Public Types | Public Member Functions

Heap< PR, IM, Comp > Class Template Reference


Detailed Description

template<typename PR, typename IM, typename Comp = std::less<PR>>
class lemon::concepts::Heap< PR, IM, Comp >

Concept class describing the main interface of heaps. 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. In a heap one can change the priority of an item, add or erase an item, etc.

Template Parameters:
PRType of the priority of the items.
IMA read and writable item map with int values, used internally to handle the cross references.
CompA functor class for the ordering of the priorities. The default is std::less<PR>.

#include <lemon/concepts/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 PR Prio
 Type of the priorities.
typedef ItemIntMap::Key Item
 Type of the items stored in the heap.

Public Member Functions

 Heap (ItemIntMap &map)
 The constructor.
int size () const
 The number of items stored in the heap.
bool empty () const
 Checks if the heap is empty.
void clear ()
void push (const Item &i, const Prio &p)
 Inserts an item into the heap with the given priority.
Item top () const
 Returns the item having minimum priority.
Prio prio () const
 The minimum priority.
void pop ()
 Removes the item having minimum priority.
void erase (const Item &i)
 Removes an item from the heap.
Prio operator[] (const Item &i) const
 The priority of an item.
void set (const Item &i, const Prio &p)
 Sets the priority of an item or inserts it, if it is not stored in the heap.
void decrease (const Item &i, const Prio &p)
 Decreases the priority of an item to the given value.
void increase (const Item &i, const Prio &p)
 Increases the priority of an item to the given value.
State state (const Item &i) const
 Returns if an 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 an item in the heap.

Member Enumeration Documentation

enum State

Each item has a state associated to it. It can be "in heap", "pre heap" or "post heap". The later two are indifferent from the point of view of the heap, but may be useful for 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. The "in heap" state constant.

PRE_HEAP 

= -1. The "pre heap" state constant.

POST_HEAP 

= -2. The "post heap" state constant.


Constructor & Destructor Documentation

Heap ( ItemIntMap map) [inline, explicit]

The constructor.

Parameters:
mapA map that assigns int values to keys of type Item. It is used internally by the heap implementations to handle the cross references. The assigned value must be PRE_HEAP (-1) for every item.

Member Function Documentation

int size ( ) const [inline]

Returns the number of items stored in the heap.

bool empty ( ) const [inline]

Returns true if the heap is empty.

void clear ( )

Makes the heap empty.

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

Inserts the given item into the heap with the given priority.

Parameters:
iThe item to insert.
pThe priority of the item.
Item top ( ) const [inline]

Returns the item having minimum priority.

Precondition:
The heap must be non-empty.
Prio prio ( ) const [inline]

Returns the minimum priority.

Precondition:
The heap must be non-empty.
void pop ( ) [inline]

Removes the item having minimum priority.

Precondition:
The heap must be non-empty.
void erase ( const Item i) [inline]

Removes the given item from the heap if it is already stored.

Parameters:
iThe item to delete.
Prio operator[] ( const Item i) const [inline]

Returns the priority of the given item.

Parameters:
iThe item.
Precondition:
i must be in the heap.
void set ( const Item i,
const Prio p 
) [inline]

This method sets the priority of the given item if it is already stored in the heap. Otherwise it inserts the given item with the given priority.

Parameters:
iThe item.
pThe priority.
void decrease ( const Item i,
const Prio p 
) [inline]

Decreases the priority of an item to the given value.

Parameters:
iThe item.
pThe priority.
Precondition:
i must be stored in the heap with priority at least p.
void increase ( const Item i,
const Prio p 
) [inline]

Increases the priority of an item to the given value.

Parameters:
iThe item.
pThe priority.
Precondition:
i must be stored in the heap with priority at most p.
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:
iThe item.
void state ( const Item i,
State  st 
) [inline]

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

Parameters:
iThe item.
stThe state. It should not be IN_HEAP.
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