475 lines
14 KiB
C++
Executable File
475 lines
14 KiB
C++
Executable File
/* -*- mode: C++; indent-tabs-mode: nil; -*-
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*
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* This file is a part of LEMON, a generic C++ optimization library.
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*
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* Copyright (C) 2003-2009
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* Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
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* (Egervary Research Group on Combinatorial Optimization, EGRES).
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*
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* Permission to use, modify and distribute this software is granted
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* provided that this copyright notice appears in all copies. For
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* precise terms see the accompanying LICENSE file.
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*
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* This software is provided "AS IS" with no warranty of any kind,
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* express or implied, and with no claim as to its suitability for any
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* purpose.
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*
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*/
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#ifndef LEMON_PAIRING_HEAP_H
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#define LEMON_PAIRING_HEAP_H
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///\file
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///\ingroup heaps
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///\brief Pairing heap implementation.
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#include <vector>
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#include <utility>
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#include <functional>
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#include <lemon/math.h>
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namespace lemon {
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/// \ingroup heaps
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///
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///\brief Pairing Heap.
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///
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/// This class implements the \e pairing \e heap data structure.
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/// It fully conforms to the \ref concepts::Heap "heap concept".
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///
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/// The methods \ref increase() and \ref erase() are not efficient
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/// in a pairing heap. In case of many calls of these operations,
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/// it is better to use other heap structure, e.g. \ref BinHeap
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/// "binary heap".
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///
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/// \tparam PR Type of the priorities of the items.
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/// \tparam IM A read-writable item map with \c int values, used
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/// internally to handle the cross references.
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/// \tparam CMP A functor class for comparing the priorities.
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/// The default is \c std::less<PR>.
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#ifdef DOXYGEN
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template <typename PR, typename IM, typename CMP>
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#else
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template <typename PR, typename IM, typename CMP = std::less<PR> >
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#endif
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class PairingHeap {
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public:
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/// Type of the item-int map.
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typedef IM ItemIntMap;
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/// Type of the priorities.
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typedef PR Prio;
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/// Type of the items stored in the heap.
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typedef typename ItemIntMap::Key Item;
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/// Functor type for comparing the priorities.
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typedef CMP Compare;
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/// \brief Type to represent the states of the items.
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///
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/// Each item has a state associated to it. It can be "in heap",
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/// "pre-heap" or "post-heap". The latter two are indifferent from the
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/// heap's point of view, but may be useful to the user.
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///
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/// The item-int map must be initialized in such way that it assigns
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/// \c PRE_HEAP (<tt>-1</tt>) to any element to be put in the heap.
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enum State {
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IN_HEAP = 0, ///< = 0.
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PRE_HEAP = -1, ///< = -1.
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POST_HEAP = -2 ///< = -2.
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};
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private:
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class store;
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std::vector<store> _data;
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int _min;
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ItemIntMap &_iim;
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Compare _comp;
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int _num_items;
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public:
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/// \brief Constructor.
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///
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/// Constructor.
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/// \param map A map that assigns \c int values to the items.
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/// It is used internally to handle the cross references.
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/// The assigned value must be \c PRE_HEAP (<tt>-1</tt>) for each item.
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explicit PairingHeap(ItemIntMap &map)
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: _min(0), _iim(map), _num_items(0) {}
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/// \brief Constructor.
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///
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/// Constructor.
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/// \param map A map that assigns \c int values to the items.
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/// It is used internally to handle the cross references.
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/// The assigned value must be \c PRE_HEAP (<tt>-1</tt>) for each item.
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/// \param comp The function object used for comparing the priorities.
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PairingHeap(ItemIntMap &map, const Compare &comp)
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: _min(0), _iim(map), _comp(comp), _num_items(0) {}
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/// \brief The number of items stored in the heap.
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///
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/// This function returns the number of items stored in the heap.
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int size() const { return _num_items; }
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/// \brief Check if the heap is empty.
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///
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/// This function returns \c true if the heap is empty.
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bool empty() const { return _num_items==0; }
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/// \brief Make the heap empty.
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///
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/// This functon makes the heap empty.
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/// It does not change the cross reference map. If you want to reuse
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/// a heap that is not surely empty, you should first clear it and
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/// then you should set the cross reference map to \c PRE_HEAP
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/// for each item.
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void clear() {
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_data.clear();
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_min = 0;
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_num_items = 0;
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}
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/// \brief Set the priority of an item or insert it, if it is
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/// not stored in the heap.
