[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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[1270] | 5 | * Copyright (C) 2003-2013 |
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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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[1336] | 32 | #include <lemon/bits/stl_iterators.h> |
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[743] | 33 | |
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| 34 | #include <limits> |
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| 35 | |
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| 36 | namespace lemon { |
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| 37 | |
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[958] | 38 | /// \brief Default OperationTraits for the BellmanFord algorithm class. |
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[956] | 39 | /// |
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[744] | 40 | /// This operation traits class defines all computational operations |
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| 41 | /// and constants that are used in the Bellman-Ford algorithm. |
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| 42 | /// The default implementation is based on the \c numeric_limits class. |
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| 43 | /// If the numeric type does not have infinity value, then the maximum |
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| 44 | /// value is used as extremal infinity value. |
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[743] | 45 | template < |
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[956] | 46 | typename V, |
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[744] | 47 | bool has_inf = std::numeric_limits<V>::has_infinity> |
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[743] | 48 | struct BellmanFordDefaultOperationTraits { |
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[958] | 49 | /// \e |
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[744] | 50 | typedef V Value; |
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[743] | 51 | /// \brief Gives back the zero value of the type. |
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| 52 | static Value zero() { |
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| 53 | return static_cast<Value>(0); |
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| 54 | } |
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| 55 | /// \brief Gives back the positive infinity value of the type. |
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| 56 | static Value infinity() { |
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| 57 | return std::numeric_limits<Value>::infinity(); |
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| 58 | } |
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| 59 | /// \brief Gives back the sum of the given two elements. |
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| 60 | static Value plus(const Value& left, const Value& right) { |
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| 61 | return left + right; |
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| 62 | } |
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[744] | 63 | /// \brief Gives back \c true only if the first value is less than |
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| 64 | /// the second. |
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[743] | 65 | static bool less(const Value& left, const Value& right) { |
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| 66 | return left < right; |
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| 67 | } |
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| 68 | }; |
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| 69 | |
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[744] | 70 | template <typename V> |
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| 71 | struct BellmanFordDefaultOperationTraits<V, false> { |
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| 72 | typedef V Value; |
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[743] | 73 | static Value zero() { |
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| 74 | return static_cast<Value>(0); |
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| 75 | } |
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| 76 | static Value infinity() { |
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| 77 | return std::numeric_limits<Value>::max(); |
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| 78 | } |
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| 79 | static Value plus(const Value& left, const Value& right) { |
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| 80 | if (left == infinity() || right == infinity()) return infinity(); |
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| 81 | return left + right; |
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| 82 | } |
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| 83 | static bool less(const Value& left, const Value& right) { |
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| 84 | return left < right; |
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| 85 | } |
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| 86 | }; |
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[956] | 87 | |
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[743] | 88 | /// \brief Default traits class of BellmanFord class. |
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| 89 | /// |
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| 90 | /// Default traits class of BellmanFord class. |
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[744] | 91 | /// \param GR The type of the digraph. |
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| 92 | /// \param LEN The type of the length map. |
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| 93 | template<typename GR, typename LEN> |
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[743] | 94 | struct BellmanFordDefaultTraits { |
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[956] | 95 | /// The type of the digraph the algorithm runs on. |
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[744] | 96 | typedef GR Digraph; |
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[743] | 97 | |
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| 98 | /// \brief The type of the map that stores the arc lengths. |
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| 99 | /// |
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| 100 | /// The type of the map that stores the arc lengths. |
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[744] | 101 | /// It must conform to the \ref concepts::ReadMap "ReadMap" concept. |
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| 102 | typedef LEN LengthMap; |
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[743] | 103 | |
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[744] | 104 | /// The type of the arc lengths. |
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| 105 | typedef typename LEN::Value Value; |
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[743] | 106 | |
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| 107 | /// \brief Operation traits for Bellman-Ford algorithm. |
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| 108 | /// |
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[744] | 109 | /// It defines the used operations and the infinity value for the |
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| 110 | /// given \c Value type. |
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[958] | 111 | /// \see BellmanFordDefaultOperationTraits |
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[743] | 112 | typedef BellmanFordDefaultOperationTraits<Value> OperationTraits; |
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[956] | 113 | |
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| 114 | /// \brief The type of the map that stores the last arcs of the |
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[743] | 115 | /// shortest paths. |
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[956] | 116 | /// |
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[743] | 117 | /// The type of the map that stores the last |
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| 118 | /// arcs of the shortest paths. |
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[744] | 119 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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| 120 | typedef typename GR::template NodeMap<typename GR::Arc> PredMap; |
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[743] | 121 | |
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[744] | 122 | /// \brief Instantiates a \c PredMap. |
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[956] | 123 | /// |
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| 124 | /// This function instantiates a \ref PredMap. |
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[744] | 125 | /// \param g is the digraph to which we would like to define the |
