[696] | 1 | /* -*- C++ -*- |
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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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[697] | 19 | #ifndef LEMON_BELLMAN_FORD_H |
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| 20 | #define LEMON_BELLMAN_FORD_H |
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[696] | 21 | |
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| 22 | /// \ingroup shortest_path |
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| 23 | /// \file |
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| 24 | /// \brief Bellman-Ford algorithm. |
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| 25 | |
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[781] | 26 | #include <lemon/list_graph.h> |
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[696] | 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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[697] | 31 | #include <lemon/path.h> |
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[696] | 32 | |
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| 33 | #include <limits> |
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| 34 | |
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| 35 | namespace lemon { |
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| 36 | |
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| 37 | /// \brief Default OperationTraits for the BellmanFord algorithm class. |
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| 38 | /// |
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[697] | 39 | /// This operation traits class defines all computational operations |
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| 40 | /// and constants that are used in the Bellman-Ford algorithm. |
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| 41 | /// The default implementation is based on the \c numeric_limits class. |
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| 42 | /// If the numeric type does not have infinity value, then the maximum |
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| 43 | /// value is used as extremal infinity value. |
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[696] | 44 | template < |
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[697] | 45 | typename V, |
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| 46 | bool has_inf = std::numeric_limits<V>::has_infinity> |
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[696] | 47 | struct BellmanFordDefaultOperationTraits { |
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[697] | 48 | /// \e |
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| 49 | typedef V Value; |
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[696] | 50 | /// \brief Gives back the zero value of the type. |
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| 51 | static Value zero() { |
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| 52 | return static_cast<Value>(0); |
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| 53 | } |
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| 54 | /// \brief Gives back the positive infinity value of the type. |
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| 55 | static Value infinity() { |
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| 56 | return std::numeric_limits<Value>::infinity(); |
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| 57 | } |
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| 58 | /// \brief Gives back the sum of the given two elements. |
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| 59 | static Value plus(const Value& left, const Value& right) { |
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| 60 | return left + right; |
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| 61 | } |
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[697] | 62 | /// \brief Gives back \c true only if the first value is less than |
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| 63 | /// the second. |
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[696] | 64 | static bool less(const Value& left, const Value& right) { |
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| 65 | return left < right; |
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| 66 | } |
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| 67 | }; |
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| 68 | |
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[697] | 69 | template <typename V> |
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| 70 | struct BellmanFordDefaultOperationTraits<V, false> { |
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| 71 | typedef V Value; |
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[696] | 72 | static Value zero() { |
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| 73 | return static_cast<Value>(0); |
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| 74 | } |
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| 75 | static Value infinity() { |
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| 76 | return std::numeric_limits<Value>::max(); |
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| 77 | } |
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| 78 | static Value plus(const Value& left, const Value& right) { |
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| 79 | if (left == infinity() || right == infinity()) return infinity(); |
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| 80 | return left + right; |
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| 81 | } |
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| 82 | static bool less(const Value& left, const Value& right) { |
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| 83 | return left < right; |
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| 84 | } |
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| 85 | }; |
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| 86 | |
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| 87 | /// \brief Default traits class of BellmanFord class. |
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| 88 | /// |
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| 89 | /// Default traits class of BellmanFord class. |
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[697] | 90 | /// \param GR The type of the digraph. |
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| 91 | /// \param LEN The type of the length map. |
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| 92 | template<typename GR, typename LEN> |
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[696] | 93 | struct BellmanFordDefaultTraits { |
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[697] | 94 | /// The type of the digraph the algorithm runs on. |
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| 95 | typedef GR Digraph; |
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[696] | 96 | |
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| 97 | /// \brief The type of the map that stores the arc lengths. |
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| 98 | /// |
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| 99 | /// The type of the map that stores the arc lengths. |
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[697] | 100 | /// It must conform to the \ref concepts::ReadMap "ReadMap" concept. |
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| 101 | typedef LEN LengthMap; |
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[696] | 102 | |
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[697] | 103 | /// The type of the arc lengths. |
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| 104 | typedef typename LEN::Value Value; |
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[696] | 105 | |
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| 106 | /// \brief Operation traits for Bellman-Ford algorithm. |
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| 107 | /// |
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[697] | 108 | /// It defines the used operations and the infinity value for the |
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| 109 | /// given \c Value type. |
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[696] | 110 | /// \see BellmanFordDefaultOperationTraits |
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| 111 | typedef BellmanFordDefaultOperationTraits<Value> OperationTraits; |
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| 112 | |
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| 113 | /// \brief The type of the map that stores the last arcs of the |
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| 114 | /// shortest paths. |
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| 115 | /// |
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| 116 | /// The type of the map that stores the last |
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| 117 | /// arcs of the shortest paths. |
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[697] | 118 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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| 119 | typedef typename GR::template NodeMap<typename GR::Arc> PredMap; |
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[696] | 120 | |
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[697] | 121 | /// \brief Instantiates a \c PredMap. |
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[696] | 122 | /// |
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| 123 | /// This function instantiates a \ref PredMap. |
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[697] | 124 | /// \param g is the digraph to which we would like to define the |
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| 125 | /// \ref PredMap. |
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| 126 | static PredMap *createPredMap(const GR& g) { |
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| 127 | return new PredMap(g); |
