; |
---|
845 | ///Instantiates a \ref PredMap. |
---|
846 | |
---|
847 | ///This function instantiates a \ref PredMap. |
---|
848 | ///\param g is the digraph, to which we would like to define the |
---|
849 | ///\ref PredMap. |
---|
850 | ///\todo The digraph alone may be insufficient to initialize |
---|
851 | #ifdef DOXYGEN |
---|
852 | static PredMap *createPredMap(const Digraph &g) |
---|
853 | #else |
---|
854 | static PredMap *createPredMap(const Digraph &) |
---|
855 | #endif |
---|
856 | { |
---|
857 | return new PredMap(); |
---|
858 | } |
---|
859 | |
---|
860 | ///The type of the map that indicates which nodes are processed. |
---|
861 | |
---|
862 | ///The type of the map that indicates which nodes are processed. |
---|
863 | ///It must meet the \ref concepts::WriteMap "WriteMap" concept. |
---|
864 | typedef NullMap<typename Digraph::Node,bool> ProcessedMap; |
---|
865 | ///Instantiates a \ref ProcessedMap. |
---|
866 | |
---|
867 | ///This function instantiates a \ref ProcessedMap. |
---|
868 | ///\param g is the digraph, to which |
---|
869 | ///we would like to define the \ref ProcessedMap. |
---|
870 | #ifdef DOXYGEN |
---|
871 | static ProcessedMap *createProcessedMap(const Digraph &g) |
---|
872 | #else |
---|
873 | static ProcessedMap *createProcessedMap(const Digraph &) |
---|
874 | #endif |
---|
875 | { |
---|
876 | return new ProcessedMap(); |
---|
877 | } |
---|
878 | |
---|
879 | ///The type of the map that indicates which nodes are reached. |
---|
880 | |
---|
881 | ///The type of the map that indicates which nodes are reached. |
---|
882 | ///It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept. |
---|
883 | typedef typename Digraph::template NodeMap<bool> ReachedMap; |
---|
884 | ///Instantiates a \ref ReachedMap. |
---|
885 | |
---|
886 | ///This function instantiates a \ref ReachedMap. |
---|
887 | ///\param g is the digraph, to which |
---|
888 | ///we would like to define the \ref ReachedMap. |
---|
889 | static ReachedMap *createReachedMap(const Digraph &g) |
---|
890 | { |
---|
891 | return new ReachedMap(g); |
---|
892 | } |
---|
893 | |
---|
894 | ///The type of the map that stores the distances of the nodes. |
---|
895 | |
---|
896 | ///The type of the map that stores the distances of the nodes. |
---|
897 | ///It must meet the \ref concepts::WriteMap "WriteMap" concept. |
---|
898 | /// |
---|
899 | typedef NullMap<typename Digraph::Node,int> DistMap; |
---|
900 | ///Instantiates a \ref DistMap. |
---|
901 | |
---|
902 | ///This function instantiates a \ref DistMap. |
---|
903 | ///\param g is the digraph, to which we would like to define |
---|
904 | ///the \ref DistMap |
---|
905 | #ifdef DOXYGEN |
---|
906 | static DistMap *createDistMap(const Digraph &g) |
---|
907 | #else |
---|
908 | static DistMap *createDistMap(const Digraph &) |
---|
909 | #endif |
---|
910 | { |
---|
911 | return new DistMap(); |
---|
912 | } |
---|
913 | }; |
---|
914 | |
---|
915 | /// Default traits class used by \ref BfsWizard |
---|
916 | |
---|
917 | /// To make it easier to use Bfs algorithm |
---|
918 | /// we have created a wizard class. |
---|
919 | /// This \ref BfsWizard class needs default traits, |
---|
920 | /// as well as the \ref Bfs class. |
---|
921 | /// The \ref BfsWizardBase is a class to be the default traits of the |
---|
922 | /// \ref BfsWizard class. |
---|
923 | template<class GR> |
---|
924 | class BfsWizardBase : public BfsWizardDefaultTraits<GR> |
---|
925 | { |
---|
926 | |
---|
927 | typedef BfsWizardDefaultTraits<GR> Base; |
---|
928 | protected: |
---|
929 | //The type of the nodes in the digraph. |
---|
930 | typedef typename Base::Digraph::Node Node; |
---|
931 | |
---|
932 | //Pointer to the digraph the algorithm runs on. |
---|
933 | void *_g; |
---|
934 | //Pointer to the map of reached nodes. |
---|
935 | void *_reached; |
---|
936 | //Pointer to the map of processed nodes. |
---|
937 | void *_processed; |
---|
938 | //Pointer to the map of predecessors arcs. |
---|
939 | void *_pred; |
---|
940 | //Pointer to the map of distances. |
---|
941 | void *_dist; |
---|
942 | //Pointer to the source node. |
---|
943 | Node _source; |
---|
944 | |
---|
945 | public: |
---|
946 | /// Constructor. |
---|
947 | |
---|
948 | /// This constructor does not require parameters, therefore it initiates |
---|
949 | /// all of the attributes to default values (0, INVALID). |
---|
950 | BfsWizardBase() : _g(0), _reached(0), _processed(0), _pred(0), |
---|
951 | _dist(0), _source(INVALID) {} |
---|
952 | |
---|
