1 | /* -*- mode: C++; indent-tabs-mode: nil; -*- |
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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) 2003-2009 |
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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_BUCKET_HEAP_H |
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20 | #define LEMON_BUCKET_HEAP_H |
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21 | |
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22 | ///\ingroup auxdat |
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23 | ///\file |
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24 | ///\brief Bucket Heap implementation. |
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25 | |
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26 | #include <vector> |
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27 | #include <utility> |
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28 | #include <functional> |
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29 | |
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30 | namespace lemon { |
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31 | |
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32 | namespace _bucket_heap_bits { |
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33 | |
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34 | template <bool minimize> |
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35 | struct DirectionTraits { |
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36 | static bool less(int left, int right) { |
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37 | return left < right; |
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38 | } |
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39 | static void increase(int& value) { |
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40 | ++value; |
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41 | } |
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42 | }; |
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43 | |
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44 | template <> |
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45 | struct DirectionTraits<false> { |
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46 | static bool less(int left, int right) { |
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47 | return left > right; |
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48 | } |
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49 | static void increase(int& value) { |
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50 | --value; |
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51 | } |
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52 | }; |
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53 | |
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54 | } |
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55 | |
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56 | /// \ingroup auxdat |
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57 | /// |
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58 | /// \brief A Bucket Heap implementation. |
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59 | /// |
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60 | /// This class implements the \e bucket \e heap data structure. A \e heap |
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61 | /// is a data structure for storing items with specified values called \e |
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62 | /// priorities in such a way that finding the item with minimum priority is |
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63 | /// efficient. The bucket heap is very simple implementation, it can store |
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64 | /// only integer priorities and it stores for each priority in the |
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65 | /// \f$ [0..C) \f$ range a list of items. So it should be used only when |
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66 | /// the priorities are small. It is not intended to use as dijkstra heap. |
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67 | /// |
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68 | /// \param _ItemIntMap A read and writable Item int map, used internally |
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69 | /// to handle the cross references. |
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70 | /// \param minimize If the given parameter is true then the heap gives back |
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71 | /// the lowest priority. |
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72 | template <typename _ItemIntMap, bool minimize = true> |
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73 | class BucketHeap { |
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74 | |
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75 | public: |
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76 | /// \e |
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77 | typedef typename _ItemIntMap::Key Item; |
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78 | /// \e |
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79 | typedef int Prio; |
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80 | /// \e |
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81 | typedef std::pair<Item, Prio> Pair; |
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82 | /// \e |
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83 | typedef _ItemIntMap ItemIntMap; |
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84 | |
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85 | private: |
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86 | |
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87 | typedef _bucket_heap_bits::DirectionTraits<minimize> Direction; |
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88 | |
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89 | public: |
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90 | |
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91 | /// \brief Type to represent the items states. |
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92 | /// |
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93 | /// Each Item element have a state associated to it. It may be "in heap", |
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94 | /// "pre heap" or "post heap". The latter two are indifferent from the |
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95 | /// heap's point of view, but may be useful to the user. |
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96 | /// |
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97 | /// The ItemIntMap \e should be initialized in such way that it maps |
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98 | /// PRE_HEAP (-1) to any element to be put in the heap... |
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99 | enum State { |
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100 | IN_HEAP = 0, |
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101 | PRE_HEAP = -1, |
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102 | POST_HEAP = -2 |
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103 | }; |
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104 | |
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105 | public: |
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106 | /// \brief The constructor. |
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107 | /// |
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108 | /// The constructor. |
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109 | /// \param _index should be given to the constructor, since it is used |
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110 | /// internally to handle the cross references. The value of the map |
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111 | /// should be PRE_HEAP (-1) for each element. |
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112 | explicit BucketHeap(ItemIntMap &_index) : index(_index), minimal(0) {} |
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113 | |
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114 | /// The number of items stored in the heap. |
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115 | /// |
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116 | /// \brief Returns the number of items stored in the heap. |
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117 | int size() const { return data.size(); } |
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118 | |
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119 | /// \brief Checks if the heap stores no items. |
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120 | /// |
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121 | /// Returns \c true if and only if the heap stores no items. |
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122 | bool empty() const { return data.empty(); } |
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123 | |
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124 | /// \brief Make empty this heap. |
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125 | /// |