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| 126 | /// \ref PredMap. |
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| 127 | static PredMap *createPredMap(const GR& g) { |
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| 128 | return new PredMap(g); |
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[743] | 129 | } |
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| 130 | |
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[744] | 131 | /// \brief The type of the map that stores the distances of the nodes. |
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[743] | 132 | /// |
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[744] | 133 | /// The type of the map that stores the distances of the nodes. |
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| 134 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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| 135 | typedef typename GR::template NodeMap<typename LEN::Value> DistMap; |
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[743] | 136 | |
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[744] | 137 | /// \brief Instantiates a \c DistMap. |
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[743] | 138 | /// |
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[956] | 139 | /// This function instantiates a \ref DistMap. |
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| 140 | /// \param g is the digraph to which we would like to define the |
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[744] | 141 | /// \ref DistMap. |
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| 142 | static DistMap *createDistMap(const GR& g) { |
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| 143 | return new DistMap(g); |
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[743] | 144 | } |
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| 145 | |
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| 146 | }; |
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[956] | 147 | |
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[743] | 148 | /// \brief %BellmanFord algorithm class. |
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| 149 | /// |
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| 150 | /// \ingroup shortest_path |
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[956] | 151 | /// This class provides an efficient implementation of the Bellman-Ford |
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[744] | 152 | /// algorithm. The maximum time complexity of the algorithm is |
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[1254] | 153 | /// <tt>O(nm)</tt>. |
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[744] | 154 | /// |
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| 155 | /// The Bellman-Ford algorithm solves the single-source shortest path |
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| 156 | /// problem when the arcs can have negative lengths, but the digraph |
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| 157 | /// should not contain directed cycles with negative total length. |
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| 158 | /// If all arc costs are non-negative, consider to use the Dijkstra |
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| 159 | /// algorithm instead, since it is more efficient. |
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| 160 | /// |
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| 161 | /// The arc lengths are passed to the algorithm using a |
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[956] | 162 | /// \ref concepts::ReadMap "ReadMap", so it is easy to change it to any |
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[744] | 163 | /// kind of length. The type of the length values is determined by the |
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| 164 | /// \ref concepts::ReadMap::Value "Value" type of the length map. |
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[743] | 165 | /// |
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[744] | 166 | /// There is also a \ref bellmanFord() "function-type interface" for the |
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| 167 | /// Bellman-Ford algorithm, which is convenient in the simplier cases and |
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| 168 | /// it can be used easier. |
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[743] | 169 | /// |
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[744] | 170 | /// \tparam GR The type of the digraph the algorithm runs on. |
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| 171 | /// The default type is \ref ListDigraph. |
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| 172 | /// \tparam LEN A \ref concepts::ReadMap "readable" arc map that specifies |
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| 173 | /// the lengths of the arcs. The default map type is |
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| 174 | /// \ref concepts::Digraph::ArcMap "GR::ArcMap<int>". |
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[891] | 175 | /// \tparam TR The traits class that defines various types used by the |
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| 176 | /// algorithm. By default, it is \ref BellmanFordDefaultTraits |
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| 177 | /// "BellmanFordDefaultTraits<GR, LEN>". |
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| 178 | /// In most cases, this parameter should not be set directly, |
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| 179 | /// consider to use the named template parameters instead. |
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[743] | 180 | #ifdef DOXYGEN |
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[744] | 181 | template <typename GR, typename LEN, typename TR> |
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[743] | 182 | #else |
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[744] | 183 | template <typename GR=ListDigraph, |
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| 184 | typename LEN=typename GR::template ArcMap<int>, |
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| 185 | typename TR=BellmanFordDefaultTraits<GR,LEN> > |
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[743] | 186 | #endif |
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| 187 | class BellmanFord { |
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| 188 | public: |
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| 189 | |
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| 190 | ///The type of the underlying digraph. |
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[744] | 191 | typedef typename TR::Digraph Digraph; |
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[956] | 192 | |
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[744] | 193 | /// \brief The type of the arc lengths. |
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| 194 | typedef typename TR::LengthMap::Value Value; |
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| 195 | /// \brief The type of the map that stores the arc lengths. |
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| 196 | typedef typename TR::LengthMap LengthMap; |
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| 197 | /// \brief The type of the map that stores the last |
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| 198 | /// arcs of the shortest paths. |
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| 199 | typedef typename TR::PredMap PredMap; |
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| 200 | /// \brief The type of the map that stores the distances of the nodes. |
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| 201 | typedef typename TR::DistMap DistMap; |
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| 202 | /// The type of the paths. |
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| 203 | typedef PredMapPath<Digraph, PredMap> Path; |
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[1250] | 204 | ///\brief The \ref lemon::BellmanFordDefaultOperationTraits |
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[744] | 205 | /// "operation traits class" of the algorithm. |
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| 206 | typedef typename TR::OperationTraits OperationTraits; |
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| 207 | |
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[1250] | 208 | ///\brief The \ref lemon::BellmanFordDefaultTraits "traits class" |
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| 209 | ///of the algorithm. |
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[744] | 210 | typedef TR Traits; |
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| 211 | |
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| 212 | private: |
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[743] | 213 | |
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| 214 | typedef typename Digraph::Node Node; |
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| 215 | typedef typename Digraph::NodeIt NodeIt; |
