1 /* -*- C++ -*- |
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2 * lemon/belmann_ford.h - Part of LEMON, a generic C++ optimization library |
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3 * |
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4 * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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5 * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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6 * |
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7 * Permission to use, modify and distribute this software is granted |
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8 * provided that this copyright notice appears in all copies. For |
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9 * precise terms see the accompanying LICENSE file. |
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10 * |
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11 * This software is provided "AS IS" with no warranty of any kind, |
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12 * express or implied, and with no claim as to its suitability for any |
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13 * purpose. |
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14 * |
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15 */ |
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16 |
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17 #ifndef LEMON_BELMANN_FORD_H |
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18 #define LEMON_BELMANN_FORD_H |
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19 |
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20 /// \ingroup flowalgs |
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21 /// \file |
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22 /// \brief BelmannFord algorithm. |
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23 /// |
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24 |
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25 #include <lemon/list_graph.h> |
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26 #include <lemon/invalid.h> |
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27 #include <lemon/error.h> |
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28 #include <lemon/maps.h> |
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29 |
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30 #include <limits> |
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31 |
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32 namespace lemon { |
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33 |
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34 /// \brief Default OperationTraits for the BelmannFord algorithm class. |
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35 /// |
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36 /// It defines all computational operations and constants which are |
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37 /// used in the belmann ford algorithm. The default implementation |
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38 /// is based on the numeric_limits class. If the numeric type does not |
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39 /// have infinity value then the maximum value is used as extremal |
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40 /// infinity value. |
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41 template < |
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42 typename Value, |
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43 bool has_infinity = std::numeric_limits<Value>::has_infinity> |
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44 struct BelmannFordDefaultOperationTraits { |
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45 /// \brief Gives back the zero value of the type. |
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46 static Value zero() { |
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47 return static_cast<Value>(0); |
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48 } |
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49 /// \brief Gives back the positive infinity value of the type. |
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50 static Value infinity() { |
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51 return std::numeric_limits<Value>::infinity(); |
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52 } |
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53 /// \brief Gives back the sum of the given two elements. |
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54 static Value plus(const Value& left, const Value& right) { |
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55 return left + right; |
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56 } |
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57 /// \brief Gives back true only if the first value less than the second. |
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58 static bool less(const Value& left, const Value& right) { |
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59 return left < right; |
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60 } |
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61 }; |
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62 |
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63 template <typename Value> |
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64 struct BelmannFordDefaultOperationTraits<Value, false> { |
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65 static Value zero() { |
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66 return static_cast<Value>(0); |
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67 } |
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68 static Value infinity() { |
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69 return std::numeric_limits<Value>::max(); |
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70 } |
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71 static Value plus(const Value& left, const Value& right) { |
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72 if (left == infinity() || right == infinity()) return infinity(); |
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73 return left + right; |
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74 } |
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75 static bool less(const Value& left, const Value& right) { |
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76 return left < right; |
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77 } |
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78 }; |
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79 |
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80 /// \brief Default traits class of BelmannFord class. |
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81 /// |
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82 /// Default traits class of BelmannFord class. |
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83 /// \param _Graph Graph type. |
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84 /// \param _LegthMap Type of length map. |
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85 template<class _Graph, class _LengthMap> |
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86 struct BelmannFordDefaultTraits { |
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87 /// The graph type the algorithm runs on. |
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88 typedef _Graph Graph; |
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89 |
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90 /// \brief The type of the map that stores the edge lengths. |
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91 /// |
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92 /// The type of the map that stores the edge lengths. |
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93 /// It must meet the \ref concept::ReadMap "ReadMap" concept. |
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94 typedef _LengthMap LengthMap; |
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95 |