953 | /// Constructor. |
---|
954 | |
---|
955 | /// This constructor requires some parameters, |
---|
956 | /// listed in the parameters list. |
---|
957 | /// Others are initiated to 0. |
---|
958 | /// \param g The digraph the algorithm runs on. |
---|
959 | /// \param s The source node. |
---|
960 | BfsWizardBase(const GR &g, Node s=INVALID) : |
---|
961 | _g(reinterpret_cast<void*>(const_cast<GR*>(&g))), |
---|
962 | _reached(0), _processed(0), _pred(0), _dist(0), _source(s) {} |
---|
963 | |
---|
964 | }; |
---|
965 | |
---|
966 | /// Auxiliary class for the function type interface of BFS algorithm. |
---|
967 | |
---|
968 | /// This auxiliary class is created to implement the function type |
---|
969 | /// interface of \ref Bfs algorithm. It uses the functions and features |
---|
970 | /// of the plain \ref Bfs, but it is much simpler to use it. |
---|
971 | /// It should only be used through the \ref bfs() function, which makes |
---|
972 | /// it easier to use the algorithm. |
---|
973 | /// |
---|
974 | /// Simplicity means that the way to change the types defined |
---|
975 | /// in the traits class is based on functions that returns the new class |
---|
976 | /// and not on templatable built-in classes. |
---|
977 | /// When using the plain \ref Bfs |
---|
978 | /// the new class with the modified type comes from |
---|
979 | /// the original class by using the :: |
---|
980 | /// operator. In the case of \ref BfsWizard only |
---|
981 | /// a function have to be called, and it will |
---|
982 | /// return the needed class. |
---|
983 | /// |
---|
984 | /// It does not have own \ref run() method. When its \ref run() method |
---|
985 | /// is called, it initiates a plain \ref Bfs object, and calls the |
---|
986 | /// \ref Bfs::run() method of it. |
---|
987 | template<class TR> |
---|
988 | class BfsWizard : public TR |
---|
989 | { |
---|
990 | typedef TR Base; |
---|
991 | |
---|
992 | ///The type of the digraph the algorithm runs on. |
---|
993 | typedef typename TR::Digraph Digraph; |
---|
994 | |
---|
995 | typedef typename Digraph::Node Node; |
---|
996 | typedef typename Digraph::NodeIt NodeIt; |
---|
997 | typedef typename Digraph::Arc Arc; |
---|
998 | typedef typename Digraph::OutArcIt OutArcIt; |
---|
999 | |
---|
1000 | ///\brief The type of the map that stores the predecessor |
---|
1001 | ///arcs of the shortest paths. |
---|
1002 | typedef typename TR::PredMap PredMap; |
---|
1003 | ///\brief The type of the map that stores the distances of the nodes. |
---|
1004 | typedef typename TR::DistMap DistMap; |
---|
1005 | ///\brief The type of the map that indicates which nodes are reached. |
---|
1006 | typedef typename TR::ReachedMap ReachedMap; |
---|
1007 | ///\brief The type of the map that indicates which nodes are processed. |
---|
1008 | typedef typename TR::ProcessedMap ProcessedMap; |
---|
1009 | |
---|
1010 | public: |
---|
1011 | |
---|
1012 | /// Constructor. |
---|
1013 | BfsWizard() : TR() {} |
---|
1014 | |
---|
1015 | /// Constructor that requires parameters. |
---|
1016 | |
---|
1017 | /// Constructor that requires parameters. |
---|
1018 | /// These parameters will be the default values for the traits class. |
---|
1019 | BfsWizard(const Digraph &g, Node s=INVALID) : |
---|
1020 | TR(g,s) {} |
---|
1021 | |
---|
1022 | ///Copy constructor |
---|
1023 | BfsWizard(const TR &b) : TR(b) {} |
---|
1024 | |
---|
1025 | ~BfsWizard() {} |
---|
1026 | |
---|
1027 | ///Runs BFS algorithm from a source node. |
---|
1028 | |
---|
1029 | ///Runs BFS algorithm from a source node. |
---|
1030 | ///The node can be given with the \ref source() function. |
---|
1031 | void run() |
---|
1032 | { |
---|
1033 | if(Base::_source==INVALID) throw UninitializedParameter(); |
---|
1034 | Bfs<Digraph,TR> alg(*reinterpret_cast<const Digraph*>(Base::_g)); |
---|
1035 | if(Base::_reached) |
---|
1036 | alg.reachedMap(*reinterpret_cast<ReachedMap*>(Base::_reached)); |
---|
1037 | if(Base::_processed) |
---|
1038 | alg.processedMap(*reinterpret_cast<ProcessedMap*>(Base::_processed)); |
---|
1039 | if(Base::_pred) |
---|
1040 | alg.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
---|
1041 | if(Base::_dist) |
---|
1042 | alg.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
---|
1043 | alg.run(Base::_source); |
---|
1044 | } |
---|
1045 | |
---|
1046 | ///Runs BFS algorithm from the given node. |
---|
1047 | |
---|
1048 | ///Runs BFS algorithm from the given node. |
---|
1049 | ///\param s is the given source. |
---|
1050 | void run(Node s) |
