[103] | 1 | /* -*- C++ -*- |
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| 2 | * |
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| 3 | * This file is a part of LEMON, a generic C++ optimization library |
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| 4 | * |
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| 5 | * Copyright (C) 2003-2008 |
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| 6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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| 7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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| 8 | * |
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| 9 | * Permission to use, modify and distribute this software is granted |
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| 10 | * provided that this copyright notice appears in all copies. For |
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| 11 | * precise terms see the accompanying LICENSE file. |
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| 12 | * |
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| 13 | * This software is provided "AS IS" with no warranty of any kind, |
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| 14 | * express or implied, and with no claim as to its suitability for any |
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| 15 | * purpose. |
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| 16 | * |
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| 17 | */ |
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| 18 | |
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| 19 | #ifndef LEMON_KRUSKAL_H |
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| 20 | #define LEMON_KRUSKAL_H |
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| 21 | |
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| 22 | #include <algorithm> |
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| 23 | #include <vector> |
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| 24 | #include <lemon/unionfind.h> |
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| 25 | // #include <lemon/graph_utils.h> |
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| 26 | #include <lemon/maps.h> |
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| 27 | |
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| 28 | // #include <lemon/radix_sort.h> |
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| 29 | |
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| 30 | #include <lemon/bits/utility.h> |
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| 31 | #include <lemon/bits/traits.h> |
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| 32 | |
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| 33 | ///\ingroup spantree |
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| 34 | ///\file |
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| 35 | ///\brief Kruskal's algorithm to compute a minimum cost tree |
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| 36 | /// |
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| 37 | ///Kruskal's algorithm to compute a minimum cost tree. |
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| 38 | /// |
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| 39 | |
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| 40 | namespace lemon { |
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| 41 | |
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| 42 | namespace _kruskal_bits { |
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| 43 | |
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| 44 | // Kruskal for directed graphs. |
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| 45 | |
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| 46 | template <typename Digraph, typename In, typename Out> |
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| 47 | typename disable_if<lemon::UndirectedTagIndicator<Digraph>, |
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| 48 | typename In::value_type::second_type >::type |
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| 49 | kruskal(const Digraph& digraph, const In& in, Out& out,dummy<0> = 0) { |
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| 50 | typedef typename In::value_type::second_type Value; |
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| 51 | typedef typename Digraph::template NodeMap<int> IndexMap; |
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| 52 | typedef typename Digraph::Node Node; |
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| 53 | |
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| 54 | IndexMap index(digraph); |
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| 55 | UnionFind<IndexMap> uf(index); |
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| 56 | for (typename Digraph::NodeIt it(digraph); it != INVALID; ++it) { |
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| 57 | uf.insert(it); |
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| 58 | } |
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| 59 | |
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| 60 | Value tree_value = 0; |
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| 61 | for (typename In::const_iterator it = in.begin(); it != in.end(); ++it) { |
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| 62 | if (uf.join(digraph.target(it->first),digraph.source(it->first))) { |
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| 63 | out.set(it->first, true); |
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| 64 | tree_value += it->second; |
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| 65 | } |
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| 66 | else { |
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| 67 | out.set(it->first, false); |
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| 68 | } |
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| 69 | } |
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| 70 | return tree_value; |
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| 71 | } |
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| 72 | |
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| 73 | // Kruskal for undirected graphs. |
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| 74 | |
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| 75 | template <typename Graph, typename In, typename Out> |
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| 76 | typename enable_if<lemon::UndirectedTagIndicator<Graph>, |
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| 77 | typename In::value_type::second_type >::type |
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| 78 | kruskal(const Graph& graph, const In& in, Out& out,dummy<1> = 1) { |
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| 79 | typedef typename In::value_type::second_type Value; |
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| 80 | typedef typename Graph::template NodeMap<int> IndexMap; |
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| 81 | typedef typename Graph::Node Node; |
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| 82 | |
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| 83 | IndexMap index(graph); |
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| 84 | UnionFind<IndexMap> uf(index); |
