[906] | 1 | /* -*- C++ -*- |
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| 2 | * |
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[1956] | 3 | * This file is a part of LEMON, a generic C++ optimization library |
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| 4 | * |
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[2391] | 5 | * Copyright (C) 2003-2007 |
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[1956] | 6 | * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
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[1359] | 7 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
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[906] | 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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[255] | 18 | |
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[921] | 19 | #ifndef LEMON_FIB_HEAP_H |
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| 20 | #define LEMON_FIB_HEAP_H |
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[255] | 21 | |
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[857] | 22 | ///\file |
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[491] | 23 | ///\ingroup auxdat |
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[255] | 24 | ///\brief Fibonacci Heap implementation. |
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| 25 | |
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| 26 | #include <vector> |
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| 27 | #include <functional> |
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[1332] | 28 | #include <cmath> |
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[255] | 29 | |
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[921] | 30 | namespace lemon { |
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[255] | 31 | |
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[1834] | 32 | /// \ingroup auxdat |
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[2529] | 33 | /// |
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| 34 | ///\brief Fibonacci Heap. |
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| 35 | /// |
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[857] | 36 | ///This class implements the \e Fibonacci \e heap data structure. A \e heap |
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| 37 | ///is a data structure for storing items with specified values called \e |
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| 38 | ///priorities in such a way that finding the item with minimum priority is |
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[911] | 39 | ///efficient. \c Compare specifies the ordering of the priorities. In a heap |
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[857] | 40 | ///one can change the priority of an item, add or erase an item, etc. |
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| 41 | /// |
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| 42 | ///The methods \ref increase and \ref erase are not efficient in a Fibonacci |
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| 43 | ///heap. In case of many calls to these operations, it is better to use a |
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[2547] | 44 | ///\ref BinHeap "binary heap". |
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[857] | 45 | /// |
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[2547] | 46 | ///\param _Prio Type of the priority of the items. |
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| 47 | ///\param _ItemIntMap A read and writable Item int map, used internally |
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[1204] | 48 | ///to handle the cross references. |
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[2547] | 49 | ///\param _Compare A class for the ordering of the priorities. The |
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| 50 | ///default is \c std::less<_Prio>. |
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[857] | 51 | /// |
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[967] | 52 | ///\sa BinHeap |
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| 53 | ///\sa Dijkstra |
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[857] | 54 | ///\author Jacint Szabo |
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| 55 | |
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[373] | 56 | #ifdef DOXYGEN |
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[2547] | 57 | template <typename _Prio, |
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| 58 | typename _ItemIntMap, |
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| 59 | typename _Compare> |
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[373] | 60 | #else |
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[2547] | 61 | template <typename _Prio, |
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| 62 | typename _ItemIntMap, |
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| 63 | typename _Compare = std::less<_Prio> > |
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[373] | 64 | #endif |
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[255] | 65 | class FibHeap { |
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[2263] | 66 | public: |
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[2547] | 67 | typedef _ItemIntMap ItemIntMap; |
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| 68 | typedef _Prio Prio; |
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[2263] | 69 | typedef typename ItemIntMap::Key Item; |
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[2547] | 70 | typedef std::pair<Item,Prio> Pair; |
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| 71 | typedef _Compare Compare; |
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[255] | 72 | |
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[373] | 73 | private: |
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[255] | 74 | class store; |
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| 75 | |
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| 76 | std::vector<store> container; |
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| 77 | int minimum; |
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| 78 | ItemIntMap &iimap; |
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| 79 | Compare comp; |
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| 80 | int num_items; |
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[373] | 81 | |
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[255] | 82 | public: |
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[1127] | 83 | ///Status of the nodes |
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[2547] | 84 | enum State { |
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[1127] | 85 | ///The node is in the heap |
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[255] | 86 | IN_HEAP = 0, |
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[1127] | 87 | ///The node has never been in the heap |
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[255] | 88 | PRE_HEAP = -1, |
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[1127] | 89 | ///The node was in the heap but it got out of it |
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[255] | 90 | POST_HEAP = -2 |
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| 91 | }; |
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| 92 | |
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[1717] | 93 | /// \brief The constructor |
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| 94 | /// |
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| 95 | /// \c _iimap should be given to the constructor, since it is |
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| 96 | /// used internally to handle the cross references. |
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[1185] | 97 | explicit FibHeap(ItemIntMap &_iimap) |
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| 98 | : minimum(0), iimap(_iimap), num_items() {} |
