[956] | 1 | /* -*- mode: C++; indent-tabs-mode: nil; -*- |
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[743] | 2 | * |
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[956] | 3 | * This file is a part of LEMON, a generic C++ optimization library. |
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[743] | 4 | * |
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[956] | 5 | * Copyright (C) 2003-2010 |
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[743] | 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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[744] | 19 | #ifndef LEMON_BELLMAN_FORD_H |
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| 20 | #define LEMON_BELLMAN_FORD_H |
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[743] | 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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[828] | 26 | #include <lemon/list_graph.h> |
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[743] | 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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[744] | 31 | #include <lemon/path.h> |
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[743] | 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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[958] | 37 | /// \brief Default OperationTraits for the BellmanFord algorithm class. |
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[956] | 38 | /// |
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[744] | 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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[743] | 44 | template < |
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[956] | 45 | typename V, |
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[744] | 46 | bool has_inf = std::numeric_limits<V>::has_infinity> |
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[743] | 47 | struct BellmanFordDefaultOperationTraits { |
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[958] | 48 | /// \e |
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[744] | 49 | typedef V Value; |
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[743] | 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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[744] | 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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[743] | 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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[744] | 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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[743] | 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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[956] | 86 | |
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[743] | 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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[744] | 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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[743] | 93 | struct BellmanFordDefaultTraits { |
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[956] | 94 | /// The type of the digraph the algorithm runs on. |
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[744] | 95 | typedef GR Digraph; |
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[743] | 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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[744] | 100 | /// It must conform to the \ref concepts::ReadMap "ReadMap" concept. |
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| 101 | typedef LEN LengthMap; |
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[743] | 102 | |
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[744] | 103 | /// The type of the arc lengths. |
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| 104 | typedef typename LEN::Value Value; |
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[743] | 105 | |
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| 106 | /// \brief Operation traits for Bellman-Ford algorithm. |
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| 107 | /// |
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[744] | 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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[958] | 110 | /// \see BellmanFordDefaultOperationTraits |
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[743] | 111 | typedef BellmanFordDefaultOperationTraits<Value> OperationTraits; |
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[956] | 112 | |
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| 113 | /// \brief The type of the map that stores the last arcs of the |
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[743] | 114 | /// shortest paths. |
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[956] | 115 | /// |
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[743] | 116 | /// The type of the map that stores the last |
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| 117 | /// arcs of the shortest paths. |
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[744] | 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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[743] | 120 | |
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[744] | 121 | /// \brief Instantiates a \c PredMap. |
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[956] | 122 | /// |
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| 123 | /// This function instantiates a \ref PredMap. |
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[744] | 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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[743] | 128 | } |
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| 129 | |
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[744] | 130 | /// \brief The type of the map that stores the distances of the nodes. |
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[743] | 131 | /// |
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[744] | 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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[743] | 135 | |
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[744] | 136 | /// \brief Instantiates a \c DistMap. |
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[743] | 137 | /// |
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[956] | 138 | /// This function instantiates a \ref DistMap. |
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| 139 | /// \param g is the digraph to which we would like to define the |
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[744] | 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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[743] | 143 | } |
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| 144 | |
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| 145 | }; |
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[956] | 146 | |
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[743] | 147 | /// \brief %BellmanFord algorithm class. |
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| 148 | /// |
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| 149 | /// \ingroup shortest_path |
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[956] | 150 | /// This class provides an efficient implementation of the Bellman-Ford |
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[744] | 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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[956] | 161 | /// \ref concepts::ReadMap "ReadMap", so it is easy to change it to any |
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[744] | 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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[743] | 164 | /// |
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[744] | 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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[743] | 168 | /// |
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[744] | 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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[891] | 174 | /// \tparam TR The traits class that defines various types used by the |
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| 175 | /// algorithm. By default, it is \ref BellmanFordDefaultTraits |
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| 176 | /// "BellmanFordDefaultTraits<GR, LEN>". |
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| 177 | /// In most cases, this parameter should not be set directly, |
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| 178 | /// consider to use the named template parameters instead. |
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[743] | 179 | #ifdef DOXYGEN |
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[744] | 180 | template <typename GR, typename LEN, typename TR> |
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[743] | 181 | #else |
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[744] | 182 | template <typename GR=ListDigraph, |
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| 183 | typename LEN=typename GR::template ArcMap<int>, |
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| 184 | typename TR=BellmanFordDefaultTraits<GR,LEN> > |
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[743] | 185 | #endif |
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| 186 | class BellmanFord { |
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| 187 | public: |