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| 85 | for (typename Graph::NodeIt it(graph); it != INVALID; ++it) { |
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| 86 | uf.insert(it); |
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| 87 | } |
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| 88 | |
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| 89 | Value tree_value = 0; |
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| 90 | for (typename In::const_iterator it = in.begin(); it != in.end(); ++it) { |
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| 91 | if (uf.join(graph.u(it->first),graph.v(it->first))) { |
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| 92 | out.set(it->first, true); |
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| 93 | tree_value += it->second; |
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| 94 | } |
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| 95 | else { |
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| 96 | out.set(it->first, false); |
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| 97 | } |
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| 98 | } |
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| 99 | return tree_value; |
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| 100 | } |
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| 101 | |
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| 102 | |
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| 103 | template <typename Sequence> |
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| 104 | struct PairComp { |
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| 105 | typedef typename Sequence::value_type Value; |
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| 106 | bool operator()(const Value& left, const Value& right) { |
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| 107 | return left.second < right.second; |
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| 108 | } |
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| 109 | }; |
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| 110 | |
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| 111 | template <typename In, typename Enable = void> |
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| 112 | struct SequenceInputIndicator { |
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| 113 | static const bool value = false; |
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| 114 | }; |
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| 115 | |
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| 116 | template <typename In> |
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| 117 | struct SequenceInputIndicator<In, |
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| 118 | typename exists<typename In::value_type::first_type>::type> { |
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| 119 | static const bool value = true; |
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| 120 | }; |
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| 121 | |
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| 122 | template <typename In, typename Enable = void> |
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| 123 | struct MapInputIndicator { |
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| 124 | static const bool value = false; |
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| 125 | }; |
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| 126 | |
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| 127 | template <typename In> |
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| 128 | struct MapInputIndicator<In, |
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| 129 | typename exists<typename In::Value>::type> { |
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| 130 | static const bool value = true; |
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| 131 | }; |
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| 132 | |
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| 133 | template <typename In, typename Enable = void> |
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| 134 | struct SequenceOutputIndicator { |
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| 135 | static const bool value = false; |
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| 136 | }; |
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| 137 | |
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| 138 | template <typename Out> |
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| 139 | struct SequenceOutputIndicator<Out, |
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| 140 | typename exists<typename Out::value_type>::type> { |
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| 141 | static const bool value = true; |
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| 142 | }; |
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| 143 | |
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| 144 | template <typename Out, typename Enable = void> |
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| 145 | struct MapOutputIndicator { |
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| 146 | static const bool value = false; |
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| 147 | }; |
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| 148 | |
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| 149 | template <typename Out> |
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| 150 | struct MapOutputIndicator<Out, |
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| 151 | typename exists<typename Out::Value>::type> { |
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| 152 | static const bool value = true; |
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| 153 | }; |
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| 154 | |
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| 155 | template <typename In, typename InEnable = void> |
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| 156 | struct KruskalValueSelector {}; |
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| 157 | |
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| 158 | template <typename In> |
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| 159 | struct KruskalValueSelector<In, |
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| 160 | typename enable_if<SequenceInputIndicator<In>, void>::type> |
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| 161 | { |
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| 162 | typedef typename In::value_type::second_type Value; |
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| 163 | }; |
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| 164 | |
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| 165 | template <typename In> |
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| 166 | struct KruskalValueSelector<In, |
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| 167 | typename enable_if<MapInputIndicator<In>, void>::type> |
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| 168 | { |
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| 169 | typedef typename In::Value Value; |
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| 170 | }; |
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| 171 | |
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| 172 | template <typename Graph, typename In, typename Out, |