---|
1051 | { |
---|
1052 | Base::_source=s; |
---|
1053 | run(); |
---|
1054 | } |
---|
1055 | |
---|
1056 | /// Sets the source node, from which the Bfs algorithm runs. |
---|
1057 | |
---|
1058 | /// Sets the source node, from which the Bfs algorithm runs. |
---|
1059 | /// \param s is the source node. |
---|
1060 | BfsWizard<TR> &source(Node s) |
---|
1061 | { |
---|
1062 | Base::_source=s; |
---|
1063 | return *this; |
---|
1064 | } |
---|
1065 | |
---|
1066 | template<class T> |
---|
1067 | struct SetPredMapBase : public Base { |
---|
1068 | typedef T PredMap; |
---|
1069 | static PredMap *createPredMap(const Digraph &) { return 0; }; |
---|
1070 | SetPredMapBase(const TR &b) : TR(b) {} |
---|
1071 | }; |
---|
1072 | ///\brief \ref named-templ-param "Named parameter" |
---|
1073 | ///for setting \ref PredMap object. |
---|
1074 | /// |
---|
1075 | /// \ref named-templ-param "Named parameter" |
---|
1076 | ///for setting \ref PredMap object. |
---|
1077 | template<class T> |
---|
1078 | BfsWizard<SetPredMapBase<T> > predMap(const T &t) |
---|
1079 | { |
---|
1080 | Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
1081 | return BfsWizard<SetPredMapBase<T> >(*this); |
---|
1082 | } |
---|
1083 | |
---|
1084 | template<class T> |
---|
1085 | struct SetReachedMapBase : public Base { |
---|
1086 | typedef T ReachedMap; |
---|
1087 | static ReachedMap *createReachedMap(const Digraph &) { return 0; }; |
---|
1088 | SetReachedMapBase(const TR &b) : TR(b) {} |
---|
1089 | }; |
---|
1090 | ///\brief \ref named-templ-param "Named parameter" |
---|
1091 | ///for setting \ref ReachedMap object. |
---|
1092 | /// |
---|
1093 | /// \ref named-templ-param "Named parameter" |
---|
1094 | ///for setting \ref ReachedMap object. |
---|
1095 | template<class T> |
---|
1096 | BfsWizard<SetReachedMapBase<T> > reachedMap(const T &t) |
---|
1097 | { |
---|
1098 | Base::_reached=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
1099 | return BfsWizard<SetReachedMapBase<T> >(*this); |
---|
1100 | } |
---|
1101 | |
---|
1102 | template<class T> |
---|
1103 | struct SetProcessedMapBase : public Base { |
---|
1104 | typedef T ProcessedMap; |
---|
1105 | static ProcessedMap *createProcessedMap(const Digraph &) { return 0; }; |
---|
1106 | SetProcessedMapBase(const TR &b) : TR(b) {} |
---|
1107 | }; |
---|
1108 | ///\brief \ref named-templ-param "Named parameter" |
---|
1109 | ///for setting \ref ProcessedMap object. |
---|
1110 | /// |
---|
1111 | /// \ref named-templ-param "Named parameter" |
---|
1112 | ///for setting \ref ProcessedMap object. |
---|
1113 | template<class T> |
---|
1114 | BfsWizard<SetProcessedMapBase<T> > processedMap(const T &t) |
---|
1115 | { |
---|
1116 | Base::_processed=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
1117 | return BfsWizard<SetProcessedMapBase<T> >(*this); |
---|
1118 | } |
---|
1119 | |
---|
1120 | template<class T> |
---|
1121 | struct SetDistMapBase : public Base { |
---|
1122 | typedef T DistMap; |
---|
1123 | static DistMap *createDistMap(const Digraph &) { return 0; }; |
---|
1124 | SetDistMapBase(const TR &b) : TR(b) {} |
---|
1125 | }; |
---|
1126 | ///\brief \ref named-templ-param "Named parameter" |
---|
1127 | ///for setting \ref DistMap object. |
---|
1128 | /// |
---|
1129 | /// \ref named-templ-param "Named parameter" |
---|
1130 | ///for setting \ref DistMap object. |
---|
1131 | template<class T> |
---|
1132 | BfsWizard<SetDistMapBase<T> > distMap(const T &t) |
---|
1133 | { |
---|
1134 | Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
1135 | return BfsWizard<SetDistMapBase<T> >(*this); |
---|
1136 | } |
---|
1137 | |
---|
1138 | }; |
---|
1139 | |
---|
1140 | ///Function type interface for Bfs algorithm. |
---|
1141 | |
---|
1142 | /// \ingroup search |
---|
1143 | ///Function type interface for Bfs algorithm. |
---|
1144 | /// |
---|
1145 | ///This function also has several |
---|
1146 | ///\ref named-templ-func-param "named parameters", |
---|
1147 | ///they are declared as the members of class \ref BfsWizard. |
---|
1148 | ///The following |
---|
1149 | ///example shows how to use these parameters. |
---|
1150 | ///\code |
---|
1151 | /// bfs(g,source).predMap(preds).run(); |
---|
1152 | ///\endcode |
---|
1153 | ///\warning Don't forget to put the \ref BfsWizard::run() "run()" |
---|
1154 | ///to the end of the parameter list. |
---|
1155 | ///\sa BfsWizard |
---|
1156 | ///\sa Bfs |
---|
1157 | template<class GR> |
---|
1158 | BfsWizard<BfsWizardBase<GR> > |
---|
1159 | bfs(const GR &g,typename GR::Node s=INVALID) |
