1 | // -*- C++ -*- |
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2 | |
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3 | #ifndef HUGO_FIB_HEAP_H |
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4 | #define HUGO_FIB_HEAP_H |
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5 | |
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6 | ///\file |
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7 | ///\brief Fibonacci Heap implementation. |
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8 | |
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9 | #include <vector> |
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10 | #include <functional> |
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11 | #include <math.h> |
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12 | |
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13 | namespace hugo { |
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14 | |
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15 | /// An implementation of the Fibonacci Heap. |
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16 | |
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17 | /** |
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18 | This class implements the \e Fibonacci \e heap data structure. A \e heap |
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19 | is a data structure for storing items with specified values called \e |
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20 | priorities, such that finding the item with minimum priority with respect |
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21 | to \e Compare is efficient. In a heap one can change the priority of an |
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22 | item, add or erase an item, etc. |
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23 | |
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24 | The methods \ref increase and \ref erase are not efficient in a Fibonacci |
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25 | heap. In case of many calls to these operations, it is better to use a |
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26 | \e binary \e heap. |
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27 | |
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28 | \param Item The type of the items to be stored. |
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29 | \param Prio The type of the priority of the items. |
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30 | \param ItemIntMap A read and writable Item int map, for the usage of |
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31 | the heap. |
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32 | \param Compare A class for the comparison of the priorities. The |
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33 | default is \c std::less<Prio>. |
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34 | |
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35 | */ |
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36 | |
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37 | #ifdef DOXYGEN |
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38 | template <typename Item, |
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39 | typename Prio, |
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40 | typename ItemIntMap, |
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41 | typename Compare> |
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42 | #else |
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43 | template <typename Item, |
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44 | typename Prio, |
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45 | typename ItemIntMap, |
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46 | typename Compare = std::less<Prio> > |
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47 | #endif |
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48 | class FibHeap { |
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49 | public: |
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50 | typedef Prio PrioType; |
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51 | |
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52 | private: |
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53 | class store; |
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54 | |
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55 | std::vector<store> container; |
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56 | int minimum; |
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57 | ItemIntMap &iimap; |
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58 | Compare comp; |
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59 | int num_items; |
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60 | |
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61 | ///\todo It is use nowhere |
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62 | ///\todo It doesn't conform to the naming conventions. |
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63 | public: |
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64 | enum state_enum { |
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65 | IN_HEAP = 0, |
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66 | PRE_HEAP = -1, |
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67 | POST_HEAP = -2 |
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68 | }; |
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69 | |
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70 | FibHeap(ItemIntMap &_iimap) : minimum(0), iimap(_iimap), num_items() {} |
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71 | FibHeap(ItemIntMap &_iimap, const Compare &_comp) : minimum(0), |
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72 | iimap(_iimap), comp(_comp), num_items() {} |
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73 | |
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74 | ///The number of items stored in the heap. |
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75 | |
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76 | /** |
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77 | Returns the number of items stored in the heap. |
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78 | */ |
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79 | int size() const { return num_items; } |
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80 | |
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81 | ///Checks if the heap stores no items. |
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82 | |
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83 | /** |
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84 | Returns \c true iff the heap stores no items. |
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85 | */ |
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86 | bool empty() const { return num_items==0; } |
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87 | |
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88 | ///\c item gets to the heap with priority \c value independently if \c item was already there. |
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89 | |
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90 | /** |
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91 | This method calls \ref push(\c item, \c value) if \c item is not |
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92 | stored in the heap and it calls \ref decrease(\c item, \c value) or |
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93 | \ref increase(\c item, \c value) otherwise. |
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94 | */ |
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95 | void set (Item const item, PrioType const value); |
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96 | |
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97 | ///Adds \c item to the heap with priority \c value. |
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98 | |
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99 | /** |
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100 | Adds \c item to the heap with priority \c value. |
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101 | \pre \c item must not be stored in the heap. |
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102 | */ |
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103 | void push (Item const item, PrioType const value); |
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104 | |
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105 | |
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106 | ///Returns the item having the minimum priority w.r.t. Compare. |
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107 | |
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108 | /** |
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109 | This method returns the item having the minimum priority w.r.t. Compare. |
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110 | \pre The heap must be nonempty. |
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111 | */ |
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112 | Item top() const { return container[minimum].name; } |
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113 | |
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114 | |
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115 | ///Returns the minimum priority w.r.t. Compare. |
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116 | |
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117 | /** |
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118 | It returns the minimum priority w.r.t. Compare. |
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119 | \pre The heap must be nonempty. |
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120 | */ |
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121 | PrioType prio() const { return container[minimum].prio; } |
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122 | |
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123 | |
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124 | ///Returns the priority of \c item. |
