[906] | 1 | /* -*- C++ -*- |
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| 2 | * src/hugo/bfs.h - Part of HUGOlib, a generic C++ optimization library |
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| 3 | * |
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| 4 | * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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| 5 | * (Egervary Combinatorial Optimization Research Group, EGRES). |
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| 6 | * |
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| 7 | * Permission to use, modify and distribute this software is granted |
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| 8 | * provided that this copyright notice appears in all copies. For |
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| 9 | * precise terms see the accompanying LICENSE file. |
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| 10 | * |
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| 11 | * This software is provided "AS IS" with no warranty of any kind, |
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| 12 | * express or implied, and with no claim as to its suitability for any |
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| 13 | * purpose. |
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| 14 | * |
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| 15 | */ |
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| 16 | |
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[774] | 17 | #ifndef HUGO_BFS_H |
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| 18 | #define HUGO_BFS_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 Bfs algorithm. |
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| 23 | /// |
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| 24 | ///\todo Revise Manual. |
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| 25 | |
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| 26 | #include <hugo/bin_heap.h> |
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| 27 | #include <hugo/invalid.h> |
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| 28 | |
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| 29 | namespace hugo { |
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| 30 | |
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| 31 | /// \addtogroup flowalgs |
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| 32 | /// @{ |
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| 33 | |
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[781] | 34 | ///%BFS algorithm class. |
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[774] | 35 | |
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[781] | 36 | ///This class provides an efficient implementation of %BFS algorithm. |
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| 37 | ///\param GR The graph type the algorithm runs on. |
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| 38 | ///This class does the same as Dijkstra does with constant 1 edge length, |
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| 39 | ///but it is faster. |
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[774] | 40 | /// |
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[781] | 41 | ///\author Alpar Juttner |
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[774] | 42 | |
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| 43 | #ifdef DOXYGEN |
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| 44 | template <typename GR> |
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| 45 | #else |
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| 46 | template <typename GR> |
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| 47 | #endif |
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| 48 | class Bfs{ |
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| 49 | public: |
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| 50 | ///The type of the underlying graph. |
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| 51 | typedef GR Graph; |
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[911] | 52 | ///\e |
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[774] | 53 | typedef typename Graph::Node Node; |
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[911] | 54 | ///\e |
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[774] | 55 | typedef typename Graph::NodeIt NodeIt; |
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[911] | 56 | ///\e |
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[774] | 57 | typedef typename Graph::Edge Edge; |
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[911] | 58 | ///\e |
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[774] | 59 | typedef typename Graph::OutEdgeIt OutEdgeIt; |
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| 60 | |
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| 61 | ///\brief The type of the map that stores the last |
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| 62 | ///edges of the shortest paths. |
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| 63 | typedef typename Graph::template NodeMap<Edge> PredMap; |
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| 64 | ///\brief The type of the map that stores the last but one |
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| 65 | ///nodes of the shortest paths. |
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| 66 | typedef typename Graph::template NodeMap<Node> PredNodeMap; |
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| 67 | ///The type of the map that stores the dists of the nodes. |
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| 68 | typedef typename Graph::template NodeMap<int> DistMap; |
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| 69 | |
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| 70 | private: |
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[802] | 71 | /// Pointer to the underlying graph. |
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[774] | 72 | const Graph *G; |
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[802] | 73 | ///Pointer to the map of predecessors edges. |
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[774] | 74 | PredMap *predecessor; |
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[802] | 75 | ///Indicates if \ref predecessor is locally allocated (\c true) or not. |
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[774] | 76 | bool local_predecessor; |
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[802] | 77 | ///Pointer to the map of predecessors nodes. |
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[774] | 78 | PredNodeMap *pred_node; |
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[802] | 79 | ///Indicates if \ref pred_node is locally allocated (\c true) or not. |
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[774] | 80 | bool local_pred_node; |
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[802] | 81 | ///Pointer to the map of distances. |
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[774] | 82 | DistMap *distance; |
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[802] | 83 | ///Indicates if \ref distance is locally allocated (\c true) or not. |
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[774] | 84 | bool local_distance; |
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| 85 | |
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[802] | 86 | ///The source node of the last execution. |
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[774] | 87 | Node source; |
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| 88 | |
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| 89 | |
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[781] | 90 | ///Initializes the maps. |
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[774] | 91 | void init_maps() |
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| 92 | { |
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| 93 | if(!predecessor) { |
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| 94 | local_predecessor = true; |
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| 95 | predecessor = new PredMap(*G); |
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| 96 | } |
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| 97 | if(!pred_node) { |
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| 98 | local_pred_node = true; |
