SimpleBucketHeap< IM, MIN > Class Template Reference

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Detailed Description

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

This class implements a simplified bucket heap data structure. It does not provide some functionality, but it is faster and simpler than BucketHeap. The main difference is that BucketHeap stores a doubly-linked list for each key while this class stores only simply-linked lists. It supports erasing only for the item having minimum priority and it does not support key increasing and decreasing.

Note that this implementation does not conform to the heap concept due to the lack of some functionality.

Template Parameters:

IM	A read-writable item map with int values, used internally to handle the cross references.
MIN	Indicate if the heap is a min-heap or a max-heap. The default is min-heap. If this parameter is set to false, then the comparison is reversed, so the top(), prio() and pop() functions deal with the item having maximum priority instead of the minimum.

See also:

BucketHeap

#include <lemon/bucket_heap.h>

List of all members.

Public Types
enum	State { IN_HEAP = 0, PRE_HEAP = -1, POST_HEAP = -2 }
	Type to represent the states of the items. More...
typedef IM	ItemIntMap
	Type of the item-int map.
typedef int	Prio
	Type of the priorities.
typedef ItemIntMap::Key	Item
	Type of the items stored in the heap.
typedef std::pair< Item, Prio >	Pair
	Type of the item-priority pairs.
Public Member Functions
	SimpleBucketHeap (ItemIntMap &map)
	Constructor.
int	size () const
	The number of items stored in the heap.
bool	empty () const
	Check if the heap is empty.
void	clear ()
	Make the heap empty.
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
	Return the item having minimum priority.
Prio	prio () const
	The minimum priority.
void	pop ()
	Remove the item having minimum priority.
Prio	operator[] (const Item &i) const
	The priority of the given item.
State	state (const Item &i) const
	Return the state of an item.

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Member Enumeration Documentation

enum State

Each item has a state associated to it. It can 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.

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Constructor & Destructor Documentation

SimpleBucketHeap

(

ItemIntMap &

map

)

[inline, explicit]

Constructor.

Parameters:

map	A map that assigns int values to the items. It is used internally to handle the cross references. The assigned value must be PRE_HEAP (-1) for each item.

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Member Function Documentation

int size

(

)

const [inline]

This function returns the number of items stored in the heap.

bool empty

(

)

const [inline]

This function returns true if the heap is empty.

void clear

(

)

[inline]

This functon makes the heap empty. It does not change the cross reference map. If you want to reuse a heap that is not surely empty, you should first clear it and then you should set the cross reference map to PRE_HEAP for each item.

void push

(

const Pair &

p

)

[inline]

This function inserts p.first to the heap with priority p.second.

Parameters:

p	The pair to insert.

Precondition:

p.first must not be stored in the heap.

void push	(	const Item &	i,
		const Prio &	p
	)		[inline]

This function inserts the given item into the heap with the given priority.

Parameters:

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

Precondition:

i must not be stored in the heap.

Item top

(

)

const [inline]

This function returns the item having minimum priority.

Precondition:

The heap must be non-empty.

Prio prio

(

)

const [inline]

This function returns the minimum priority.

Precondition:

The heap must be non-empty.

void pop

(

)

[inline]

This function removes the item having minimum priority.

Precondition:

The heap must be non-empty.

Prio operator[]

(

const Item &

i

)

const [inline]

This function returns the priority of the given item.

Parameters:

i

The item.

Precondition:

i must be in the heap.

Warning:

This operator is not a constant time function because it scans the whole data structure to find the proper value.

State state

(

const Item &

i

)

const [inline]

This method returns PRE_HEAP if the given 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 the item will get back to the heap again.

Parameters:

i

The item.