RadixHeap< IM > Class Template Reference

Detailed Description

template<typename IM>
class lemon::RadixHeap< IM >

This class implements the radix 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. This heap type can store only items with int priority. In a heap one can change the priority of an item, add or erase an item, but the priority cannot be decreased under the last removed item's priority.

Parameters

IM	A read and writable Item int map, used internally to handle the cross references.

See Also

BinHeap

Dijkstra

#include <lemon/radix_heap.h>

Classes
class	UnderFlowPriorityError
	Exception thrown by RadixHeap. More...

Public Types
enum	State
	Type to represent the items states. More...

Public Member Functions
	RadixHeap (ItemIntMap &map, int minimal=0, int capacity=0)
	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 (int minimal=0, int capacity=0)
	Make empty this 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.

Private Member Functions
void	remove (int index)
	Remove item from the box list.
void	insert (int box, int index)
	Insert item into the box list.
void	extend ()
	Add a new box to the box list.
void	bubble_up (int index)
	Move an item up into the proper box.
int	findUp (int start, int pr)
	Find up the proper box for the item with the given prio.
void	bubble_down (int index)
	Move an item down into the proper box.
int	findDown (int start, int pr)
	Find up the proper box for the item with the given prio.
int	findFirst ()
	Find the first not empty box.
int	minValue (int box)
	Gives back the minimal prio of the box.
void	moveDown ()
	Rearrange the items of the heap and makes the first box not empty.

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 ItemIntMap should be initialized in such way that it maps PRE_HEAP (-1) to any element to be put in the heap...

Constructor & Destructor Documentation

RadixHeap ( ItemIntMap &  map, int  minimal = 0, int  capacity = 0  )

inline

The constructor.

Parameters

map	It 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.
minimal	The initial minimal value of the heap.
capacity	It determines the initial capacity of the heap.

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 ( int  minimal = 0, int  capacity = 0  )

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 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.

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. It may throw an UnderFlowPriorityException.

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, and should be greater or equal to the last removed item's priority.

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

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.