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[1270] | 99 | |
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[1717] | 100 | /// \brief The constructor |
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| 101 | /// |
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| 102 | /// \c _iimap should be given to the constructor, since it is used |
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| 103 | /// internally to handle the cross references. \c _comp is an |
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| 104 | /// object for ordering of the priorities. |
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[2547] | 105 | FibHeap(ItemIntMap &_iimap, const Compare &_comp) |
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| 106 | : minimum(0), iimap(_iimap), comp(_comp), num_items() {} |
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[255] | 107 | |
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[1717] | 108 | /// \brief The number of items stored in the heap. |
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| 109 | /// |
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| 110 | /// Returns the number of items stored in the heap. |
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[373] | 111 | int size() const { return num_items; } |
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| 112 | |
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[1717] | 113 | /// \brief Checks if the heap stores no items. |
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| 114 | /// |
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| 115 | /// Returns \c true if and only if the heap stores no items. |
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[373] | 116 | bool empty() const { return num_items==0; } |
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| 117 | |
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[1717] | 118 | /// \brief Make empty this heap. |
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| 119 | /// |
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[2050] | 120 | /// Make empty this heap. It does not change the cross reference |
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| 121 | /// map. If you want to reuse a heap what is not surely empty you |
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| 122 | /// should first clear the heap and after that you should set the |
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| 123 | /// cross reference map for each item to \c PRE_HEAP. |
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[1753] | 124 | void clear() { |
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[1717] | 125 | container.clear(); minimum = 0; num_items = 0; |
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| 126 | } |
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[373] | 127 | |
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[1717] | 128 | /// \brief \c item gets to the heap with priority \c value independently |
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| 129 | /// if \c item was already there. |
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| 130 | /// |
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| 131 | /// This method calls \ref push(\c item, \c value) if \c item is not |
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| 132 | /// stored in the heap and it calls \ref decrease(\c item, \c value) or |
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| 133 | /// \ref increase(\c item, \c value) otherwise. |
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[2547] | 134 | void set (const Item& item, const Prio& value) { |
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| 135 | int i=iimap[item]; |
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| 136 | if ( i >= 0 && container[i].in ) { |
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| 137 | if ( comp(value, container[i].prio) ) decrease(item, value); |
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| 138 | if ( comp(container[i].prio, value) ) increase(item, value); |
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| 139 | } else push(item, value); |
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| 140 | } |
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[373] | 141 | |
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[1717] | 142 | /// \brief Adds \c item to the heap with priority \c value. |
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| 143 | /// |
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| 144 | /// Adds \c item to the heap with priority \c value. |
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| 145 | /// \pre \c item must not be stored in the heap. |
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[2547] | 146 | void push (const Item& item, const Prio& value) { |
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[387] | 147 | int i=iimap[item]; |
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[255] | 148 | if ( i < 0 ) { |
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| 149 | int s=container.size(); |
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[387] | 150 | iimap.set( item, s ); |
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[255] | 151 | store st; |
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[387] | 152 | st.name=item; |
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[255] | 153 | container.push_back(st); |
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| 154 | i=s; |
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| 155 | } else { |
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| 156 | container[i].parent=container[i].child=-1; |
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| 157 | container[i].degree=0; |
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| 158 | container[i].in=true; |
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| 159 | container[i].marked=false; |
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| 160 | } |
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| 161 | |
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| 162 | if ( num_items ) { |
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| 163 | container[container[minimum].right_neighbor].left_neighbor=i; |
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| 164 | container[i].right_neighbor=container[minimum].right_neighbor; |
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| 165 | container[minimum].right_neighbor=i; |
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| 166 | container[i].left_neighbor=minimum; |
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| 167 | if ( comp( value, container[minimum].prio) ) minimum=i; |
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| 168 | } else { |
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| 169 | container[i].right_neighbor=container[i].left_neighbor=i; |
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| 170 | minimum=i; |
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| 171 | } |
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| 172 | container[i].prio=value; |
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| 173 | ++num_items; |
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| 174 | } |
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| 175 | |
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[2547] | 176 | /// \brief Returns the item with minimum priority relative to \c Compare. |
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| 177 | /// |
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| 178 | /// This method returns the item with minimum priority relative to \c |
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| 179 | /// Compare. |
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| 180 | /// \pre The heap must be nonempty. |
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| 181 | Item top() const { return container[minimum].name; } |
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| 182 | |
