OpenTTD: CBinaryHeapT< T > Class Template Reference

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CBinaryHeapT< T > Class Template Reference

Binary Heap as C++ template. More...

`#include <binaryheap.hpp>`

## Public Member Functions
| CBinaryHeapT (uint max_items)
| Create a binary heap.
uint | Length () const
| Get the number of items stored in the priority queue.
bool | IsEmpty () const
| Test if the priority queue is empty.
bool | IsFull () const
| Test if the priority queue is full.
T * | Begin ()
| Get the smallest item in the binary tree.
T * | End ()
| Get the LAST item in the binary tree.
void | Include (T *new_item)
| Insert new item into the priority queue, maintaining heap order.
T * | Shift ()
| Remove and return the smallest (and also first) item from the priority queue.
void | Remove (uint index)
| Remove item at given index from the priority queue.
uint | FindIndex (const T &item) const
| Search for an item in the priority queue.
void | Clear ()
| Make the priority queue empty.

## Protected Member Functions
uint | HeapifyDown (uint gap, T *item)
| Get position for fixing a gap (downwards).
uint | HeapifyUp (uint gap, T *item)
| Get position for fixing a gap (upwards).

## Private Attributes
uint | items
| Number of items in the heap.
uint | capacity
| Maximum number of items the heap can hold.
T ** | data
| The pointer to the heap item pointers.

## Detailed Description

### template<class T>
class CBinaryHeapT< T >

Binary Heap as C++ template.

A carrier which keeps its items automatically holds the smallest item at the first position. The order of items is maintained by using a binary tree. The implementation is used for priority queue's.

Usage information:
  Item of the binary heap should support the 'lower-than' operator '<'. It is used for comparing items before moving them to their position.

  This binary heap allocates just the space for item pointers. The items are allocated elsewhere.

Implementation notes:
  Internally the first item is never used, because that simplifies the implementation.

  For further information about the Binary Heap algorithm, see http://www.policyalmanac.org/games/binaryHeaps.htm

Template Parameters

  T | Type of the items stored in the binary heap

Definition at line 53 of file binaryheap.hpp.

## Constructor & Destructor Documentation

template<class T>

CBinaryHeapT< T >::CBinaryHeapT | ( | uint | max_items | ) |
| inlineexplicit

Create a binary heap.

Parameters

  max_items | The limit of the heap

Definition at line 64 of file binaryheap.hpp.

## Member Function Documentation

template<class T>

T* CBinaryHeapT< T >::Begin | ( |  | ) |
| inline

Get the smallest item in the binary tree.

Returns
  The smallest item, or throw assert if empty.

Definition at line 181 of file binaryheap.hpp.

Referenced by CNodeList_HashTableT< Titem_, Thash_bits_open_, Thash_bits_closed_ >::GetBestOpenNode(), and CBinaryHeapT< Titem_ >::Shift().

template<class T>

void CBinaryHeapT< T >::Clear | ( |  | ) |
| inline

Make the priority queue empty.

All remaining items will remain untouched.

Definition at line 290 of file binaryheap.hpp.

template<class T>

T* CBinaryHeapT< T >::End | ( |  | ) |
| inline

Get the LAST item in the binary tree.

Note
  The last item is not necessary the biggest!

Returns
  The last item

Definition at line 194 of file binaryheap.hpp.

Referenced by CBinaryHeapT< Titem_ >::Remove(), and CBinaryHeapT< Titem_ >::Shift().

template<class T>

uint CBinaryHeapT< T >::FindIndex | ( | const T & | item | ) | const
| inline

Search for an item in the priority queue.

Matching is done by comparing address of the item.

Parameters

  item | The reference to the item

Returns
  The index of the item or zero if not found

Definition at line 275 of file binaryheap.hpp.

Referenced by CNodeList_HashTableT< Titem_, Thash_bits_open_, Thash_bits_closed_ >::PopOpenNode().

template<class T>

uint CBinaryHeapT< T >::HeapifyDown | ( | uint | gap,
|  | T * | item
| ) |  |
| inlineprotected

Get position for fixing a gap (downwards).

The gap is moved downwards in the binary tree until it is in order again.

Parameters

  gap | The position of the gap
  item | The proposed item for filling the gap

Returns
  The (gap)position where the item fits

Definition at line 88 of file binaryheap.hpp.

Referenced by CBinaryHeapT< Titem_ >::Remove(), and CBinaryHeapT< Titem_ >::Shift().

template<class T>

uint CBinaryHeapT< T >::HeapifyUp | ( | uint | gap,
|  | T * | item
| ) |  |
| inlineprotected

Get position for fixing a gap (upwards).

The gap is moved upwards in the binary tree until the is in order again.

Parameters

  gap | The position of the gap
  item | The proposed item for filling the gap

Returns
  The (gap)position where the item fits

Definition at line 124 of file binaryheap.hpp.

Referenced by CBinaryHeapT< Titem_ >::Include(), and CBinaryHeapT< Titem_ >::Remove().

template<class T>

void CBinaryHeapT< T >::Include | ( | T * | new_item | ) |
| inline

Insert new item into the priority queue, maintaining heap order.

Parameters

  new_item | The pointer to the new item

Definition at line 204 of file binaryheap.hpp.

Referenced by CNodeList_HashTableT< Titem_, Thash_bits_open_, Thash_bits_closed_ >::InsertOpenNode().

template<class T>

bool CBinaryHeapT< T >::IsEmpty | ( |  | ) | const
| inline

Test if the priority queue is empty.

Returns
  True if empty

Definition at line 167 of file binaryheap.hpp.

Referenced by CBinaryHeapT< Titem_ >::Begin(), CBinaryHeapT< Titem_ >::FindIndex(), CNodeList_HashTableT< Titem_, Thash_bits_open_, Thash_bits_closed_ >::GetBestOpenNode(), CNodeList_HashTableT< Titem_, Thash_bits_open_, Thash_bits_closed_ >::PopBestOpenNode(), CBinaryHeapT< Titem_ >::Remove(), and CBinaryHeapT< Titem_ >::Shift().

template<class T>

bool CBinaryHeapT< T >::IsFull | ( |  | ) | const
| inline

Test if the priority queue is full.

Returns
  True if full.

Definition at line 174 of file binaryheap.hpp.

Referenced by CBinaryHeapT< Titem_ >::Include().

template<class T>

uint CBinaryHeapT< T >::Length | ( |  | ) | const
| inline

Get the number of items stored in the priority queue.

Returns
  The number of items in the queue

Definition at line 160 of file binaryheap.hpp.

template<class T>

void CBinaryHeapT< T >::Remove | ( | uint | index | ) |
| inline

Remove item at given index from the priority queue.

Parameters

  index | The position of the item in the heap

Definition at line 247 of file binaryheap.hpp.

Referenced by CNodeList_HashTableT< Titem_, Thash_bits_open_, Thash_bits_closed_ >::PopOpenNode().

template<class T>

T* CBinaryHeapT< T >::Shift | ( |  | ) |
| inline

Remove and return the smallest (and also first) item from the priority queue.

Returns
  The pointer to the removed item

Definition at line 225 of file binaryheap.hpp.

Referenced by CNodeList_HashTableT< Titem_, Thash_bits_open_, Thash_bits_closed_ >::PopBestOpenNode().

The documentation for this class was generated from the following file:

- src/misc/binaryheap.hpp