1 | /*********************************************************************** |
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2 | * Software License Agreement (BSD License) |
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3 | * |
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4 | * Copyright 2008-2009 Marius Muja (mariusm@cs.ubc.ca). All rights reserved. |
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5 | * Copyright 2008-2009 David G. Lowe (lowe@cs.ubc.ca). All rights reserved. |
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6 | * |
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7 | * THE BSD LICENSE |
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8 | * |
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9 | * Redistribution and use in source and binary forms, with or without |
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10 | * modification, are permitted provided that the following conditions |
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11 | * are met: |
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12 | * |
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13 | * 1. Redistributions of source code must retain the above copyright |
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14 | * notice, this list of conditions and the following disclaimer. |
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15 | * 2. Redistributions in binary form must reproduce the above copyright |
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16 | * notice, this list of conditions and the following disclaimer in the |
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17 | * documentation and/or other materials provided with the distribution. |
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18 | * |
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19 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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20 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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21 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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22 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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23 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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24 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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25 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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26 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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27 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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28 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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29 | *************************************************************************/ |
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30 | |
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31 | #ifndef FLANN_HEAP_H_ |
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32 | #define FLANN_HEAP_H_ |
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33 | |
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34 | #include <algorithm> |
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35 | #include <vector> |
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36 | |
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37 | namespace flann |
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38 | { |
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39 | |
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40 | /** |
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41 | * Priority Queue Implementation |
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42 | * |
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43 | * The priority queue is implemented with a heap. A heap is a complete |
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44 | * (full) binary tree in which each parent is less than both of its |
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45 | * children, but the order of the children is unspecified. |
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46 | */ |
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47 | template <typename T> |
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48 | class Heap |
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49 | { |
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50 | |
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51 | /** |
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52 | * Storage array for the heap. |
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53 | * Type T must be comparable. |
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54 | */ |
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55 | std::vector<T> heap; |
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56 | int length; |
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57 | |
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58 | /** |
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59 | * Number of element in the heap |
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60 | */ |
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61 | int count; |
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62 | |
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63 | |
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64 | |
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65 | public: |
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66 | /** |
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67 | * Constructor. |
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68 | * |
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69 | * Params: |
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70 | * size = heap size |
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71 | */ |
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72 | |
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73 | Heap(int size) |
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74 | { |
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75 | length = size; |
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76 | heap.reserve(length); |
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77 | count = 0; |
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78 | } |
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79 | |
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80 | /** |
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81 | * |
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82 | * Returns: heap size |
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83 | */ |
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84 | int size() |
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85 | { |
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86 | return count; |
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87 | } |
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88 | |
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89 | /** |
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90 | * Tests if the heap is empty |
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91 | * |
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92 | * Returns: true is heap empty, false otherwise |
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93 | */ |
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94 | bool empty() |
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95 | { |
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96 | return size()==0; |
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97 | } |
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98 | |
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99 | /** |
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100 | * Clears the heap. |
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101 | */ |
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102 | void clear() |
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103 | { |
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104 | heap.clear(); |
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105 | count = 0; |
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106 | } |
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107 | |
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108 | struct CompareT |
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109 | { |
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110 | bool operator()(const T& t_1, const T& t_2) const |
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111 | { |
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112 | return t_2 < t_1; |
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113 | } |
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114 | }; |
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115 | |
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116 | /** |
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117 | * Insert a new element in the heap. |
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118 | * |
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119 | * We select the next empty leaf node, and then keep moving any larger |
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120 | * parents down until the right location is found to store this element. |
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121 | * |
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122 | * Params: |
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123 | * value = the new element to be inserted in the heap |
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124 | */ |
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125 | void insert(T value) |
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126 | { |
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127 | /* If heap is full, then return without adding this element. */ |
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128 | if (count == length) { |
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129 | return; |
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130 | } |
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131 | |
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132 | heap.push_back(value); |
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133 | static CompareT compareT; |
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134 | std::push_heap(heap.begin(), heap.end(), compareT); |
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135 | ++count; |
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136 | } |
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137 | |
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138 | |
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139 | |
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140 | /** |
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141 | * Returns the node of minimum value from the heap (top of the heap). |
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142 | * |
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143 | * Params: |
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144 | * value = out parameter used to return the min element |
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145 | * Returns: false if heap empty |
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146 | */ |
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147 | bool popMin(T& value) |
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148 | { |
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149 | if (count == 0) { |
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150 | return false; |
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151 | } |
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152 | |
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153 | value = heap[0]; |
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154 | static CompareT compareT; |
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155 | std::pop_heap(heap.begin(), heap.end(), compareT); |
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156 | heap.pop_back(); |
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157 | --count; |
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158 | |
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159 | return true; /* Return old last node. */ |
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160 | } |
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161 | }; |
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162 | |
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163 | } |
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164 | |
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165 | #endif //FLANN_HEAP_H_ |
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