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///
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/// This method sets the priority of the given item if it is
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/// already stored in the heap. Otherwise it inserts the given
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/// item into the heap with the given priority.
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/// \param item The item.
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/// \param value The priority.
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void set (const Item& item, const Prio& value) {
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int i=_iim[item];
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if ( i>=0 && _data[i].in ) {
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if ( _comp(value, _data[i].prio) ) decrease(item, value);
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if ( _comp(_data[i].prio, value) ) increase(item, value);
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} else push(item, value);
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}
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/// \brief Insert an item into the heap with the given priority.
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///
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/// This function inserts the given item into the heap with the
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/// given priority.
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/// \param item The item to insert.
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/// \param value The priority of the item.
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/// \pre \e item must not be stored in the heap.
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void push (const Item& item, const Prio& value) {
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int i=_iim[item];
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if( i<0 ) {
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int s=_data.size();
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_iim.set(item, s);
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store st;
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st.name=item;
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_data.push_back(st);
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i=s;
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} else {
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_data[i].parent=_data[i].child=-1;
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_data[i].left_child=false;
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_data[i].degree=0;
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_data[i].in=true;
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}
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_data[i].prio=value;
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if ( _num_items!=0 ) {
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if ( _comp( value, _data[_min].prio) ) {
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fuse(i,_min);
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_min=i;
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}
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else fuse(_min,i);
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}
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else _min=i;
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++_num_items;
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}
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/// \brief Return the item having minimum priority.
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///
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/// This function returns the item having minimum priority.
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/// \pre The heap must be non-empty.
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Item top() const { return _data[_min].name; }
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/// \brief The minimum priority.
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///
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/// This function returns the minimum priority.
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/// \pre The heap must be non-empty.
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const Prio& prio() const { return _data[_min].prio; }
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/// \brief The priority of the given item.
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///
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/// This function returns the priority of the given item.
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/// \param item The item.
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/// \pre \e item must be in the heap.
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const Prio& operator[](const Item& item) const {
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return _data[_iim[item]].prio;
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}
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/// \brief Remove the item having minimum priority.
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///
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/// This function removes the item having minimum priority.
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/// \pre The heap must be non-empty.
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void pop() {
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std::vector<int> trees;
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int i=0, child_right = 0;
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_data[_min].in=false;
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if( -1!=_data[_min].child ) {
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i=_data[_min].child;
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trees.push_back(i);
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_data[i].parent = -1;
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_data[_min].child = -1;
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int ch=-1;
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while( _data[i].child!=-1 ) {
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ch=_data[i].child;
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if( _data[ch].left_child && i==_data[ch].parent ) {
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break;
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} else {
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if( _data[ch].left_child ) {
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child_right=_data[ch].parent;
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_data[ch].parent = i;
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--_data[i].degree;
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}
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else {
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child_right=ch;
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_data[i].child=-1;
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_data[i].degree=0;
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}
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_data[child_right].parent = -1;
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trees.push_back(child_right);
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i = child_right;
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}
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}
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int num_child = trees.size();
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int other;
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for( i=0; i<num_child-1; i+=2 ) {
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if ( !_comp(_data[trees[i]].prio, _data[trees[i+1]].prio) ) {
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other=trees[i];
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trees[i]=trees[i+1];
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trees[i+1]=other;
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}
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fuse( trees[i], trees[i+1] );
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}
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i = (0==(num_child % 2)) ? num_child-2 : num_child-1;
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while(i>=2) {
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if ( _comp(_data[trees[i]].prio, _data[trees[i-2]].prio) ) {
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other=trees[i];
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trees[i]=trees[i-2];
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trees[i-2]=other;
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}
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fuse( trees[i-2], trees[i] );
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i-=2;
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}
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_min = trees[0];
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}
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else {
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_min = _data[_min].child;
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}
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if (_min >= 0) _data[_min].left_child = false;
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--_num_items;
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}
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/// \brief Remove the given item from the heap.
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///
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/// This function removes the given item from the heap if it is
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/// already stored.
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/// \param item The item to delete.
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/// \pre \e item must be in the heap.
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void erase (const Item& item) {
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int i=_iim[item];
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if ( i>=0 && _data[i].in ) {
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decrease( item, _data[_min].prio-1 );
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pop();
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}
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}
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/// \brief Decrease the priority of an item to the given value.
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///
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/// This function decreases the priority of an item to the given value.
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/// \param item The item.
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/// \param value The priority.
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/// \pre \e item must be stored in the heap with priority at least \e value.