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126 | /// Make empty this heap. It does not change the cross reference |
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127 | /// map. If you want to reuse a heap what is not surely empty you |
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128 | /// should first clear the heap and after that you should set the |
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129 | /// cross reference map for each item to \c PRE_HEAP. |
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130 | void clear() { |
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131 | data.clear(); first.clear(); minimal = 0; |
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132 | } |
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133 | |
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134 | private: |
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135 | |
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136 | void relocate_last(int idx) { |
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137 | if (idx + 1 < int(data.size())) { |
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138 | data[idx] = data.back(); |
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139 | if (data[idx].prev != -1) { |
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140 | data[data[idx].prev].next = idx; |
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141 | } else { |
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142 | first[data[idx].value] = idx; |
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143 | } |
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144 | if (data[idx].next != -1) { |
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145 | data[data[idx].next].prev = idx; |
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146 | } |
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147 | index[data[idx].item] = idx; |
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148 | } |
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149 | data.pop_back(); |
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150 | } |
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151 | |
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152 | void unlace(int idx) { |
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153 | if (data[idx].prev != -1) { |
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154 | data[data[idx].prev].next = data[idx].next; |
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155 | } else { |
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156 | first[data[idx].value] = data[idx].next; |
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157 | } |
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158 | if (data[idx].next != -1) { |
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159 | data[data[idx].next].prev = data[idx].prev; |
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160 | } |
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161 | } |
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162 | |
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163 | void lace(int idx) { |
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164 | if (int(first.size()) <= data[idx].value) { |
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165 | first.resize(data[idx].value + 1, -1); |
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166 | } |
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167 | data[idx].next = first[data[idx].value]; |
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168 | if (data[idx].next != -1) { |
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169 | data[data[idx].next].prev = idx; |
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170 | } |
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171 | first[data[idx].value] = idx; |
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172 | data[idx].prev = -1; |
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173 | } |
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174 | |
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175 | public: |
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176 | /// \brief Insert a pair of item and priority into the heap. |
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177 | /// |
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178 | /// Adds \c p.first to the heap with priority \c p.second. |
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179 | /// \param p The pair to insert. |
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180 | void push(const Pair& p) { |
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181 | push(p.first, p.second); |
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182 | } |
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183 | |
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184 | /// \brief Insert an item into the heap with the given priority. |
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185 | /// |
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186 | /// Adds \c i to the heap with priority \c p. |
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187 | /// \param i The item to insert. |
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188 | /// \param p The priority of the item. |
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189 | void push(const Item &i, const Prio &p) { |
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190 | int idx = data.size(); |
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191 | index[i] = idx; |
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192 | data.push_back(BucketItem(i, p)); |
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193 | lace(idx); |
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194 | if (Direction::less(p, minimal)) { |
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195 | minimal = p; |
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196 | } |
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197 | } |
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198 | |
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199 | /// \brief Returns the item with minimum priority. |
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200 | /// |
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201 | /// This method returns the item with minimum priority. |
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202 | /// \pre The heap must be nonempty. |
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203 | Item top() const { |
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204 | while (first[minimal] == -1) { |
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205 | Direction::increase(minimal); |
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206 | } |
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207 | return data[first[minimal]].item; |
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208 | } |
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209 | |
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210 | /// \brief Returns the minimum priority. |
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211 | /// |
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212 | /// It returns the minimum priority. |
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213 | /// \pre The heap must be nonempty. |
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214 | Prio prio() const { |
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215 | while (first[minimal] == -1) { |
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216 | Direction::increase(minimal); |
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217 | } |
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218 | return minimal; |
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219 | } |
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220 | |
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221 | /// \brief Deletes the item with minimum priority. |
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222 | /// |
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223 | /// This method deletes the item with minimum priority from the heap. |
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224 | /// \pre The heap must be non-empty. |
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225 | void pop() { |
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226 | while (first[minimal] == -1) { |
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227 | Direction::increase(minimal); |
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228 | } |
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229 | int idx = first[minimal]; |
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230 | index[data[idx].item] = -2; |
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231 | unlace(idx); |
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232 | relocate_last(idx); |
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233 | } |
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234 | |
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235 | /// \brief Deletes \c i from the heap. |
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236 | /// |
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237 | /// This method deletes item \c i from the heap, if \c i was |
