FibHeap< PRIO, IM, CMP > Class Template Reference

Detailed Description

template<typename PRIO, typename IM, typename CMP>
class lemon::FibHeap< PRIO, IM, CMP >

This class implements the Fibonacci heap data structure. A heap is a data structure for storing items with specified values called priorities in such a way that finding the item with minimum priority is efficient. CMP specifies the ordering of the priorities. In a heap one can change the priority of an item, add or erase an item, etc.

The methods increase and erase are not efficient in a Fibonacci heap. In case of many calls to these operations, it is better to use a binary heap.

Parameters

PRIO	Type of the priority of the items.
IM	A read and writable Item int map, used internally to handle the cross references.
CMP	A class for the ordering of the priorities. The default is std::less<PRIO>.

See Also

BinHeap

Dijkstra

#include <lemon/fib_heap.h>

Public Types
enum	State { IN_HEAP = 0, PRE_HEAP = -1, POST_HEAP = -2 }
	Type to represent the items states. More...
typedef IM	ItemIntMap
typedef PRIO	Prio
typedef ItemIntMap::Key	Item
typedef std::pair< Item, Prio >	Pair
typedef CMP	Compare

Public Member Functions
	FibHeap (ItemIntMap &map)
	The constructor.
	FibHeap (ItemIntMap &map, const Compare &comp)
	The constructor.
int	size () const
	The number of items stored in the heap.
bool	empty () const
	Checks if the heap stores no items.
void	clear ()
	Make empty this heap.
void	set (const Item &item, const Prio &value)
	item gets to the heap with priority value independently if item was already there.
void	push (const Item &item, const Prio &value)
	Adds item to the heap with priority value.
Item	top () const
	Returns the item with minimum priority relative to Compare.
const Prio &	prio () const
	Returns the minimum priority relative to Compare.
const Prio &	operator[] (const Item &item) const
	Returns the priority of item.
void	pop ()
	Deletes the item with minimum priority relative to Compare.
void	erase (const Item &item)
	Deletes item from the heap.
void	decrease (Item item, const Prio &value)
	Decreases the priority of item to value.
void	increase (Item item, const Prio &value)
	Increases the priority of item to value.
State	state (const Item &item) const
	Returns if item is in, has already been in, or has never been in the heap.
void	state (const Item &i, State st)
	Sets the state of the item in the heap.

Member Enumeration Documentation

enum State

Each Item element have a state associated to it. It may be "in heap", "pre heap" or "post heap". The latter two are indifferent from the heap's point of view, but may be useful to the user.

The item-int map must be initialized in such way that it assigns PRE_HEAP (-1) to any element to be put in the heap.

Enumerator:

IN_HEAP	= 0.
PRE_HEAP	= -1.
POST_HEAP	= -2.

Constructor & Destructor Documentation

FibHeap ( ItemIntMap &  map )

inlineexplicit

map should be given to the constructor, since it is used internally to handle the cross references.

FibHeap ( ItemIntMap &  map, const Compare &  comp  )

inline

map should be given to the constructor, since it is used internally to handle the cross references. comp is an object for ordering of the priorities.

Member Function Documentation

int size ( ) const

inline

Returns the number of items stored in the heap.

bool empty ( ) const

inline

Returns true if and only if the heap stores no items.

void clear ( )

inline

Make empty this heap. It does not change the cross reference map. If you want to reuse a heap what is not surely empty you should first clear the heap and after that you should set the cross reference map for each item to PRE_HEAP.

void set ( const Item &  item, const Prio &  value  )

inline

This method calls push(item, value) if item is not stored in the heap and it calls decrease(item, value) or increase(item, value) otherwise.

void push ( const Item &  item, const Prio &  value  )

inline

Adds item to the heap with priority value.

Precondition

item must not be stored in the heap.

Item top ( ) const

inline

This method returns the item with minimum priority relative to Compare.

Precondition

The heap must be nonempty.

const Prio& prio ( ) const

inline

It returns the minimum priority relative to Compare.

Precondition

The heap must be nonempty.

const Prio& operator[] ( const Item &  item ) const

inline

It returns the priority of item.

Precondition

item must be in the heap.

void pop ( )

inline

This method deletes the item with minimum priority relative to Compare from the heap.

Precondition

The heap must be non-empty.

void erase ( const Item &  item )

inline

This method deletes item from the heap, if item was already stored in the heap. It is quite inefficient in Fibonacci heaps.

void decrease ( Item  item, const Prio &  value  )

inline

This method decreases the priority of item to value.

Precondition

item must be stored in the heap with priority at least value relative to Compare.

void increase ( Item  item, const Prio &  value  )

inline

This method sets the priority of item to value. Though there is no precondition on the priority of item, this method should be used only if it is indeed necessary to increase (relative to Compare) the priority of item, because this method is inefficient.

State state ( const Item &  item ) const

inline

This method returns PRE_HEAP if item has never been in the heap, IN_HEAP if it is in the heap at the moment, and POST_HEAP otherwise. In the latter case it is possible that item will get back to the heap again.

void state ( const Item &  i, State  st  )

inline

Sets the state of the item in the heap. It can be used to manually clear the heap when it is important to achive the better time _complexity.

Parameters

i	The item.
st	The state. It should not be IN_HEAP.