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96 // The type of the length of the edges. |
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97 typedef typename _LengthMap::Value Value; |
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98 |
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99 /// \brief Operation traits for belmann-ford algorithm. |
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100 /// |
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101 /// It defines the infinity type on the given Value type |
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102 /// and the used operation. |
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103 /// \see BelmannFordDefaultOperationTraits |
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104 typedef BelmannFordDefaultOperationTraits<Value> OperationTraits; |
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105 |
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106 /// \brief The type of the map that stores the last edges of the |
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107 /// shortest paths. |
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108 /// |
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109 /// The type of the map that stores the last |
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110 /// edges of the shortest paths. |
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111 /// It must meet the \ref concept::WriteMap "WriteMap" concept. |
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112 /// |
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113 typedef typename Graph::template NodeMap<typename _Graph::Edge> PredMap; |
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114 |
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115 /// \brief Instantiates a PredMap. |
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116 /// |
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117 /// This function instantiates a \ref PredMap. |
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118 /// \param graph is the graph, to which we would like to define the PredMap. |
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119 static PredMap *createPredMap(const _Graph& graph) { |
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120 return new PredMap(graph); |
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121 } |
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122 |
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123 /// \brief The type of the map that stores the dists of the nodes. |
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124 /// |
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125 /// The type of the map that stores the dists of the nodes. |
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126 /// It must meet the \ref concept::WriteMap "WriteMap" concept. |
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127 /// |
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128 typedef typename Graph::template NodeMap<typename _LengthMap::Value> |
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129 DistMap; |
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130 |
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131 /// \brief Instantiates a DistMap. |
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132 /// |
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133 /// This function instantiates a \ref DistMap. |
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134 /// \param graph is the graph, to which we would like to define the |
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135 /// \ref DistMap |
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136 static DistMap *createDistMap(const _Graph& graph) { |
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137 return new DistMap(graph); |
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138 } |
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139 |
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140 }; |
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141 |
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142 /// \brief %BelmannFord algorithm class. |
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143 /// |
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144 /// \ingroup flowalgs |
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145 /// This class provides an efficient implementation of \c Belmann-Ford |
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146 /// algorithm. The edge lengths are passed to the algorithm using a |
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147 /// \ref concept::ReadMap "ReadMap", so it is easy to change it to any |
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148 /// kind of length. |
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149 /// |
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150 /// The Belmann-Ford algorithm solves the shortest path from one node |
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151 /// problem when the edges can have negative length but the graph should |
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152 /// not contain cycles with negative sum of length. If we can assume |
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153 /// that all edge is non-negative in the graph then the dijkstra algorithm |
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154 /// should be used rather. |
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155 /// |
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156 /// The complexity of the algorithm is O(n * e). |
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157 /// |
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158 /// The type of the length is determined by the |
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159 /// \ref concept::ReadMap::Value "Value" of the length map. |
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160 /// |
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161 /// \param _Graph The graph type the algorithm runs on. The default value |
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162 /// is \ref ListGraph. The value of _Graph is not used directly by |
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163 /// BelmannFord, it is only passed to \ref BelmannFordDefaultTraits. |
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164 /// \param _LengthMap This read-only EdgeMap determines the lengths of the |
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165 /// edges. The default map type is \ref concept::StaticGraph::EdgeMap |
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166 /// "Graph::EdgeMap<int>". The value of _LengthMap is not used directly |
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167 /// by BelmannFord, it is only passed to \ref BelmannFordDefaultTraits. |
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168 /// \param _Traits Traits class to set various data types used by the |
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169 /// algorithm. The default traits class is \ref BelmannFordDefaultTraits |
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170 /// "BelmannFordDefaultTraits<_Graph,_LengthMap>". See \ref |
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171 /// BelmannFordDefaultTraits for the documentation of a BelmannFord traits |
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172 /// class. |
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173 /// |
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174 /// \author Balazs Dezso |
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175 |
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176 #ifdef DOXYGEN |
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177 template <typename _Graph, typename _LengthMap, typename _Traits> |
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178 #else |
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179 template <typename _Graph=ListGraph, |
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180 typename _LengthMap=typename _Graph::template EdgeMap<int>, |
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181 typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> > |