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238 | /// already stored in the heap. |
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239 | /// \param i The item to erase. |
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240 | void erase(const Item &i) { |
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241 | int idx = index[i]; |
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242 | index[data[idx].item] = -2; |
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243 | unlace(idx); |
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244 | relocate_last(idx); |
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245 | } |
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246 | |
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247 | |
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248 | /// \brief Returns the priority of \c i. |
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249 | /// |
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250 | /// This function returns the priority of item \c i. |
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251 | /// \pre \c i must be in the heap. |
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252 | /// \param i The item. |
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253 | Prio operator[](const Item &i) const { |
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254 | int idx = index[i]; |
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255 | return data[idx].value; |
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256 | } |
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257 | |
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258 | /// \brief \c i gets to the heap with priority \c p independently |
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259 | /// if \c i was already there. |
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260 | /// |
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261 | /// This method calls \ref push(\c i, \c p) if \c i is not stored |
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262 | /// in the heap and sets the priority of \c i to \c p otherwise. |
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263 | /// \param i The item. |
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264 | /// \param p The priority. |
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265 | void set(const Item &i, const Prio &p) { |
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266 | int idx = index[i]; |
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267 | if (idx < 0) { |
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268 | push(i, p); |
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269 | } else if (Direction::less(p, data[idx].value)) { |
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270 | decrease(i, p); |
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271 | } else { |
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272 | increase(i, p); |
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273 | } |
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274 | } |
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275 | |
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276 | /// \brief Decreases the priority of \c i to \c p. |
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277 | /// |
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278 | /// This method decreases the priority of item \c i to \c p. |
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279 | /// \pre \c i must be stored in the heap with priority at least \c |
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280 | /// p relative to \c Compare. |
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281 | /// \param i The item. |
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282 | /// \param p The priority. |
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283 | void decrease(const Item &i, const Prio &p) { |
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284 | int idx = index[i]; |
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285 | unlace(idx); |
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286 | data[idx].value = p; |
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287 | if (Direction::less(p, minimal)) { |
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288 | minimal = p; |
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289 | } |
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290 | lace(idx); |
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291 | } |
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292 | |
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293 | /// \brief Increases the priority of \c i to \c p. |
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294 | /// |
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295 | /// This method sets the priority of item \c i to \c p. |
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296 | /// \pre \c i must be stored in the heap with priority at most \c |
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297 | /// p relative to \c Compare. |
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298 | /// \param i The item. |
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299 | /// \param p The priority. |
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300 | void increase(const Item &i, const Prio &p) { |
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301 | int idx = index[i]; |
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302 | unlace(idx); |
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303 | data[idx].value = p; |
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304 | lace(idx); |
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305 | } |
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306 | |
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307 | /// \brief Returns if \c item is in, has already been in, or has |
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308 | /// never been in the heap. |
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309 | /// |
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310 | /// This method returns PRE_HEAP if \c item has never been in the |
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311 | /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP |
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312 | /// otherwise. In the latter case it is possible that \c item will |
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313 | /// get back to the heap again. |
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314 | /// \param i The item. |
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315 | State state(const Item &i) const { |
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316 | int idx = index[i]; |
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317 | if (idx >= 0) idx = 0; |
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318 | return State(idx); |
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319 | } |
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320 | |
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321 | /// \brief Sets the state of the \c item in the heap. |
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322 | /// |
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323 | /// Sets the state of the \c item in the heap. It can be used to |
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324 | /// manually clear the heap when it is important to achive the |
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325 | /// better time complexity. |
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326 | /// \param i The item. |
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327 | /// \param st The state. It should not be \c IN_HEAP. |
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328 | void state(const Item& i, State st) { |
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329 | switch (st) { |
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330 | case POST_HEAP: |
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331 | case PRE_HEAP: |
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332 | if (state(i) == IN_HEAP) { |
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333 | erase(i); |
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334 | } |
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335 | index[i] = st; |
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336 | break; |
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337 | case IN_HEAP: |
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338 | break; |
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339 | } |
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340 | } |
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341 | |
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342 | private: |
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343 | |
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344 | struct BucketItem { |
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345 | BucketItem(const Item& _item, int _value) |
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346 | : item(_item), value(_value) {} |
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347 | |
