SimpleBucketHeap< IM, MIN > Class Template Reference

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 faster and simplier data structure than the BucketHeap. The main difference is that the BucketHeap stores for every key a double linked list while this class stores just simple lists. In the other way it does not support erasing each elements just the minimal and it does not supports key increasing, decreasing.

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.

See Also

BucketHeap

#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...

Public Member Functions
	SimpleBucketHeap (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.
Prio	operator[] (const Item &i) const
	Returns the priority of i.
State	state (const Item &i) const
	Returns if item is in, has already been in, or has never been 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

SimpleBucketHeap ( 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.

Prio operator[] ( const Item &  i ) const

inline

This function returns the priority of item i.

Warning

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

Precondition

i must be in the heap.

Parameters

i

The item.

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.