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| 173 | typename InEnable = void> |
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| 174 | struct KruskalInputSelector {}; |
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| 175 | |
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| 176 | template <typename Graph, typename In, typename Out, |
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| 177 | typename InEnable = void> |
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| 178 | struct KruskalOutputSelector {}; |
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| 179 | |
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| 180 | template <typename Graph, typename In, typename Out> |
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| 181 | struct KruskalInputSelector<Graph, In, Out, |
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| 182 | typename enable_if<SequenceInputIndicator<In>, void>::type > |
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| 183 | { |
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| 184 | typedef typename In::value_type::second_type Value; |
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| 185 | |
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| 186 | static Value kruskal(const Graph& graph, const In& in, Out& out) { |
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| 187 | return KruskalOutputSelector<Graph, In, Out>:: |
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| 188 | kruskal(graph, in, out); |
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| 189 | } |
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| 190 | |
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| 191 | }; |
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| 192 | |
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| 193 | template <typename Graph, typename In, typename Out> |
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| 194 | struct KruskalInputSelector<Graph, In, Out, |
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| 195 | typename enable_if<MapInputIndicator<In>, void>::type > |
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| 196 | { |
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| 197 | typedef typename In::Value Value; |
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| 198 | static Value kruskal(const Graph& graph, const In& in, Out& out) { |
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| 199 | typedef typename In::Key MapArc; |
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| 200 | typedef typename In::Value Value; |
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| 201 | typedef typename ItemSetTraits<Graph, MapArc>::ItemIt MapArcIt; |
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| 202 | typedef std::vector<std::pair<MapArc, Value> > Sequence; |
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| 203 | Sequence seq; |
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| 204 | |
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| 205 | for (MapArcIt it(graph); it != INVALID; ++it) { |
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| 206 | seq.push_back(std::make_pair(it, in[it])); |
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| 207 | } |
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| 208 | |
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| 209 | std::sort(seq.begin(), seq.end(), PairComp<Sequence>()); |
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| 210 | return KruskalOutputSelector<Graph, Sequence, Out>:: |
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| 211 | kruskal(graph, seq, out); |
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| 212 | } |
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| 213 | }; |
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| 214 | |
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[136] | 215 | template <typename T> |
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| 216 | struct RemoveConst { |
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| 217 | typedef T type; |
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| 218 | }; |
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| 219 | |
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| 220 | template <typename T> |
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| 221 | struct RemoveConst<const T> { |
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| 222 | typedef T type; |
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| 223 | }; |
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| 224 | |
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[103] | 225 | template <typename Graph, typename In, typename Out> |
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| 226 | struct KruskalOutputSelector<Graph, In, Out, |
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| 227 | typename enable_if<SequenceOutputIndicator<Out>, void>::type > |
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| 228 | { |
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| 229 | typedef typename In::value_type::second_type Value; |
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| 230 | |
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| 231 | static Value kruskal(const Graph& graph, const In& in, Out& out) { |
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[167] | 232 | typedef LoggerBoolMap<typename RemoveConst<Out>::type> Map; |
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[103] | 233 | Map map(out); |
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| 234 | return _kruskal_bits::kruskal(graph, in, map); |
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| 235 | } |
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| 236 | |
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| 237 | }; |
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| 238 | |
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| 239 | template <typename Graph, typename In, typename Out> |
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| 240 | struct KruskalOutputSelector<Graph, In, Out, |
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| 241 | typename enable_if<MapOutputIndicator<Out>, void>::type > |
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| 242 | { |
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| 243 | typedef typename In::value_type::second_type Value; |
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| 244 | |
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| 245 | static Value kruskal(const Graph& graph, const In& in, Out& out) { |
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| 246 | return _kruskal_bits::kruskal(graph, in, out); |
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| 247 | } |
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| 248 | }; |
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| 249 | |
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| 250 | } |
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| 251 | |
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| 252 | /// \ingroup spantree |
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| 253 | /// |
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| 254 | /// \brief Kruskal's algorithm to find a minimum cost tree of a graph. |