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| 188 | |
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| 189 | ///The type of the underlying digraph. |
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[744] | 190 | typedef typename TR::Digraph Digraph; |
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[956] | 191 | |
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[744] | 192 | /// \brief The type of the arc lengths. |
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| 193 | typedef typename TR::LengthMap::Value Value; |
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| 194 | /// \brief The type of the map that stores the arc lengths. |
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| 195 | typedef typename TR::LengthMap LengthMap; |
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| 196 | /// \brief The type of the map that stores the last |
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| 197 | /// arcs of the shortest paths. |
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| 198 | typedef typename TR::PredMap PredMap; |
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| 199 | /// \brief The type of the map that stores the distances of the nodes. |
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| 200 | typedef typename TR::DistMap DistMap; |
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| 201 | /// The type of the paths. |
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| 202 | typedef PredMapPath<Digraph, PredMap> Path; |
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| 203 | ///\brief The \ref BellmanFordDefaultOperationTraits |
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| 204 | /// "operation traits class" of the algorithm. |
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| 205 | typedef typename TR::OperationTraits OperationTraits; |
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| 206 | |
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| 207 | ///The \ref BellmanFordDefaultTraits "traits class" of the algorithm. |
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| 208 | typedef TR Traits; |
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| 209 | |
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| 210 | private: |
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[743] | 211 | |
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| 212 | typedef typename Digraph::Node Node; |
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| 213 | typedef typename Digraph::NodeIt NodeIt; |
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| 214 | typedef typename Digraph::Arc Arc; |
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| 215 | typedef typename Digraph::OutArcIt OutArcIt; |
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[744] | 216 | |
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| 217 | // Pointer to the underlying digraph. |
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| 218 | const Digraph *_gr; |
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| 219 | // Pointer to the length map |
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| 220 | const LengthMap *_length; |
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| 221 | // Pointer to the map of predecessors arcs. |
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[743] | 222 | PredMap *_pred; |
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[744] | 223 | // Indicates if _pred is locally allocated (true) or not. |
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| 224 | bool _local_pred; |
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| 225 | // Pointer to the map of distances. |
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[743] | 226 | DistMap *_dist; |
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[744] | 227 | // Indicates if _dist is locally allocated (true) or not. |
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| 228 | bool _local_dist; |
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[743] | 229 | |
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| 230 | typedef typename Digraph::template NodeMap<bool> MaskMap; |
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| 231 | MaskMap *_mask; |
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| 232 | |
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| 233 | std::vector<Node> _process; |
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| 234 | |
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[744] | 235 | // Creates the maps if necessary. |
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[743] | 236 | void create_maps() { |
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| 237 | if(!_pred) { |
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[956] | 238 | _local_pred = true; |
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| 239 | _pred = Traits::createPredMap(*_gr); |
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[743] | 240 | } |
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| 241 | if(!_dist) { |
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[956] | 242 | _local_dist = true; |
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| 243 | _dist = Traits::createDistMap(*_gr); |
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[743] | 244 | } |
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[870] | 245 | if(!_mask) { |
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| 246 | _mask = new MaskMap(*_gr); |
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| 247 | } |
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[743] | 248 | } |
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[956] | 249 | |
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[743] | 250 | public : |
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[956] | 251 | |
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[743] | 252 | typedef BellmanFord Create; |
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| 253 | |
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[744] | 254 | /// \name Named Template Parameters |
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[743] | 255 | |
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| 256 | ///@{ |
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| 257 | |
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| 258 | template <class T> |
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[744] | 259 | struct SetPredMapTraits : public Traits { |
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[743] | 260 | typedef T PredMap; |
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| 261 | static PredMap *createPredMap(const Digraph&) { |
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| 262 | LEMON_ASSERT(false, "PredMap is not initialized"); |
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| 263 | return 0; // ignore warnings |
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| 264 | } |
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| 265 | }; |
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| 266 | |
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[744] | 267 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 268 | /// \c PredMap type. |
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[743] | 269 | /// |
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[744] | 270 | /// \ref named-templ-param "Named parameter" for setting |
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| 271 | /// \c PredMap type. |
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| 272 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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[743] | 273 | template <class T> |
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[956] | 274 | struct SetPredMap |
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[744] | 275 | : public BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > { |
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| 276 | typedef BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > Create; |
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[743] | 277 | }; |
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[956] | 278 | |
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[743] | 279 | template <class T> |
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[744] | 280 | struct SetDistMapTraits : public Traits { |
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[743] | 281 | typedef T DistMap; |
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| 282 | static DistMap *createDistMap(const Digraph&) { |
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| 283 | LEMON_ASSERT(false, "DistMap is not initialized"); |
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| 284 | return 0; // ignore warnings |
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| 285 | } |
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| 286 | }; |
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| 287 | |
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[744] | 288 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 289 | /// \c DistMap type. |
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[743] | 290 | /// |
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[744] | 291 | /// \ref named-templ-param "Named parameter" for setting |
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| 292 | /// \c DistMap type. |
