BucketHeap< IM, MIN > Class Template Reference

Detailed Description

template<typename IM, bool MIN = true>
class lemon::BucketHeap< IM, MIN >

This class implements the bucket 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. The bucket heap is very simple implementation, it can store only integer priorities and it stores for each priority in the range a list of items. So it should be used only when the priorities are small. It is not intended to use as dijkstra heap.

Parameters

IM	A read and write Item int map, used internally to handle the cross references.
MIN	If the given parameter is false then instead of the minimum value the maximum can be retrivied with the top() and prio() member functions.

#include <lemon/bucket_heap.h>

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

Public Member Functions
	BucketHeap (ItemIntMap &map)
	The constructor.
int	size () const
	Returns 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	push (const Pair &p)
	Insert a pair of item and priority into the heap.
void	push (const Item &i, const Prio &p)
	Insert an item into the heap with the given priority.
Item	top () const
	Returns the item with minimum priority.
Prio	prio () const
	Returns the minimum priority.
void	pop ()
	Deletes the item with minimum priority.
void	erase (const Item &i)
	Deletes i from the heap.
Prio	operator[] (const Item &i) const
	Returns the priority of i.
void	set (const Item &i, const Prio &p)
	i gets to the heap with priority p independently if i was already there.
void	decrease (const Item &i, const Prio &p)
	Decreases the priority of i to p.
void	increase (const Item &i, const Prio &p)
	Increases the priority of i to p.
State	state (const Item &i) 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

BucketHeap ( ItemIntMap &  map )

inlineexplicit

The constructor.

Parameters

map	should be given to the constructor, since it is used internally to handle the cross references. The value of the map should be PRE_HEAP (-1) for each element.

Member Function Documentation

int size ( ) const

inline

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 push ( const Pair &  p )

inline

Adds p.first to the heap with priority p.second.

Parameters

p	The pair to insert.

void push ( const Item &  i, const Prio &  p  )

inline

Adds i to the heap with priority p.

Parameters

i	The item to insert.
p	The priority of the item.

Item top ( ) const

inline

This method returns the item with minimum priority.

Precondition

The heap must be nonempty.

Prio prio ( ) const

inline

It returns the minimum priority.

Precondition

The heap must be nonempty.

void pop ( )

inline

This method deletes the item with minimum priority from the heap.

Precondition

The heap must be non-empty.

void erase ( const Item &  i )

inline

This method deletes item i from the heap, if i was already stored in the heap.

Parameters

i	The item to erase.

Prio operator[] ( const Item &  i ) const

inline

This function returns the priority of item i.

Precondition

i must be in the heap.

Parameters

i

The item.

void set ( const Item &  i, const Prio &  p  )

inline

This method calls push(i, p) if i is not stored in the heap and sets the priority of i to p otherwise.

Parameters

i	The item.
p	The priority.

void decrease ( const Item &  i, const Prio &  p  )

inline

This method decreases the priority of item i to p.

Precondition

i must be stored in the heap with priority at least p relative to Compare.

Parameters

i	The item.
p	The priority.

void increase ( const Item &  i, const Prio &  p  )

inline

This method sets the priority of item i to p.

Precondition

i must be stored in the heap with priority at most p relative to Compare.

Parameters

i	The item.
p	The priority.

State state ( const Item &  i ) 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.

Parameters

i

The item.

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.