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182 #endif |
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183 class BelmannFord { |
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184 public: |
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185 |
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186 /// \brief \ref Exception for uninitialized parameters. |
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187 /// |
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188 /// This error represents problems in the initialization |
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189 /// of the parameters of the algorithms. |
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190 |
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191 class UninitializedParameter : public lemon::UninitializedParameter { |
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192 public: |
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193 virtual const char* exceptionName() const { |
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194 return "lemon::BelmannFord::UninitializedParameter"; |
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195 } |
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196 }; |
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197 |
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198 typedef _Traits Traits; |
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199 ///The type of the underlying graph. |
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200 typedef typename _Traits::Graph Graph; |
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201 |
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202 typedef typename Graph::Node Node; |
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203 typedef typename Graph::NodeIt NodeIt; |
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204 typedef typename Graph::Edge Edge; |
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205 typedef typename Graph::OutEdgeIt OutEdgeIt; |
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206 |
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207 /// \brief The type of the length of the edges. |
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208 typedef typename _Traits::LengthMap::Value Value; |
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209 /// \brief The type of the map that stores the edge lengths. |
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210 typedef typename _Traits::LengthMap LengthMap; |
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211 /// \brief The type of the map that stores the last |
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212 /// edges of the shortest paths. |
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213 typedef typename _Traits::PredMap PredMap; |
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214 /// \brief The type of the map that stores the dists of the nodes. |
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215 typedef typename _Traits::DistMap DistMap; |
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216 /// \brief The operation traits. |
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217 typedef typename _Traits::OperationTraits OperationTraits; |
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218 private: |
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219 /// Pointer to the underlying graph. |
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220 const Graph *graph; |
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221 /// Pointer to the length map |
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222 const LengthMap *length; |
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223 ///Pointer to the map of predecessors edges. |
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224 PredMap *_pred; |
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225 ///Indicates if \ref _pred is locally allocated (\c true) or not. |
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226 bool local_pred; |
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227 ///Pointer to the map of distances. |
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228 DistMap *_dist; |
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229 ///Indicates if \ref _dist is locally allocated (\c true) or not. |
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230 bool local_dist; |
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231 |
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232 typedef typename Graph::template NodeMap<bool> MaskMap; |
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233 MaskMap *_mask; |
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234 |
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235 std::vector<Node> _process; |
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236 |
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237 /// Creates the maps if necessary. |
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238 void create_maps() { |
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239 if(!_pred) { |
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240 local_pred = true; |
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241 _pred = Traits::createPredMap(*graph); |
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242 } |
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243 if(!_dist) { |
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244 local_dist = true; |
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245 _dist = Traits::createDistMap(*graph); |
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246 } |
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247 _mask = new MaskMap(*graph, false); |
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248 } |
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249 |
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250 public : |
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251 |
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252 typedef BelmannFord Create; |
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253 |
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254 /// \name Named template parameters |
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255 |
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256 ///@{ |
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257 |
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258 template <class T> |
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259 struct DefPredMapTraits : public Traits { |
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260 typedef T PredMap; |
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261 static PredMap *createPredMap(const Graph&) { |
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262 throw UninitializedParameter(); |
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263 } |
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264 }; |
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265 |
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266 /// \brief \ref named-templ-param "Named parameter" for setting PredMap |
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267 /// type |
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268 /// \ref named-templ-param "Named parameter" for setting PredMap type |
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269 /// |
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270 template <class T> |
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271 struct DefPredMap |
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272 : public BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > { |
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273 typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create; |
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274 }; |
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275 |
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276 template <class T> |
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277 struct DefDistMapTraits : public Traits { |
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278 typedef T DistMap; |