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void decrease (Item item, const Prio& value) {
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int i=_iim[item];
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_data[i].prio=value;
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int p=_data[i].parent;
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if( _data[i].left_child && i!=_data[p].child ) {
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p=_data[p].parent;
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}
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if ( p!=-1 && _comp(value,_data[p].prio) ) {
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cut(i,p);
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if ( _comp(_data[_min].prio,value) ) {
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fuse(_min,i);
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} else {
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fuse(i,_min);
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_min=i;
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}
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}
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}
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/// \brief Increase the priority of an item to the given value.
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///
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/// This function increases the priority of an item to the given value.
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/// \param item The item.
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/// \param value The priority.
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/// \pre \e item must be stored in the heap with priority at most \e value.
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void increase (Item item, const Prio& value) {
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erase(item);
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push(item,value);
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}
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/// \brief Return the state of an item.
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///
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/// This method returns \c PRE_HEAP if the given item has never
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/// been in the heap, \c IN_HEAP if it is in the heap at the moment,
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/// and \c POST_HEAP otherwise.
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/// In the latter case it is possible that the item will get back
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/// to the heap again.
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/// \param item The item.
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State state(const Item &item) const {
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int i=_iim[item];
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if( i>=0 ) {
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if( _data[i].in ) i=0;
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else i=-2;
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}
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return State(i);
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}
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/// \brief Set the state of an item in the heap.
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///
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/// This function sets the state of the given item in the heap.
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/// It can be used to manually clear the heap when it is important
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/// to achive better time complexity.
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/// \param i The item.
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/// \param st The state. It should not be \c IN_HEAP.
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void state(const Item& i, State st) {
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switch (st) {
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case POST_HEAP:
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case PRE_HEAP:
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if (state(i) == IN_HEAP) erase(i);
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_iim[i]=st;
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break;
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case IN_HEAP:
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break;
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}
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}
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private:
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void cut(int a, int b) {
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int child_a;
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switch (_data[a].degree) {
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case 2:
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child_a = _data[_data[a].child].parent;
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if( _data[a].left_child ) {
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_data[child_a].left_child=true;
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_data[b].child=child_a;
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_data[child_a].parent=_data[a].parent;
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}
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else {
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_data[child_a].left_child=false;
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_data[child_a].parent=b;
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if( a!=_data[b].child )
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_data[_data[b].child].parent=child_a;
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else
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_data[b].child=child_a;
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}
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--_data[a].degree;
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_data[_data[a].child].parent=a;
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break;
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case 1:
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child_a = _data[a].child;
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if( !_data[child_a].left_child ) {
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--_data[a].degree;
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if( _data[a].left_child ) {
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_data[child_a].left_child=true;
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_data[child_a].parent=_data[a].parent;
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_data[b].child=child_a;
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}
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else {
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_data[child_a].left_child=false;
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_data[child_a].parent=b;
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if( a!=_data[b].child )
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_data[_data[b].child].parent=child_a;
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else
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_data[b].child=child_a;
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}
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_data[a].child=-1;
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}
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else {
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--_data[b].degree;
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if( _data[a].left_child ) {
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_data[b].child =
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(1==_data[b].degree) ? _data[a].parent : -1;
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} else {
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if (1==_data[b].degree)
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_data[_data[b].child].parent=b;
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else
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_data[b].child=-1;
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}
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}
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break;
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case 0:
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--_data[b].degree;
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if( _data[a].left_child ) {
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_data[b].child =
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(0!=_data[b].degree) ? _data[a].parent : -1;
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} else {
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if( 0!=_data[b].degree )
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_data[_data[b].child].parent=b;
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else
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_data[b].child=-1;
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}
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break;
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}
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_data[a].parent=-1;
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_data[a].left_child=false;
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}
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void fuse(int a, int b) {
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int child_a = _data[a].child;
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int child_b = _data[b].child;
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_data[a].child=b;
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_data[b].parent=a;
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_data[b].left_child=true;
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if( -1!=child_a ) {
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_data[b].child=child_a;
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_data[child_a].parent=b;
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_data[child_a].left_child=false;
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++_data[b].degree;
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if( -1!=child_b ) {
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_data[b].child=child_b;
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_data[child_b].parent=child_a;
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}
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}
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else { ++_data[a].degree; }
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}
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class store {
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friend class PairingHeap;
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Item name;
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int parent;
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int child;
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bool left_child;
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int degree;
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bool in;
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Prio prio;
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store() : parent(-1), child(-1), left_child(false), degree(0), in(true) {}
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};
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};
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} //namespace lemon
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#endif //LEMON_PAIRING_HEAP_H
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