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[696] | 128 | } |
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| 129 | |
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[697] | 130 | /// \brief The type of the map that stores the distances of the nodes. |
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[696] | 131 | /// |
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[697] | 132 | /// The type of the map that stores the distances of the nodes. |
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| 133 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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| 134 | typedef typename GR::template NodeMap<typename LEN::Value> DistMap; |
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[696] | 135 | |
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[697] | 136 | /// \brief Instantiates a \c DistMap. |
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[696] | 137 | /// |
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| 138 | /// This function instantiates a \ref DistMap. |
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[697] | 139 | /// \param g is the digraph to which we would like to define the |
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| 140 | /// \ref DistMap. |
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| 141 | static DistMap *createDistMap(const GR& g) { |
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| 142 | return new DistMap(g); |
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[696] | 143 | } |
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| 144 | |
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| 145 | }; |
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| 146 | |
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| 147 | /// \brief %BellmanFord algorithm class. |
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| 148 | /// |
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| 149 | /// \ingroup shortest_path |
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[697] | 150 | /// This class provides an efficient implementation of the Bellman-Ford |
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| 151 | /// algorithm. The maximum time complexity of the algorithm is |
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| 152 | /// <tt>O(ne)</tt>. |
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| 153 | /// |
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| 154 | /// The Bellman-Ford algorithm solves the single-source shortest path |
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| 155 | /// problem when the arcs can have negative lengths, but the digraph |
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| 156 | /// should not contain directed cycles with negative total length. |
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| 157 | /// If all arc costs are non-negative, consider to use the Dijkstra |
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| 158 | /// algorithm instead, since it is more efficient. |
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| 159 | /// |
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| 160 | /// The arc lengths are passed to the algorithm using a |
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[696] | 161 | /// \ref concepts::ReadMap "ReadMap", so it is easy to change it to any |
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[697] | 162 | /// kind of length. The type of the length values is determined by the |
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| 163 | /// \ref concepts::ReadMap::Value "Value" type of the length map. |
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[696] | 164 | /// |
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[697] | 165 | /// There is also a \ref bellmanFord() "function-type interface" for the |
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| 166 | /// Bellman-Ford algorithm, which is convenient in the simplier cases and |
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| 167 | /// it can be used easier. |
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[696] | 168 | /// |
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[697] | 169 | /// \tparam GR The type of the digraph the algorithm runs on. |
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| 170 | /// The default type is \ref ListDigraph. |
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| 171 | /// \tparam LEN A \ref concepts::ReadMap "readable" arc map that specifies |
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| 172 | /// the lengths of the arcs. The default map type is |
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| 173 | /// \ref concepts::Digraph::ArcMap "GR::ArcMap<int>". |
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[696] | 174 | #ifdef DOXYGEN |
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[697] | 175 | template <typename GR, typename LEN, typename TR> |
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[696] | 176 | #else |
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[697] | 177 | template <typename GR=ListDigraph, |
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| 178 | typename LEN=typename GR::template ArcMap<int>, |
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| 179 | typename TR=BellmanFordDefaultTraits<GR,LEN> > |
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[696] | 180 | #endif |
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| 181 | class BellmanFord { |
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| 182 | public: |
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| 183 | |
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| 184 | ///The type of the underlying digraph. |
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[697] | 185 | typedef typename TR::Digraph Digraph; |
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| 186 | |
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| 187 | /// \brief The type of the arc lengths. |
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| 188 | typedef typename TR::LengthMap::Value Value; |
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| 189 | /// \brief The type of the map that stores the arc lengths. |
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| 190 | typedef typename TR::LengthMap LengthMap; |
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| 191 | /// \brief The type of the map that stores the last |
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| 192 | /// arcs of the shortest paths. |
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| 193 | typedef typename TR::PredMap PredMap; |
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| 194 | /// \brief The type of the map that stores the distances of the nodes. |
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| 195 | typedef typename TR::DistMap DistMap; |
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| 196 | /// The type of the paths. |
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| 197 | typedef PredMapPath<Digraph, PredMap> Path; |
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| 198 | ///\brief The \ref BellmanFordDefaultOperationTraits |
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| 199 | /// "operation traits class" of the algorithm. |
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| 200 | typedef typename TR::OperationTraits OperationTraits; |
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| 201 | |
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| 202 | ///The \ref BellmanFordDefaultTraits "traits class" of the algorithm. |
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| 203 | typedef TR Traits; |
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| 204 | |
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| 205 | private: |
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[696] | 206 | |
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| 207 | typedef typename Digraph::Node Node; |
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| 208 | typedef typename Digraph::NodeIt NodeIt; |
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| 209 | typedef typename Digraph::Arc Arc; |
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| 210 | typedef typename Digraph::OutArcIt OutArcIt; |
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[697] | 211 | |
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| 212 | // Pointer to the underlying digraph. |
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| 213 | const Digraph *_gr; |
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| 214 | // Pointer to the length map |
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| 215 | const LengthMap *_length; |
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| 216 | // Pointer to the map of predecessors arcs. |
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[696] | 217 | PredMap *_pred; |
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[697] | 218 | // Indicates if _pred is locally allocated (true) or not. |
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| 219 | bool _local_pred; |
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| 220 | // Pointer to the map of distances. |
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[696] | 221 | DistMap *_dist; |
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[697] | 222 | // Indicates if _dist is locally allocated (true) or not. |
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| 223 | bool _local_dist; |
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[696] | 224 | |
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| 225 | typedef typename Digraph::template NodeMap<bool> MaskMap; |
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| 226 | MaskMap *_mask; |
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| 227 | |
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| 228 | std::vector<Node> _process; |
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| 229 | |