---|
1160 | { |
---|
1161 | return BfsWizard<BfsWizardBase<GR> >(g,s); |
---|
1162 | } |
---|
1163 | |
---|
1164 | #ifdef DOXYGEN |
---|
1165 | /// \brief Visitor class for BFS. |
---|
1166 | /// |
---|
1167 | /// This class defines the interface of the BfsVisit events, and |
---|
1168 | /// it could be the base of a real visitor class. |
---|
1169 | template <typename _Digraph> |
---|
1170 | struct BfsVisitor { |
---|
1171 | typedef _Digraph Digraph; |
---|
1172 | typedef typename Digraph::Arc Arc; |
---|
1173 | typedef typename Digraph::Node Node; |
---|
1174 | /// \brief Called for the source node(s) of the BFS. |
---|
1175 | /// |
---|
1176 | /// This function is called for the source node(s) of the BFS. |
---|
1177 | void start(const Node& node) {} |
---|
1178 | /// \brief Called when a node is reached first time. |
---|
1179 | /// |
---|
1180 | /// This function is called when a node is reached first time. |
---|
1181 | void reach(const Node& node) {} |
---|
1182 | /// \brief Called when a node is processed. |
---|
1183 | /// |
---|
1184 | /// This function is called when a node is processed. |
---|
1185 | void process(const Node& node) {} |
---|
1186 | /// \brief Called when an arc reaches a new node. |
---|
1187 | /// |
---|
1188 | /// This function is called when the BFS finds an arc whose target node |
---|
1189 | /// is not reached yet. |
---|
1190 | void discover(const Arc& arc) {} |
---|
1191 | /// \brief Called when an arc is examined but its target node is |
---|
1192 | /// already discovered. |
---|
1193 | /// |
---|
1194 | /// This function is called when an arc is examined but its target node is |
---|
1195 | /// already discovered. |
---|
1196 | void examine(const Arc& arc) {} |
---|
1197 | }; |
---|
1198 | #else |
---|
1199 | template <typename _Digraph> |
---|
1200 | struct BfsVisitor { |
---|
1201 | typedef _Digraph Digraph; |
---|
1202 | typedef typename Digraph::Arc Arc; |
---|
1203 | typedef typename Digraph::Node Node; |
---|
1204 | void start(const Node&) {} |
---|
1205 | void reach(const Node&) {} |
---|
1206 | void process(const Node&) {} |
---|
1207 | void discover(const Arc&) {} |
---|
1208 | void examine(const Arc&) {} |
---|
1209 | |
---|
1210 | template <typename _Visitor> |
---|
1211 | struct Constraints { |
---|
1212 | void constraints() { |
---|
1213 | Arc arc; |
---|
1214 | Node node; |
---|
1215 | visitor.start(node); |
---|
1216 | visitor.reach(node); |
---|
1217 | visitor.process(node); |
---|
1218 | visitor.discover(arc); |
---|
1219 | visitor.examine(arc); |
---|
1220 | } |
---|
1221 | _Visitor& visitor; |
---|
1222 | }; |
---|
1223 | }; |
---|
1224 | #endif |
---|
1225 | |
---|
1226 | /// \brief Default traits class of BfsVisit class. |
---|
1227 | /// |
---|
1228 | /// Default traits class of BfsVisit class. |
---|
1229 | /// \tparam _Digraph The type of the digraph the algorithm runs on. |
---|
1230 | template<class _Digraph> |
---|
1231 | struct BfsVisitDefaultTraits { |
---|
1232 | |
---|
1233 | /// \brief The type of the digraph the algorithm runs on. |
---|
1234 | typedef _Digraph Digraph; |
---|
1235 | |
---|
1236 | /// \brief The type of the map that indicates which nodes are reached. |
---|
1237 | /// |
---|
1238 | /// The type of the map that indicates which nodes are reached. |
---|
1239 | /// It must meet the \ref concepts::ReadWriteMap "ReadWriteMap" concept. |
---|
1240 | typedef typename Digraph::template NodeMap<bool> ReachedMap; |
---|
1241 | |
---|
1242 | /// \brief Instantiates a \ref ReachedMap. |
---|
1243 | /// |
---|
1244 | /// This function instantiates a \ref ReachedMap. |
---|
1245 | /// \param digraph is the digraph, to which |
---|
1246 | /// we would like to define the \ref ReachedMap. |
---|
1247 | static ReachedMap *createReachedMap(const Digraph &digraph) { |
---|
1248 | return new ReachedMap(digraph); |
---|
1249 | } |
---|
1250 | |
---|
1251 | }; |
---|
1252 | |
---|
1253 | /// \ingroup search |
---|
1254 | /// |
---|
1255 | /// \brief %BFS algorithm class with visitor interface. |
---|
1256 | /// |
---|
1257 | /// This class provides an efficient implementation of the %BFS algorithm |
---|
1258 | /// with visitor interface. |
---|
1259 | /// |
---|
1260 | /// The %BfsVisit class provides an alternative interface to the Bfs |
---|
1261 | /// class. It works with callback mechanism, the BfsVisit object calls |
---|
1262 | /// the member functions of the \c Visitor class on every BFS event. |
---|
1263 | /// |
---|
1264 | /// \tparam _Digraph The type of the digraph the algorithm runs on. |