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| 293 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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[743] | 294 | template <class T> |
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[956] | 295 | struct SetDistMap |
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[744] | 296 | : public BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > { |
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| 297 | typedef BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > Create; |
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[743] | 298 | }; |
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[744] | 299 | |
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[743] | 300 | template <class T> |
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[744] | 301 | struct SetOperationTraitsTraits : public Traits { |
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[743] | 302 | typedef T OperationTraits; |
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| 303 | }; |
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[956] | 304 | |
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| 305 | /// \brief \ref named-templ-param "Named parameter" for setting |
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[744] | 306 | /// \c OperationTraits type. |
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[743] | 307 | /// |
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[744] | 308 | /// \ref named-templ-param "Named parameter" for setting |
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| 309 | /// \c OperationTraits type. |
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[833] | 310 | /// For more information, see \ref BellmanFordDefaultOperationTraits. |
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[743] | 311 | template <class T> |
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| 312 | struct SetOperationTraits |
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[744] | 313 | : public BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > { |
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| 314 | typedef BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > |
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[743] | 315 | Create; |
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| 316 | }; |
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[956] | 317 | |
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[743] | 318 | ///@} |
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| 319 | |
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| 320 | protected: |
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[956] | 321 | |
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[743] | 322 | BellmanFord() {} |
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| 323 | |
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[956] | 324 | public: |
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| 325 | |
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[743] | 326 | /// \brief Constructor. |
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| 327 | /// |
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[744] | 328 | /// Constructor. |
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| 329 | /// \param g The digraph the algorithm runs on. |
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| 330 | /// \param length The length map used by the algorithm. |
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| 331 | BellmanFord(const Digraph& g, const LengthMap& length) : |
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| 332 | _gr(&g), _length(&length), |
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| 333 | _pred(0), _local_pred(false), |
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| 334 | _dist(0), _local_dist(false), _mask(0) {} |
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[956] | 335 | |
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[743] | 336 | ///Destructor. |
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| 337 | ~BellmanFord() { |
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[744] | 338 | if(_local_pred) delete _pred; |
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| 339 | if(_local_dist) delete _dist; |
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[743] | 340 | if(_mask) delete _mask; |
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| 341 | } |
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| 342 | |
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| 343 | /// \brief Sets the length map. |
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| 344 | /// |
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| 345 | /// Sets the length map. |
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[744] | 346 | /// \return <tt>(*this)</tt> |
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| 347 | BellmanFord &lengthMap(const LengthMap &map) { |
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| 348 | _length = ↦ |
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[743] | 349 | return *this; |
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| 350 | } |
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| 351 | |
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[744] | 352 | /// \brief Sets the map that stores the predecessor arcs. |
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[743] | 353 | /// |
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[744] | 354 | /// Sets the map that stores the predecessor arcs. |
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| 355 | /// If you don't use this function before calling \ref run() |
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| 356 | /// or \ref init(), an instance will be allocated automatically. |
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| 357 | /// The destructor deallocates this automatically allocated map, |
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| 358 | /// of course. |
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| 359 | /// \return <tt>(*this)</tt> |
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| 360 | BellmanFord &predMap(PredMap &map) { |
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| 361 | if(_local_pred) { |
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[956] | 362 | delete _pred; |
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| 363 | _local_pred=false; |
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[743] | 364 | } |
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[744] | 365 | _pred = ↦ |
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[743] | 366 | return *this; |
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| 367 | } |
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| 368 | |
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[744] | 369 | /// \brief Sets the map that stores the distances of the nodes. |
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[743] | 370 | /// |
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[744] | 371 | /// Sets the map that stores the distances of the nodes calculated |
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| 372 | /// by the algorithm. |
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| 373 | /// If you don't use this function before calling \ref run() |
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| 374 | /// or \ref init(), an instance will be allocated automatically. |
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| 375 | /// The destructor deallocates this automatically allocated map, |
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| 376 | /// of course. |
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| 377 | /// \return <tt>(*this)</tt> |
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| 378 | BellmanFord &distMap(DistMap &map) { |
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| 379 | if(_local_dist) { |
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[956] | 380 | delete _dist; |
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| 381 | _local_dist=false; |
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[743] | 382 | } |
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[744] | 383 | _dist = ↦ |
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[743] | 384 | return *this; |
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| 385 | } |
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| 386 | |
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[744] | 387 | /// \name Execution Control |
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| 388 | /// The simplest way to execute the Bellman-Ford algorithm is to use |
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| 389 | /// one of the member functions called \ref run().\n |
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| 390 | /// If you need better control on the execution, you have to call |
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| 391 | /// \ref init() first, then you can add several source nodes |
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| 392 | /// with \ref addSource(). Finally the actual path computation can be |
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| 393 | /// performed with \ref start(), \ref checkedStart() or |
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| 394 | /// \ref limitedStart(). |
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[743] | 395 | |
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| 396 | ///@{ |
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| 397 | |