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[697] | 230 | // Creates the maps if necessary. |
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[696] | 231 | void create_maps() { |
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| 232 | if(!_pred) { |
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[697] | 233 | _local_pred = true; |
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| 234 | _pred = Traits::createPredMap(*_gr); |
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[696] | 235 | } |
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| 236 | if(!_dist) { |
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[697] | 237 | _local_dist = true; |
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| 238 | _dist = Traits::createDistMap(*_gr); |
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[696] | 239 | } |
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[804] | 240 | if(!_mask) { |
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| 241 | _mask = new MaskMap(*_gr); |
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| 242 | } |
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[696] | 243 | } |
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| 244 | |
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| 245 | public : |
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| 246 | |
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| 247 | typedef BellmanFord Create; |
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| 248 | |
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[697] | 249 | /// \name Named Template Parameters |
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[696] | 250 | |
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| 251 | ///@{ |
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| 252 | |
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| 253 | template <class T> |
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[697] | 254 | struct SetPredMapTraits : public Traits { |
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[696] | 255 | typedef T PredMap; |
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| 256 | static PredMap *createPredMap(const Digraph&) { |
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| 257 | LEMON_ASSERT(false, "PredMap is not initialized"); |
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| 258 | return 0; // ignore warnings |
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| 259 | } |
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| 260 | }; |
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| 261 | |
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[697] | 262 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 263 | /// \c PredMap type. |
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[696] | 264 | /// |
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[697] | 265 | /// \ref named-templ-param "Named parameter" for setting |
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| 266 | /// \c PredMap type. |
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| 267 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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[696] | 268 | template <class T> |
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| 269 | struct SetPredMap |
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[697] | 270 | : public BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > { |
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| 271 | typedef BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > Create; |
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[696] | 272 | }; |
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| 273 | |
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| 274 | template <class T> |
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[697] | 275 | struct SetDistMapTraits : public Traits { |
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[696] | 276 | typedef T DistMap; |
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| 277 | static DistMap *createDistMap(const Digraph&) { |
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| 278 | LEMON_ASSERT(false, "DistMap is not initialized"); |
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| 279 | return 0; // ignore warnings |
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| 280 | } |
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| 281 | }; |
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| 282 | |
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[697] | 283 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 284 | /// \c DistMap type. |
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[696] | 285 | /// |
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[697] | 286 | /// \ref named-templ-param "Named parameter" for setting |
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| 287 | /// \c DistMap type. |
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| 288 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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[696] | 289 | template <class T> |
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| 290 | struct SetDistMap |
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[697] | 291 | : public BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > { |
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| 292 | typedef BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > Create; |
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[696] | 293 | }; |
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[697] | 294 | |
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[696] | 295 | template <class T> |
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[697] | 296 | struct SetOperationTraitsTraits : public Traits { |
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[696] | 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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[697] | 301 | /// \c OperationTraits type. |
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[696] | 302 | /// |
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[697] | 303 | /// \ref named-templ-param "Named parameter" for setting |
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| 304 | /// \c OperationTraits type. |
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[786] | 305 | /// For more information, see \ref BellmanFordDefaultOperationTraits. |
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[696] | 306 | template <class T> |
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| 307 | struct SetOperationTraits |
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[697] | 308 | : public BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > { |
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| 309 | typedef BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > |
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[696] | 310 | Create; |
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| 311 | }; |
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| 312 | |
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| 313 | ///@} |
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| 314 | |
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| 315 | protected: |
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| 316 | |
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| 317 | BellmanFord() {} |
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| 318 | |
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| 319 | public: |
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| 320 | |
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| 321 | /// \brief Constructor. |
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| 322 | /// |
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[697] | 323 | /// Constructor. |
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| 324 | /// \param g The digraph the algorithm runs on. |
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| 325 | /// \param length The length map used by the algorithm. |
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| 326 | BellmanFord(const Digraph& g, const LengthMap& length) : |
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| 327 | _gr(&g), _length(&length), |
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| 328 | _pred(0), _local_pred(false), |
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| 329 | _dist(0), _local_dist(false), _mask(0) {} |
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[696] | 330 | |
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| 331 | ///Destructor. |
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| 332 | ~BellmanFord() { |
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[697] | 333 | if(_local_pred) delete _pred; |
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| 334 | if(_local_dist) delete _dist; |
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[696] | 335 | if(_mask) delete _mask; |
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| 336 | } |
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| 337 | |
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| 338 | /// \brief Sets the length map. |
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| 339 | /// |
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| 340 | /// Sets the length map. |
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[697] | 341 | /// \return <tt>(*this)</tt> |
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| 342 | BellmanFord &lengthMap(const LengthMap &map) { |
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| 343 | _length = ↦ |
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[696] | 344 | return *this; |
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| 345 | } |
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| 346 | |
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[697] | 347 | /// \brief Sets the map that stores the predecessor arcs. |