---|
1265 | /// The default value is |
---|
1266 | /// \ref ListDigraph. The value of _Digraph is not used directly by |
---|
1267 | /// \ref BfsVisit, it is only passed to \ref BfsVisitDefaultTraits. |
---|
1268 | /// \tparam _Visitor The Visitor type that is used by the algorithm. |
---|
1269 | /// \ref BfsVisitor "BfsVisitor<_Digraph>" is an empty visitor, which |
---|
1270 | /// does not observe the BFS events. If you want to observe the BFS |
---|
1271 | /// events, you should implement your own visitor class. |
---|
1272 | /// \tparam _Traits Traits class to set various data types used by the |
---|
1273 | /// algorithm. The default traits class is |
---|
1274 | /// \ref BfsVisitDefaultTraits "BfsVisitDefaultTraits<_Digraph>". |
---|
1275 | /// See \ref BfsVisitDefaultTraits for the documentation of |
---|
1276 | /// a BFS visit traits class. |
---|
1277 | #ifdef DOXYGEN |
---|
1278 | template <typename _Digraph, typename _Visitor, typename _Traits> |
---|
1279 | #else |
---|
1280 | template <typename _Digraph = ListDigraph, |
---|
1281 | typename _Visitor = BfsVisitor<_Digraph>, |
---|
1282 | typename _Traits = BfsDefaultTraits<_Digraph> > |
---|
1283 | #endif |
---|
1284 | class BfsVisit { |
---|
1285 | public: |
---|
1286 | |
---|
1287 | /// \brief \ref Exception for uninitialized parameters. |
---|
1288 | /// |
---|
1289 | /// This error represents problems in the initialization |
---|
1290 | /// of the parameters of the algorithm. |
---|
1291 | class UninitializedParameter : public lemon::UninitializedParameter { |
---|
1292 | public: |
---|
1293 | virtual const char* what() const throw() |
---|
1294 | { |
---|
1295 | return "lemon::BfsVisit::UninitializedParameter"; |
---|
1296 | } |
---|
1297 | }; |
---|
1298 | |
---|
1299 | ///The traits class. |
---|
1300 | typedef _Traits Traits; |
---|
1301 | |
---|
1302 | ///The type of the digraph the algorithm runs on. |
---|
1303 | typedef typename Traits::Digraph Digraph; |
---|
1304 | |
---|
1305 | ///The visitor type used by the algorithm. |
---|
1306 | typedef _Visitor Visitor; |
---|
1307 | |
---|
1308 | ///The type of the map that indicates which nodes are reached. |
---|
1309 | typedef typename Traits::ReachedMap ReachedMap; |
---|
1310 | |
---|
1311 | private: |
---|
1312 | |
---|
1313 | typedef typename Digraph::Node Node; |
---|
1314 | typedef typename Digraph::NodeIt NodeIt; |
---|
1315 | typedef typename Digraph::Arc Arc; |
---|
1316 | typedef typename Digraph::OutArcIt OutArcIt; |
---|
1317 | |
---|
1318 | //Pointer to the underlying digraph. |
---|
1319 | const Digraph *_digraph; |
---|
1320 | //Pointer to the visitor object. |
---|
1321 | Visitor *_visitor; |
---|
1322 | //Pointer to the map of reached status of the nodes. |
---|
1323 | ReachedMap *_reached; |
---|
1324 | //Indicates if _reached is locally allocated (true) or not. |
---|
1325 | bool local_reached; |
---|
1326 | |
---|
1327 | std::vector<typename Digraph::Node> _list; |
---|
1328 | int _list_front, _list_back; |
---|
1329 | |
---|
1330 | ///Creates the maps if necessary. |
---|
1331 | ///\todo Better memory allocation (instead of new). |
---|
1332 | void create_maps() { |
---|
1333 | if(!_reached) { |
---|
1334 | local_reached = true; |
---|
1335 | _reached = Traits::createReachedMap(*_digraph); |
---|
1336 | } |
---|
1337 | } |
---|
1338 | |
---|
1339 | protected: |
---|
1340 | |
---|
1341 | BfsVisit() {} |
---|
1342 | |
---|
1343 | public: |
---|
1344 | |
---|
1345 | typedef BfsVisit Create; |
---|
1346 | |
---|
1347 | /// \name Named template parameters |
---|
1348 | |
---|
1349 | ///@{ |
---|
1350 | template <class T> |
---|
1351 | struct SetReachedMapTraits : public Traits { |
---|
1352 | typedef T ReachedMap; |
---|
1353 | static ReachedMap *createReachedMap(const Digraph &digraph) { |
---|
1354 | throw UninitializedParameter(); |
---|
1355 | } |
---|
1356 | }; |
---|
1357 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
1358 | /// ReachedMap type. |
---|
1359 | /// |
---|
1360 | /// \ref named-templ-param "Named parameter" for setting ReachedMap type. |
---|
1361 | template <class T> |
---|
1362 | struct SetReachedMap : public BfsVisit< Digraph, Visitor, |
---|
1363 | SetReachedMapTraits<T> > { |
---|
1364 | typedef BfsVisit< Digraph, Visitor, SetReachedMapTraits<T> > Create; |
---|
1365 | }; |
---|
1366 | ///@} |
---|
1367 | |
---|
1368 | public: |
---|
1369 | |
---|
1370 | /// \brief Constructor. |
---|
1371 | /// |
---|
1372 | /// Constructor. |
---|
1373 | /// |
---|