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| 398 | /// \brief Initializes the internal data structures. |
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[956] | 399 | /// |
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[744] | 400 | /// Initializes the internal data structures. The optional parameter |
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| 401 | /// is the initial distance of each node. |
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[743] | 402 | void init(const Value value = OperationTraits::infinity()) { |
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| 403 | create_maps(); |
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[744] | 404 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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[956] | 405 | _pred->set(it, INVALID); |
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| 406 | _dist->set(it, value); |
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[743] | 407 | } |
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| 408 | _process.clear(); |
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| 409 | if (OperationTraits::less(value, OperationTraits::infinity())) { |
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[956] | 410 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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| 411 | _process.push_back(it); |
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| 412 | _mask->set(it, true); |
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| 413 | } |
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[870] | 414 | } else { |
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[956] | 415 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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| 416 | _mask->set(it, false); |
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| 417 | } |
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[743] | 418 | } |
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| 419 | } |
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[956] | 420 | |
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[743] | 421 | /// \brief Adds a new source node. |
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| 422 | /// |
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[744] | 423 | /// This function adds a new source node. The optional second parameter |
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| 424 | /// is the initial distance of the node. |
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[743] | 425 | void addSource(Node source, Value dst = OperationTraits::zero()) { |
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| 426 | _dist->set(source, dst); |
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| 427 | if (!(*_mask)[source]) { |
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[956] | 428 | _process.push_back(source); |
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| 429 | _mask->set(source, true); |
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[743] | 430 | } |
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| 431 | } |
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| 432 | |
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| 433 | /// \brief Executes one round from the Bellman-Ford algorithm. |
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| 434 | /// |
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| 435 | /// If the algoritm calculated the distances in the previous round |
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[744] | 436 | /// exactly for the paths of at most \c k arcs, then this function |
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| 437 | /// will calculate the distances exactly for the paths of at most |
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| 438 | /// <tt>k+1</tt> arcs. Performing \c k iterations using this function |
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| 439 | /// calculates the shortest path distances exactly for the paths |
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| 440 | /// consisting of at most \c k arcs. |
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[743] | 441 | /// |
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| 442 | /// \warning The paths with limited arc number cannot be retrieved |
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[744] | 443 | /// easily with \ref path() or \ref predArc() functions. If you also |
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| 444 | /// need the shortest paths and not only the distances, you should |
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| 445 | /// store the \ref predMap() "predecessor map" after each iteration |
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| 446 | /// and build the path manually. |
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[743] | 447 | /// |
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| 448 | /// \return \c true when the algorithm have not found more shorter |
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| 449 | /// paths. |
---|
[744] | 450 | /// |
---|
| 451 | /// \see ActiveIt |
---|
[743] | 452 | bool processNextRound() { |
---|
| 453 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 454 | _mask->set(_process[i], false); |
---|
[743] | 455 | } |
---|
| 456 | std::vector<Node> nextProcess; |
---|
| 457 | std::vector<Value> values(_process.size()); |
---|
| 458 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 459 | values[i] = (*_dist)[_process[i]]; |
---|
[743] | 460 | } |
---|
| 461 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 462 | for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) { |
---|
| 463 | Node target = _gr->target(it); |
---|
| 464 | Value relaxed = OperationTraits::plus(values[i], (*_length)[it]); |
---|
| 465 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 466 | _pred->set(target, it); |
---|
| 467 | _dist->set(target, relaxed); |
---|
| 468 | if (!(*_mask)[target]) { |
---|
| 469 | _mask->set(target, true); |
---|
| 470 | nextProcess.push_back(target); |
---|
| 471 | } |
---|
| 472 | } |
---|
| 473 | } |
---|
[743] | 474 | } |
---|
| 475 | _process.swap(nextProcess); |
---|
| 476 | return _process.empty(); |
---|
| 477 | } |
---|
| 478 | |
---|
| 479 | /// \brief Executes one weak round from the Bellman-Ford algorithm. |
---|
| 480 | /// |
---|
[744] | 481 | /// If the algorithm calculated the distances in the previous round |
---|
| 482 | /// at least for the paths of at most \c k arcs, then this function |
---|
| 483 | /// will calculate the distances at least for the paths of at most |
---|
| 484 | /// <tt>k+1</tt> arcs. |
---|
| 485 | /// This function does not make it possible to calculate the shortest |
---|
| 486 | /// path distances exactly for paths consisting of at most \c k arcs, |
---|
| 487 | /// this is why it is called weak round. |
---|
| 488 | /// |
---|
| 489 | /// \return \c true when the algorithm have not found more shorter |
---|
| 490 | /// paths. |
---|
| 491 | /// |
---|
| 492 | /// \see ActiveIt |
---|
[743] | 493 | bool processNextWeakRound() { |
---|
| 494 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 495 | _mask->set(_process[i], false); |
---|
[743] | 496 | } |
---|
| 497 | std::vector<Node> nextProcess; |
---|
| 498 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 499 | for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) { |
---|
| 500 | Node target = _gr->target(it); |
---|
| 501 | Value relaxed = |
---|
| 502 | OperationTraits::plus((*_dist)[_process[i]], (*_length)[it]); |
---|
| 503 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 504 | _pred->set(target, it); |
---|
| 505 | _dist->set(target, relaxed); |
---|
| 506 | if (!(*_mask)[target]) { |
---|
| 507 | _mask->set(target, true); |
---|
| 508 | nextProcess.push_back(target); |
---|
| 509 | } |
---|
| 510 | } |
---|
| 511 | } |
---|
[743] | 512 | } |
---|
| 513 | _process.swap(nextProcess); |
---|
| 514 | return _process.empty(); |
---|
| 515 | } |
---|
| 516 | |
---|
| 517 | /// \brief Executes the algorithm. |
---|
| 518 | /// |
---|
[744] | 519 | /// Executes the algorithm. |
---|
[743] | 520 | /// |
---|
[744] | 521 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 522 | /// in order to compute the shortest path to each node. |
---|
| 523 | /// |
---|
| 524 | /// The algorithm computes |
---|
| 525 | /// - the shortest path tree (forest), |
---|
| 526 | /// - the distance of each node from the root(s). |
---|
| 527 | /// |
---|
| 528 | /// \pre init() must be called and at least one root node should be |
---|
| 529 | /// added with addSource() before using this function. |
---|
[743] | 530 | void start() { |
---|
[744] | 531 | int num = countNodes(*_gr) - 1; |
---|
[743] | 532 | for (int i = 0; i < num; ++i) { |
---|
[956] | 533 | if (processNextWeakRound()) break; |
---|
[743] | 534 | } |
---|
| 535 | } |
---|
| 536 | |
---|
| 537 | /// \brief Executes the algorithm and checks the negative cycles. |
---|
| 538 | /// |
---|
[744] | 539 | /// Executes the algorithm and checks the negative cycles. |
---|
[743] | 540 | /// |
---|
[744] | 541 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 542 | /// in order to compute the shortest path to each node and also checks |
---|
| 543 | /// if the digraph contains cycles with negative total length. |
---|
| 544 | /// |
---|
[956] | 545 | /// The algorithm computes |
---|
[744] | 546 | /// - the shortest path tree (forest), |
---|