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| 183 | /// \brief Returns the minimum priority relative to \c Compare. |
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| 184 | /// |
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| 185 | /// It returns the minimum priority relative to \c Compare. |
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| 186 | /// \pre The heap must be nonempty. |
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| 187 | const Prio& prio() const { return container[minimum].prio; } |
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| 188 | |
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| 189 | /// \brief Returns the priority of \c item. |
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| 190 | /// |
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| 191 | /// It returns the priority of \c item. |
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| 192 | /// \pre \c item must be in the heap. |
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| 193 | const Prio& operator[](const Item& item) const { |
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| 194 | return container[iimap[item]].prio; |
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| 195 | } |
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| 196 | |
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| 197 | /// \brief Deletes the item with minimum priority relative to \c Compare. |
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| 198 | /// |
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| 199 | /// This method deletes the item with minimum priority relative to \c |
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| 200 | /// Compare from the heap. |
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| 201 | /// \pre The heap must be non-empty. |
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| 202 | void pop() { |
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[255] | 203 | /*The first case is that there are only one root.*/ |
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| 204 | if ( container[minimum].left_neighbor==minimum ) { |
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| 205 | container[minimum].in=false; |
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| 206 | if ( container[minimum].degree!=0 ) { |
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| 207 | makeroot(container[minimum].child); |
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| 208 | minimum=container[minimum].child; |
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| 209 | balance(); |
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| 210 | } |
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| 211 | } else { |
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| 212 | int right=container[minimum].right_neighbor; |
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| 213 | unlace(minimum); |
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| 214 | container[minimum].in=false; |
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| 215 | if ( container[minimum].degree > 0 ) { |
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| 216 | int left=container[minimum].left_neighbor; |
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| 217 | int child=container[minimum].child; |
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| 218 | int last_child=container[child].left_neighbor; |
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[2547] | 219 | |
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[255] | 220 | makeroot(child); |
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| 221 | |
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| 222 | container[left].right_neighbor=child; |
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| 223 | container[child].left_neighbor=left; |
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| 224 | container[right].left_neighbor=last_child; |
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| 225 | container[last_child].right_neighbor=right; |
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| 226 | } |
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| 227 | minimum=right; |
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| 228 | balance(); |
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| 229 | } // the case where there are more roots |
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| 230 | --num_items; |
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| 231 | } |
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| 232 | |
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[2547] | 233 | /// \brief Deletes \c item from the heap. |
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| 234 | /// |
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| 235 | /// This method deletes \c item from the heap, if \c item was already |
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| 236 | /// stored in the heap. It is quite inefficient in Fibonacci heaps. |
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| 237 | void erase (const Item& item) { |
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[387] | 238 | int i=iimap[item]; |
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[255] | 239 | |
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| 240 | if ( i >= 0 && container[i].in ) { |
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| 241 | if ( container[i].parent!=-1 ) { |
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| 242 | int p=container[i].parent; |
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| 243 | cut(i,p); |
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| 244 | cascade(p); |
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| 245 | } |
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| 246 | minimum=i; //As if its prio would be -infinity |
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| 247 | pop(); |
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| 248 | } |
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[2547] | 249 | } |
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| 250 | |
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| 251 | /// \brief Decreases the priority of \c item to \c value. |
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| 252 | /// |
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| 253 | /// This method decreases the priority of \c item to \c value. |
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| 254 | /// \pre \c item must be stored in the heap with priority at least \c |
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| 255 | /// value relative to \c Compare. |
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| 256 | void decrease (Item item, const Prio& value) { |
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[387] | 257 | int i=iimap[item]; |
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[255] | 258 | container[i].prio=value; |
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| 259 | int p=container[i].parent; |
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| 260 | |
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| 261 | if ( p!=-1 && comp(value, container[p].prio) ) { |
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| 262 | cut(i,p); |
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| 263 | cascade(p); |
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| 264 | } |
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| 265 | if ( comp(value, container[minimum].prio) ) minimum=i; |
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[2547] | 266 | } |
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[255] | 267 | |
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[2547] | 268 | /// \brief Increases the priority of \c item to \c value. |
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| 269 | /// |
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| 270 | /// This method sets the priority of \c item to \c value. Though |
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| 271 | /// there is no precondition on the priority of \c item, this |