1374 | /// \param digraph The digraph the algorithm runs on. |
---|
1375 | /// \param visitor The visitor object of the algorithm. |
---|
1376 | BfsVisit(const Digraph& digraph, Visitor& visitor) |
---|
1377 | : _digraph(&digraph), _visitor(&visitor), |
---|
1378 | _reached(0), local_reached(false) {} |
---|
1379 | |
---|
1380 | /// \brief Destructor. |
---|
1381 | ~BfsVisit() { |
---|
1382 | if(local_reached) delete _reached; |
---|
1383 | } |
---|
1384 | |
---|
1385 | /// \brief Sets the map that indicates which nodes are reached. |
---|
1386 | /// |
---|
1387 | /// Sets the map that indicates which nodes are reached. |
---|
1388 | /// If you don't use this function before calling \ref run(), |
---|
1389 | /// it will allocate one. The destructor deallocates this |
---|
1390 | /// automatically allocated map, of course. |
---|
1391 | /// \return <tt> (*this) </tt> |
---|
1392 | BfsVisit &reachedMap(ReachedMap &m) { |
---|
1393 | if(local_reached) { |
---|
1394 | delete _reached; |
---|
1395 | local_reached = false; |
---|
1396 | } |
---|
1397 | _reached = &m; |
---|
1398 | return *this; |
---|
1399 | } |
---|
1400 | |
---|
1401 | public: |
---|
1402 | |
---|
1403 | /// \name Execution control |
---|
1404 | /// The simplest way to execute the algorithm is to use |
---|
1405 | /// one of the member functions called \ref lemon::BfsVisit::run() |
---|
1406 | /// "run()". |
---|
1407 | /// \n |
---|
1408 | /// If you need more control on the execution, first you must call |
---|
1409 | /// \ref lemon::BfsVisit::init() "init()", then you can add several |
---|
1410 | /// source nodes with \ref lemon::BfsVisit::addSource() "addSource()". |
---|
1411 | /// Finally \ref lemon::BfsVisit::start() "start()" will perform the |
---|
1412 | /// actual path computation. |
---|
1413 | |
---|
1414 | /// @{ |
---|
1415 | |
---|
1416 | /// \brief Initializes the internal data structures. |
---|
1417 | /// |
---|
1418 | /// Initializes the internal data structures. |
---|
1419 | void init() { |
---|
1420 | create_maps(); |
---|
1421 | _list.resize(countNodes(*_digraph)); |
---|
1422 | _list_front = _list_back = -1; |
---|
1423 | for (NodeIt u(*_digraph) ; u != INVALID ; ++u) { |
---|
1424 | _reached->set(u, false); |
---|
1425 | } |
---|
1426 | } |
---|
1427 | |
---|
1428 | /// \brief Adds a new source node. |
---|
1429 | /// |
---|
1430 | /// Adds a new source node to the set of nodes to be processed. |
---|
1431 | void addSource(Node s) { |
---|
1432 | if(!(*_reached)[s]) { |
---|
1433 | _reached->set(s,true); |
---|
1434 | _visitor->start(s); |
---|
1435 | _visitor->reach(s); |
---|
1436 | _list[++_list_back] = s; |
---|
1437 | } |
---|
1438 | } |
---|
1439 | |
---|
1440 | /// \brief Processes the next node. |
---|
1441 | /// |
---|
1442 | /// Processes the next node. |
---|
1443 | /// |
---|
1444 | /// \return The processed node. |
---|
1445 | /// |
---|
1446 | /// \pre The queue must not be empty. |
---|
1447 | Node processNextNode() { |
---|
1448 | Node n = _list[++_list_front]; |
---|
1449 | _visitor->process(n); |
---|
1450 | Arc e; |
---|
1451 | for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) { |
---|
1452 | Node m = _digraph->target(e); |
---|
1453 | if (!(*_reached)[m]) { |
---|
1454 | _visitor->discover(e); |
---|
1455 | _visitor->reach(m); |
---|
1456 | _reached->set(m, true); |
---|
1457 | _list[++_list_back] = m; |
---|
1458 | } else { |
---|
1459 | _visitor->examine(e); |
---|
1460 | } |
---|
1461 | } |
---|
1462 | return n; |
---|
1463 | } |
---|
1464 | |
---|
1465 | /// \brief Processes the next node. |
---|
1466 | /// |
---|
1467 | /// Processes the next node and checks if the given target node |
---|
1468 | /// is reached. If the target node is reachable from the processed |
---|
1469 | /// node, then the \c reach parameter will be set to \c true. |
---|
1470 | /// |
---|
1471 | /// \param target The target node. |
---|
1472 | /// \retval reach Indicates if the target node is reached. |
---|
1473 | /// It should be initially \c false. |
---|
1474 | /// |
---|
1475 | /// \return The processed node. |
---|
1476 | /// |
---|
1477 | /// \pre The queue must not be empty. |
---|
1478 | Node processNextNode(Node target, bool& reach) { |
---|
1479 | Node n = _list[++_list_front]; |
---|
1480 | _visitor->process(n); |
---|
1481 | Arc e; |
---|
1482 | for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) { |
---|
1483 | Node m = _digraph->target(e); |
---|
1484 | if (!(*_reached)[m]) { |
---|
1485 | _visitor->discover(e); |
---|
1486 | _visitor->reach(m); |
---|