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[696] | 348 | /// |
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[697] | 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 | /// or \ref init(), an instance will be allocated automatically. |
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| 352 | /// The destructor deallocates this automatically allocated map, |
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| 353 | /// of course. |
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| 354 | /// \return <tt>(*this)</tt> |
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| 355 | BellmanFord &predMap(PredMap &map) { |
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| 356 | if(_local_pred) { |
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[696] | 357 | delete _pred; |
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[697] | 358 | _local_pred=false; |
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[696] | 359 | } |
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[697] | 360 | _pred = ↦ |
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[696] | 361 | return *this; |
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| 362 | } |
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| 363 | |
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[697] | 364 | /// \brief Sets the map that stores the distances of the nodes. |
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[696] | 365 | /// |
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[697] | 366 | /// Sets the map that stores the distances of the nodes calculated |
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| 367 | /// by the algorithm. |
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| 368 | /// If you don't use this function before calling \ref run() |
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| 369 | /// or \ref init(), an instance will be allocated automatically. |
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| 370 | /// The destructor deallocates this automatically allocated map, |
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| 371 | /// of course. |
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| 372 | /// \return <tt>(*this)</tt> |
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| 373 | BellmanFord &distMap(DistMap &map) { |
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| 374 | if(_local_dist) { |
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[696] | 375 | delete _dist; |
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[697] | 376 | _local_dist=false; |
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[696] | 377 | } |
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[697] | 378 | _dist = ↦ |
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[696] | 379 | return *this; |
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| 380 | } |
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| 381 | |
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[697] | 382 | /// \name Execution Control |
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| 383 | /// The simplest way to execute the Bellman-Ford algorithm is to use |
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| 384 | /// one of the member functions called \ref run().\n |
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| 385 | /// If you need better control on the execution, you have to call |
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| 386 | /// \ref init() first, then you can add several source nodes |
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| 387 | /// with \ref addSource(). Finally the actual path computation can be |
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| 388 | /// performed with \ref start(), \ref checkedStart() or |
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| 389 | /// \ref limitedStart(). |
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[696] | 390 | |
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| 391 | ///@{ |
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| 392 | |
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| 393 | /// \brief Initializes the internal data structures. |
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| 394 | /// |
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[697] | 395 | /// Initializes the internal data structures. The optional parameter |
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| 396 | /// is the initial distance of each node. |
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[696] | 397 | void init(const Value value = OperationTraits::infinity()) { |
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| 398 | create_maps(); |
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[697] | 399 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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[696] | 400 | _pred->set(it, INVALID); |
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| 401 | _dist->set(it, value); |
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| 402 | } |
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| 403 | _process.clear(); |
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| 404 | if (OperationTraits::less(value, OperationTraits::infinity())) { |
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[697] | 405 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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[696] | 406 | _process.push_back(it); |
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| 407 | _mask->set(it, true); |
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| 408 | } |
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[804] | 409 | } else { |
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| 410 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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| 411 | _mask->set(it, false); |
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| 412 | } |
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[696] | 413 | } |
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| 414 | } |
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| 415 | |
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| 416 | /// \brief Adds a new source node. |
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| 417 | /// |
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[697] | 418 | /// This function adds a new source node. The optional second parameter |
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| 419 | /// is the initial distance of the node. |
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[696] | 420 | void addSource(Node source, Value dst = OperationTraits::zero()) { |
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| 421 | _dist->set(source, dst); |
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| 422 | if (!(*_mask)[source]) { |
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| 423 | _process.push_back(source); |
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| 424 | _mask->set(source, true); |
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| 425 | } |
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| 426 | } |
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| 427 | |
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| 428 | /// \brief Executes one round from the Bellman-Ford algorithm. |
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| 429 | /// |
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| 430 | /// If the algoritm calculated the distances in the previous round |
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[697] | 431 | /// exactly for the paths of at most \c k arcs, then this function |
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| 432 | /// will calculate the distances exactly for the paths of at most |
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| 433 | /// <tt>k+1</tt> arcs. Performing \c k iterations using this function |
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| 434 | /// calculates the shortest path distances exactly for the paths |
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| 435 | /// consisting of at most \c k arcs. |
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[696] | 436 | /// |
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| 437 | /// \warning The paths with limited arc number cannot be retrieved |
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[697] | 438 | /// easily with \ref path() or \ref predArc() functions. If you also |
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| 439 | /// need the shortest paths and not only the distances, you should |
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| 440 | /// store the \ref predMap() "predecessor map" after each iteration |
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| 441 | /// and build the path manually. |
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[696] | 442 | /// |
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| 443 | /// \return \c true when the algorithm have not found more shorter |
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| 444 | /// paths. |
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[697] | 445 | /// |
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| 446 | /// \see ActiveIt |
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[696] | 447 | bool processNextRound() { |
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| 448 | for (int i = 0; i < int(_process.size()); ++i) { |
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| 449 | _mask->set(_process[i], false); |
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| 450 | } |
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| 451 | std::vector<Node> nextProcess; |
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| 452 | std::vector<Value> values(_process.size()); |
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| 453 | for (int i = 0; i < int(_process.size()); ++i) { |
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| 454 | values[i] = (*_dist)[_process[i]]; |