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279 static DistMap *createDistMap(const Graph& graph) { |
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280 throw UninitializedParameter(); |
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281 } |
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282 }; |
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283 |
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284 /// \brief \ref named-templ-param "Named parameter" for setting DistMap |
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285 /// type |
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286 /// |
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287 /// \ref named-templ-param "Named parameter" for setting DistMap type |
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288 /// |
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289 template <class T> |
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290 struct DefDistMap |
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291 : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > { |
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292 typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create; |
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293 }; |
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294 |
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295 template <class T> |
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296 struct DefOperationTraitsTraits : public Traits { |
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297 typedef T OperationTraits; |
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298 }; |
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299 |
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300 /// \brief \ref named-templ-param "Named parameter" for setting |
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301 /// OperationTraits type |
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302 /// |
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303 /// \ref named-templ-param "Named parameter" for setting OperationTraits |
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304 /// type |
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305 template <class T> |
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306 struct DefOperationTraits |
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307 : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > { |
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308 typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > |
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309 Create; |
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310 }; |
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311 |
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312 ///@} |
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313 |
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314 protected: |
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315 |
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316 BelmannFord() {} |
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317 |
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318 public: |
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319 |
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320 /// \brief Constructor. |
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321 /// |
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322 /// \param _graph the graph the algorithm will run on. |
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323 /// \param _length the length map used by the algorithm. |
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324 BelmannFord(const Graph& _graph, const LengthMap& _length) : |
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325 graph(&_graph), length(&_length), |
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326 _pred(0), local_pred(false), |
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327 _dist(0), local_dist(false) {} |
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328 |
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329 ///Destructor. |
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330 ~BelmannFord() { |
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331 if(local_pred) delete _pred; |
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332 if(local_dist) delete _dist; |
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333 delete _mask; |
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334 } |
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335 |
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336 /// \brief Sets the length map. |
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337 /// |
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338 /// Sets the length map. |
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339 /// \return \c (*this) |
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340 BelmannFord &lengthMap(const LengthMap &m) { |
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341 length = &m; |
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342 return *this; |
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343 } |
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344 |
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345 /// \brief Sets the map storing the predecessor edges. |
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346 /// |
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347 /// Sets the map storing the predecessor edges. |
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348 /// If you don't use this function before calling \ref run(), |
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349 /// it will allocate one. The destuctor deallocates this |
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350 /// automatically allocated map, of course. |
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351 /// \return \c (*this) |
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352 BelmannFord &predMap(PredMap &m) { |
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353 if(local_pred) { |
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354 delete _pred; |
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355 local_pred=false; |
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356 } |
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357 _pred = &m; |
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358 return *this; |
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359 } |
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360 |
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361 /// \brief Sets the map storing the distances calculated by the algorithm. |
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362 /// |
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363 /// Sets the map storing the distances calculated by the algorithm. |
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364 /// If you don't use this function before calling \ref run(), |
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365 /// it will allocate one. The destuctor deallocates this |
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366 /// automatically allocated map, of course. |
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367 /// \return \c (*this) |
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368 BelmannFord &distMap(DistMap &m) { |
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369 if(local_dist) { |
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370 delete _dist; |
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371 local_dist=false; |
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372 } |
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373 _dist = &m; |
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374 return *this; |
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375 } |
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376 |
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377 /// \name Execution control |
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378 /// The simplest way to execute the algorithm is to use |