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348 | Item item; |
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349 | int value; |
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350 | |
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351 | int prev, next; |
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352 | }; |
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353 | |
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354 | ItemIntMap& index; |
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355 | std::vector<int> first; |
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356 | std::vector<BucketItem> data; |
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357 | mutable int minimal; |
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358 | |
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359 | }; // class BucketHeap |
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360 | |
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361 | /// \ingroup auxdat |
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362 | /// |
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363 | /// \brief A Simplified Bucket Heap implementation. |
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364 | /// |
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365 | /// This class implements a simplified \e bucket \e heap data |
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366 | /// structure. It does not provide some functionality but it faster |
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367 | /// and simplier data structure than the BucketHeap. The main |
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368 | /// difference is that the BucketHeap stores for every key a double |
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369 | /// linked list while this class stores just simple lists. In the |
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370 | /// other way it does not support erasing each elements just the |
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371 | /// minimal and it does not supports key increasing, decreasing. |
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372 | /// |
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373 | /// \param _ItemIntMap A read and writable Item int map, used internally |
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374 | /// to handle the cross references. |
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375 | /// \param minimize If the given parameter is true then the heap gives back |
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376 | /// the lowest priority. |
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377 | /// |
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378 | /// \sa BucketHeap |
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379 | template <typename _ItemIntMap, bool minimize = true > |
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380 | class SimpleBucketHeap { |
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381 | |
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382 | public: |
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383 | typedef typename _ItemIntMap::Key Item; |
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384 | typedef int Prio; |
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385 | typedef std::pair<Item, Prio> Pair; |
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386 | typedef _ItemIntMap ItemIntMap; |
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387 | |
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388 | private: |
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389 | |
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390 | typedef _bucket_heap_bits::DirectionTraits<minimize> Direction; |
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391 | |
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392 | public: |
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393 | |
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394 | /// \brief Type to represent the items states. |
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395 | /// |
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396 | /// Each Item element have a state associated to it. It may be "in heap", |
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397 | /// "pre heap" or "post heap". The latter two are indifferent from the |
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398 | /// heap's point of view, but may be useful to the user. |
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399 | /// |
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400 | /// The ItemIntMap \e should be initialized in such way that it maps |
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401 | /// PRE_HEAP (-1) to any element to be put in the heap... |
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402 | enum State { |
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403 | IN_HEAP = 0, |
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404 | PRE_HEAP = -1, |
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405 | POST_HEAP = -2 |
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406 | }; |
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407 | |
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408 | public: |
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409 | |
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410 | /// \brief The constructor. |
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411 | /// |
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412 | /// The constructor. |
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413 | /// \param _index should be given to the constructor, since it is used |
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414 | /// internally to handle the cross references. The value of the map |
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415 | /// should be PRE_HEAP (-1) for each element. |
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416 | explicit SimpleBucketHeap(ItemIntMap &_index) |
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417 | : index(_index), free(-1), num(0), minimal(0) {} |
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418 | |
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419 | /// \brief Returns the number of items stored in the heap. |
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420 | /// |
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421 | /// The number of items stored in the heap. |
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422 | int size() const { return num; } |
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423 | |
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424 | /// \brief Checks if the heap stores no items. |
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425 | /// |
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426 | /// Returns \c true if and only if the heap stores no items. |
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427 | bool empty() const { return num == 0; } |
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428 | |
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429 | /// \brief Make empty this heap. |
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430 | /// |
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431 | /// Make empty this heap. It does not change the cross reference |
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432 | /// map. If you want to reuse a heap what is not surely empty you |
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433 | /// should first clear the heap and after that you should set the |
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434 | /// cross reference map for each item to \c PRE_HEAP. |
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435 | void clear() { |
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436 | data.clear(); first.clear(); free = -1; num = 0; minimal = 0; |
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437 | } |
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438 | |
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439 | /// \brief Insert a pair of item and priority into the heap. |
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440 | /// |
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441 | /// Adds \c p.first to the heap with priority \c p.second. |
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442 | /// \param p The pair to insert. |
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443 | void push(const Pair& p) { |
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444 | push(p.first, p.second); |
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445 | } |
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446 | |
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447 | /// \brief Insert an item into the heap with the given priority. |
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448 | /// |
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449 | /// Adds \c i to the heap with priority \c p. |
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450 | /// \param i The item to insert. |
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451 | /// \param p The priority of the item. |