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| 455 | } |
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| 456 | for (int i = 0; i < int(_process.size()); ++i) { |
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[697] | 457 | for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) { |
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| 458 | Node target = _gr->target(it); |
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| 459 | Value relaxed = OperationTraits::plus(values[i], (*_length)[it]); |
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[696] | 460 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 461 | _pred->set(target, it); |
---|
| 462 | _dist->set(target, relaxed); |
---|
| 463 | if (!(*_mask)[target]) { |
---|
| 464 | _mask->set(target, true); |
---|
| 465 | nextProcess.push_back(target); |
---|
| 466 | } |
---|
| 467 | } |
---|
| 468 | } |
---|
| 469 | } |
---|
| 470 | _process.swap(nextProcess); |
---|
| 471 | return _process.empty(); |
---|
| 472 | } |
---|
| 473 | |
---|
| 474 | /// \brief Executes one weak round from the Bellman-Ford algorithm. |
---|
| 475 | /// |
---|
[697] | 476 | /// If the algorithm calculated the distances in the previous round |
---|
| 477 | /// at least for the paths of at most \c k arcs, then this function |
---|
| 478 | /// will calculate the distances at least for the paths of at most |
---|
| 479 | /// <tt>k+1</tt> arcs. |
---|
| 480 | /// This function does not make it possible to calculate the shortest |
---|
| 481 | /// path distances exactly for paths consisting of at most \c k arcs, |
---|
| 482 | /// this is why it is called weak round. |
---|
| 483 | /// |
---|
| 484 | /// \return \c true when the algorithm have not found more shorter |
---|
| 485 | /// paths. |
---|
| 486 | /// |
---|
| 487 | /// \see ActiveIt |
---|
[696] | 488 | bool processNextWeakRound() { |
---|
| 489 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
| 490 | _mask->set(_process[i], false); |
---|
| 491 | } |
---|
| 492 | std::vector<Node> nextProcess; |
---|
| 493 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[697] | 494 | for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) { |
---|
| 495 | Node target = _gr->target(it); |
---|
[696] | 496 | Value relaxed = |
---|
[697] | 497 | OperationTraits::plus((*_dist)[_process[i]], (*_length)[it]); |
---|
[696] | 498 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 499 | _pred->set(target, it); |
---|
| 500 | _dist->set(target, relaxed); |
---|
| 501 | if (!(*_mask)[target]) { |
---|
| 502 | _mask->set(target, true); |
---|
| 503 | nextProcess.push_back(target); |
---|
| 504 | } |
---|
| 505 | } |
---|
| 506 | } |
---|
| 507 | } |
---|
| 508 | _process.swap(nextProcess); |
---|
| 509 | return _process.empty(); |
---|
| 510 | } |
---|
| 511 | |
---|
| 512 | /// \brief Executes the algorithm. |
---|
| 513 | /// |
---|
[697] | 514 | /// Executes the algorithm. |
---|
[696] | 515 | /// |
---|
[697] | 516 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 517 | /// in order to compute the shortest path to each node. |
---|
| 518 | /// |
---|
| 519 | /// The algorithm computes |
---|
| 520 | /// - the shortest path tree (forest), |
---|
| 521 | /// - the distance of each node from the root(s). |
---|
| 522 | /// |
---|
| 523 | /// \pre init() must be called and at least one root node should be |
---|
| 524 | /// added with addSource() before using this function. |
---|
[696] | 525 | void start() { |
---|
[697] | 526 | int num = countNodes(*_gr) - 1; |
---|
[696] | 527 | for (int i = 0; i < num; ++i) { |
---|
| 528 | if (processNextWeakRound()) break; |
---|
| 529 | } |
---|
| 530 | } |
---|
| 531 | |
---|
| 532 | /// \brief Executes the algorithm and checks the negative cycles. |
---|
| 533 | /// |
---|
[697] | 534 | /// Executes the algorithm and checks the negative cycles. |
---|
[696] | 535 | /// |
---|
[697] | 536 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 537 | /// in order to compute the shortest path to each node and also checks |
---|
| 538 | /// if the digraph contains cycles with negative total length. |
---|
| 539 | /// |
---|
| 540 | /// The algorithm computes |
---|
| 541 | /// - the shortest path tree (forest), |
---|
| 542 | /// - the distance of each node from the root(s). |
---|
[696] | 543 | /// |
---|
| 544 | /// \return \c false if there is a negative cycle in the digraph. |
---|
[697] | 545 | /// |
---|
| 546 | /// \pre init() must be called and at least one root node should be |
---|
| 547 | /// added with addSource() before using this function. |
---|
[696] | 548 | bool checkedStart() { |
---|
[697] | 549 | int num = countNodes(*_gr); |
---|
[696] | 550 | for (int i = 0; i < num; ++i) { |
---|
| 551 | if (processNextWeakRound()) return true; |
---|
| 552 | } |
---|
| 553 | return _process.empty(); |
---|
| 554 | } |
---|
| 555 | |
---|
[697] | 556 | /// \brief Executes the algorithm with arc number limit. |
---|
[696] | 557 | /// |
---|
[697] | 558 | /// Executes the algorithm with arc number limit. |
---|
[696] | 559 | /// |
---|
[697] | 560 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 561 | /// in order to compute the shortest path distance for each node |
---|
| 562 | /// using only the paths consisting of at most \c num arcs. |
---|
| 563 | /// |
---|
| 564 | /// The algorithm computes |
---|
| 565 | /// - the limited distance of each node from the root(s), |
---|
| 566 | /// - the predecessor arc for each node. |
---|
[696] | 567 | /// |
---|
| 568 | /// \warning The paths with limited arc number cannot be retrieved |
---|
[697] | 569 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 570 | /// need the shortest paths and not only the distances, you should |
---|
| 571 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 572 | /// and build the path manually. |
---|
[696] | 573 | /// |
---|
[697] | 574 | /// \pre init() must be called and at least one root node should be |
---|
| 575 | /// added with addSource() before using this function. |
---|
[696] | 576 | void limitedStart(int num) { |
---|
| 577 | for (int i = 0; i < num; ++i) { |
---|
| 578 | if (processNextRound()) break; |
---|
| 579 | } |
---|
| 580 | } |
---|
| 581 | |
---|
[697] | 582 | /// \brief Runs the algorithm from the given root node. |
---|
[696] | 583 | /// |
---|
[697] | 584 | /// This method runs the Bellman-Ford algorithm from the given root |
---|
| 585 | /// node \c s in order to compute the shortest path to each node. |
---|
[696] | 586 | /// |
---|
[697] | 587 | /// The algorithm computes |
---|
| 588 | /// - the shortest path tree (forest), |
---|
| 589 | /// - the distance of each node from the root(s). |
---|
| 590 | /// |
---|
| 591 | /// \note bf.run(s) is just a shortcut of the following code. |
---|
| 592 | /// \code |
---|
| 593 | /// bf.init(); |
---|
| 594 | /// bf.addSource(s); |
---|
| 595 | /// bf.start(); |
---|
| 596 | /// \endcode |
---|
[696] | 597 | void run(Node s) { |
---|
| 598 | init(); |
---|
| 599 | addSource(s); |
---|
| 600 | start(); |
---|
| 601 | } |
---|
| 602 | |
---|
[697] | 603 | /// \brief Runs the algorithm from the given root node with arc |
---|
| 604 | /// number limit. |
---|
[696] | 605 | /// |
---|
[697] | 606 | /// This method runs the Bellman-Ford algorithm from the given root |
---|
| 607 | /// node \c s in order to compute the shortest path distance for each |
---|
| 608 | /// node using only the paths consisting of at most \c num arcs. |
---|
[696] | 609 | /// |
---|
[697] | 610 | /// The algorithm computes |
---|
| 611 | /// - the limited distance of each node from the root(s), |
---|
| 612 | /// - the predecessor arc for each node. |
---|
| 613 | /// |
---|
| 614 | /// \warning The paths with limited arc number cannot be retrieved |
---|
| 615 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 616 | /// need the shortest paths and not only the distances, you should |
---|
| 617 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 618 | /// and build the path manually. |
---|
| 619 | /// |
---|
| 620 | /// \note bf.run(s, num) is just a shortcut of the following code. |
---|
| 621 | /// \code |
---|
| 622 | /// bf.init(); |
---|
| 623 | /// bf.addSource(s); |
---|
| 624 | /// bf.limitedStart(num); |
---|
| 625 | /// \endcode |
---|
[696] | 626 | void run(Node s, int num) { |
---|
| 627 | init(); |
---|
| 628 | addSource(s); |
---|
| 629 | limitedStart(num); |
---|
| 630 | } |
---|
| 631 | |
---|
| 632 | ///@} |
---|
| 633 | |
---|
[697] | 634 | /// \brief LEMON iterator for getting the active nodes. |
---|
[696] | 635 | /// |
---|
[697] | 636 | /// This class provides a common style LEMON iterator that traverses |
---|
| 637 | /// the active nodes of the Bellman-Ford algorithm after the last |
---|
| 638 | /// phase. These nodes should be checked in the next phase to |
---|
| 639 | /// find augmenting arcs outgoing from them. |
---|
[696] | 640 | class ActiveIt { |
---|
| 641 | public: |
---|
| 642 | |
---|
| 643 | /// \brief Constructor. |
---|
| 644 | /// |
---|
[697] | 645 | /// Constructor for getting the active nodes of the given BellmanFord |
---|
| 646 | /// instance. |
---|
[696] | 647 | ActiveIt(const BellmanFord& algorithm) : _algorithm(&algorithm) |
---|
| 648 | { |
---|
| 649 | _index = _algorithm->_process.size() - 1; |
---|
| 650 | } |
---|
| 651 | |
---|
| 652 | /// \brief Invalid constructor. |
---|
| 653 | /// |
---|
| 654 | /// Invalid constructor. |
---|
| 655 | ActiveIt(Invalid) : _algorithm(0), _index(-1) {} |
---|
| 656 | |
---|
[697] | 657 | /// \brief Conversion to \c Node. |
---|
[696] | 658 | /// |
---|
[697] | 659 | /// Conversion to \c Node. |
---|
[696] | 660 | operator Node() const { |
---|
| 661 | return _index >= 0 ? _algorithm->_process[_index] : INVALID; |
---|
| 662 | } |
---|
| 663 | |
---|
| 664 | /// \brief Increment operator. |
---|
| 665 | /// |
---|
| 666 | /// Increment operator. |
---|
| 667 | ActiveIt& operator++() { |
---|
| 668 | --_index; |
---|
| 669 | return *this; |
---|
| 670 | } |
---|
| 671 | |
---|