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125 | |
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126 | /** |
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127 | It returns the priority of \c item. |
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128 | \pre \c item must be in the heap. |
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129 | */ |
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130 | PrioType& operator[](const Item& item) { |
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131 | return container[iimap[item]].prio; |
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132 | } |
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133 | |
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134 | ///Returns the priority of \c item. |
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135 | |
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136 | /** |
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137 | It returns the priority of \c item. |
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138 | \pre \c item must be in the heap. |
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139 | */ |
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140 | const PrioType& operator[](const Item& item) const { |
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141 | return container[iimap[item]].prio; |
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142 | } |
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143 | |
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144 | |
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145 | ///Deletes the item with minimum priority w.r.t. Compare. |
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146 | |
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147 | /** |
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148 | This method deletes the item with minimum priority w.r.t. |
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149 | Compare from the heap. |
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150 | \pre The heap must be non-empty. |
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151 | */ |
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152 | void pop(); |
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153 | |
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154 | ///Deletes \c item from the heap. |
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155 | |
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156 | /** |
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157 | This method deletes \c item from the heap, if \c item was already |
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158 | stored in the heap. It is quite inefficient in Fibonacci heaps. |
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159 | */ |
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160 | void erase (const Item& item); |
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161 | |
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162 | ///Decreases the priority of \c item to \c value. |
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163 | |
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164 | /** |
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165 | This method decreases the priority of \c item to \c value. |
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166 | \pre \c item must be stored in the heap with priority at least \c |
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167 | value w.r.t. Compare. |
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168 | */ |
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169 | void decrease (Item item, PrioType const value); |
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170 | |
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171 | |
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172 | ///Increases the priority of \c item to \c value. |
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173 | |
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174 | /** |
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175 | This method sets the priority of \c item to \c value. Though |
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176 | there is no precondition on the priority of \c item, this |
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177 | method should be used only if there is a need to really \e increase |
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178 | (w.r.t. Compare) the priority of \c item, because this |
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179 | method is inefficient. |
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180 | */ |
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181 | void increase (Item item, PrioType const value) { |
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182 | erase(item); |
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183 | push(item, value); |
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184 | } |
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185 | |
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186 | |
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187 | ///Tells if \c item is in, was already in, or has never been in the heap. |
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188 | |
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189 | /** |
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190 | This method returns PRE_HEAP if \c item has never been in the |
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191 | heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP |
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192 | otherwise. In the latter case it is possible that \c item will |
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193 | get back to the heap again. |
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194 | */ |
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195 | state_enum state(const Item &item) const { |
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196 | int i=iimap[item]; |
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197 | if( i>=0 ) { |
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198 | if ( container[i].in ) i=0; |
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199 | else i=-2; |
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200 | } |
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201 | return state_enum(i); |
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202 | } |
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203 | |
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204 | private: |
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205 | |
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206 | void balance(); |
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207 | void makeroot(int c); |
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208 | void cut(int a, int b); |
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209 | void cascade(int a); |
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210 | void fuse(int a, int b); |
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211 | void unlace(int a); |
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212 | |
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213 | |
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214 | class store { |
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215 | friend class FibHeap; |
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216 | |
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217 | Item name; |
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218 | int parent; |
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219 | int left_neighbor; |
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220 | int right_neighbor; |
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221 | int child; |
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222 | int degree; |
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223 | bool marked; |
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224 | bool in; |
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225 | PrioType prio; |
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226 | |
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227 | store() : parent(-1), child(-1), degree(), marked(false), in(true) {} |
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228 | }; |
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229 | }; |
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230 | |
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231 | |
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232 | |
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233 | // ********************************************************************** |
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234 | // IMPLEMENTATIONS |
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235 | // ********************************************************************** |
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236 | |
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237 | template <typename Item, typename Prio, typename ItemIntMap, |
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238 | typename Compare> |
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239 | void FibHeap<Item, Prio, ItemIntMap, Compare>::set |
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240 | (Item const item, PrioType const value) |
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241 | { |
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242 | int i=iimap[item]; |
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243 | if ( i >= 0 && container[i].in ) { |
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244 | if ( comp(value, container[i].prio) ) decrease(item, value); |
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245 | if ( comp(container[i].prio, value) ) increase(item, value); |
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246 | } else push(item, value); |
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247 | } |
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248 | |