| 547 | /// - the distance of each node from the root(s). |
---|
[956] | 548 | /// |
---|
[743] | 549 | /// \return \c false if there is a negative cycle in the digraph. |
---|
[744] | 550 | /// |
---|
| 551 | /// \pre init() must be called and at least one root node should be |
---|
[956] | 552 | /// added with addSource() before using this function. |
---|
[743] | 553 | bool checkedStart() { |
---|
[744] | 554 | int num = countNodes(*_gr); |
---|
[743] | 555 | for (int i = 0; i < num; ++i) { |
---|
[956] | 556 | if (processNextWeakRound()) return true; |
---|
[743] | 557 | } |
---|
| 558 | return _process.empty(); |
---|
| 559 | } |
---|
| 560 | |
---|
[744] | 561 | /// \brief Executes the algorithm with arc number limit. |
---|
[743] | 562 | /// |
---|
[744] | 563 | /// Executes the algorithm with arc number limit. |
---|
[743] | 564 | /// |
---|
[744] | 565 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 566 | /// in order to compute the shortest path distance for each node |
---|
| 567 | /// using only the paths consisting of at most \c num arcs. |
---|
| 568 | /// |
---|
| 569 | /// The algorithm computes |
---|
| 570 | /// - the limited distance of each node from the root(s), |
---|
| 571 | /// - the predecessor arc for each node. |
---|
[743] | 572 | /// |
---|
| 573 | /// \warning The paths with limited arc number cannot be retrieved |
---|
[744] | 574 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 575 | /// need the shortest paths and not only the distances, you should |
---|
| 576 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 577 | /// and build the path manually. |
---|
[743] | 578 | /// |
---|
[744] | 579 | /// \pre init() must be called and at least one root node should be |
---|
[956] | 580 | /// added with addSource() before using this function. |
---|
[743] | 581 | void limitedStart(int num) { |
---|
| 582 | for (int i = 0; i < num; ++i) { |
---|
[956] | 583 | if (processNextRound()) break; |
---|
[743] | 584 | } |
---|
| 585 | } |
---|
[956] | 586 | |
---|
[744] | 587 | /// \brief Runs the algorithm from the given root node. |
---|
[956] | 588 | /// |
---|
[744] | 589 | /// This method runs the Bellman-Ford algorithm from the given root |
---|
| 590 | /// node \c s in order to compute the shortest path to each node. |
---|
[743] | 591 | /// |
---|
[744] | 592 | /// The algorithm computes |
---|
| 593 | /// - the shortest path tree (forest), |
---|
| 594 | /// - the distance of each node from the root(s). |
---|
| 595 | /// |
---|
| 596 | /// \note bf.run(s) is just a shortcut of the following code. |
---|
| 597 | /// \code |
---|
| 598 | /// bf.init(); |
---|
| 599 | /// bf.addSource(s); |
---|
| 600 | /// bf.start(); |
---|
| 601 | /// \endcode |
---|
[743] | 602 | void run(Node s) { |
---|
| 603 | init(); |
---|
| 604 | addSource(s); |
---|
| 605 | start(); |
---|
| 606 | } |
---|
[956] | 607 | |
---|
[744] | 608 | /// \brief Runs the algorithm from the given root node with arc |
---|
| 609 | /// number limit. |
---|
[956] | 610 | /// |
---|
[744] | 611 | /// This method runs the Bellman-Ford algorithm from the given root |
---|
| 612 | /// node \c s in order to compute the shortest path distance for each |
---|
| 613 | /// node using only the paths consisting of at most \c num arcs. |
---|
[743] | 614 | /// |
---|
[744] | 615 | /// The algorithm computes |
---|
| 616 | /// - the limited distance of each node from the root(s), |
---|
| 617 | /// - the predecessor arc for each node. |
---|
| 618 | /// |
---|
| 619 | /// \warning The paths with limited arc number cannot be retrieved |
---|
| 620 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 621 | /// need the shortest paths and not only the distances, you should |
---|
| 622 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 623 | /// and build the path manually. |
---|
| 624 | /// |
---|
| 625 | /// \note bf.run(s, num) is just a shortcut of the following code. |
---|
| 626 | /// \code |
---|
| 627 | /// bf.init(); |
---|
| 628 | /// bf.addSource(s); |
---|
| 629 | /// bf.limitedStart(num); |
---|
| 630 | /// \endcode |
---|
[743] | 631 | void run(Node s, int num) { |
---|
| 632 | init(); |
---|
| 633 | addSource(s); |
---|
| 634 | limitedStart(num); |
---|
| 635 | } |
---|
[956] | 636 | |
---|
[743] | 637 | ///@} |
---|
| 638 | |
---|
[744] | 639 | /// \brief LEMON iterator for getting the active nodes. |
---|
[743] | 640 | /// |
---|
[744] | 641 | /// This class provides a common style LEMON iterator that traverses |
---|
| 642 | /// the active nodes of the Bellman-Ford algorithm after the last |
---|
| 643 | /// phase. These nodes should be checked in the next phase to |
---|
| 644 | /// find augmenting arcs outgoing from them. |
---|
[743] | 645 | class ActiveIt { |
---|
| 646 | public: |
---|
| 647 | |
---|
| 648 | /// \brief Constructor. |
---|
| 649 | /// |
---|
[744] | 650 | /// Constructor for getting the active nodes of the given BellmanFord |
---|
[956] | 651 | /// instance. |
---|
[743] | 652 | ActiveIt(const BellmanFord& algorithm) : _algorithm(&algorithm) |
---|
| 653 | { |
---|
| 654 | _index = _algorithm->_process.size() - 1; |
---|
| 655 | } |
---|
| 656 | |
---|
| 657 | /// \brief Invalid constructor. |
---|
| 658 | /// |
---|
| 659 | /// Invalid constructor. |
---|
| 660 | ActiveIt(Invalid) : _algorithm(0), _index(-1) {} |
---|
| 661 | |
---|
[744] | 662 | /// \brief Conversion to \c Node. |
---|
[743] | 663 | /// |
---|
[744] | 664 | /// Conversion to \c Node. |
---|
[956] | 665 | operator Node() const { |
---|
[743] | 666 | return _index >= 0 ? _algorithm->_process[_index] : INVALID; |
---|
| 667 | } |
---|
| 668 | |
---|
| 669 | /// \brief Increment operator. |
---|
| 670 | /// |
---|
| 671 | /// Increment operator. |
---|
| 672 | ActiveIt& operator++() { |
---|
| 673 | --_index; |
---|
[956] | 674 | return *this; |
---|
[743] | 675 | } |
---|
| 676 | |
---|
[956] | 677 | bool operator==(const ActiveIt& it) const { |
---|
| 678 | return static_cast<Node>(*this) == static_cast<Node>(it); |
---|
[743] | 679 | } |
---|
[956] | 680 | bool operator!=(const ActiveIt& it) const { |
---|
| 681 | return static_cast<Node>(*this) != static_cast<Node>(it); |
---|
[743] | 682 | } |
---|
[956] | 683 | bool operator<(const ActiveIt& it) const { |
---|
| 684 | return static_cast<Node>(*this) < static_cast<Node>(it); |
---|
[743] | 685 | } |
---|
[956] | 686 | |
---|
[743] | 687 | private: |
---|
| 688 | const BellmanFord* _algorithm; |
---|
| 689 | int _index; |
---|
| 690 | }; |
---|
[956] | 691 | |
---|
[744] | 692 | /// \name Query Functions |
---|
| 693 | /// The result of the Bellman-Ford algorithm can be obtained using these |
---|
| 694 | /// functions.\n |
---|
| 695 | /// Either \ref run() or \ref init() should be called before using them. |
---|
[956] | 696 | |
---|
[744] | 697 | ///@{ |
---|
[743] | 698 | |
---|
[744] | 699 | /// \brief The shortest path to the given node. |
---|
[956] | 700 | /// |
---|
[744] | 701 | /// Gives back the shortest path to the given node from the root(s). |
---|
| 702 | /// |
---|
| 703 | /// \warning \c t should be reached from the root(s). |
---|
| 704 | /// |
---|
| 705 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 706 | /// using this function. |
---|
| 707 | Path path(Node t) const |
---|
| 708 | { |
---|
| 709 | return Path(*_gr, *_pred, t); |
---|
| 710 | } |
---|
[956] | 711 | |
---|
[744] | 712 | /// \brief The distance of the given node from the root(s). |
---|
| 713 | /// |
---|
| 714 | /// Returns the distance of the given node from the root(s). |
---|
| 715 | /// |
---|
| 716 | /// \warning If node \c v is not reached from the root(s), then |
---|
| 717 | /// the return value of this function is undefined. |
---|
| 718 | /// |
---|
| 719 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 720 | /// using this function. |
---|
| 721 | Value dist(Node v) const { return (*_dist)[v]; } |
---|
[743] | 722 | |
---|
[744] | 723 | /// \brief Returns the 'previous arc' of the shortest path tree for |
---|
| 724 | /// the given node. |
---|
| 725 | /// |
---|
| 726 | /// This function returns the 'previous arc' of the shortest path |
---|
| 727 | /// tree for node \c v, i.e. it returns the last arc of a |
---|
| 728 | /// shortest path from a root to \c v. It is \c INVALID if \c v |
---|
| 729 | /// is not reached from the root(s) or if \c v is a root. |
---|
| 730 | /// |
---|
| 731 | /// The shortest path tree used here is equal to the shortest path |
---|
[833] | 732 | /// tree used in \ref predNode() and \ref predMap(). |
---|
[744] | 733 | /// |
---|
| 734 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 735 | /// using this function. |
---|
| 736 | Arc predArc(Node v) const { return (*_pred)[v]; } |
---|
| 737 | |
---|
| 738 | /// \brief Returns the 'previous node' of the shortest path tree for |
---|
| 739 | /// the given node. |
---|
| 740 | /// |
---|
| 741 | /// This function returns the 'previous node' of the shortest path |
---|
| 742 | /// tree for node \c v, i.e. it returns the last but one node of |
---|
| 743 | /// a shortest path from a root to \c v. It is \c INVALID if \c v |
---|
| 744 | /// is not reached from the root(s) or if \c v is a root. |
---|
| 745 | /// |
---|
| 746 | /// The shortest path tree used here is equal to the shortest path |
---|
[833] | 747 | /// tree used in \ref predArc() and \ref predMap(). |
---|
[744] | 748 | /// |
---|
| 749 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 750 | /// using this function. |
---|
[956] | 751 | Node predNode(Node v) const { |
---|
| 752 | return (*_pred)[v] == INVALID ? INVALID : _gr->source((*_pred)[v]); |