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| 99 | pred_node = new PredNodeMap(*G); |
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| 100 | } |
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| 101 | if(!distance) { |
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| 102 | local_distance = true; |
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| 103 | distance = new DistMap(*G); |
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| 104 | } |
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| 105 | } |
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| 106 | |
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| 107 | public : |
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[802] | 108 | ///Constructor. |
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| 109 | |
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| 110 | ///\param _G the graph the algorithm will run on. |
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[911] | 111 | /// |
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[774] | 112 | Bfs(const Graph& _G) : |
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| 113 | G(&_G), |
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| 114 | predecessor(NULL), local_predecessor(false), |
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| 115 | pred_node(NULL), local_pred_node(false), |
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| 116 | distance(NULL), local_distance(false) |
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| 117 | { } |
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| 118 | |
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[802] | 119 | ///Destructor. |
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[774] | 120 | ~Bfs() |
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| 121 | { |
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| 122 | if(local_predecessor) delete predecessor; |
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| 123 | if(local_pred_node) delete pred_node; |
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| 124 | if(local_distance) delete distance; |
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| 125 | } |
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| 126 | |
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| 127 | ///Sets the map storing the predecessor edges. |
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| 128 | |
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| 129 | ///Sets the map storing the predecessor edges. |
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| 130 | ///If you don't use this function before calling \ref run(), |
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| 131 | ///it will allocate one. The destuctor deallocates this |
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| 132 | ///automatically allocated map, of course. |
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| 133 | ///\return <tt> (*this) </tt> |
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| 134 | Bfs &setPredMap(PredMap &m) |
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| 135 | { |
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| 136 | if(local_predecessor) { |
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| 137 | delete predecessor; |
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| 138 | local_predecessor=false; |
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| 139 | } |
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| 140 | predecessor = &m; |
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| 141 | return *this; |
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| 142 | } |
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| 143 | |
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| 144 | ///Sets the map storing the predecessor nodes. |
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| 145 | |
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| 146 | ///Sets the map storing the predecessor nodes. |
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| 147 | ///If you don't use this function before calling \ref run(), |
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| 148 | ///it will allocate one. The destuctor deallocates this |
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| 149 | ///automatically allocated map, of course. |
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| 150 | ///\return <tt> (*this) </tt> |
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| 151 | Bfs &setPredNodeMap(PredNodeMap &m) |
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| 152 | { |
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| 153 | if(local_pred_node) { |
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| 154 | delete pred_node; |
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| 155 | local_pred_node=false; |
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| 156 | } |
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| 157 | pred_node = &m; |
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| 158 | return *this; |
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| 159 | } |
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| 160 | |
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| 161 | ///Sets the map storing the distances calculated by the algorithm. |
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| 162 | |
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| 163 | ///Sets the map storing the distances calculated by the algorithm. |
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| 164 | ///If you don't use this function before calling \ref run(), |
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| 165 | ///it will allocate one. The destuctor deallocates this |
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| 166 | ///automatically allocated map, of course. |
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| 167 | ///\return <tt> (*this) </tt> |
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| 168 | Bfs &setDistMap(DistMap &m) |
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| 169 | { |
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| 170 | if(local_distance) { |
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| 171 | delete distance; |
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| 172 | local_distance=false; |
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| 173 | } |
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| 174 | distance = &m; |
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| 175 | return *this; |
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| 176 | } |
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| 177 | |
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| 178 | ///Runs %BFS algorithm from node \c s. |
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| 179 | |
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| 180 | ///This method runs the %BFS algorithm from a root node \c s |
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| 181 | ///in order to |
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[781] | 182 | ///compute a |
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[774] | 183 | ///shortest path to each node. The algorithm computes |
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[781] | 184 | ///- The %BFS tree. |
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[774] | 185 | ///- The distance of each node from the root. |
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| 186 | |
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| 187 | void run(Node s) { |
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| 188 | |
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| 189 | init_maps(); |
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| 190 | |
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| 191 | source = s; |
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| 192 | |
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| 193 | for ( NodeIt u(*G) ; u!=INVALID ; ++u ) { |
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| 194 | predecessor->set(u,INVALID); |
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| 195 | pred_node->set(u,INVALID); |
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| 196 | } |
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| 197 | |