| 672 | bool operator==(const ActiveIt& it) const { |
---|
| 673 | return static_cast<Node>(*this) == static_cast<Node>(it); |
---|
| 674 | } |
---|
| 675 | bool operator!=(const ActiveIt& it) const { |
---|
| 676 | return static_cast<Node>(*this) != static_cast<Node>(it); |
---|
| 677 | } |
---|
| 678 | bool operator<(const ActiveIt& it) const { |
---|
| 679 | return static_cast<Node>(*this) < static_cast<Node>(it); |
---|
| 680 | } |
---|
| 681 | |
---|
| 682 | private: |
---|
| 683 | const BellmanFord* _algorithm; |
---|
| 684 | int _index; |
---|
| 685 | }; |
---|
[697] | 686 | |
---|
| 687 | /// \name Query Functions |
---|
| 688 | /// The result of the Bellman-Ford algorithm can be obtained using these |
---|
| 689 | /// functions.\n |
---|
| 690 | /// Either \ref run() or \ref init() should be called before using them. |
---|
| 691 | |
---|
| 692 | ///@{ |
---|
[696] | 693 | |
---|
[697] | 694 | /// \brief The shortest path to the given node. |
---|
| 695 | /// |
---|
| 696 | /// Gives back the shortest path to the given node from the root(s). |
---|
| 697 | /// |
---|
| 698 | /// \warning \c t should be reached from the root(s). |
---|
| 699 | /// |
---|
| 700 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 701 | /// using this function. |
---|
| 702 | Path path(Node t) const |
---|
| 703 | { |
---|
| 704 | return Path(*_gr, *_pred, t); |
---|
| 705 | } |
---|
| 706 | |
---|
| 707 | /// \brief The distance of the given node from the root(s). |
---|
| 708 | /// |
---|
| 709 | /// Returns the distance of the given node from the root(s). |
---|
| 710 | /// |
---|
| 711 | /// \warning If node \c v is not reached from the root(s), then |
---|
| 712 | /// the return value of this function is undefined. |
---|
| 713 | /// |
---|
| 714 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 715 | /// using this function. |
---|
| 716 | Value dist(Node v) const { return (*_dist)[v]; } |
---|
[696] | 717 | |
---|
[697] | 718 | /// \brief Returns the 'previous arc' of the shortest path tree for |
---|
| 719 | /// the given node. |
---|
| 720 | /// |
---|
| 721 | /// This function returns the 'previous arc' of the shortest path |
---|
| 722 | /// tree for node \c v, i.e. it returns the last arc of a |
---|
| 723 | /// shortest path from a root to \c v. It is \c INVALID if \c v |
---|
| 724 | /// is not reached from the root(s) or if \c v is a root. |
---|
| 725 | /// |
---|
| 726 | /// The shortest path tree used here is equal to the shortest path |
---|
[786] | 727 | /// tree used in \ref predNode() and \ref predMap(). |
---|
[697] | 728 | /// |
---|
| 729 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 730 | /// using this function. |
---|
| 731 | Arc predArc(Node v) const { return (*_pred)[v]; } |
---|
| 732 | |
---|
| 733 | /// \brief Returns the 'previous node' of the shortest path tree for |
---|
| 734 | /// the given node. |
---|
| 735 | /// |
---|
| 736 | /// This function returns the 'previous node' of the shortest path |
---|
| 737 | /// tree for node \c v, i.e. it returns the last but one node of |
---|
| 738 | /// a shortest path from a root to \c v. It is \c INVALID if \c v |
---|
| 739 | /// is not reached from the root(s) or if \c v is a root. |
---|
| 740 | /// |
---|
| 741 | /// The shortest path tree used here is equal to the shortest path |
---|
[786] | 742 | /// tree used in \ref predArc() and \ref predMap(). |
---|
[697] | 743 | /// |
---|
| 744 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 745 | /// using this function. |
---|
| 746 | Node predNode(Node v) const { |
---|
| 747 | return (*_pred)[v] == INVALID ? INVALID : _gr->source((*_pred)[v]); |
---|
| 748 | } |
---|
| 749 | |
---|
| 750 | /// \brief Returns a const reference to the node map that stores the |
---|
| 751 | /// distances of the nodes. |
---|
| 752 | /// |
---|
| 753 | /// Returns a const reference to the node map that stores the distances |
---|
| 754 | /// of the nodes calculated by the algorithm. |
---|
| 755 | /// |
---|
| 756 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 757 | /// using this function. |
---|
| 758 | const DistMap &distMap() const { return *_dist;} |
---|
| 759 | |
---|
| 760 | /// \brief Returns a const reference to the node map that stores the |
---|
| 761 | /// predecessor arcs. |
---|
| 762 | /// |
---|
| 763 | /// Returns a const reference to the node map that stores the predecessor |
---|
| 764 | /// arcs, which form the shortest path tree (forest). |
---|
| 765 | /// |
---|
| 766 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 767 | /// using this function. |
---|
| 768 | const PredMap &predMap() const { return *_pred; } |
---|
| 769 | |
---|
| 770 | /// \brief Checks if a node is reached from the root(s). |
---|
| 771 | /// |
---|
| 772 | /// Returns \c true if \c v is reached from the root(s). |
---|
| 773 | /// |
---|
| 774 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 775 | /// using this function. |
---|
| 776 | bool reached(Node v) const { |
---|
| 777 | return (*_dist)[v] != OperationTraits::infinity(); |
---|
[696] | 778 | } |
---|
| 779 | |
---|
[699] | 780 | /// \brief Gives back a negative cycle. |
---|
| 781 | /// |
---|
| 782 | /// This function gives back a directed cycle with negative total |
---|
| 783 | /// length if the algorithm has already found one. |
---|
| 784 | /// Otherwise it gives back an empty path. |
---|
[781] | 785 | lemon::Path<Digraph> negativeCycle() const { |
---|
[699] | 786 | typename Digraph::template NodeMap<int> state(*_gr, -1); |
---|
| 787 | lemon::Path<Digraph> cycle; |
---|
| 788 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
| 789 | if (state[_process[i]] != -1) continue; |
---|
| 790 | for (Node v = _process[i]; (*_pred)[v] != INVALID; |
---|
| 791 | v = _gr->source((*_pred)[v])) { |
---|
| 792 | if (state[v] == i) { |
---|
| 793 | cycle.addFront((*_pred)[v]); |
---|
| 794 | for (Node u = _gr->source((*_pred)[v]); u != v; |
---|
| 795 | u = _gr->source((*_pred)[u])) { |
---|
| 796 | cycle.addFront((*_pred)[u]); |
---|
| 797 | } |
---|
| 798 | return cycle; |
---|
| 799 | } |
---|
| 800 | else if (state[v] >= 0) { |
---|
| 801 | break; |
---|
| 802 | } |
---|
| 803 | state[v] = i; |
---|
| 804 | } |
---|
| 805 | } |
---|
| 806 | return cycle; |
---|
| 807 | } |
---|
[696] | 808 | |
---|
| 809 | ///@} |
---|
| 810 | }; |
---|
| 811 | |
---|
[697] | 812 | /// \brief Default traits class of bellmanFord() function. |
---|
[696] | 813 | /// |
---|
[697] | 814 | /// Default traits class of bellmanFord() function. |
---|
| 815 | /// \tparam GR The type of the digraph. |
---|
| 816 | /// \tparam LEN The type of the length map. |
---|
| 817 | template <typename GR, typename LEN> |
---|
[696] | 818 | struct BellmanFordWizardDefaultTraits { |
---|
[697] | 819 | /// The type of the digraph the algorithm runs on. |
---|
| 820 | typedef GR Digraph; |
---|
[696] | 821 | |
---|
| 822 | /// \brief The type of the map that stores the arc lengths. |
---|
| 823 | /// |
---|
| 824 | /// The type of the map that stores the arc lengths. |
---|
| 825 | /// It must meet the \ref concepts::ReadMap "ReadMap" concept. |
---|
[697] | 826 | typedef LEN LengthMap; |
---|
[696] | 827 | |
---|
[697] | 828 | /// The type of the arc lengths. |
---|
| 829 | typedef typename LEN::Value Value; |
---|
[696] | 830 | |
---|
| 831 | /// \brief Operation traits for Bellman-Ford algorithm. |
---|
| 832 | /// |
---|
[697] | 833 | /// It defines the used operations and the infinity value for the |
---|
| 834 | /// given \c Value type. |
---|
[696] | 835 | /// \see BellmanFordDefaultOperationTraits |
---|
| 836 | typedef BellmanFordDefaultOperationTraits<Value> OperationTraits; |
---|
| 837 | |
---|
| 838 | /// \brief The type of the map that stores the last |
---|
| 839 | /// arcs of the shortest paths. |
---|
| 840 | /// |
---|
[697] | 841 | /// The type of the map that stores the last arcs of the shortest paths. |
---|
| 842 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 843 | typedef typename GR::template NodeMap<typename GR::Arc> PredMap; |
---|
[696] | 844 | |
---|
[697] | 845 | /// \brief Instantiates a \c PredMap. |
---|
[696] | 846 | /// |
---|
[697] | 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 | static PredMap *createPredMap(const GR &g) { |
---|
| 851 | return new PredMap(g); |
---|
[696] | 852 | } |
---|
[697] | 853 | |
---|
| 854 | /// \brief The type of the map that stores the distances of the nodes. |
---|
[696] | 855 | /// |
---|
[697] | 856 | /// The type of the map that stores the distances of the nodes. |
---|
| 857 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 858 | typedef typename GR::template NodeMap<Value> DistMap; |
---|
| 859 | |
---|
| 860 | /// \brief Instantiates a \c DistMap. |
---|
[696] | 861 | /// |
---|
| 862 | /// This function instantiates a \ref DistMap. |
---|
[697] | 863 | /// \param g is the digraph to which we would like to define the |
---|
| 864 | /// \ref DistMap. |
---|
| 865 | static DistMap *createDistMap(const GR &g) { |
---|
| 866 | return new DistMap(g); |
---|
[696] | 867 | } |
---|
[697] | 868 | |
---|
| 869 | ///The type of the shortest paths. |
---|
| 870 | |
---|
| 871 | ///The type of the shortest paths. |
---|
| 872 | ///It must meet the \ref concepts::Path "Path" concept. |
---|
| 873 | typedef lemon::Path<Digraph> Path; |
---|
[696] | 874 | }; |
---|
| 875 | |
---|
[697] | 876 | /// \brief Default traits class used by BellmanFordWizard. |
---|
[696] | 877 | /// |
---|
[697] | 878 | /// Default traits class used by BellmanFordWizard. |
---|
| 879 | /// \tparam GR The type of the digraph. |
---|
| 880 | /// \tparam LEN The type of the length map. |
---|
| 881 | template <typename GR, typename LEN> |
---|
[696] | 882 | class BellmanFordWizardBase |
---|
[697] | 883 | : public BellmanFordWizardDefaultTraits<GR, LEN> { |
---|
[696] | 884 | |
---|
[697] | 885 | typedef BellmanFordWizardDefaultTraits<GR, LEN> Base; |
---|
[696] | 886 | protected: |
---|
[697] | 887 | // Type of the nodes in the digraph. |
---|
[696] | 888 | typedef typename Base::Digraph::Node Node; |
---|
| 889 | |
---|