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| 272 | /// method should be used only if it is indeed necessary to increase |
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| 273 | /// (relative to \c Compare) the priority of \c item, because this |
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| 274 | /// method is inefficient. |
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| 275 | void increase (Item item, const Prio& value) { |
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| 276 | erase(item); |
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| 277 | push(item, value); |
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| 278 | } |
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[255] | 279 | |
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[2547] | 280 | |
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| 281 | /// \brief Returns if \c item is in, has already been in, or has never |
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| 282 | /// been in the heap. |
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| 283 | /// |
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| 284 | /// This method returns PRE_HEAP if \c item has never been in the |
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| 285 | /// heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP |
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| 286 | /// otherwise. In the latter case it is possible that \c item will |
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| 287 | /// get back to the heap again. |
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| 288 | State state(const Item &item) const { |
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| 289 | int i=iimap[item]; |
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| 290 | if( i>=0 ) { |
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| 291 | if ( container[i].in ) i=0; |
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| 292 | else i=-2; |
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| 293 | } |
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| 294 | return State(i); |
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| 295 | } |
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| 296 | |
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| 297 | /// \brief Sets the state of the \c item in the heap. |
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| 298 | /// |
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| 299 | /// Sets the state of the \c item in the heap. It can be used to |
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| 300 | /// manually clear the heap when it is important to achive the |
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| 301 | /// better time complexity. |
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| 302 | /// \param i The item. |
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| 303 | /// \param st The state. It should not be \c IN_HEAP. |
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| 304 | void state(const Item& i, State st) { |
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| 305 | switch (st) { |
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| 306 | case POST_HEAP: |
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| 307 | case PRE_HEAP: |
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| 308 | if (state(i) == IN_HEAP) { |
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| 309 | erase(i); |
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| 310 | } |
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| 311 | iimap[i] = st; |
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| 312 | break; |
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| 313 | case IN_HEAP: |
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| 314 | break; |
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| 315 | } |
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| 316 | } |
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| 317 | |
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| 318 | private: |
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| 319 | |
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| 320 | void balance() { |
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| 321 | |
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| 322 | int maxdeg=int( std::floor( 2.08*log(double(container.size()))))+1; |
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[255] | 323 | |
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[2547] | 324 | std::vector<int> A(maxdeg,-1); |
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[255] | 325 | |
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[2547] | 326 | /* |
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| 327 | *Recall that now minimum does not point to the minimum prio element. |
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| 328 | *We set minimum to this during balance(). |
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| 329 | */ |
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| 330 | int anchor=container[minimum].left_neighbor; |
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| 331 | int next=minimum; |
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| 332 | bool end=false; |
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[255] | 333 | |
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[2547] | 334 | do { |
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[255] | 335 | int active=next; |
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| 336 | if ( anchor==active ) end=true; |
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| 337 | int d=container[active].degree; |
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| 338 | next=container[active].right_neighbor; |
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| 339 | |
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| 340 | while (A[d]!=-1) { |
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| 341 | if( comp(container[active].prio, container[A[d]].prio) ) { |
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| 342 | fuse(active,A[d]); |
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| 343 | } else { |
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| 344 | fuse(A[d],active); |
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| 345 | active=A[d]; |
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| 346 | } |
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| 347 | A[d]=-1; |
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| 348 | ++d; |
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| 349 | } |
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| 350 | A[d]=active; |
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[2547] | 351 | } while ( !end ); |
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[255] | 352 | |
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| 353 | |
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[2547] | 354 | while ( container[minimum].parent >=0 ) |
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| 355 | minimum=container[minimum].parent; |
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| 356 | int s=minimum; |
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| 357 | int m=minimum; |
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| 358 | do { |
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| 359 | if ( comp(container[s].prio, container[minimum].prio) ) minimum=s; |
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| 360 | s=container[s].right_neighbor; |
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| 361 | } while ( s != m ); |
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[255] | 362 | } |
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| 363 | |
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[2547] | 364 | void makeroot(int c) { |
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[255] | 365 | int s=c; |