1487 | _reached->set(m, true); |
---|
1488 | _list[++_list_back] = m; |
---|
1489 | reach = reach || (target == m); |
---|
1490 | } else { |
---|
1491 | _visitor->examine(e); |
---|
1492 | } |
---|
1493 | } |
---|
1494 | return n; |
---|
1495 | } |
---|
1496 | |
---|
1497 | /// \brief Processes the next node. |
---|
1498 | /// |
---|
1499 | /// Processes the next node and checks if at least one of reached |
---|
1500 | /// nodes has \c true value in the \c nm node map. If one node |
---|
1501 | /// with \c true value is reachable from the processed node, then the |
---|
1502 | /// \c rnode parameter will be set to the first of such nodes. |
---|
1503 | /// |
---|
1504 | /// \param nm A \c bool (or convertible) node map that indicates the |
---|
1505 | /// possible targets. |
---|
1506 | /// \retval rnode The reached target node. |
---|
1507 | /// It should be initially \c INVALID. |
---|
1508 | /// |
---|
1509 | /// \return The processed node. |
---|
1510 | /// |
---|
1511 | /// \pre The queue must not be empty. |
---|
1512 | template <typename NM> |
---|
1513 | Node processNextNode(const NM& nm, Node& rnode) { |
---|
1514 | Node n = _list[++_list_front]; |
---|
1515 | _visitor->process(n); |
---|
1516 | Arc e; |
---|
1517 | for (_digraph->firstOut(e, n); e != INVALID; _digraph->nextOut(e)) { |
---|
1518 | Node m = _digraph->target(e); |
---|
1519 | if (!(*_reached)[m]) { |
---|
1520 | _visitor->discover(e); |
---|
1521 | _visitor->reach(m); |
---|
1522 | _reached->set(m, true); |
---|
1523 | _list[++_list_back] = m; |
---|
1524 | if (nm[m] && rnode == INVALID) rnode = m; |
---|
1525 | } else { |
---|
1526 | _visitor->examine(e); |
---|
1527 | } |
---|
1528 | } |
---|
1529 | return n; |
---|
1530 | } |
---|
1531 | |
---|
1532 | /// \brief The next node to be processed. |
---|
1533 | /// |
---|
1534 | /// Returns the next node to be processed or \c INVALID if the queue |
---|
1535 | /// is empty. |
---|
1536 | Node nextNode() const { |
---|
1537 | return _list_front != _list_back ? _list[_list_front + 1] : INVALID; |
---|
1538 | } |
---|
1539 | |
---|
1540 | /// \brief Returns \c false if there are nodes |
---|
1541 | /// to be processed. |
---|
1542 | /// |
---|
1543 | /// Returns \c false if there are nodes |
---|
1544 | /// to be processed in the queue. |
---|
1545 | bool emptyQueue() const { return _list_front == _list_back; } |
---|
1546 | |
---|
1547 | /// \brief Returns the number of the nodes to be processed. |
---|
1548 | /// |
---|
1549 | /// Returns the number of the nodes to be processed in the queue. |
---|
1550 | int queueSize() const { return _list_back - _list_front; } |
---|
1551 | |
---|
1552 | /// \brief Executes the algorithm. |
---|
1553 | /// |
---|
1554 | /// Executes the algorithm. |
---|
1555 | /// |
---|
1556 | /// This method runs the %BFS algorithm from the root node(s) |
---|
1557 | /// in order to compute the shortest path to each node. |
---|
1558 | /// |
---|
1559 | /// The algorithm computes |
---|
1560 | /// - the shortest path tree (forest), |
---|
1561 | /// - the distance of each node from the root(s). |
---|
1562 | /// |
---|
1563 | /// \pre init() must be called and at least one root node should be added |
---|
1564 | /// with addSource() before using this function. |
---|
1565 | /// |
---|
1566 | /// \note <tt>b.start()</tt> is just a shortcut of the following code. |
---|
1567 | /// \code |
---|
1568 | /// while ( !b.emptyQueue() ) { |
---|
1569 | /// b.processNextNode(); |
---|
1570 | /// } |
---|
1571 | /// \endcode |
---|
1572 | void start() { |
---|
1573 | while ( !emptyQueue() ) processNextNode(); |
---|
1574 | } |
---|
1575 | |
---|
1576 | /// \brief Executes the algorithm until the given target node is reached. |
---|
1577 | /// |
---|
1578 | /// Executes the algorithm until the given target node is reached. |
---|
1579 | /// |
---|
1580 | /// This method runs the %BFS algorithm from the root node(s) |
---|
1581 | /// in order to compute the shortest path to \c dest. |
---|
1582 | /// |
---|
1583 | /// The algorithm computes |
---|
1584 | /// - the shortest path to \c dest, |
---|
1585 | /// - the distance of \c dest from the root(s). |
---|
1586 | /// |
---|
1587 | /// \pre init() must be called and at least one root node should be |
---|
1588 | /// added with addSource() before using this function. |
---|
1589 | /// |
---|
1590 | /// \note <tt>b.start(t)</tt> is just a shortcut of the following code. |
---|
1591 | /// \code |
---|
1592 | /// bool reach = false; |
---|
1593 | /// while ( !b.emptyQueue() && !reach ) { |