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| 255 | /// |
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| 256 | /// This function runs Kruskal's algorithm to find a minimum cost tree. |
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| 257 | /// Due to some C++ hacking, it accepts various input and output types. |
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| 258 | /// |
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| 259 | /// \param g The graph the algorithm runs on. |
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| 260 | /// It can be either \ref concepts::Digraph "directed" or |
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| 261 | /// \ref concepts::Graph "undirected". |
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| 262 | /// If the graph is directed, the algorithm consider it to be |
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| 263 | /// undirected by disregarding the direction of the arcs. |
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| 264 | /// |
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| 265 | /// \param in This object is used to describe the arc costs. It can be one |
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| 266 | /// of the following choices. |
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| 267 | /// - An STL compatible 'Forward Container' with |
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| 268 | /// <tt>std::pair<GR::Edge,X></tt> or |
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| 269 | /// <tt>std::pair<GR::Arc,X></tt> as its <tt>value_type</tt>, where |
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| 270 | /// \c X is the type of the costs. The pairs indicates the arcs |
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| 271 | /// along with the assigned cost. <em>They must be in a |
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| 272 | /// cost-ascending order.</em> |
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| 273 | /// - Any readable Arc map. The values of the map indicate the arc costs. |
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| 274 | /// |
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| 275 | /// \retval out Here we also have a choise. |
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| 276 | /// - It can be a writable \c bool arc map. After running the |
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| 277 | /// algorithm this will contain the found minimum cost spanning |
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| 278 | /// tree: the value of an arc will be set to \c true if it belongs |
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| 279 | /// to the tree, otherwise it will be set to \c false. The value of |
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| 280 | /// each arc will be set exactly once. |
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| 281 | /// - It can also be an iteraror of an STL Container with |
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| 282 | /// <tt>GR::Edge</tt> or <tt>GR::Arc</tt> as its |
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| 283 | /// <tt>value_type</tt>. The algorithm copies the elements of the |
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| 284 | /// found tree into this sequence. For example, if we know that the |
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| 285 | /// spanning tree of the graph \c g has say 53 arcs, then we can |
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| 286 | /// put its arcs into an STL vector \c tree with a code like this. |
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| 287 | ///\code |
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| 288 | /// std::vector<Arc> tree(53); |
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| 289 | /// kruskal(g,cost,tree.begin()); |
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| 290 | ///\endcode |
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| 291 | /// Or if we don't know in advance the size of the tree, we can |
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| 292 | /// write this. |
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| 293 | ///\code std::vector<Arc> tree; |
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| 294 | /// kruskal(g,cost,std::back_inserter(tree)); |
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| 295 | ///\endcode |
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| 296 | /// |
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| 297 | /// \return The total cost of the found tree. |
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| 298 | /// |
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| 299 | /// \warning If kruskal runs on an be consistent of using the same |
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| 300 | /// Arc type for input and output. |
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| 301 | /// |
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| 302 | |
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| 303 | #ifdef DOXYGEN |
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| 304 | template <class Graph, class In, class Out> |
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| 305 | Value kruskal(GR const& g, const In& in, Out& out) |
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| 306 | #else |
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| 307 | template <class Graph, class In, class Out> |
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| 308 | inline typename _kruskal_bits::KruskalValueSelector<In>::Value |
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| 309 | kruskal(const Graph& graph, const In& in, Out& out) |
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| 310 | #endif |
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| 311 | { |
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| 312 | return _kruskal_bits::KruskalInputSelector<Graph, In, Out>:: |
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| 313 | kruskal(graph, in, out); |
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| 314 | } |
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| 315 | |
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| 316 | |
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| 317 | |
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| 318 | |
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| 319 | template <class Graph, class In, class Out> |
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| 320 | inline typename _kruskal_bits::KruskalValueSelector<In>::Value |
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| 321 | kruskal(const Graph& graph, const In& in, const Out& out) |
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| 322 | { |
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| 323 | return _kruskal_bits::KruskalInputSelector<Graph, In, const Out>:: |
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| 324 | kruskal(graph, in, out); |
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| 325 | } |
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| 326 | |
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| 327 | } //namespace lemon |
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| 328 | |
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| 329 | #endif //LEMON_KRUSKAL_H |
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