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| 366 | do { |
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| 367 | container[s].parent=-1; |
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| 368 | s=container[s].right_neighbor; |
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| 369 | } while ( s != c ); |
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| 370 | } |
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[2547] | 371 | |
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| 372 | void cut(int a, int b) { |
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| 373 | /* |
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| 374 | *Replacing a from the children of b. |
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| 375 | */ |
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| 376 | --container[b].degree; |
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[255] | 377 | |
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[2547] | 378 | if ( container[b].degree !=0 ) { |
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| 379 | int child=container[b].child; |
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| 380 | if ( child==a ) |
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| 381 | container[b].child=container[child].right_neighbor; |
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| 382 | unlace(a); |
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| 383 | } |
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| 384 | |
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| 385 | |
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| 386 | /*Lacing a to the roots.*/ |
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| 387 | int right=container[minimum].right_neighbor; |
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| 388 | container[minimum].right_neighbor=a; |
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| 389 | container[a].left_neighbor=minimum; |
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| 390 | container[a].right_neighbor=right; |
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| 391 | container[right].left_neighbor=a; |
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| 392 | |
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| 393 | container[a].parent=-1; |
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| 394 | container[a].marked=false; |
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[387] | 395 | } |
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[255] | 396 | |
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[2547] | 397 | void cascade(int a) { |
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[255] | 398 | if ( container[a].parent!=-1 ) { |
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| 399 | int p=container[a].parent; |
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| 400 | |
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| 401 | if ( container[a].marked==false ) container[a].marked=true; |
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| 402 | else { |
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| 403 | cut(a,p); |
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| 404 | cascade(p); |
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| 405 | } |
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| 406 | } |
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| 407 | } |
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| 408 | |
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[2547] | 409 | void fuse(int a, int b) { |
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[255] | 410 | unlace(b); |
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| 411 | |
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| 412 | /*Lacing b under a.*/ |
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| 413 | container[b].parent=a; |
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| 414 | |
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| 415 | if (container[a].degree==0) { |
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| 416 | container[b].left_neighbor=b; |
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| 417 | container[b].right_neighbor=b; |
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| 418 | container[a].child=b; |
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| 419 | } else { |
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| 420 | int child=container[a].child; |
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| 421 | int last_child=container[child].left_neighbor; |
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| 422 | container[child].left_neighbor=b; |
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| 423 | container[b].right_neighbor=child; |
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| 424 | container[last_child].right_neighbor=b; |
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| 425 | container[b].left_neighbor=last_child; |
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| 426 | } |
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| 427 | |
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| 428 | ++container[a].degree; |
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| 429 | |
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| 430 | container[b].marked=false; |
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| 431 | } |
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| 432 | |
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[2547] | 433 | /* |
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| 434 | *It is invoked only if a has siblings. |
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| 435 | */ |
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| 436 | void unlace(int a) { |
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[255] | 437 | int leftn=container[a].left_neighbor; |
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| 438 | int rightn=container[a].right_neighbor; |
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| 439 | container[leftn].right_neighbor=rightn; |
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| 440 | container[rightn].left_neighbor=leftn; |
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[2547] | 441 | } |
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| 442 | |
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| 443 | |
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| 444 | class store { |
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| 445 | friend class FibHeap; |
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| 446 | |
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| 447 | Item name; |
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| 448 | int parent; |
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| 449 | int left_neighbor; |
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| 450 | int right_neighbor; |
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| 451 | int child; |
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| 452 | int degree; |
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| 453 | bool marked; |
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| 454 | bool in; |
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| 455 | Prio prio; |
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| 456 | |
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| 457 | store() : parent(-1), child(-1), degree(), marked(false), in(true) {} |
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| 458 | }; |
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| 459 | }; |
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[430] | 460 | |
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[921] | 461 | } //namespace lemon |
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[477] | 462 | |
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[921] | 463 | #endif //LEMON_FIB_HEAP_H |
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[477] | 464 | |
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