---|
[744] | 753 | } |
---|
[956] | 754 | |
---|
[744] | 755 | /// \brief Returns a const reference to the node map that stores the |
---|
| 756 | /// distances of the nodes. |
---|
| 757 | /// |
---|
| 758 | /// Returns a const reference to the node map that stores the distances |
---|
| 759 | /// of the nodes calculated by the algorithm. |
---|
| 760 | /// |
---|
| 761 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 762 | /// using this function. |
---|
| 763 | const DistMap &distMap() const { return *_dist;} |
---|
[956] | 764 | |
---|
[744] | 765 | /// \brief Returns a const reference to the node map that stores the |
---|
| 766 | /// predecessor arcs. |
---|
| 767 | /// |
---|
| 768 | /// Returns a const reference to the node map that stores the predecessor |
---|
| 769 | /// arcs, which form the shortest path tree (forest). |
---|
| 770 | /// |
---|
| 771 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 772 | /// using this function. |
---|
| 773 | const PredMap &predMap() const { return *_pred; } |
---|
[956] | 774 | |
---|
[744] | 775 | /// \brief Checks if a node is reached from the root(s). |
---|
| 776 | /// |
---|
| 777 | /// Returns \c true if \c v is reached from the root(s). |
---|
| 778 | /// |
---|
| 779 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 780 | /// using this function. |
---|
| 781 | bool reached(Node v) const { |
---|
| 782 | return (*_dist)[v] != OperationTraits::infinity(); |
---|
[743] | 783 | } |
---|
| 784 | |
---|
[746] | 785 | /// \brief Gives back a negative cycle. |
---|
[956] | 786 | /// |
---|
[746] | 787 | /// This function gives back a directed cycle with negative total |
---|
| 788 | /// length if the algorithm has already found one. |
---|
| 789 | /// Otherwise it gives back an empty path. |
---|
[828] | 790 | lemon::Path<Digraph> negativeCycle() const { |
---|
[746] | 791 | typename Digraph::template NodeMap<int> state(*_gr, -1); |
---|
| 792 | lemon::Path<Digraph> cycle; |
---|
| 793 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
| 794 | if (state[_process[i]] != -1) continue; |
---|
| 795 | for (Node v = _process[i]; (*_pred)[v] != INVALID; |
---|
| 796 | v = _gr->source((*_pred)[v])) { |
---|
| 797 | if (state[v] == i) { |
---|
| 798 | cycle.addFront((*_pred)[v]); |
---|
| 799 | for (Node u = _gr->source((*_pred)[v]); u != v; |
---|
| 800 | u = _gr->source((*_pred)[u])) { |
---|
| 801 | cycle.addFront((*_pred)[u]); |
---|
| 802 | } |
---|
| 803 | return cycle; |
---|
| 804 | } |
---|
| 805 | else if (state[v] >= 0) { |
---|
| 806 | break; |
---|
| 807 | } |
---|
| 808 | state[v] = i; |
---|
| 809 | } |
---|
| 810 | } |
---|
| 811 | return cycle; |
---|
| 812 | } |
---|
[956] | 813 | |
---|
[743] | 814 | ///@} |
---|
| 815 | }; |
---|
[956] | 816 | |
---|
[744] | 817 | /// \brief Default traits class of bellmanFord() function. |
---|
[743] | 818 | /// |
---|
[744] | 819 | /// Default traits class of bellmanFord() function. |
---|
| 820 | /// \tparam GR The type of the digraph. |
---|
| 821 | /// \tparam LEN The type of the length map. |
---|
| 822 | template <typename GR, typename LEN> |
---|
[743] | 823 | struct BellmanFordWizardDefaultTraits { |
---|
[956] | 824 | /// The type of the digraph the algorithm runs on. |
---|
[744] | 825 | typedef GR Digraph; |
---|
[743] | 826 | |
---|
| 827 | /// \brief The type of the map that stores the arc lengths. |
---|
| 828 | /// |
---|
| 829 | /// The type of the map that stores the arc lengths. |
---|
| 830 | /// It must meet the \ref concepts::ReadMap "ReadMap" concept. |
---|
[744] | 831 | typedef LEN LengthMap; |
---|
[743] | 832 | |
---|
[744] | 833 | /// The type of the arc lengths. |
---|
| 834 | typedef typename LEN::Value Value; |
---|
[743] | 835 | |
---|
| 836 | /// \brief Operation traits for Bellman-Ford algorithm. |
---|
| 837 | /// |
---|
[744] | 838 | /// It defines the used operations and the infinity value for the |
---|
| 839 | /// given \c Value type. |
---|
[958] | 840 | /// \see BellmanFordDefaultOperationTraits |
---|
[743] | 841 | typedef BellmanFordDefaultOperationTraits<Value> OperationTraits; |
---|
| 842 | |
---|
| 843 | /// \brief The type of the map that stores the last |
---|
| 844 | /// arcs of the shortest paths. |
---|
[956] | 845 | /// |
---|
[744] | 846 | /// The type of the map that stores the last arcs of the shortest paths. |
---|
| 847 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 848 | typedef typename GR::template NodeMap<typename GR::Arc> PredMap; |
---|
[743] | 849 | |
---|
[744] | 850 | /// \brief Instantiates a \c PredMap. |
---|
[956] | 851 | /// |
---|
[744] | 852 | /// This function instantiates a \ref PredMap. |
---|
| 853 | /// \param g is the digraph to which we would like to define the |
---|
| 854 | /// \ref PredMap. |
---|
| 855 | static PredMap *createPredMap(const GR &g) { |
---|
| 856 | return new PredMap(g); |
---|
[743] | 857 | } |
---|
[744] | 858 | |
---|
| 859 | /// \brief The type of the map that stores the distances of the nodes. |
---|
[743] | 860 | /// |
---|
[744] | 861 | /// The type of the map that stores the distances of the nodes. |
---|
| 862 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 863 | typedef typename GR::template NodeMap<Value> DistMap; |
---|
| 864 | |
---|
| 865 | /// \brief Instantiates a \c DistMap. |
---|
[743] | 866 | /// |
---|
[956] | 867 | /// This function instantiates a \ref DistMap. |
---|
[744] | 868 | /// \param g is the digraph to which we would like to define the |
---|
| 869 | /// \ref DistMap. |
---|
| 870 | static DistMap *createDistMap(const GR &g) { |
---|
| 871 | return new DistMap(g); |
---|
[743] | 872 | } |
---|
[744] | 873 | |
---|
| 874 | ///The type of the shortest paths. |
---|
| 875 | |
---|
| 876 | ///The type of the shortest paths. |
---|
| 877 | ///It must meet the \ref concepts::Path "Path" concept. |
---|
| 878 | typedef lemon::Path<Digraph> Path; |
---|
[743] | 879 | }; |
---|
[956] | 880 | |
---|
[744] | 881 | /// \brief Default traits class used by BellmanFordWizard. |
---|
[743] | 882 | /// |
---|
[744] | 883 | /// Default traits class used by BellmanFordWizard. |
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| 884 | /// \tparam GR The type of the digraph. |
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| 885 | /// \tparam LEN The type of the length map. |
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| 886 | template <typename GR, typename LEN> |
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[956] | 887 | class BellmanFordWizardBase |
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[744] | 888 | : public BellmanFordWizardDefaultTraits<GR, LEN> { |
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[743] | 889 | |
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[744] | 890 | typedef BellmanFordWizardDefaultTraits<GR, LEN> Base; |
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[743] | 891 | protected: |
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[744] | 892 | // Type of the nodes in the digraph. |
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[743] | 893 | typedef typename Base::Digraph::Node Node; |
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| 894 | |
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[744] | 895 | // Pointer to the underlying digraph. |
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[743] | 896 | void *_graph; |
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[744] | 897 | // Pointer to the length map |
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[743] | 898 | void *_length; |
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[744] | 899 | // Pointer to the map of predecessors arcs. |
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[743] | 900 | void *_pred; |
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[744] | 901 | // Pointer to the map of distances. |
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[743] | 902 | void *_dist; |
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[744] | 903 | //Pointer to the shortest path to the target node. |
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| 904 | void *_path; |
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| 905 | //Pointer to the distance of the target node. |
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| 906 | void *_di; |
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[743] | 907 | |
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| 908 | public: |
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| 909 | /// Constructor. |
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[956] | 910 | |
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[744] | 911 | /// This constructor does not require parameters, it initiates |
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| 912 | /// all of the attributes to default values \c 0. |
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| 913 | BellmanFordWizardBase() : |
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| 914 | _graph(0), _length(0), _pred(0), _dist(0), _path(0), _di(0) {} |
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[743] | 915 | |
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| 916 | /// Constructor. |
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[956] | 917 | |
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[744] | 918 | /// This constructor requires two parameters, |
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| 919 | /// others are initiated to \c 0. |