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379 /// one of the member functions called \c run(...). |
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380 /// \n |
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381 /// If you need more control on the execution, |
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382 /// first you must call \ref init(), then you can add several source nodes |
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383 /// with \ref addSource(). |
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384 /// Finally \ref start() will perform the actual path |
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385 /// computation. |
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386 |
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387 ///@{ |
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388 |
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389 /// \brief Initializes the internal data structures. |
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390 /// |
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391 /// Initializes the internal data structures. |
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392 void init(const Value value = OperationTraits::infinity()) { |
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393 create_maps(); |
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394 for (NodeIt it(*graph); it != INVALID; ++it) { |
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395 _pred->set(it, INVALID); |
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396 _dist->set(it, value); |
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397 } |
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398 _process.clear(); |
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399 if (OperationTraits::less(value, OperationTraits::infinity())) { |
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400 for (NodeIt it(*graph); it != INVALID; ++it) { |
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401 _process.push_back(it); |
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402 _mask->set(it, true); |
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403 } |
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404 } |
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405 } |
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406 |
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407 /// \brief Adds a new source node. |
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408 /// |
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409 /// The optional second parameter is the initial distance of the node. |
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410 /// It just sets the distance of the node to the given value. |
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411 void addSource(Node source, Value dst = OperationTraits::zero()) { |
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412 _dist->set(source, dst); |
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413 if (!(*_mask)[source]) { |
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414 _process.push_back(source); |
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415 _mask->set(source, true); |
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416 } |
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417 } |
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418 |
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419 /// \brief Executes one round from the belmann ford algorithm. |
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420 /// |
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421 /// If the algoritm calculated the distances in the previous round |
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422 /// strictly for all at most k length paths then it will calculate the |
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423 /// distances strictly for all at most k + 1 length paths. With k |
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424 /// iteration this function calculates the at most k length paths. |
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425 /// \return %True when the algorithm have not found more shorter paths. |
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426 bool processNextRound() { |
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427 for (int i = 0; i < (int)_process.size(); ++i) { |
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428 _mask->set(_process[i], false); |
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429 } |
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430 std::vector<Node> nextProcess; |
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431 std::vector<Value> values(_process.size()); |
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432 for (int i = 0; i < (int)_process.size(); ++i) { |
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433 values[i] = (*_dist)[_process[i]]; |
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434 } |
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435 for (int i = 0; i < (int)_process.size(); ++i) { |
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436 for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) { |
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437 Node target = graph->target(it); |
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438 Value relaxed = OperationTraits::plus(values[i], (*length)[it]); |
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439 if (OperationTraits::less(relaxed, (*_dist)[target])) { |
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440 _pred->set(target, it); |
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441 _dist->set(target, relaxed); |
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442 if (!(*_mask)[target]) { |
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443 _mask->set(target, true); |
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444 nextProcess.push_back(target); |
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445 } |
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446 } |
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447 } |
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448 } |
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449 _process.swap(nextProcess); |
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450 return _process.empty(); |
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451 } |
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452 |
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453 /// \brief Executes one weak round from the belmann ford algorithm. |
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454 /// |
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455 /// If the algorithm calculated the distances in the |
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456 /// previous round at least for all at most k length paths then it will |
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457 /// calculate the distances at least for all at most k + 1 length paths. |
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458 /// This function does not make it possible to calculate strictly the |
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459 /// at most k length minimal paths, this is why it is |
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460 /// called just weak round. |
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461 /// \return %True when the algorithm have not found more shorter paths. |
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462 bool processNextWeakRound() { |
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463 for (int i = 0; i < (int)_process.size(); ++i) { |
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464 _mask->set(_process[i], false); |
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465 } |
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466 std::vector<Node> nextProcess; |
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467 for (int i = 0; i < (int)_process.size(); ++i) { |
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468 for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) { |