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| 216 | typedef typename Digraph::Arc Arc; |
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| 217 | typedef typename Digraph::OutArcIt OutArcIt; |
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[744] | 218 | |
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| 219 | // Pointer to the underlying digraph. |
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| 220 | const Digraph *_gr; |
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| 221 | // Pointer to the length map |
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| 222 | const LengthMap *_length; |
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| 223 | // Pointer to the map of predecessors arcs. |
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[743] | 224 | PredMap *_pred; |
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[744] | 225 | // Indicates if _pred is locally allocated (true) or not. |
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| 226 | bool _local_pred; |
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| 227 | // Pointer to the map of distances. |
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[743] | 228 | DistMap *_dist; |
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[744] | 229 | // Indicates if _dist is locally allocated (true) or not. |
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| 230 | bool _local_dist; |
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[743] | 231 | |
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| 232 | typedef typename Digraph::template NodeMap<bool> MaskMap; |
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| 233 | MaskMap *_mask; |
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| 234 | |
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| 235 | std::vector<Node> _process; |
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| 236 | |
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[744] | 237 | // Creates the maps if necessary. |
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[743] | 238 | void create_maps() { |
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| 239 | if(!_pred) { |
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[956] | 240 | _local_pred = true; |
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| 241 | _pred = Traits::createPredMap(*_gr); |
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[743] | 242 | } |
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| 243 | if(!_dist) { |
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[956] | 244 | _local_dist = true; |
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| 245 | _dist = Traits::createDistMap(*_gr); |
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[743] | 246 | } |
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[870] | 247 | if(!_mask) { |
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| 248 | _mask = new MaskMap(*_gr); |
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| 249 | } |
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[743] | 250 | } |
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[956] | 251 | |
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[743] | 252 | public : |
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[956] | 253 | |
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[743] | 254 | typedef BellmanFord Create; |
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| 255 | |
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[744] | 256 | /// \name Named Template Parameters |
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[743] | 257 | |
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| 258 | ///@{ |
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| 259 | |
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| 260 | template <class T> |
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[744] | 261 | struct SetPredMapTraits : public Traits { |
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[743] | 262 | typedef T PredMap; |
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| 263 | static PredMap *createPredMap(const Digraph&) { |
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| 264 | LEMON_ASSERT(false, "PredMap is not initialized"); |
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| 265 | return 0; // ignore warnings |
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| 266 | } |
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| 267 | }; |
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| 268 | |
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[744] | 269 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 270 | /// \c PredMap type. |
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[743] | 271 | /// |
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[744] | 272 | /// \ref named-templ-param "Named parameter" for setting |
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| 273 | /// \c PredMap type. |
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| 274 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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[743] | 275 | template <class T> |
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[956] | 276 | struct SetPredMap |
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[744] | 277 | : public BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > { |
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| 278 | typedef BellmanFord< Digraph, LengthMap, SetPredMapTraits<T> > Create; |
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[743] | 279 | }; |
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[956] | 280 | |
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[743] | 281 | template <class T> |
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[744] | 282 | struct SetDistMapTraits : public Traits { |
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[743] | 283 | typedef T DistMap; |
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| 284 | static DistMap *createDistMap(const Digraph&) { |
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| 285 | LEMON_ASSERT(false, "DistMap is not initialized"); |
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| 286 | return 0; // ignore warnings |
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| 287 | } |
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| 288 | }; |
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| 289 | |
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[744] | 290 | /// \brief \ref named-templ-param "Named parameter" for setting |
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| 291 | /// \c DistMap type. |
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[743] | 292 | /// |
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[744] | 293 | /// \ref named-templ-param "Named parameter" for setting |
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| 294 | /// \c DistMap type. |
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| 295 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
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[743] | 296 | template <class T> |
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[956] | 297 | struct SetDistMap |
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[744] | 298 | : public BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > { |
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| 299 | typedef BellmanFord< Digraph, LengthMap, SetDistMapTraits<T> > Create; |
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[743] | 300 | }; |
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[744] | 301 | |
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[743] | 302 | template <class T> |
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[744] | 303 | struct SetOperationTraitsTraits : public Traits { |
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[743] | 304 | typedef T OperationTraits; |
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| 305 | }; |
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[956] | 306 | |
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| 307 | /// \brief \ref named-templ-param "Named parameter" for setting |
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[744] | 308 | /// \c OperationTraits type. |
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[743] | 309 | /// |
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[744] | 310 | /// \ref named-templ-param "Named parameter" for setting |
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| 311 | /// \c OperationTraits type. |
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[833] | 312 | /// For more information, see \ref BellmanFordDefaultOperationTraits. |
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[743] | 313 | template <class T> |
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| 314 | struct SetOperationTraits |
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[744] | 315 | : public BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > { |
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| 316 | typedef BellmanFord< Digraph, LengthMap, SetOperationTraitsTraits<T> > |
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[743] | 317 | Create; |