---|
1594 | /// b.processNextNode(t, reach); |
---|
1595 | /// } |
---|
1596 | /// \endcode |
---|
1597 | void start(Node dest) { |
---|
1598 | bool reach = false; |
---|
1599 | while ( !emptyQueue() && !reach ) processNextNode(dest, reach); |
---|
1600 | } |
---|
1601 | |
---|
1602 | /// \brief Executes the algorithm until a condition is met. |
---|
1603 | /// |
---|
1604 | /// Executes the algorithm until a condition is met. |
---|
1605 | /// |
---|
1606 | /// This method runs the %BFS algorithm from the root node(s) in |
---|
1607 | /// order to compute the shortest path to a node \c v with |
---|
1608 | /// <tt>nm[v]</tt> true, if such a node can be found. |
---|
1609 | /// |
---|
1610 | /// \param nm must be a bool (or convertible) node map. The |
---|
1611 | /// algorithm will stop when it reaches a node \c v with |
---|
1612 | /// <tt>nm[v]</tt> true. |
---|
1613 | /// |
---|
1614 | /// \return The reached node \c v with <tt>nm[v]</tt> true or |
---|
1615 | /// \c INVALID if no such node was found. |
---|
1616 | /// |
---|
1617 | /// \pre init() must be called and at least one root node should be |
---|
1618 | /// added with addSource() before using this function. |
---|
1619 | /// |
---|
1620 | /// \note <tt>b.start(nm)</tt> is just a shortcut of the following code. |
---|
1621 | /// \code |
---|
1622 | /// Node rnode = INVALID; |
---|
1623 | /// while ( !b.emptyQueue() && rnode == INVALID ) { |
---|
1624 | /// b.processNextNode(nm, rnode); |
---|
1625 | /// } |
---|
1626 | /// return rnode; |
---|
1627 | /// \endcode |
---|
1628 | template <typename NM> |
---|
1629 | Node start(const NM &nm) { |
---|
1630 | Node rnode = INVALID; |
---|
1631 | while ( !emptyQueue() && rnode == INVALID ) { |
---|
1632 | processNextNode(nm, rnode); |
---|
1633 | } |
---|
1634 | return rnode; |
---|
1635 | } |
---|
1636 | |
---|
1637 | /// \brief Runs the algorithm from the given node. |
---|
1638 | /// |
---|
1639 | /// This method runs the %BFS algorithm from node \c s |
---|
1640 | /// in order to compute the shortest path to each node. |
---|
1641 | /// |
---|
1642 | /// The algorithm computes |
---|
1643 | /// - the shortest path tree, |
---|
1644 | /// - the distance of each node from the root. |
---|
1645 | /// |
---|
1646 | /// \note <tt>b.run(s)</tt> is just a shortcut of the following code. |
---|
1647 | ///\code |
---|
1648 | /// b.init(); |
---|
1649 | /// b.addSource(s); |
---|
1650 | /// b.start(); |
---|
1651 | ///\endcode |
---|
1652 | void run(Node s) { |
---|
1653 | init(); |
---|
1654 | addSource(s); |
---|
1655 | start(); |
---|
1656 | } |
---|
1657 | |
---|
1658 | /// \brief Runs the algorithm to visit all nodes in the digraph. |
---|
1659 | /// |
---|
1660 | /// This method runs the %BFS algorithm in order to |
---|
1661 | /// compute the shortest path to each node. |
---|
1662 | /// |
---|
1663 | /// The algorithm computes |
---|
1664 | /// - the shortest path tree (forest), |
---|
1665 | /// - the distance of each node from the root(s). |
---|
1666 | /// |
---|
1667 | /// \note <tt>b.run(s)</tt> is just a shortcut of the following code. |
---|
1668 | ///\code |
---|
1669 | /// b.init(); |
---|
1670 | /// for (NodeIt n(gr); n != INVALID; ++n) { |
---|
1671 | /// if (!b.reached(n)) { |
---|
1672 | /// b.addSource(n); |
---|
1673 | /// b.start(); |
---|
1674 | /// } |
---|
1675 | /// } |
---|
1676 | ///\endcode |
---|
1677 | void run() { |
---|
1678 | init(); |
---|
1679 | for (NodeIt it(*_digraph); it != INVALID; ++it) { |
---|
1680 | if (!reached(it)) { |
---|
1681 | addSource(it); |
---|
1682 | start(); |
---|
1683 | } |
---|
1684 | } |
---|
1685 | } |
---|
1686 | |
---|
1687 | ///@} |
---|
1688 | |
---|
1689 | /// \name Query Functions |
---|
1690 | /// The result of the %BFS algorithm can be obtained using these |
---|
1691 | /// functions.\n |
---|
1692 | /// Either \ref lemon::BfsVisit::run() "run()" or |
---|
1693 | /// \ref lemon::BfsVisit::start() "start()" must be called before |
---|
1694 | /// using them. |
---|
1695 | ///@{ |
---|
1696 | |
---|
1697 | /// \brief Checks if a node is reachable from the root(s). |
---|
1698 | /// |
---|
1699 | /// Returns \c true if \c v is reachable from the root(s). |
---|
1700 | /// \pre Either \ref run() or \ref start() |
---|
1701 | /// must be called before using this function. |
---|
1702 | bool reached(Node v) { return (*_reached)[v]; } |
---|
1703 | |
---|
1704 | ///@} |
---|
1705 | |
---|
1706 | }; |
---|
1707 | |
---|
1708 | } //END OF NAMESPACE LEMON |
---|
1709 | |
---|
1710 | #endif |
---|