[697] | 890 | // Pointer to the underlying digraph. |
---|
[696] | 891 | void *_graph; |
---|
[697] | 892 | // Pointer to the length map |
---|
[696] | 893 | void *_length; |
---|
[697] | 894 | // Pointer to the map of predecessors arcs. |
---|
[696] | 895 | void *_pred; |
---|
[697] | 896 | // Pointer to the map of distances. |
---|
[696] | 897 | void *_dist; |
---|
[697] | 898 | //Pointer to the shortest path to the target node. |
---|
| 899 | void *_path; |
---|
| 900 | //Pointer to the distance of the target node. |
---|
| 901 | void *_di; |
---|
[696] | 902 | |
---|
| 903 | public: |
---|
| 904 | /// Constructor. |
---|
| 905 | |
---|
[697] | 906 | /// This constructor does not require parameters, it initiates |
---|
| 907 | /// all of the attributes to default values \c 0. |
---|
| 908 | BellmanFordWizardBase() : |
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| 909 | _graph(0), _length(0), _pred(0), _dist(0), _path(0), _di(0) {} |
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[696] | 910 | |
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| 911 | /// Constructor. |
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| 912 | |
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[697] | 913 | /// This constructor requires two parameters, |
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| 914 | /// others are initiated to \c 0. |
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| 915 | /// \param gr The digraph the algorithm runs on. |
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| 916 | /// \param len The length map. |
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| 917 | BellmanFordWizardBase(const GR& gr, |
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| 918 | const LEN& len) : |
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| 919 | _graph(reinterpret_cast<void*>(const_cast<GR*>(&gr))), |
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| 920 | _length(reinterpret_cast<void*>(const_cast<LEN*>(&len))), |
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| 921 | _pred(0), _dist(0), _path(0), _di(0) {} |
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[696] | 922 | |
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| 923 | }; |
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| 924 | |
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[697] | 925 | /// \brief Auxiliary class for the function-type interface of the |
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| 926 | /// \ref BellmanFord "Bellman-Ford" algorithm. |
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| 927 | /// |
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| 928 | /// This auxiliary class is created to implement the |
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| 929 | /// \ref bellmanFord() "function-type interface" of the |
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| 930 | /// \ref BellmanFord "Bellman-Ford" algorithm. |
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| 931 | /// It does not have own \ref run() method, it uses the |
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| 932 | /// functions and features of the plain \ref BellmanFord. |
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| 933 | /// |
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| 934 | /// This class should only be used through the \ref bellmanFord() |
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| 935 | /// function, which makes it easier to use the algorithm. |
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| 936 | template<class TR> |
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| 937 | class BellmanFordWizard : public TR { |
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| 938 | typedef TR Base; |
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[696] | 939 | |
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[697] | 940 | typedef typename TR::Digraph Digraph; |
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[696] | 941 | |
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| 942 | typedef typename Digraph::Node Node; |
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| 943 | typedef typename Digraph::NodeIt NodeIt; |
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| 944 | typedef typename Digraph::Arc Arc; |
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| 945 | typedef typename Digraph::OutArcIt ArcIt; |
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| 946 | |
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[697] | 947 | typedef typename TR::LengthMap LengthMap; |
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[696] | 948 | typedef typename LengthMap::Value Value; |
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[697] | 949 | typedef typename TR::PredMap PredMap; |
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| 950 | typedef typename TR::DistMap DistMap; |
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| 951 | typedef typename TR::Path Path; |
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[696] | 952 | |
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| 953 | public: |
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| 954 | /// Constructor. |
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[697] | 955 | BellmanFordWizard() : TR() {} |
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[696] | 956 | |
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| 957 | /// \brief Constructor that requires parameters. |
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| 958 | /// |
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| 959 | /// Constructor that requires parameters. |
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| 960 | /// These parameters will be the default values for the traits class. |
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[697] | 961 | /// \param gr The digraph the algorithm runs on. |
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| 962 | /// \param len The length map. |
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| 963 | BellmanFordWizard(const Digraph& gr, const LengthMap& len) |
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| 964 | : TR(gr, len) {} |
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[696] | 965 | |
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| 966 | /// \brief Copy constructor |
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[697] | 967 | BellmanFordWizard(const TR &b) : TR(b) {} |
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[696] | 968 | |
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| 969 | ~BellmanFordWizard() {} |
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| 970 | |
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[697] | 971 | /// \brief Runs the Bellman-Ford algorithm from the given source node. |
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[696] | 972 | /// |
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[697] | 973 | /// This method runs the Bellman-Ford algorithm from the given source |
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| 974 | /// node in order to compute the shortest path to each node. |
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| 975 | void run(Node s) { |
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| 976 | BellmanFord<Digraph,LengthMap,TR> |
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[696] | 977 | bf(*reinterpret_cast<const Digraph*>(Base::_graph), |
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| 978 | *reinterpret_cast<const LengthMap*>(Base::_length)); |
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| 979 | if (Base::_pred) bf.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
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| 980 | if (Base::_dist) bf.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
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[697] | 981 | bf.run(s); |
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[696] | 982 | } |
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| 983 | |
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[697] | 984 | /// \brief Runs the Bellman-Ford algorithm to find the shortest path |
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| 985 | /// between \c s and \c t. |
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[696] | 986 | /// |
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[697] | 987 | /// This method runs the Bellman-Ford algorithm from node \c s |
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| 988 | /// in order to compute the shortest path to node \c t. |
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| 989 | /// Actually, it computes the shortest path to each node, but using |
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| 990 | /// this function you can retrieve the distance and the shortest path |
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| 991 | /// for a single target node easier. |
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| 992 | /// |
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| 993 | /// \return \c true if \c t is reachable form \c s. |
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| 994 | bool run(Node s, Node t) { |
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| 995 | BellmanFord<Digraph,LengthMap,TR> |
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| 996 | bf(*reinterpret_cast<const Digraph*>(Base::_graph), |
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| 997 | *reinterpret_cast<const LengthMap*>(Base::_length)); |
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| 998 | if (Base::_pred) bf.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
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| 999 | if (Base::_dist) bf.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
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| 1000 | bf.run(s); |
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| 1001 | if (Base::_path) *reinterpret_cast<Path*>(Base::_path) = bf.path(t); |