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249 | template <typename Item, typename Prio, typename ItemIntMap, |
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250 | typename Compare> |
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251 | void FibHeap<Item, Prio, ItemIntMap, Compare>::push |
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252 | (Item const item, PrioType const value) { |
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253 | int i=iimap[item]; |
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254 | if ( i < 0 ) { |
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255 | int s=container.size(); |
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256 | iimap.set( item, s ); |
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257 | store st; |
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258 | st.name=item; |
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259 | container.push_back(st); |
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260 | i=s; |
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261 | } else { |
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262 | container[i].parent=container[i].child=-1; |
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263 | container[i].degree=0; |
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264 | container[i].in=true; |
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265 | container[i].marked=false; |
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266 | } |
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267 | |
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268 | if ( num_items ) { |
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269 | container[container[minimum].right_neighbor].left_neighbor=i; |
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270 | container[i].right_neighbor=container[minimum].right_neighbor; |
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271 | container[minimum].right_neighbor=i; |
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272 | container[i].left_neighbor=minimum; |
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273 | if ( comp( value, container[minimum].prio) ) minimum=i; |
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274 | } else { |
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275 | container[i].right_neighbor=container[i].left_neighbor=i; |
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276 | minimum=i; |
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277 | } |
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278 | container[i].prio=value; |
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279 | ++num_items; |
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280 | } |
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281 | |
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282 | template <typename Item, typename Prio, typename ItemIntMap, |
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283 | typename Compare> |
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284 | void FibHeap<Item, Prio, ItemIntMap, Compare>::pop() { |
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285 | /*The first case is that there are only one root.*/ |
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286 | if ( container[minimum].left_neighbor==minimum ) { |
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287 | container[minimum].in=false; |
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288 | if ( container[minimum].degree!=0 ) { |
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289 | makeroot(container[minimum].child); |
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290 | minimum=container[minimum].child; |
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291 | balance(); |
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292 | } |
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293 | } else { |
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294 | int right=container[minimum].right_neighbor; |
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295 | unlace(minimum); |
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296 | container[minimum].in=false; |
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297 | if ( container[minimum].degree > 0 ) { |
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298 | int left=container[minimum].left_neighbor; |
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299 | int child=container[minimum].child; |
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300 | int last_child=container[child].left_neighbor; |
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301 | |
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302 | makeroot(child); |
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303 | |
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304 | container[left].right_neighbor=child; |
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305 | container[child].left_neighbor=left; |
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306 | container[right].left_neighbor=last_child; |
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307 | container[last_child].right_neighbor=right; |
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308 | } |
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309 | minimum=right; |
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310 | balance(); |
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311 | } // the case where there are more roots |
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312 | --num_items; |
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313 | } |
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314 | |
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315 | |
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316 | template <typename Item, typename Prio, typename ItemIntMap, |
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317 | typename Compare> |
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318 | void FibHeap<Item, Prio, ItemIntMap, Compare>::erase |
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319 | (const Item& item) { |
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320 | int i=iimap[item]; |
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321 | |
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322 | if ( i >= 0 && container[i].in ) { |
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323 | if ( container[i].parent!=-1 ) { |
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324 | int p=container[i].parent; |
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325 | cut(i,p); |
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326 | cascade(p); |
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327 | } |
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328 | minimum=i; //As if its prio would be -infinity |
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329 | pop(); |
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330 | } |
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331 | } |
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332 | |
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333 | template <typename Item, typename Prio, typename ItemIntMap, |
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334 | typename Compare> |
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335 | void FibHeap<Item, Prio, ItemIntMap, Compare>::decrease |
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336 | (Item item, PrioType const value) { |
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337 | int i=iimap[item]; |
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338 | container[i].prio=value; |
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339 | int p=container[i].parent; |
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340 | |
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341 | if ( p!=-1 && comp(value, container[p].prio) ) { |
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342 | cut(i,p); |
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343 | cascade(p); |
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344 | } |
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345 | if ( comp(value, container[minimum].prio) ) minimum=i; |
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346 | } |
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347 | |
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348 | |
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349 | template <typename Item, typename Prio, typename ItemIntMap, |
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350 | typename Compare> |
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351 | void FibHeap<Item, Prio, ItemIntMap, Compare>::balance() { |
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352 | |
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353 | int maxdeg=int( floor( 2.08*log(double(container.size()))))+1; |
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354 | |
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355 | std::vector<int> A(maxdeg,-1); |
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356 | |
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357 | /* |
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358 | *Recall that now minimum does not point to the minimum prio element. |
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359 | *We set minimum to this during balance(). |
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360 | */ |
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361 | int anchor=container[minimum].left_neighbor; |
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362 | int next=minimum; |
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363 | bool end=false; |
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364 | |
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365 | do { |
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366 | int active=next; |
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367 | if ( anchor==active ) end=true; |
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368 | int d=container[active].degree; |