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| 318 | }; |
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[956] | 319 | |
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[743] | 320 | ///@} |
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| 321 | |
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| 322 | protected: |
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[956] | 323 | |
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[743] | 324 | BellmanFord() {} |
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| 325 | |
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[956] | 326 | public: |
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| 327 | |
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[743] | 328 | /// \brief Constructor. |
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| 329 | /// |
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[744] | 330 | /// Constructor. |
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| 331 | /// \param g The digraph the algorithm runs on. |
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| 332 | /// \param length The length map used by the algorithm. |
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| 333 | BellmanFord(const Digraph& g, const LengthMap& length) : |
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| 334 | _gr(&g), _length(&length), |
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| 335 | _pred(0), _local_pred(false), |
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| 336 | _dist(0), _local_dist(false), _mask(0) {} |
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[956] | 337 | |
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[743] | 338 | ///Destructor. |
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| 339 | ~BellmanFord() { |
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[744] | 340 | if(_local_pred) delete _pred; |
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| 341 | if(_local_dist) delete _dist; |
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[743] | 342 | if(_mask) delete _mask; |
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| 343 | } |
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| 344 | |
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| 345 | /// \brief Sets the length map. |
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| 346 | /// |
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| 347 | /// Sets the length map. |
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[744] | 348 | /// \return <tt>(*this)</tt> |
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| 349 | BellmanFord &lengthMap(const LengthMap &map) { |
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| 350 | _length = ↦ |
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[743] | 351 | return *this; |
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| 352 | } |
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| 353 | |
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[744] | 354 | /// \brief Sets the map that stores the predecessor arcs. |
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[743] | 355 | /// |
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[744] | 356 | /// Sets the map that stores the predecessor arcs. |
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| 357 | /// If you don't use this function before calling \ref run() |
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| 358 | /// or \ref init(), an instance will be allocated automatically. |
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| 359 | /// The destructor deallocates this automatically allocated map, |
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| 360 | /// of course. |
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| 361 | /// \return <tt>(*this)</tt> |
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| 362 | BellmanFord &predMap(PredMap &map) { |
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| 363 | if(_local_pred) { |
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[956] | 364 | delete _pred; |
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| 365 | _local_pred=false; |
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[743] | 366 | } |
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[744] | 367 | _pred = ↦ |
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[743] | 368 | return *this; |
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| 369 | } |
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| 370 | |
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[744] | 371 | /// \brief Sets the map that stores the distances of the nodes. |
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[743] | 372 | /// |
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[744] | 373 | /// Sets the map that stores the distances of the nodes calculated |
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| 374 | /// by the algorithm. |
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| 375 | /// If you don't use this function before calling \ref run() |
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| 376 | /// or \ref init(), an instance will be allocated automatically. |
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| 377 | /// The destructor deallocates this automatically allocated map, |
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| 378 | /// of course. |
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| 379 | /// \return <tt>(*this)</tt> |
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| 380 | BellmanFord &distMap(DistMap &map) { |
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| 381 | if(_local_dist) { |
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[956] | 382 | delete _dist; |
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| 383 | _local_dist=false; |
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[743] | 384 | } |
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[744] | 385 | _dist = ↦ |
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[743] | 386 | return *this; |
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| 387 | } |
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| 388 | |
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[744] | 389 | /// \name Execution Control |
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| 390 | /// The simplest way to execute the Bellman-Ford algorithm is to use |
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| 391 | /// one of the member functions called \ref run().\n |
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| 392 | /// If you need better control on the execution, you have to call |
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| 393 | /// \ref init() first, then you can add several source nodes |
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| 394 | /// with \ref addSource(). Finally the actual path computation can be |
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| 395 | /// performed with \ref start(), \ref checkedStart() or |
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| 396 | /// \ref limitedStart(). |
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[743] | 397 | |
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| 398 | ///@{ |
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| 399 | |
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| 400 | /// \brief Initializes the internal data structures. |
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[956] | 401 | /// |
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[744] | 402 | /// Initializes the internal data structures. The optional parameter |
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| 403 | /// is the initial distance of each node. |
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[743] | 404 | void init(const Value value = OperationTraits::infinity()) { |
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| 405 | create_maps(); |
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[744] | 406 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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[956] | 407 | _pred->set(it, INVALID); |
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| 408 | _dist->set(it, value); |
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[743] | 409 | } |
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| 410 | _process.clear(); |
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| 411 | if (OperationTraits::less(value, OperationTraits::infinity())) { |
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[956] | 412 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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| 413 | _process.push_back(it); |
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| 414 | _mask->set(it, true); |
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| 415 | } |
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[870] | 416 | } else { |
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[956] | 417 | for (NodeIt it(*_gr); it != INVALID; ++it) { |
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| 418 | _mask->set(it, false); |