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| 1002 | if (Base::_di) *reinterpret_cast<Value*>(Base::_di) = bf.dist(t); |
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| 1003 | return bf.reached(t); |
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[696] | 1004 | } |
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| 1005 | |
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| 1006 | template<class T> |
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[697] | 1007 | struct SetPredMapBase : public Base { |
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[696] | 1008 | typedef T PredMap; |
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| 1009 | static PredMap *createPredMap(const Digraph &) { return 0; }; |
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[697] | 1010 | SetPredMapBase(const TR &b) : TR(b) {} |
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[696] | 1011 | }; |
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| 1012 | |
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[697] | 1013 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 1014 | /// the predecessor map. |
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[696] | 1015 | /// |
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[697] | 1016 | /// \ref named-templ-param "Named parameter" for setting |
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| 1017 | /// the map that stores the predecessor arcs of the nodes. |
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[696] | 1018 | template<class T> |
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[697] | 1019 | BellmanFordWizard<SetPredMapBase<T> > predMap(const T &t) { |
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[696] | 1020 | Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t)); |
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[697] | 1021 | return BellmanFordWizard<SetPredMapBase<T> >(*this); |
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[696] | 1022 | } |
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| 1023 | |
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| 1024 | template<class T> |
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[697] | 1025 | struct SetDistMapBase : public Base { |
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[696] | 1026 | typedef T DistMap; |
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| 1027 | static DistMap *createDistMap(const Digraph &) { return 0; }; |
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[697] | 1028 | SetDistMapBase(const TR &b) : TR(b) {} |
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[696] | 1029 | }; |
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| 1030 | |
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[697] | 1031 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 1032 | /// the distance map. |
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[696] | 1033 | /// |
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[697] | 1034 | /// \ref named-templ-param "Named parameter" for setting |
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| 1035 | /// the map that stores the distances of the nodes calculated |
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| 1036 | /// by the algorithm. |
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[696] | 1037 | template<class T> |
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[697] | 1038 | BellmanFordWizard<SetDistMapBase<T> > distMap(const T &t) { |
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[696] | 1039 | Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t)); |
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[697] | 1040 | return BellmanFordWizard<SetDistMapBase<T> >(*this); |
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[696] | 1041 | } |
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| 1042 | |
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| 1043 | template<class T> |
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[697] | 1044 | struct SetPathBase : public Base { |
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| 1045 | typedef T Path; |
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| 1046 | SetPathBase(const TR &b) : TR(b) {} |
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[696] | 1047 | }; |
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[697] | 1048 | |
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| 1049 | /// \brief \ref named-func-param "Named parameter" for getting |
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| 1050 | /// the shortest path to the target node. |
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[696] | 1051 | /// |
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[697] | 1052 | /// \ref named-func-param "Named parameter" for getting |
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| 1053 | /// the shortest path to the target node. |
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| 1054 | template<class T> |
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| 1055 | BellmanFordWizard<SetPathBase<T> > path(const T &t) |
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| 1056 | { |
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| 1057 | Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t)); |
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| 1058 | return BellmanFordWizard<SetPathBase<T> >(*this); |
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| 1059 | } |
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| 1060 | |
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| 1061 | /// \brief \ref named-func-param "Named parameter" for getting |
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| 1062 | /// the distance of the target node. |
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[696] | 1063 | /// |
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[697] | 1064 | /// \ref named-func-param "Named parameter" for getting |
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| 1065 | /// the distance of the target node. |
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| 1066 | BellmanFordWizard dist(const Value &d) |
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| 1067 | { |
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| 1068 | Base::_di=reinterpret_cast<void*>(const_cast<Value*>(&d)); |
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[696] | 1069 | return *this; |
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| 1070 | } |
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| 1071 | |
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| 1072 | }; |
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| 1073 | |
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[697] | 1074 | /// \brief Function type interface for the \ref BellmanFord "Bellman-Ford" |
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| 1075 | /// algorithm. |
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[696] | 1076 | /// |
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| 1077 | /// \ingroup shortest_path |
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[697] | 1078 | /// Function type interface for the \ref BellmanFord "Bellman-Ford" |
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| 1079 | /// algorithm. |
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[696] | 1080 | /// |
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| 1081 | /// This function also has several \ref named-templ-func-param |
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| 1082 | /// "named parameters", they are declared as the members of class |
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| 1083 | /// \ref BellmanFordWizard. |
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[697] | 1084 | /// The following examples show how to use these parameters. |
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| 1085 | /// \code |
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| 1086 | /// // Compute shortest path from node s to each node |
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| 1087 | /// bellmanFord(g,length).predMap(preds).distMap(dists).run(s); |
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| 1088 | /// |
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| 1089 | /// // Compute shortest path from s to t |
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| 1090 | /// bool reached = bellmanFord(g,length).path(p).dist(d).run(s,t); |
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| 1091 | /// \endcode |
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[696] | 1092 | /// \warning Don't forget to put the \ref BellmanFordWizard::run() "run()" |
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| 1093 | /// to the end of the parameter list. |
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| 1094 | /// \sa BellmanFordWizard |
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| 1095 | /// \sa BellmanFord |
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[697] | 1096 | template<typename GR, typename LEN> |
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| 1097 | BellmanFordWizard<BellmanFordWizardBase<GR,LEN> > |
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| 1098 | bellmanFord(const GR& digraph, |
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| 1099 | const LEN& length) |
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| 1100 | { |
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| 1101 | return BellmanFordWizard<BellmanFordWizardBase<GR,LEN> >(digraph, length); |
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[696] | 1102 | } |
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| 1103 | |
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| 1104 | } //END OF NAMESPACE LEMON |
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| 1105 | |
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| 1106 | #endif |
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| 1107 | |
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