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369 | next=container[active].right_neighbor; |
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370 | |
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371 | while (A[d]!=-1) { |
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372 | if( comp(container[active].prio, container[A[d]].prio) ) { |
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373 | fuse(active,A[d]); |
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374 | } else { |
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375 | fuse(A[d],active); |
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376 | active=A[d]; |
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377 | } |
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378 | A[d]=-1; |
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379 | ++d; |
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380 | } |
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381 | A[d]=active; |
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382 | } while ( !end ); |
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383 | |
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384 | |
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385 | while ( container[minimum].parent >=0 ) minimum=container[minimum].parent; |
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386 | int s=minimum; |
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387 | int m=minimum; |
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388 | do { |
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389 | if ( comp(container[s].prio, container[minimum].prio) ) minimum=s; |
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390 | s=container[s].right_neighbor; |
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391 | } while ( s != m ); |
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392 | } |
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393 | |
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394 | template <typename Item, typename Prio, typename ItemIntMap, |
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395 | typename Compare> |
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396 | void FibHeap<Item, Prio, ItemIntMap, Compare>::makeroot |
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397 | (int c) { |
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398 | int s=c; |
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399 | do { |
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400 | container[s].parent=-1; |
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401 | s=container[s].right_neighbor; |
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402 | } while ( s != c ); |
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403 | } |
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404 | |
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405 | |
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406 | template <typename Item, typename Prio, typename ItemIntMap, |
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407 | typename Compare> |
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408 | void FibHeap<Item, Prio, ItemIntMap, Compare>::cut |
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409 | (int a, int b) { |
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410 | /* |
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411 | *Replacing a from the children of b. |
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412 | */ |
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413 | --container[b].degree; |
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414 | |
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415 | if ( container[b].degree !=0 ) { |
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416 | int child=container[b].child; |
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417 | if ( child==a ) |
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418 | container[b].child=container[child].right_neighbor; |
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419 | unlace(a); |
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420 | } |
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421 | |
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422 | |
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423 | /*Lacing a to the roots.*/ |
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424 | int right=container[minimum].right_neighbor; |
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425 | container[minimum].right_neighbor=a; |
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426 | container[a].left_neighbor=minimum; |
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427 | container[a].right_neighbor=right; |
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428 | container[right].left_neighbor=a; |
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429 | |
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430 | container[a].parent=-1; |
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431 | container[a].marked=false; |
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432 | } |
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433 | |
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434 | |
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435 | template <typename Item, typename Prio, typename ItemIntMap, |
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436 | typename Compare> |
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437 | void FibHeap<Item, Prio, ItemIntMap, Compare>::cascade |
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438 | (int a) |
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439 | { |
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440 | if ( container[a].parent!=-1 ) { |
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441 | int p=container[a].parent; |
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442 | |
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443 | if ( container[a].marked==false ) container[a].marked=true; |
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444 | else { |
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445 | cut(a,p); |
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446 | cascade(p); |
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447 | } |
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448 | } |
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449 | } |
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450 | |
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451 | |
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452 | template <typename Item, typename Prio, typename ItemIntMap, |
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453 | typename Compare> |
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454 | void FibHeap<Item, Prio, ItemIntMap, Compare>::fuse |
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455 | (int a, int b) { |
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456 | unlace(b); |
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457 | |
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458 | /*Lacing b under a.*/ |
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459 | container[b].parent=a; |
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460 | |
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461 | if (container[a].degree==0) { |
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462 | container[b].left_neighbor=b; |
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463 | container[b].right_neighbor=b; |
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464 | container[a].child=b; |
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465 | } else { |
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466 | int child=container[a].child; |
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467 | int last_child=container[child].left_neighbor; |
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468 | container[child].left_neighbor=b; |
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469 | container[b].right_neighbor=child; |
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470 | container[last_child].right_neighbor=b; |
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471 | container[b].left_neighbor=last_child; |
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472 | } |
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473 | |
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474 | ++container[a].degree; |
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475 | |
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476 | container[b].marked=false; |
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477 | } |
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478 | |
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479 | |
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480 | /* |
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481 | *It is invoked only if a has siblings. |
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482 | */ |
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483 | template <typename Item, typename Prio, typename ItemIntMap, |
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484 | typename Compare> |
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485 | void FibHeap<Item, Prio, ItemIntMap, Compare>::unlace |
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486 | (int a) { |
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487 | int leftn=container[a].left_neighbor; |
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488 | int rightn=container[a].right_neighbor; |
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489 | container[leftn].right_neighbor=rightn; |
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490 | container[rightn].left_neighbor=leftn; |
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491 | } |
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492 | |
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493 | } //namespace hugo |
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494 | #endif |
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