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469 Node target = graph->target(it); |
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470 Value relaxed = |
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471 OperationTraits::plus((*_dist)[_process[i]], (*length)[it]); |
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472 if (OperationTraits::less(relaxed, (*_dist)[target])) { |
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473 _pred->set(target, it); |
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474 _dist->set(target, relaxed); |
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475 if (!(*_mask)[target]) { |
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476 _mask->set(target, true); |
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477 nextProcess.push_back(target); |
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478 } |
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479 } |
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480 } |
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481 } |
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482 _process.swap(nextProcess); |
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483 return _process.empty(); |
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484 } |
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485 |
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486 /// \brief Executes the algorithm. |
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487 /// |
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488 /// \pre init() must be called and at least one node should be added |
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489 /// with addSource() before using this function. |
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490 /// |
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491 /// This method runs the %BelmannFord algorithm from the root node(s) |
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492 /// in order to compute the shortest path to each node. The algorithm |
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493 /// computes |
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494 /// - The shortest path tree. |
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495 /// - The distance of each node from the root(s). |
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496 void start() { |
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497 int num = countNodes(*graph) - 1; |
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498 for (int i = 0; i < num; ++i) { |
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499 if (processNextWeakRound()) break; |
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500 } |
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501 } |
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502 |
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503 /// \brief Executes the algorithm and checks the negative cycles. |
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504 /// |
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505 /// \pre init() must be called and at least one node should be added |
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506 /// with addSource() before using this function. If there is |
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507 /// a negative cycles in the graph it gives back false. |
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508 /// |
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509 /// This method runs the %BelmannFord algorithm from the root node(s) |
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510 /// in order to compute the shortest path to each node. The algorithm |
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511 /// computes |
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512 /// - The shortest path tree. |
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513 /// - The distance of each node from the root(s). |
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514 bool checkedStart() { |
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515 int num = countNodes(*graph); |
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516 for (int i = 0; i < num; ++i) { |
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517 if (processNextWeakRound()) return true; |
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518 } |
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519 return false; |
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520 } |
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521 |
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522 /// \brief Executes the algorithm with path length limit. |
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523 /// |
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524 /// \pre init() must be called and at least one node should be added |
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525 /// with addSource() before using this function. |
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526 /// |
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527 /// This method runs the %BelmannFord algorithm from the root node(s) |
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528 /// in order to compute the shortest path with at most \c length edge |
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529 /// long paths to each node. The algorithm computes |
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530 /// - The shortest path tree. |
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531 /// - The limited distance of each node from the root(s). |
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532 void limitedStart(int length) { |
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533 for (int i = 0; i < length; ++i) { |
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534 if (processNextRound()) break; |
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535 } |
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536 } |
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537 |
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538 /// \brief Runs %BelmannFord algorithm from node \c s. |
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539 /// |
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540 /// This method runs the %BelmannFord algorithm from a root node \c s |
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541 /// in order to compute the shortest path to each node. The algorithm |
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542 /// computes |
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543 /// - The shortest path tree. |
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544 /// - The distance of each node from the root. |
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545 /// |
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546 /// \note d.run(s) is just a shortcut of the following code. |
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547 /// \code |
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548 /// d.init(); |
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549 /// d.addSource(s); |
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550 /// d.start(); |
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551 /// \endcode |
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552 void run(Node s) { |
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553 init(); |
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554 addSource(s); |
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555 start(); |
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556 } |
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557 |
|
558 /// \brief Runs %BelmannFord algorithm with limited path length |
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559 /// from node \c s. |
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560 /// |
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561 /// This method runs the %BelmannFord algorithm from a root node \c s |
|
562 /// in order to compute the shortest path with at most \c len edges |