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452 | void push(const Item &i, const Prio &p) { |
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453 | int idx; |
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454 | if (free == -1) { |
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455 | idx = data.size(); |
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456 | data.push_back(BucketItem(i)); |
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457 | } else { |
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458 | idx = free; |
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459 | free = data[idx].next; |
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460 | data[idx].item = i; |
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461 | } |
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462 | index[i] = idx; |
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463 | if (p >= int(first.size())) first.resize(p + 1, -1); |
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464 | data[idx].next = first[p]; |
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465 | first[p] = idx; |
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466 | if (Direction::less(p, minimal)) { |
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467 | minimal = p; |
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468 | } |
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469 | ++num; |
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470 | } |
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471 | |
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472 | /// \brief Returns the item with minimum priority. |
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473 | /// |
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474 | /// This method returns the item with minimum priority. |
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475 | /// \pre The heap must be nonempty. |
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476 | Item top() const { |
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477 | while (first[minimal] == -1) { |
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478 | Direction::increase(minimal); |
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479 | } |
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480 | return data[first[minimal]].item; |
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481 | } |
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482 | |
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483 | /// \brief Returns the minimum priority. |
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484 | /// |
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485 | /// It returns the minimum priority. |
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486 | /// \pre The heap must be nonempty. |
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487 | Prio prio() const { |
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488 | while (first[minimal] == -1) { |
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489 | Direction::increase(minimal); |
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490 | } |
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491 | return minimal; |
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492 | } |
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493 | |
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494 | /// \brief Deletes the item with minimum priority. |
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495 | /// |
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496 | /// This method deletes the item with minimum priority from the heap. |
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497 | /// \pre The heap must be non-empty. |
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498 | void pop() { |
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499 | while (first[minimal] == -1) { |
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500 | Direction::increase(minimal); |
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501 | } |
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502 | int idx = first[minimal]; |
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503 | index[data[idx].item] = -2; |
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504 | first[minimal] = data[idx].next; |
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505 | data[idx].next = free; |
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506 | free = idx; |
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507 | --num; |
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508 | } |
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509 | |
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510 | /// \brief Returns the priority of \c i. |
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511 | /// |
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512 | /// This function returns the priority of item \c i. |
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513 | /// \warning This operator is not a constant time function |
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514 | /// because it scans the whole data structure to find the proper |
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515 | /// value. |
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516 | /// \pre \c i must be in the heap. |
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517 | /// \param i The item. |
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518 | Prio operator[](const Item &i) const { |
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519 | for (int k = 0; k < first.size(); ++k) { |
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520 | int idx = first[k]; |
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521 | while (idx != -1) { |
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522 | if (data[idx].item == i) { |
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523 | return k; |
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524 | } |
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525 | idx = data[idx].next; |
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526 | } |
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527 | } |
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528 | return -1; |
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529 | } |
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530 | |
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531 | /// \brief Returns if \c item is in, has already been in, or has |
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532 | /// never been in the heap. |
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533 | /// |
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534 | /// This method returns PRE_HEAP if \c item has never been in the |
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535 | /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP |
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536 | /// otherwise. In the latter case it is possible that \c item will |
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537 | /// get back to the heap again. |
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538 | /// \param i The item. |
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539 | State state(const Item &i) const { |
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540 | int idx = index[i]; |
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541 | if (idx >= 0) idx = 0; |
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542 | return State(idx); |
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543 | } |
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544 | |
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545 | private: |
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546 | |
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547 | struct BucketItem { |
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548 | BucketItem(const Item& _item) |
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549 | : item(_item) {} |
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550 | |
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551 | Item item; |
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552 | int next; |
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553 | }; |
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554 | |
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555 | ItemIntMap& index; |
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556 | std::vector<int> first; |
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557 | std::vector<BucketItem> data; |
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558 | int free, num; |
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559 | mutable int minimal; |
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560 | |
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561 | }; // class SimpleBucketHeap |
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562 | |
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563 | } |
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564 | |
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565 | #endif |
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