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| 920 | /// \param gr The digraph the algorithm runs on. |
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| 921 | /// \param len The length map. |
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[956] | 922 | BellmanFordWizardBase(const GR& gr, |
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| 923 | const LEN& len) : |
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| 924 | _graph(reinterpret_cast<void*>(const_cast<GR*>(&gr))), |
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| 925 | _length(reinterpret_cast<void*>(const_cast<LEN*>(&len))), |
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[744] | 926 | _pred(0), _dist(0), _path(0), _di(0) {} |
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[743] | 927 | |
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| 928 | }; |
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[956] | 929 | |
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[744] | 930 | /// \brief Auxiliary class for the function-type interface of the |
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| 931 | /// \ref BellmanFord "Bellman-Ford" algorithm. |
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| 932 | /// |
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| 933 | /// This auxiliary class is created to implement the |
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| 934 | /// \ref bellmanFord() "function-type interface" of the |
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| 935 | /// \ref BellmanFord "Bellman-Ford" algorithm. |
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| 936 | /// It does not have own \ref run() method, it uses the |
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| 937 | /// functions and features of the plain \ref BellmanFord. |
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| 938 | /// |
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| 939 | /// This class should only be used through the \ref bellmanFord() |
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| 940 | /// function, which makes it easier to use the algorithm. |
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[891] | 941 | /// |
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| 942 | /// \tparam TR The traits class that defines various types used by the |
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| 943 | /// algorithm. |
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[744] | 944 | template<class TR> |
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| 945 | class BellmanFordWizard : public TR { |
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| 946 | typedef TR Base; |
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[743] | 947 | |
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[744] | 948 | typedef typename TR::Digraph Digraph; |
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[743] | 949 | |
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| 950 | typedef typename Digraph::Node Node; |
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| 951 | typedef typename Digraph::NodeIt NodeIt; |
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| 952 | typedef typename Digraph::Arc Arc; |
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| 953 | typedef typename Digraph::OutArcIt ArcIt; |
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[956] | 954 | |
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[744] | 955 | typedef typename TR::LengthMap LengthMap; |
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[743] | 956 | typedef typename LengthMap::Value Value; |
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[744] | 957 | typedef typename TR::PredMap PredMap; |
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| 958 | typedef typename TR::DistMap DistMap; |
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| 959 | typedef typename TR::Path Path; |
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[743] | 960 | |
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| 961 | public: |
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| 962 | /// Constructor. |
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[744] | 963 | BellmanFordWizard() : TR() {} |
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[743] | 964 | |
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| 965 | /// \brief Constructor that requires parameters. |
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| 966 | /// |
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| 967 | /// Constructor that requires parameters. |
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| 968 | /// These parameters will be the default values for the traits class. |
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[744] | 969 | /// \param gr The digraph the algorithm runs on. |
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| 970 | /// \param len The length map. |
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[956] | 971 | BellmanFordWizard(const Digraph& gr, const LengthMap& len) |
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[744] | 972 | : TR(gr, len) {} |
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[743] | 973 | |
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| 974 | /// \brief Copy constructor |
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[744] | 975 | BellmanFordWizard(const TR &b) : TR(b) {} |
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[743] | 976 | |
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| 977 | ~BellmanFordWizard() {} |
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| 978 | |
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[744] | 979 | /// \brief Runs the Bellman-Ford algorithm from the given source node. |
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[956] | 980 | /// |
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[744] | 981 | /// This method runs the Bellman-Ford algorithm from the given source |
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| 982 | /// node in order to compute the shortest path to each node. |
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| 983 | void run(Node s) { |
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[956] | 984 | BellmanFord<Digraph,LengthMap,TR> |
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| 985 | bf(*reinterpret_cast<const Digraph*>(Base::_graph), |
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[743] | 986 | *reinterpret_cast<const LengthMap*>(Base::_length)); |
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| 987 | if (Base::_pred) bf.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
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| 988 | if (Base::_dist) bf.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
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[744] | 989 | bf.run(s); |
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[743] | 990 | } |
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| 991 | |
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[744] | 992 | /// \brief Runs the Bellman-Ford algorithm to find the shortest path |
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| 993 | /// between \c s and \c t. |
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[743] | 994 | /// |
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[744] | 995 | /// This method runs the Bellman-Ford algorithm from node \c s |
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| 996 | /// in order to compute the shortest path to node \c t. |
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| 997 | /// Actually, it computes the shortest path to each node, but using |
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| 998 | /// this function you can retrieve the distance and the shortest path |
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| 999 | /// for a single target node easier. |
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| 1000 | /// |
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| 1001 | /// \return \c true if \c t is reachable form \c s. |
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| 1002 | bool run(Node s, Node t) { |
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| 1003 | BellmanFord<Digraph,LengthMap,TR> |
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| 1004 | bf(*reinterpret_cast<const Digraph*>(Base::_graph), |
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| 1005 | *reinterpret_cast<const LengthMap*>(Base::_length)); |
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| 1006 | if (Base::_pred) bf.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
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| 1007 | if (Base::_dist) bf.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
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| 1008 | bf.run(s); |
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| 1009 | if (Base::_path) *reinterpret_cast<Path*>(Base::_path) = bf.path(t); |
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| 1010 | if (Base::_di) *reinterpret_cast<Value*>(Base::_di) = bf.dist(t); |
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| 1011 | return bf.reached(t); |
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[743] | 1012 | } |
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| 1013 | |
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| 1014 | template<class T> |
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[744] | 1015 | struct SetPredMapBase : public Base { |