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563 /// to each node. The algorithm computes |
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564 /// - The shortest path tree. |
|
565 /// - The distance of each node from the root. |
|
566 /// |
|
567 /// \note d.run(s, len) is just a shortcut of the following code. |
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568 /// \code |
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569 /// d.init(); |
|
570 /// d.addSource(s); |
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571 /// d.limitedStart(len); |
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572 /// \endcode |
|
573 void run(Node s, int len) { |
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574 init(); |
|
575 addSource(s); |
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576 limitedStart(len); |
|
577 } |
|
578 |
|
579 ///@} |
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580 |
|
581 /// \name Query Functions |
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582 /// The result of the %BelmannFord algorithm can be obtained using these |
|
583 /// functions.\n |
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584 /// Before the use of these functions, |
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585 /// either run() or start() must be called. |
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586 |
|
587 ///@{ |
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588 |
|
589 /// \brief Copies the shortest path to \c t into \c p |
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590 /// |
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591 /// This function copies the shortest path to \c t into \c p. |
|
592 /// If it \c t is a source itself or unreachable, then it does not |
|
593 /// alter \c p. |
|
594 /// |
|
595 /// \return Returns \c true if a path to \c t was actually copied to \c p, |
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596 /// \c false otherwise. |
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597 /// \sa DirPath |
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598 template <typename Path> |
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599 bool getPath(Path &p, Node t) { |
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600 if(reached(t)) { |
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601 p.clear(); |
|
602 typename Path::Builder b(p); |
|
603 for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t)) |
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604 b.pushFront(predEdge(t)); |
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605 b.commit(); |
|
606 return true; |
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607 } |
|
608 return false; |
|
609 } |
|
610 |
|
611 /// \brief The distance of a node from the root. |
|
612 /// |
|
613 /// Returns the distance of a node from the root. |
|
614 /// \pre \ref run() must be called before using this function. |
|
615 /// \warning If node \c v in unreachable from the root the return value |
|
616 /// of this funcion is undefined. |
|
617 Value dist(Node v) const { return (*_dist)[v]; } |
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618 |
|
619 /// \brief Returns the 'previous edge' of the shortest path tree. |
|
620 /// |
|
621 /// For a node \c v it returns the 'previous edge' of the shortest path |
|
622 /// tree, i.e. it returns the last edge of a shortest path from the root |
|
623 /// to \c v. It is \ref INVALID if \c v is unreachable from the root or |
|
624 /// if \c v=s. The shortest path tree used here is equal to the shortest |
|
625 /// path tree used in \ref predNode(). |
|
626 /// \pre \ref run() must be called before using |
|
627 /// this function. |
|
628 Edge predEdge(Node v) const { return (*_pred)[v]; } |
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629 |
|
630 /// \brief Returns the 'previous node' of the shortest path tree. |
|
631 /// |
|
632 /// For a node \c v it returns the 'previous node' of the shortest path |
|
633 /// tree, i.e. it returns the last but one node from a shortest path from |
|
634 /// the root to \c /v. It is INVALID if \c v is unreachable from the root |
|
635 /// or if \c v=s. The shortest path tree used here is equal to the |
|
636 /// shortest path tree used in \ref predEdge(). \pre \ref run() must be |
|
637 /// called before using this function. |
|
638 Node predNode(Node v) const { |
|
639 return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]); |
|
640 } |
|
641 |
|
642 /// \brief Returns a reference to the NodeMap of distances. |
|
643 /// |
|
644 /// Returns a reference to the NodeMap of distances. \pre \ref run() must |
|
645 /// be called before using this function. |
|
646 const DistMap &distMap() const { return *_dist;} |
|
647 |
|
648 /// \brief Returns a reference to the shortest path tree map. |
|
649 /// |
|
650 /// Returns a reference to the NodeMap of the edges of the |
|
651 /// shortest path tree. |
|
652 /// \pre \ref run() must be called before using this function. |
|
653 const PredMap &predMap() const { return *_pred; } |
|
654 |
|
655 /// \brief Checks if a node is reachable from the root. |
|
656 /// |
|
657 /// Returns \c true if \c v is reachable from the root. |
|
658 /// \pre \ref run() must be called before using this function. |
|
659 /// |
|
660 bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); } |
|
661 |
|
662 ///@} |
|
663 }; |
|
664 |
|
665 /// \brief Default traits class of BelmannFord function. |
|
666 /// |
|
667 /// Default traits class of BelmannFord function. |
|
668 /// \param _Graph Graph type. |
|
669 /// \param _LengthMap Type of length map. |
|
670 template <typename _Graph, typename _LengthMap> |
|
671 struct BelmannFordWizardDefaultTraits { |
|
672 /// \brief The graph type the algorithm runs on. |
|
673 typedef _Graph Graph; |
|
674 |
|
675 /// \brief The type of the map that stores the edge lengths. |
|
676 /// |
|
677 /// The type of the map that stores the edge lengths. |
|
678 /// It must meet the \ref concept::ReadMap "ReadMap" concept. |
|
679 typedef _LengthMap LengthMap; |
|
680 |
|
681 /// \brief The value type of the length map. |
|
682 typedef typename _LengthMap::Value Value; |
|
683 |
|
684 /// \brief Operation traits for belmann-ford algorithm. |
|
685 /// |
|
686 /// It defines the infinity type on the given Value type |
|
687 /// and the used operation. |
|
688 /// \see BelmannFordDefaultOperationTraits |
|
689 typedef BelmannFordDefaultOperationTraits<Value> OperationTraits; |
|
690 |
|
691 /// \brief The type of the map that stores the last |
|
692 /// edges of the shortest paths. |
|
693 /// |
|
694 /// The type of the map that stores the last |
|
695 /// edges of the shortest paths. |
|
696 /// It must meet the \ref concept::WriteMap "WriteMap" concept. |
|
697 typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap; |
|
698 |
|
699 /// \brief Instantiates a PredMap. |
|
700 /// |
|
701 /// This function instantiates a \ref PredMap. |
|
702 static PredMap *createPredMap(const _Graph &) { |
|
703 return new PredMap(); |
|
704 } |
|
705 /// \brief The type of the map that stores the dists of the nodes. |
|
706 /// |
|
707 /// The type of the map that stores the dists of the nodes. |
|
708 /// It must meet the \ref concept::WriteMap "WriteMap" concept. |
|
709 typedef NullMap<typename Graph::Node, Value> DistMap; |
|
710 /// \brief Instantiates a DistMap. |
|
711 /// |
|
712 /// This function instantiates a \ref DistMap. |
|
713 static DistMap *createDistMap(const _Graph &) { |
|
714 return new DistMap(); |
|
715 } |
|
716 }; |
|
717 |
|
718 /// \brief Default traits used by \ref BelmannFordWizard |
|
719 /// |
|
720 /// To make it easier to use BelmannFord algorithm |
|
721 /// we have created a wizard class. |
|
722 /// This \ref BelmannFordWizard class needs default traits, |
|
723 /// as well as the \ref BelmannFord class. |
|
724 /// The \ref BelmannFordWizardBase is a class to be the default traits of the |
|
725 /// \ref BelmannFordWizard class. |
|
726 /// \todo More named parameters are required... |
|
727 template<class _Graph,class _LengthMap> |
|
728 class BelmannFordWizardBase |
|
729 : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> { |
|
730 |
|
731 typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base; |