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| 198 | int N=G->nodeNum(); |
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| 199 | std::vector<typename Graph::Node> Q(N); |
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| 200 | int Qh=0; |
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| 201 | int Qt=0; |
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| 202 | |
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| 203 | Q[Qh++]=source; |
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| 204 | distance->set(s, 0); |
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| 205 | do { |
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| 206 | Node m; |
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| 207 | Node n=Q[Qt++]; |
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| 208 | int d= (*distance)[n]+1; |
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| 209 | |
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| 210 | for(OutEdgeIt e(*G,n);e!=INVALID;++e) |
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| 211 | if((m=G->head(e))!=s && (*predecessor)[m]==INVALID) { |
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| 212 | Q[Qh++]=m; |
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| 213 | predecessor->set(m,e); |
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| 214 | pred_node->set(m,n); |
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| 215 | distance->set(m,d); |
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| 216 | } |
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| 217 | } while(Qt!=Qh); |
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| 218 | } |
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| 219 | |
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| 220 | ///The distance of a node from the root. |
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| 221 | |
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| 222 | ///Returns the distance of a node from the root. |
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| 223 | ///\pre \ref run() must be called before using this function. |
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| 224 | ///\warning If node \c v in unreachable from the root the return value |
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| 225 | ///of this funcion is undefined. |
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| 226 | int dist(Node v) const { return (*distance)[v]; } |
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| 227 | |
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[781] | 228 | ///Returns the 'previous edge' of the %BFS path tree. |
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[774] | 229 | |
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[781] | 230 | ///For a node \c v it returns the 'previous edge' of the %BFS tree, |
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| 231 | ///i.e. it returns the last edge of a shortest path from the root to \c |
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[774] | 232 | ///v. It is \ref INVALID |
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| 233 | ///if \c v is unreachable from the root or if \c v=s. The |
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[781] | 234 | ///%BFS tree used here is equal to the %BFS tree used in |
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[774] | 235 | ///\ref predNode(Node v). \pre \ref run() must be called before using |
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| 236 | ///this function. |
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| 237 | Edge pred(Node v) const { return (*predecessor)[v]; } |
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| 238 | |
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[781] | 239 | ///Returns the 'previous node' of the %BFS tree. |
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[774] | 240 | |
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[781] | 241 | ///For a node \c v it returns the 'previous node' on the %BFS tree, |
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[774] | 242 | ///i.e. it returns the last but one node from a shortest path from the |
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| 243 | ///root to \c /v. It is INVALID if \c v is unreachable from the root or if |
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[781] | 244 | ///\c v=s. The shortest path tree used here is equal to the %BFS |
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[774] | 245 | ///tree used in \ref pred(Node v). \pre \ref run() must be called before |
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| 246 | ///using this function. |
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| 247 | Node predNode(Node v) const { return (*pred_node)[v]; } |
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| 248 | |
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| 249 | ///Returns a reference to the NodeMap of distances. |
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| 250 | |
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| 251 | ///Returns a reference to the NodeMap of distances. \pre \ref run() must |
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| 252 | ///be called before using this function. |
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| 253 | const DistMap &distMap() const { return *distance;} |
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| 254 | |
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[781] | 255 | ///Returns a reference to the %BFS tree map. |
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[774] | 256 | |
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| 257 | ///Returns a reference to the NodeMap of the edges of the |
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[781] | 258 | ///%BFS tree. |
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[774] | 259 | ///\pre \ref run() must be called before using this function. |
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| 260 | const PredMap &predMap() const { return *predecessor;} |
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| 261 | |
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[781] | 262 | ///Returns a reference to the map of last but one nodes of shortest paths. |
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[774] | 263 | |
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[781] | 264 | ///Returns a reference to the NodeMap of the last but one nodes on the |
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| 265 | ///%BFS tree. |
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[774] | 266 | ///\pre \ref run() must be called before using this function. |
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| 267 | const PredNodeMap &predNodeMap() const { return *pred_node;} |
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| 268 | |
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| 269 | ///Checks if a node is reachable from the root. |
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| 270 | |
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| 271 | ///Returns \c true if \c v is reachable from the root. |
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[802] | 272 | ///\note The root node is reported to be reached! |
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[774] | 273 | /// |
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| 274 | ///\pre \ref run() must be called before using this function. |
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| 275 | /// |
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[780] | 276 | bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; } |
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[774] | 277 | |
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| 278 | }; |
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| 279 | |
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| 280 | /// @} |
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| 281 | |
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| 282 | } //END OF NAMESPACE HUGO |
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| 283 | |
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| 284 | #endif |
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| 285 | |
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| 286 | |
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