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[743] | 1016 | typedef T PredMap; |
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| 1017 | static PredMap *createPredMap(const Digraph &) { return 0; }; |
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[744] | 1018 | SetPredMapBase(const TR &b) : TR(b) {} |
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[743] | 1019 | }; |
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[956] | 1020 | |
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[744] | 1021 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 1022 | /// the predecessor map. |
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[743] | 1023 | /// |
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[744] | 1024 | /// \ref named-templ-param "Named parameter" for setting |
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| 1025 | /// the map that stores the predecessor arcs of the nodes. |
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[743] | 1026 | template<class T> |
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[744] | 1027 | BellmanFordWizard<SetPredMapBase<T> > predMap(const T &t) { |
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[743] | 1028 | Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t)); |
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[744] | 1029 | return BellmanFordWizard<SetPredMapBase<T> >(*this); |
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[743] | 1030 | } |
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[956] | 1031 | |
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[743] | 1032 | template<class T> |
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[744] | 1033 | struct SetDistMapBase : public Base { |
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[743] | 1034 | typedef T DistMap; |
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| 1035 | static DistMap *createDistMap(const Digraph &) { return 0; }; |
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[744] | 1036 | SetDistMapBase(const TR &b) : TR(b) {} |
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[743] | 1037 | }; |
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[956] | 1038 | |
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[744] | 1039 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 1040 | /// the distance map. |
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[743] | 1041 | /// |
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[744] | 1042 | /// \ref named-templ-param "Named parameter" for setting |
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| 1043 | /// the map that stores the distances of the nodes calculated |
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| 1044 | /// by the algorithm. |
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[743] | 1045 | template<class T> |
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[744] | 1046 | BellmanFordWizard<SetDistMapBase<T> > distMap(const T &t) { |
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[743] | 1047 | Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t)); |
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[744] | 1048 | return BellmanFordWizard<SetDistMapBase<T> >(*this); |
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[743] | 1049 | } |
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| 1050 | |
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| 1051 | template<class T> |
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[744] | 1052 | struct SetPathBase : public Base { |
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| 1053 | typedef T Path; |
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| 1054 | SetPathBase(const TR &b) : TR(b) {} |
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[743] | 1055 | }; |
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[744] | 1056 | |
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| 1057 | /// \brief \ref named-func-param "Named parameter" for getting |
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| 1058 | /// the shortest path to the target node. |
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[743] | 1059 | /// |
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[744] | 1060 | /// \ref named-func-param "Named parameter" for getting |
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| 1061 | /// the shortest path to the target node. |
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| 1062 | template<class T> |
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| 1063 | BellmanFordWizard<SetPathBase<T> > path(const T &t) |
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| 1064 | { |
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| 1065 | Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t)); |
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| 1066 | return BellmanFordWizard<SetPathBase<T> >(*this); |
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| 1067 | } |
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| 1068 | |
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| 1069 | /// \brief \ref named-func-param "Named parameter" for getting |
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| 1070 | /// the distance of the target node. |
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[743] | 1071 | /// |
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[744] | 1072 | /// \ref named-func-param "Named parameter" for getting |
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| 1073 | /// the distance of the target node. |
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| 1074 | BellmanFordWizard dist(const Value &d) |
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| 1075 | { |
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| 1076 | Base::_di=reinterpret_cast<void*>(const_cast<Value*>(&d)); |
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[743] | 1077 | return *this; |
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| 1078 | } |
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[956] | 1079 | |
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[743] | 1080 | }; |
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[956] | 1081 | |
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[744] | 1082 | /// \brief Function type interface for the \ref BellmanFord "Bellman-Ford" |
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| 1083 | /// algorithm. |
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[743] | 1084 | /// |
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| 1085 | /// \ingroup shortest_path |
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[744] | 1086 | /// Function type interface for the \ref BellmanFord "Bellman-Ford" |
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| 1087 | /// algorithm. |
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[743] | 1088 | /// |
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[956] | 1089 | /// This function also has several \ref named-templ-func-param |
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| 1090 | /// "named parameters", they are declared as the members of class |
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[743] | 1091 | /// \ref BellmanFordWizard. |
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[744] | 1092 | /// The following examples show how to use these parameters. |
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| 1093 | /// \code |
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| 1094 | /// // Compute shortest path from node s to each node |
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| 1095 | /// bellmanFord(g,length).predMap(preds).distMap(dists).run(s); |
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| 1096 | /// |
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| 1097 | /// // Compute shortest path from s to t |
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| 1098 | /// bool reached = bellmanFord(g,length).path(p).dist(d).run(s,t); |
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| 1099 | /// \endcode |
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[743] | 1100 | /// \warning Don't forget to put the \ref BellmanFordWizard::run() "run()" |
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| 1101 | /// to the end of the parameter list. |
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| 1102 | /// \sa BellmanFordWizard |
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| 1103 | /// \sa BellmanFord |
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[744] | 1104 | template<typename GR, typename LEN> |
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| 1105 | BellmanFordWizard<BellmanFordWizardBase<GR,LEN> > |
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| 1106 | bellmanFord(const GR& digraph, |
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[956] | 1107 | const LEN& length) |
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[744] | 1108 | { |
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| 1109 | return BellmanFordWizard<BellmanFordWizardBase<GR,LEN> >(digraph, length); |
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[743] | 1110 | } |
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| 1111 | |
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| 1112 | } //END OF NAMESPACE LEMON |
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| 1113 | |
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| 1114 | #endif |
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| 1115 | |
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