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| 419 | } |
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[743] | 420 | } |
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| 421 | } |
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[956] | 422 | |
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[743] | 423 | /// \brief Adds a new source node. |
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| 424 | /// |
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[744] | 425 | /// This function adds a new source node. The optional second parameter |
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| 426 | /// is the initial distance of the node. |
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[743] | 427 | void addSource(Node source, Value dst = OperationTraits::zero()) { |
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| 428 | _dist->set(source, dst); |
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| 429 | if (!(*_mask)[source]) { |
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[956] | 430 | _process.push_back(source); |
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| 431 | _mask->set(source, true); |
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[743] | 432 | } |
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| 433 | } |
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| 434 | |
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| 435 | /// \brief Executes one round from the Bellman-Ford algorithm. |
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| 436 | /// |
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| 437 | /// If the algoritm calculated the distances in the previous round |
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[744] | 438 | /// exactly for the paths of at most \c k arcs, then this function |
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| 439 | /// will calculate the distances exactly for the paths of at most |
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| 440 | /// <tt>k+1</tt> arcs. Performing \c k iterations using this function |
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| 441 | /// calculates the shortest path distances exactly for the paths |
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| 442 | /// consisting of at most \c k arcs. |
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[743] | 443 | /// |
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| 444 | /// \warning The paths with limited arc number cannot be retrieved |
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[744] | 445 | /// easily with \ref path() or \ref predArc() functions. If you also |
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| 446 | /// need the shortest paths and not only the distances, you should |
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| 447 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 448 | /// and build the path manually. |
---|
[743] | 449 | /// |
---|
| 450 | /// \return \c true when the algorithm have not found more shorter |
---|
| 451 | /// paths. |
---|
[744] | 452 | /// |
---|
| 453 | /// \see ActiveIt |
---|
[743] | 454 | bool processNextRound() { |
---|
| 455 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 456 | _mask->set(_process[i], false); |
---|
[743] | 457 | } |
---|
| 458 | std::vector<Node> nextProcess; |
---|
| 459 | std::vector<Value> values(_process.size()); |
---|
| 460 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 461 | values[i] = (*_dist)[_process[i]]; |
---|
[743] | 462 | } |
---|
| 463 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 464 | for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) { |
---|
| 465 | Node target = _gr->target(it); |
---|
| 466 | Value relaxed = OperationTraits::plus(values[i], (*_length)[it]); |
---|
| 467 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 468 | _pred->set(target, it); |
---|
| 469 | _dist->set(target, relaxed); |
---|
| 470 | if (!(*_mask)[target]) { |
---|
| 471 | _mask->set(target, true); |
---|
| 472 | nextProcess.push_back(target); |
---|
| 473 | } |
---|
| 474 | } |
---|
| 475 | } |
---|
[743] | 476 | } |
---|
| 477 | _process.swap(nextProcess); |
---|
| 478 | return _process.empty(); |
---|
| 479 | } |
---|
| 480 | |
---|
| 481 | /// \brief Executes one weak round from the Bellman-Ford algorithm. |
---|
| 482 | /// |
---|
[744] | 483 | /// If the algorithm calculated the distances in the previous round |
---|
| 484 | /// at least for the paths of at most \c k arcs, then this function |
---|
| 485 | /// will calculate the distances at least for the paths of at most |
---|
| 486 | /// <tt>k+1</tt> arcs. |
---|
| 487 | /// This function does not make it possible to calculate the shortest |
---|
| 488 | /// path distances exactly for paths consisting of at most \c k arcs, |
---|
| 489 | /// this is why it is called weak round. |
---|
| 490 | /// |
---|
| 491 | /// \return \c true when the algorithm have not found more shorter |
---|
| 492 | /// paths. |
---|
| 493 | /// |
---|
| 494 | /// \see ActiveIt |
---|
[743] | 495 | bool processNextWeakRound() { |
---|
| 496 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 497 | _mask->set(_process[i], false); |
---|
[743] | 498 | } |
---|
| 499 | std::vector<Node> nextProcess; |
---|
| 500 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
[956] | 501 | for (OutArcIt it(*_gr, _process[i]); it != INVALID; ++it) { |
---|
| 502 | Node target = _gr->target(it); |
---|
| 503 | Value relaxed = |
---|
| 504 | OperationTraits::plus((*_dist)[_process[i]], (*_length)[it]); |
---|
| 505 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 506 | _pred->set(target, it); |
---|
| 507 | _dist->set(target, relaxed); |
---|
| 508 | if (!(*_mask)[target]) { |
---|
| 509 | _mask->set(target, true); |
---|
| 510 | nextProcess.push_back(target); |
---|
| 511 | } |
---|
| 512 | } |
---|
| 513 | } |
---|
[743] | 514 | } |
---|
| 515 | _process.swap(nextProcess); |
---|
| 516 | return _process.empty(); |
---|
| 517 | } |
---|
| 518 | |
---|
| 519 | /// \brief Executes the algorithm. |
---|
| 520 | /// |
---|
[744] | 521 | /// Executes the algorithm. |
---|
[743] | 522 | /// |
---|
[744] | 523 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 524 | /// in order to compute the shortest path to each node. |
---|
| 525 | /// |
---|
| 526 | /// The algorithm computes |
---|
| 527 | /// - the shortest path tree (forest), |
---|
| 528 | /// - the distance of each node from the root(s). |
---|
| 529 | /// |
---|
| 530 | /// \pre init() must be called and at least one root node should be |
---|
| 531 | /// added with addSource() before using this function. |
---|
[743] | 532 | void start() { |
---|
[744] | 533 | int num = countNodes(*_gr) - 1; |
---|
[743] | 534 | for (int i = 0; i < num; ++i) { |
---|
[956] | 535 | if (processNextWeakRound()) break; |
---|
[743] | 536 | } |
---|
| 537 | } |
---|
| 538 | |
---|
| 539 | /// \brief Executes the algorithm and checks the negative cycles. |
---|
| 540 | /// |
---|
[744] | 541 | /// Executes the algorithm and checks the negative cycles. |
---|
[743] | 542 | /// |
---|
[744] | 543 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 544 | /// in order to compute the shortest path to each node and also checks |
---|
| 545 | /// if the digraph contains cycles with negative total length. |
---|
| 546 | /// |
---|
[956] | 547 | /// The algorithm computes |
---|
[744] | 548 | /// - the shortest path tree (forest), |
---|
| 549 | /// - the distance of each node from the root(s). |
---|
[956] | 550 | /// |
---|
[743] | 551 | /// \return \c false if there is a negative cycle in the digraph. |
---|
[744] | 552 | /// |
---|
| 553 | /// \pre init() must be called and at least one root node should be |
---|
[956] | 554 | /// added with addSource() before using this function. |
---|
[743] | 555 | bool checkedStart() { |
---|
[744] | 556 | int num = countNodes(*_gr); |
---|
[743] | 557 | for (int i = 0; i < num; ++i) { |
---|
[956] | 558 | if (processNextWeakRound()) return true; |
---|
[743] | 559 | } |
---|
| 560 | return _process.empty(); |
---|
| 561 | } |
---|
| 562 | |
---|
[744] | 563 | /// \brief Executes the algorithm with arc number limit. |
---|
[743] | 564 | /// |
---|
[744] | 565 | /// Executes the algorithm with arc number limit. |
---|
[743] | 566 | /// |
---|
[744] | 567 | /// This method runs the Bellman-Ford algorithm from the root node(s) |
---|
| 568 | /// in order to compute the shortest path distance for each node |
---|
| 569 | /// using only the paths consisting of at most \c num arcs. |
---|
| 570 | /// |
---|
| 571 | /// The algorithm computes |
---|
| 572 | /// - the limited distance of each node from the root(s), |
---|
| 573 | /// - the predecessor arc for each node. |
---|
[743] | 574 | /// |
---|
| 575 | /// \warning The paths with limited arc number cannot be retrieved |
---|
[744] | 576 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 577 | /// need the shortest paths and not only the distances, you should |
---|
| 578 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 579 | /// and build the path manually. |
---|
[743] | 580 | /// |
---|
[744] | 581 | /// \pre init() must be called and at least one root node should be |