|
732 protected: |
|
733 /// Type of the nodes in the graph. |
|
734 typedef typename Base::Graph::Node Node; |
|
735 |
|
736 /// Pointer to the underlying graph. |
|
737 void *_graph; |
|
738 /// Pointer to the length map |
|
739 void *_length; |
|
740 ///Pointer to the map of predecessors edges. |
|
741 void *_pred; |
|
742 ///Pointer to the map of distances. |
|
743 void *_dist; |
|
744 ///Pointer to the source node. |
|
745 Node _source; |
|
746 |
|
747 public: |
|
748 /// Constructor. |
|
749 |
|
750 /// This constructor does not require parameters, therefore it initiates |
|
751 /// all of the attributes to default values (0, INVALID). |
|
752 BelmannFordWizardBase() : _graph(0), _length(0), _pred(0), |
|
753 _dist(0), _source(INVALID) {} |
|
754 |
|
755 /// Constructor. |
|
756 |
|
757 /// This constructor requires some parameters, |
|
758 /// listed in the parameters list. |
|
759 /// Others are initiated to 0. |
|
760 /// \param graph is the initial value of \ref _graph |
|
761 /// \param length is the initial value of \ref _length |
|
762 /// \param source is the initial value of \ref _source |
|
763 BelmannFordWizardBase(const _Graph& graph, |
|
764 const _LengthMap& length, |
|
765 Node source = INVALID) : |
|
766 _graph((void *)&graph), _length((void *)&length), _pred(0), |
|
767 _dist(0), _source(source) {} |
|
768 |
|
769 }; |
|
770 |
|
771 /// A class to make the usage of BelmannFord algorithm easier |
|
772 |
|
773 /// This class is created to make it easier to use BelmannFord algorithm. |
|
774 /// It uses the functions and features of the plain \ref BelmannFord, |
|
775 /// but it is much simpler to use it. |
|
776 /// |
|
777 /// Simplicity means that the way to change the types defined |
|
778 /// in the traits class is based on functions that returns the new class |
|
779 /// and not on templatable built-in classes. |
|
780 /// When using the plain \ref BelmannFord |
|
781 /// the new class with the modified type comes from |
|
782 /// the original class by using the :: |
|
783 /// operator. In the case of \ref BelmannFordWizard only |
|
784 /// a function have to be called and it will |
|
785 /// return the needed class. |
|
786 /// |
|
787 /// It does not have own \ref run method. When its \ref run method is called |
|
788 /// it initiates a plain \ref BelmannFord class, and calls the \ref |
|
789 /// BelmannFord::run method of it. |
|
790 template<class _Traits> |
|
791 class BelmannFordWizard : public _Traits { |
|
792 typedef _Traits Base; |
|
793 |
|
794 ///The type of the underlying graph. |
|
795 typedef typename _Traits::Graph Graph; |
|
796 |
|
797 typedef typename Graph::Node Node; |
|
798 typedef typename Graph::NodeIt NodeIt; |
|
799 typedef typename Graph::Edge Edge; |
|
800 typedef typename Graph::OutEdgeIt EdgeIt; |
|
801 |
|
802 ///The type of the map that stores the edge lengths. |
|
803 typedef typename _Traits::LengthMap LengthMap; |
|
804 |
|
805 ///The type of the length of the edges. |
|
806 typedef typename LengthMap::Value Value; |
|
807 |
|
808 ///\brief The type of the map that stores the last |
|
809 ///edges of the shortest paths. |
|
810 typedef typename _Traits::PredMap PredMap; |
|
811 |
|
812 ///The type of the map that stores the dists of the nodes. |
|
813 typedef typename _Traits::DistMap DistMap; |
|
814 |
|
815 public: |
|
816 /// Constructor. |
|
817 BelmannFordWizard() : _Traits() {} |
|
818 |
|
819 /// \brief Constructor that requires parameters. |
|
820 /// |
|
821 /// Constructor that requires parameters. |
|
822 /// These parameters will be the default values for the traits class. |
|
823 BelmannFordWizard(const Graph& graph, const LengthMap& length, |
|
824 Node source = INVALID) |
|
825 : _Traits(graph, length, source) {} |
|
826 |
|
827 /// \brief Copy constructor |
|
828 BelmannFordWizard(const _Traits &b) : _Traits(b) {} |
|
829 |
|
830 ~BelmannFordWizard() {} |
|
831 |
|
832 /// \brief Runs BelmannFord algorithm from a given node. |
|
833 /// |
|
834 /// Runs BelmannFord algorithm from a given node. |
|
835 /// The node can be given by the \ref source function. |
|
836 void run() { |
|
837 if(Base::_source == INVALID) throw UninitializedParameter(); |
|
838 BelmannFord<Graph,LengthMap,_Traits> |
|
839 bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length); |
|
840 if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred); |
|
841 if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist); |
|
842 bf.run(Base::_source); |
|
843 } |
|
844 |
|
845 /// \brief Runs BelmannFord algorithm from the given node. |
|
846 /// |
|
847 /// Runs BelmannFord algorithm from the given node. |
|
848 /// \param source is the given source. |
|
849 void run(Node source) { |
|
850 Base::_source = source; |
|
851 run(); |
|
852 } |
|
853 |
|
854 template<class T> |
|
855 struct DefPredMapBase : public Base { |
|
856 typedef T PredMap; |
|
857 static PredMap *createPredMap(const Graph &) { return 0; }; |
|
858 DefPredMapBase(const _Traits &b) : _Traits(b) {} |
|
859 }; |
|
860 |
|
861 ///\brief \ref named-templ-param "Named parameter" |
|
862 ///function for setting PredMap type |
|
863 /// |
|
864 /// \ref named-templ-param "Named parameter" |
|
865 ///function for setting PredMap type |
|
866 /// |
|
867 template<class T> |
|
868 BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t) |
|
869 { |
|
870 Base::_pred=(void *)&t; |
|
871 return BelmannFordWizard<DefPredMapBase<T> >(*this); |
|
872 } |
|
873 |
|
874 template<class T> |
|
875 struct DefDistMapBase : public Base { |
|
876 typedef T DistMap; |
|
877 static DistMap *createDistMap(const Graph &) { return 0; }; |
|
878 DefDistMapBase(const _Traits &b) : _Traits(b) {} |
|
879 }; |
|
880 |
|
881 ///\brief \ref named-templ-param "Named parameter" |
|
882 ///function for setting DistMap type |
|
883 /// |
|
884 /// \ref named-templ-param "Named parameter" |
|
885 ///function for setting DistMap type |
|
886 /// |
|
887 template<class T> |
|
888 BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) { |
|
889 Base::_dist=(void *)&t; |
|
890 return BelmannFordWizard<DefDistMapBase<T> >(*this); |
|
891 } |
|
892 |
|
893 template<class T> |
|
894 struct DefOperationTraitsBase : public Base { |
|
895 typedef T OperationTraits; |
|
896 DefOperationTraitsBase(const _Traits &b) : _Traits(b) {} |
|
897 }; |
|
898 |
|
899 ///\brief \ref named-templ-param "Named parameter" |
|
900 ///function for setting OperationTraits type |
|
901 /// |
|
902 /// \ref named-templ-param "Named parameter" |
|
903 ///function for setting OperationTraits type |
|
904 /// |
|
905 template<class T> |
|
906 BelmannFordWizard<DefOperationTraitsBase<T> > distMap() { |
|
907 return BelmannFordWizard<DefDistMapBase<T> >(*this); |
|
908 } |
|
909 |
|
910 /// \brief Sets the source node, from which the BelmannFord algorithm runs. |
|
911 /// |
|
912 /// Sets the source node, from which the BelmannFord algorithm runs. |
|
913 /// \param source is the source node. |
|
914 BelmannFordWizard<_Traits>& source(Node source) { |
|
915 Base::_source = source; |
|
916 return *this; |
|
917 } |
|
918 |
|
919 }; |
|
920 |
|
921 /// \brief Function type interface for BelmannFord algorithm. |
|
922 /// |
|
923 /// \ingroup flowalgs |
|
924 /// Function type interface for BelmannFord algorithm. |
|
925 /// |
|
926 /// This function also has several \ref named-templ-func-param |
|
927 /// "named parameters", they are declared as the members of class |
|
928 /// \ref BelmannFordWizard. |
|
929 /// The following |
|
930 /// example shows how to use these parameters. |
|
931 /// \code |
|
932 /// belmannford(g,length,source).predMap(preds).run(); |
|
933 /// \endcode |
|
934 /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()" |
|
935 /// to the end of the parameter list. |
|
936 /// \sa BelmannFordWizard |
|
937 /// \sa BelmannFord |
|
938 template<class _Graph, class _LengthMap> |
|
939 BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> > |
|
940 belmannFord(const _Graph& graph, |
|
941 const _LengthMap& length, |
|
942 typename _Graph::Node source = INVALID) { |
|
943 return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> > |
|
944 (graph, length, source); |
|
945 } |
|
946 |
|
947 } //END OF NAMESPACE LEMON |
|
948 |
|
949 #endif |
|
950 |
|