---|
[956] | 582 | /// added with addSource() before using this function. |
---|
[743] | 583 | void limitedStart(int num) { |
---|
| 584 | for (int i = 0; i < num; ++i) { |
---|
[956] | 585 | if (processNextRound()) break; |
---|
[743] | 586 | } |
---|
| 587 | } |
---|
[956] | 588 | |
---|
[744] | 589 | /// \brief Runs the algorithm from the given root node. |
---|
[956] | 590 | /// |
---|
[744] | 591 | /// This method runs the Bellman-Ford algorithm from the given root |
---|
| 592 | /// node \c s in order to compute the shortest path to each node. |
---|
[743] | 593 | /// |
---|
[744] | 594 | /// The algorithm computes |
---|
| 595 | /// - the shortest path tree (forest), |
---|
| 596 | /// - the distance of each node from the root(s). |
---|
| 597 | /// |
---|
| 598 | /// \note bf.run(s) is just a shortcut of the following code. |
---|
| 599 | /// \code |
---|
| 600 | /// bf.init(); |
---|
| 601 | /// bf.addSource(s); |
---|
| 602 | /// bf.start(); |
---|
| 603 | /// \endcode |
---|
[743] | 604 | void run(Node s) { |
---|
| 605 | init(); |
---|
| 606 | addSource(s); |
---|
| 607 | start(); |
---|
| 608 | } |
---|
[956] | 609 | |
---|
[744] | 610 | /// \brief Runs the algorithm from the given root node with arc |
---|
| 611 | /// number limit. |
---|
[956] | 612 | /// |
---|
[744] | 613 | /// This method runs the Bellman-Ford algorithm from the given root |
---|
| 614 | /// node \c s in order to compute the shortest path distance for each |
---|
| 615 | /// node using only the paths consisting of at most \c num arcs. |
---|
[743] | 616 | /// |
---|
[744] | 617 | /// The algorithm computes |
---|
| 618 | /// - the limited distance of each node from the root(s), |
---|
| 619 | /// - the predecessor arc for each node. |
---|
| 620 | /// |
---|
| 621 | /// \warning The paths with limited arc number cannot be retrieved |
---|
| 622 | /// easily with \ref path() or \ref predArc() functions. If you also |
---|
| 623 | /// need the shortest paths and not only the distances, you should |
---|
| 624 | /// store the \ref predMap() "predecessor map" after each iteration |
---|
| 625 | /// and build the path manually. |
---|
| 626 | /// |
---|
| 627 | /// \note bf.run(s, num) is just a shortcut of the following code. |
---|
| 628 | /// \code |
---|
| 629 | /// bf.init(); |
---|
| 630 | /// bf.addSource(s); |
---|
| 631 | /// bf.limitedStart(num); |
---|
| 632 | /// \endcode |
---|
[743] | 633 | void run(Node s, int num) { |
---|
| 634 | init(); |
---|
| 635 | addSource(s); |
---|
| 636 | limitedStart(num); |
---|
| 637 | } |
---|
[956] | 638 | |
---|
[743] | 639 | ///@} |
---|
| 640 | |
---|
[744] | 641 | /// \brief LEMON iterator for getting the active nodes. |
---|
[743] | 642 | /// |
---|
[744] | 643 | /// This class provides a common style LEMON iterator that traverses |
---|
| 644 | /// the active nodes of the Bellman-Ford algorithm after the last |
---|
| 645 | /// phase. These nodes should be checked in the next phase to |
---|
| 646 | /// find augmenting arcs outgoing from them. |
---|
[743] | 647 | class ActiveIt { |
---|
| 648 | public: |
---|
| 649 | |
---|
| 650 | /// \brief Constructor. |
---|
| 651 | /// |
---|
[744] | 652 | /// Constructor for getting the active nodes of the given BellmanFord |
---|
[956] | 653 | /// instance. |
---|
[743] | 654 | ActiveIt(const BellmanFord& algorithm) : _algorithm(&algorithm) |
---|
| 655 | { |
---|
| 656 | _index = _algorithm->_process.size() - 1; |
---|
| 657 | } |
---|
| 658 | |
---|
| 659 | /// \brief Invalid constructor. |
---|
| 660 | /// |
---|
| 661 | /// Invalid constructor. |
---|
| 662 | ActiveIt(Invalid) : _algorithm(0), _index(-1) {} |
---|
| 663 | |
---|
[744] | 664 | /// \brief Conversion to \c Node. |
---|
[743] | 665 | /// |
---|
[744] | 666 | /// Conversion to \c Node. |
---|
[956] | 667 | operator Node() const { |
---|
[743] | 668 | return _index >= 0 ? _algorithm->_process[_index] : INVALID; |
---|
| 669 | } |
---|
| 670 | |
---|
| 671 | /// \brief Increment operator. |
---|
| 672 | /// |
---|
| 673 | /// Increment operator. |
---|
| 674 | ActiveIt& operator++() { |
---|
| 675 | --_index; |
---|
[956] | 676 | return *this; |
---|
[743] | 677 | } |
---|
| 678 | |
---|
[956] | 679 | bool operator==(const ActiveIt& it) const { |
---|
| 680 | return static_cast<Node>(*this) == static_cast<Node>(it); |
---|
[743] | 681 | } |
---|
[956] | 682 | bool operator!=(const ActiveIt& it) const { |
---|
| 683 | return static_cast<Node>(*this) != static_cast<Node>(it); |
---|
[743] | 684 | } |
---|
[956] | 685 | bool operator<(const ActiveIt& it) const { |
---|
| 686 | return static_cast<Node>(*this) < static_cast<Node>(it); |
---|
[743] | 687 | } |
---|
[956] | 688 | |
---|
[743] | 689 | private: |
---|
| 690 | const BellmanFord* _algorithm; |
---|
| 691 | int _index; |
---|
| 692 | }; |
---|
[956] | 693 | |
---|
[1336] | 694 | /// \brief Gets the collection of the active nodes. |
---|
| 695 | /// |
---|
| 696 | /// This function can be used for iterating on the active nodes of the |
---|
| 697 | /// Bellman-Ford algorithm after the last phase. |
---|
| 698 | /// These nodes should be checked in the next phase to |
---|
| 699 | /// find augmenting arcs outgoing from them. |
---|
| 700 | /// It returns a wrapped ActiveIt, which looks |
---|
| 701 | /// like an STL container (by having begin() and end()) |
---|
| 702 | /// which you can use in range-based for loops, STL algorithms, etc. |
---|
| 703 | LemonRangeWrapper1<ActiveIt, BellmanFord> |
---|
[1337] | 704 | activeNodes() const { |
---|
| 705 | return LemonRangeWrapper1<ActiveIt, BellmanFord>(*this); |
---|
[1336] | 706 | } |
---|
| 707 | |
---|
| 708 | |
---|
[744] | 709 | /// \name Query Functions |
---|
| 710 | /// The result of the Bellman-Ford algorithm can be obtained using these |
---|
| 711 | /// functions.\n |
---|
| 712 | /// Either \ref run() or \ref init() should be called before using them. |
---|
[956] | 713 | |
---|
[744] | 714 | ///@{ |
---|
[743] | 715 | |
---|
[744] | 716 | /// \brief The shortest path to the given node. |
---|
[956] | 717 | /// |
---|
[744] | 718 | /// Gives back the shortest path to the given node from the root(s). |
---|
| 719 | /// |
---|
| 720 | /// \warning \c t should be reached from the root(s). |
---|
| 721 | /// |
---|
| 722 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 723 | /// using this function. |
---|
| 724 | Path path(Node t) const |
---|
| 725 | { |
---|
| 726 | return Path(*_gr, *_pred, t); |
---|
| 727 | } |
---|
[956] | 728 | |
---|
[744] | 729 | /// \brief The distance of the given node from the root(s). |
---|
| 730 | /// |
---|
| 731 | /// Returns the distance of the given node from the root(s). |
---|
| 732 | /// |
---|
| 733 | /// \warning If node \c v is not reached from the root(s), then |
---|
| 734 | /// the return value of this function is undefined. |
---|
| 735 | /// |
---|
| 736 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 737 | /// using this function. |
---|
| 738 | Value dist(Node v) const { return (*_dist)[v]; } |
---|
[743] | 739 | |
---|
[744] | 740 | /// \brief Returns the 'previous arc' of the shortest path tree for |
---|
| 741 | /// the given node. |
---|
| 742 | /// |
---|
| 743 | /// This function returns the 'previous arc' of the shortest path |
---|
| 744 | /// tree for node \c v, i.e. it returns the last arc of a |
---|
| 745 | /// shortest path from a root to \c v. It is \c INVALID if \c v |
---|
| 746 | /// is not reached from the root(s) or if \c v is a root. |
---|
| 747 | /// |
---|
| 748 | /// The shortest path tree used here is equal to the shortest path |
---|
[833] | 749 | /// tree used in \ref predNode() and \ref predMap(). |
---|
[744] | 750 | /// |
---|
| 751 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 752 | /// using this function. |
---|
| 753 | Arc predArc(Node v) const { return (*_pred)[v]; } |
---|
| 754 | |
---|
| 755 | /// \brief Returns the 'previous node' of the shortest path tree for |
---|
| 756 | /// the given node. |
---|
| 757 | /// |
---|
| 758 | /// This function returns the 'previous node' of the shortest path |
---|
| 759 | /// tree for node \c v, i.e. it returns the last but one node of |
---|
| 760 | /// a shortest path from a root to \c v. It is \c INVALID if \c v |
---|
| 761 | /// is not reached from the root(s) or if \c v is a root. |
---|
| 762 | /// |
---|
| 763 | /// The shortest path tree used here is equal to the shortest path |
---|
[833] | 764 | /// tree used in \ref predArc() and \ref predMap(). |
---|
[744] | 765 | /// |
---|
| 766 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 767 | /// using this function. |
---|
[956] | 768 | Node predNode(Node v) const { |
---|
| 769 | return (*_pred)[v] == INVALID ? INVALID : _gr->source((*_pred)[v]); |
---|
[744] | 770 | } |
---|
[956] | 771 | |
---|
[744] | 772 | /// \brief Returns a const reference to the node map that stores the |
---|
| 773 | /// distances of the nodes. |
---|
| 774 | /// |
---|
| 775 | /// Returns a const reference to the node map that stores the distances |
---|
| 776 | /// of the nodes calculated by the algorithm. |
---|
| 777 | /// |
---|
| 778 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 779 | /// using this function. |
---|
| 780 | const DistMap &distMap() const { return *_dist;} |
---|
[956] | 781 | |
---|
[744] | 782 | /// \brief Returns a const reference to the node map that stores the |
---|
| 783 | /// predecessor arcs. |
---|
| 784 | /// |
---|
| 785 | /// Returns a const reference to the node map that stores the predecessor |
---|
| 786 | /// arcs, which form the shortest path tree (forest). |
---|
| 787 | /// |
---|
| 788 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 789 | /// using this function. |
---|
| 790 | const PredMap &predMap() const { return *_pred; } |
---|
[956] | 791 | |
---|
[744] | 792 | /// \brief Checks if a node is reached from the root(s). |
---|
| 793 | /// |
---|
| 794 | /// Returns \c true if \c v is reached from the root(s). |
---|
| 795 | /// |
---|
| 796 | /// \pre Either \ref run() or \ref init() must be called before |
---|
| 797 | /// using this function. |
---|
| 798 | bool reached(Node v) const { |
---|
| 799 | return (*_dist)[v] != OperationTraits::infinity(); |
---|
[743] | 800 | } |
---|
| 801 | |
---|
[746] | 802 | /// \brief Gives back a negative cycle. |
---|
[956] | 803 | /// |
---|
[746] | 804 | /// This function gives back a directed cycle with negative total |
---|
| 805 | /// length if the algorithm has already found one. |
---|
| 806 | /// Otherwise it gives back an empty path. |
---|
[828] | 807 | lemon::Path<Digraph> negativeCycle() const { |
---|
[746] | 808 | typename Digraph::template NodeMap<int> state(*_gr, -1); |
---|
| 809 | lemon::Path<Digraph> cycle; |
---|
| 810 | for (int i = 0; i < int(_process.size()); ++i) { |
---|
| 811 | if (state[_process[i]] != -1) continue; |
---|
| 812 | for (Node v = _process[i]; (*_pred)[v] != INVALID; |
---|
| 813 | v = _gr->source((*_pred)[v])) { |
---|
| 814 | if (state[v] == i) { |
---|
| 815 | cycle.addFront((*_pred)[v]); |
---|
| 816 | for (Node u = _gr->source((*_pred)[v]); u != v; |
---|
| 817 | u = _gr->source((*_pred)[u])) { |
---|
| 818 | cycle.addFront((*_pred)[u]); |
---|
| 819 | } |
---|
| 820 | return cycle; |
---|
| 821 | } |
---|
| 822 | else if (state[v] >= 0) { |
---|
| 823 | break; |
---|
| 824 | } |
---|
| 825 | state[v] = i; |
---|
| 826 | } |
---|
| 827 | } |
---|
| 828 | return cycle; |
---|
| 829 | } |
---|
[956] | 830 | |
---|
[743] | 831 | ///@} |
---|
| 832 | }; |
---|
[956] | 833 | |
---|
[744] | 834 | /// \brief Default traits class of bellmanFord() function. |
---|
[743] | 835 | /// |
---|
[744] | 836 | /// Default traits class of bellmanFord() function. |
---|
| 837 | /// \tparam GR The type of the digraph. |
---|
| 838 | /// \tparam LEN The type of the length map. |
---|
| 839 | template <typename GR, typename LEN> |
---|
[743] | 840 | struct BellmanFordWizardDefaultTraits { |
---|
[956] | 841 | /// The type of the digraph the algorithm runs on. |
---|
[744] | 842 | typedef GR Digraph; |
---|
[743] | 843 | |
---|
| 844 | /// \brief The type of the map that stores the arc lengths. |
---|
| 845 | /// |
---|
| 846 | /// The type of the map that stores the arc lengths. |
---|
| 847 | /// It must meet the \ref concepts::ReadMap "ReadMap" concept. |
---|
[744] | 848 | typedef LEN LengthMap; |
---|
[743] | 849 | |
---|
[744] | 850 | /// The type of the arc lengths. |
---|
| 851 | typedef typename LEN::Value Value; |
---|
[743] | 852 | |
---|
| 853 | /// \brief Operation traits for Bellman-Ford algorithm. |
---|
| 854 | /// |
---|
[744] | 855 | /// It defines the used operations and the infinity value for the |
---|
| 856 | /// given \c Value type. |
---|
[958] | 857 | /// \see BellmanFordDefaultOperationTraits |
---|
[743] | 858 | typedef BellmanFordDefaultOperationTraits<Value> OperationTraits; |
---|
| 859 | |
---|
| 860 | /// \brief The type of the map that stores the last |
---|
| 861 | /// arcs of the shortest paths. |
---|
[956] | 862 | /// |
---|
[744] | 863 | /// The type of the map that stores the last arcs of the shortest paths. |
---|
| 864 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 865 | typedef typename GR::template NodeMap<typename GR::Arc> PredMap; |
---|
[743] | 866 | |
---|
[744] | 867 | /// \brief Instantiates a \c PredMap. |
---|
[956] | 868 | /// |
---|
[744] | 869 | /// This function instantiates a \ref PredMap. |
---|
| 870 | /// \param g is the digraph to which we would like to define the |
---|
| 871 | /// \ref PredMap. |
---|
| 872 | static PredMap *createPredMap(const GR &g) { |
---|
| 873 | return new PredMap(g); |
---|
[743] | 874 | } |
---|
[744] | 875 | |
---|
| 876 | /// \brief The type of the map that stores the distances of the nodes. |
---|
[743] | 877 | /// |
---|
[744] | 878 | /// The type of the map that stores the distances of the nodes. |
---|
| 879 | /// It must conform to the \ref concepts::WriteMap "WriteMap" concept. |
---|
| 880 | typedef typename GR::template NodeMap<Value> DistMap; |
---|
| 881 | |
---|
| 882 | /// \brief Instantiates a \c DistMap. |
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[743] | 883 | /// |
---|
[956] | 884 | /// This function instantiates a \ref DistMap. |
---|
[744] | 885 | /// \param g is the digraph to which we would like to define the |
---|
| 886 | /// \ref DistMap. |
---|
| 887 | static DistMap *createDistMap(const GR &g) { |
---|
| 888 | return new DistMap(g); |
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[743] | 889 | } |
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[744] | 890 | |
---|
| 891 | ///The type of the shortest paths. |
---|
| 892 | |
---|
| 893 | ///The type of the shortest paths. |
---|
| 894 | ///It must meet the \ref concepts::Path "Path" concept. |
---|
| 895 | typedef lemon::Path<Digraph> Path; |
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[743] | 896 | }; |
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[956] | 897 | |
---|
[744] | 898 | /// \brief Default traits class used by BellmanFordWizard. |
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[743] | 899 | /// |
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[744] | 900 | /// Default traits class used by BellmanFordWizard. |
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| 901 | /// \tparam GR The type of the digraph. |
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| 902 | /// \tparam LEN The type of the length map. |
---|
| 903 | template <typename GR, typename LEN> |
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[956] | 904 | class BellmanFordWizardBase |
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[744] | 905 | : public BellmanFordWizardDefaultTraits<GR, LEN> { |
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[743] | 906 | |
---|
[744] | 907 | typedef BellmanFordWizardDefaultTraits<GR, LEN> Base; |
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[743] | 908 | protected: |
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[744] | 909 | // Type of the nodes in the digraph. |
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[743] | 910 | typedef typename Base::Digraph::Node Node; |
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| 911 | |
---|
[744] | 912 | // Pointer to the underlying digraph. |
---|
[743] | 913 | void *_graph; |
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[744] | 914 | // Pointer to the length map |
---|
[743] | 915 | void *_length; |
---|
[744] | 916 | // Pointer to the map of predecessors arcs. |
---|
[743] | 917 | void *_pred; |
---|
[744] | 918 | // Pointer to the map of distances. |
---|
[743] | 919 | void *_dist; |
---|
[744] | 920 | //Pointer to the shortest path to the target node. |
---|
| 921 | void *_path; |
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| 922 | //Pointer to the distance of the target node. |
---|
| 923 | void *_di; |
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[743] | 924 | |
---|
| 925 | public: |
---|
| 926 | /// Constructor. |
---|
[956] | 927 | |
---|
[744] | 928 | /// This constructor does not require parameters, it initiates |
---|
| 929 | /// all of the attributes to default values \c 0. |
---|
| 930 | BellmanFordWizardBase() : |
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| 931 | _graph(0), _length(0), _pred(0), _dist(0), _path(0), _di(0) {} |
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[743] | 932 | |
---|
| 933 | /// Constructor. |
---|
[956] | 934 | |
---|
[744] | 935 | /// This constructor requires two parameters, |
---|
| 936 | /// others are initiated to \c 0. |
---|
| 937 | /// \param gr The digraph the algorithm runs on. |
---|
| 938 | /// \param len The length map. |
---|
[956] | 939 | BellmanFordWizardBase(const GR& gr, |
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| 940 | const LEN& len) : |
---|
| 941 | _graph(reinterpret_cast<void*>(const_cast<GR*>(&gr))), |
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| 942 | _length(reinterpret_cast<void*>(const_cast<LEN*>(&len))), |
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[744] | 943 | _pred(0), _dist(0), _path(0), _di(0) {} |
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[743] | 944 | |
---|
| 945 | }; |
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[956] | 946 | |
---|
[744] | 947 | /// \brief Auxiliary class for the function-type interface of the |
---|
| 948 | /// \ref BellmanFord "Bellman-Ford" algorithm. |
---|
| 949 | /// |
---|
| 950 | /// This auxiliary class is created to implement the |
---|
| 951 | /// \ref bellmanFord() "function-type interface" of the |
---|
| 952 | /// \ref BellmanFord "Bellman-Ford" algorithm. |
---|
| 953 | /// It does not have own \ref run() method, it uses the |
---|
| 954 | /// functions and features of the plain \ref BellmanFord. |
---|
| 955 | /// |
---|
| 956 | /// This class should only be used through the \ref bellmanFord() |
---|
| 957 | /// function, which makes it easier to use the algorithm. |
---|
[891] | 958 | /// |
---|
| 959 | /// \tparam TR The traits class that defines various types used by the |
---|
| 960 | /// algorithm. |
---|
[744] | 961 | template<class TR> |
---|
| 962 | class BellmanFordWizard : public TR { |
---|
| 963 | typedef TR Base; |
---|
[743] | 964 | |
---|
[744] | 965 | typedef typename TR::Digraph Digraph; |
---|
[743] | 966 | |
---|
| 967 | typedef typename Digraph::Node Node; |
---|
| 968 | typedef typename Digraph::NodeIt NodeIt; |
---|
| 969 | typedef typename Digraph::Arc Arc; |
---|
| 970 | typedef typename Digraph::OutArcIt ArcIt; |
---|
[956] | 971 | |
---|
[744] | 972 | typedef typename TR::LengthMap LengthMap; |
---|
[743] | 973 | typedef typename LengthMap::Value Value; |
---|
[744] | 974 | typedef typename TR::PredMap PredMap; |
---|
| 975 | typedef typename TR::DistMap DistMap; |
---|
| 976 | typedef typename TR::Path Path; |
---|
[743] | 977 | |
---|
| 978 | public: |
---|
| 979 | /// Constructor. |
---|
[744] | 980 | BellmanFordWizard() : TR() {} |
---|
[743] | 981 | |
---|
| 982 | /// \brief Constructor that requires parameters. |
---|
| 983 | /// |
---|
| 984 | /// Constructor that requires parameters. |
---|
| 985 | /// These parameters will be the default values for the traits class. |
---|
[744] | 986 | /// \param gr The digraph the algorithm runs on. |
---|
| 987 | /// \param len The length map. |
---|
[956] | 988 | BellmanFordWizard(const Digraph& gr, const LengthMap& len) |
---|
[744] | 989 | : TR(gr, len) {} |
---|
[743] | 990 | |
---|
| 991 | /// \brief Copy constructor |
---|
[744] | 992 | BellmanFordWizard(const TR &b) : TR(b) {} |
---|
[743] | 993 | |
---|
| 994 | ~BellmanFordWizard() {} |
---|
| 995 | |
---|
[744] | 996 | /// \brief Runs the Bellman-Ford algorithm from the given source node. |
---|
[956] | 997 | /// |
---|
[744] | 998 | /// This method runs the Bellman-Ford algorithm from the given source |
---|
| 999 | /// node in order to compute the shortest path to each node. |
---|
| 1000 | void run(Node s) { |
---|
[956] | 1001 | BellmanFord<Digraph,LengthMap,TR> |
---|
| 1002 | bf(*reinterpret_cast<const Digraph*>(Base::_graph), |
---|
[743] | 1003 | *reinterpret_cast<const LengthMap*>(Base::_length)); |
---|
| 1004 | if (Base::_pred) bf.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
---|
| 1005 | if (Base::_dist) bf.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
---|
[744] | 1006 | bf.run(s); |
---|
[743] | 1007 | } |
---|
| 1008 | |
---|
[744] | 1009 | /// \brief Runs the Bellman-Ford algorithm to find the shortest path |
---|
| 1010 | /// between \c s and \c t. |
---|
[743] | 1011 | /// |
---|
[744] | 1012 | /// This method runs the Bellman-Ford algorithm from node \c s |
---|
| 1013 | /// in order to compute the shortest path to node \c t. |
---|
| 1014 | /// Actually, it computes the shortest path to each node, but using |
---|
| 1015 | /// this function you can retrieve the distance and the shortest path |
---|
| 1016 | /// for a single target node easier. |
---|
| 1017 | /// |
---|
| 1018 | /// \return \c true if \c t is reachable form \c s. |
---|
| 1019 | bool run(Node s, Node t) { |
---|
| 1020 | BellmanFord<Digraph,LengthMap,TR> |
---|
| 1021 | bf(*reinterpret_cast<const Digraph*>(Base::_graph), |
---|
| 1022 | *reinterpret_cast<const LengthMap*>(Base::_length)); |
---|
| 1023 | if (Base::_pred) bf.predMap(*reinterpret_cast<PredMap*>(Base::_pred)); |
---|
| 1024 | if (Base::_dist) bf.distMap(*reinterpret_cast<DistMap*>(Base::_dist)); |
---|
| 1025 | bf.run(s); |
---|
| 1026 | if (Base::_path) *reinterpret_cast<Path*>(Base::_path) = bf.path(t); |
---|
| 1027 | if (Base::_di) *reinterpret_cast<Value*>(Base::_di) = bf.dist(t); |
---|
| 1028 | return bf.reached(t); |
---|
[743] | 1029 | } |
---|
| 1030 | |
---|
| 1031 | template<class T> |
---|
[744] | 1032 | struct SetPredMapBase : public Base { |
---|
[743] | 1033 | typedef T PredMap; |
---|
| 1034 | static PredMap *createPredMap(const Digraph &) { return 0; }; |
---|
[744] | 1035 | SetPredMapBase(const TR &b) : TR(b) {} |
---|
[743] | 1036 | }; |
---|
[956] | 1037 | |
---|
[744] | 1038 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
| 1039 | /// the predecessor map. |
---|
[743] | 1040 | /// |
---|
[744] | 1041 | /// \ref named-templ-param "Named parameter" for setting |
---|
| 1042 | /// the map that stores the predecessor arcs of the nodes. |
---|
[743] | 1043 | template<class T> |
---|
[744] | 1044 | BellmanFordWizard<SetPredMapBase<T> > predMap(const T &t) { |
---|
[743] | 1045 | Base::_pred=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
[744] | 1046 | return BellmanFordWizard<SetPredMapBase<T> >(*this); |
---|
[743] | 1047 | } |
---|
[956] | 1048 | |
---|
[743] | 1049 | template<class T> |
---|
[744] | 1050 | struct SetDistMapBase : public Base { |
---|
[743] | 1051 | typedef T DistMap; |
---|
| 1052 | static DistMap *createDistMap(const Digraph &) { return 0; }; |
---|
[744] | 1053 | SetDistMapBase(const TR &b) : TR(b) {} |
---|
[743] | 1054 | }; |
---|
[956] | 1055 | |
---|
[744] | 1056 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
| 1057 | /// the distance map. |
---|
[743] | 1058 | /// |
---|
[744] | 1059 | /// \ref named-templ-param "Named parameter" for setting |
---|
| 1060 | /// the map that stores the distances of the nodes calculated |
---|
| 1061 | /// by the algorithm. |
---|
[743] | 1062 | template<class T> |
---|
[744] | 1063 | BellmanFordWizard<SetDistMapBase<T> > distMap(const T &t) { |
---|
[743] | 1064 | Base::_dist=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
[744] | 1065 | return BellmanFordWizard<SetDistMapBase<T> >(*this); |
---|
[743] | 1066 | } |
---|
| 1067 | |
---|
| 1068 | template<class T> |
---|
[744] | 1069 | struct SetPathBase : public Base { |
---|
| 1070 | typedef T Path; |
---|
| 1071 | SetPathBase(const TR &b) : TR(b) {} |
---|
[743] | 1072 | }; |
---|
[744] | 1073 | |
---|
| 1074 | /// \brief \ref named-func-param "Named parameter" for getting |
---|
| 1075 | /// the shortest path to the target node. |
---|
[743] | 1076 | /// |
---|
[744] | 1077 | /// \ref named-func-param "Named parameter" for getting |
---|
| 1078 | /// the shortest path to the target node. |
---|
| 1079 | template<class T> |
---|
| 1080 | BellmanFordWizard<SetPathBase<T> > path(const T &t) |
---|
| 1081 | { |
---|
| 1082 | Base::_path=reinterpret_cast<void*>(const_cast<T*>(&t)); |
---|
| 1083 | return BellmanFordWizard<SetPathBase<T> >(*this); |
---|
| 1084 | } |
---|
| 1085 | |
---|
| 1086 | /// \brief \ref named-func-param "Named parameter" for getting |
---|
| 1087 | /// the distance of the target node. |
---|
[743] | 1088 | /// |
---|
[744] | 1089 | /// \ref named-func-param "Named parameter" for getting |
---|
| 1090 | /// the distance of the target node. |
---|
| 1091 | BellmanFordWizard dist(const Value &d) |
---|
| 1092 | { |
---|
| 1093 | Base::_di=reinterpret_cast<void*>(const_cast<Value*>(&d)); |
---|
[743] | 1094 | return *this; |
---|
| 1095 | } |
---|
[956] | 1096 | |
---|
[743] | 1097 | }; |
---|
[956] | 1098 | |
---|
[744] | 1099 | /// \brief Function type interface for the \ref BellmanFord "Bellman-Ford" |
---|
| 1100 | /// algorithm. |
---|
[743] | 1101 | /// |
---|
| 1102 | /// \ingroup shortest_path |
---|
[744] | 1103 | /// Function type interface for the \ref BellmanFord "Bellman-Ford" |
---|
| 1104 | /// algorithm. |
---|
[743] | 1105 | /// |
---|
[956] | 1106 | /// This function also has several \ref named-templ-func-param |
---|
| 1107 | /// "named parameters", they are declared as the members of class |
---|
[743] | 1108 | /// \ref BellmanFordWizard. |
---|
[744] | 1109 | /// The following examples show how to use these parameters. |
---|
| 1110 | /// \code |
---|
| 1111 | /// // Compute shortest path from node s to each node |
---|
| 1112 | /// bellmanFord(g,length).predMap(preds).distMap(dists).run(s); |
---|
| 1113 | /// |
---|
| 1114 | /// // Compute shortest path from s to t |
---|
| 1115 | /// bool reached = bellmanFord(g,length).path(p).dist(d).run(s,t); |
---|
| 1116 | /// \endcode |
---|
[743] | 1117 | /// \warning Don't forget to put the \ref BellmanFordWizard::run() "run()" |
---|
| 1118 | /// to the end of the parameter list. |
---|
| 1119 | /// \sa BellmanFordWizard |
---|
| 1120 | /// \sa BellmanFord |
---|
[744] | 1121 | template<typename GR, typename LEN> |
---|
| 1122 | BellmanFordWizard<BellmanFordWizardBase<GR,LEN> > |
---|
| 1123 | bellmanFord(const GR& digraph, |
---|
[956] | 1124 | const LEN& length) |
---|
[744] | 1125 | { |
---|
| 1126 | return BellmanFordWizard<BellmanFordWizardBase<GR,LEN> >(digraph, length); |
---|
[743] | 1127 | } |
---|
| 1128 | |
---|
| 1129 | } //END OF NAMESPACE LEMON |
---|
| 1130 | |
---|
| 1131 | #endif |
---|
| 1132 | |
---|