OpenTTD Source  20241111-master-gce64d5f5d9
CBinaryHeapT< T > Class Template Reference

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

#include <binaryheap.hpp>

Public Member Functions

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

Protected Member Functions

size_t HeapifyDown (size_t gap, T *item)
 Get position for fixing a gap (downwards). More...
 
size_t HeapifyUp (size_t gap, T *item)
 Get position for fixing a gap (upwards). More...
 

Private Attributes

size_t items = 0
 Number of valid items in the heap.
 
std::vector< 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 queues.

There are two major differences compared to std::priority_queue. First the std::priority_queue does not support indexing/removing elements in the middle of the heap/queue and second it has the biggest item first.

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
TType of the items stored in the binary heap

Definition at line 53 of file binaryheap.hpp.

Constructor & Destructor Documentation

◆ CBinaryHeapT()

template<class T >
CBinaryHeapT< T >::CBinaryHeapT ( size_t  initial_capacity)
inlineexplicit

Create a binary heap.

Parameters
initial_capacityThe initial reserved capacity for the heap.

Definition at line 63 of file binaryheap.hpp.

References CBinaryHeapT< T >::Clear().

Member Function Documentation

◆ Begin()

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 172 of file binaryheap.hpp.

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

◆ Clear()

template<class T >
void CBinaryHeapT< T >::Clear ( )
inline

Make the priority queue empty.

All remaining items will remain untouched.

Definition at line 273 of file binaryheap.hpp.

References CHECK_CONSISTY.

Referenced by CBinaryHeapT< T >::CBinaryHeapT().

◆ End()

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 185 of file binaryheap.hpp.

◆ FindIndex()

template<class T >
size_t 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
itemThe reference to the item
Returns
The index of the item or zero if not found

Definition at line 263 of file binaryheap.hpp.

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

◆ HeapifyDown()

template<class T >
size_t CBinaryHeapT< T >::HeapifyDown ( size_t  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
gapThe position of the gap
itemThe proposed item for filling the gap
Returns
The (gap)position where the item fits

Definition at line 79 of file binaryheap.hpp.

◆ HeapifyUp()

template<class T >
size_t CBinaryHeapT< T >::HeapifyUp ( size_t  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
gapThe position of the gap
itemThe proposed item for filling the gap
Returns
The (gap)position where the item fits

Definition at line 115 of file binaryheap.hpp.

◆ Include()

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

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

Parameters
new_itemThe pointer to the new item

Definition at line 195 of file binaryheap.hpp.

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

◆ IsEmpty()

template<class T >
bool CBinaryHeapT< T >::IsEmpty ( ) const
inline

◆ Length()

template<class T >
size_t 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 152 of file binaryheap.hpp.

References CBinaryHeapT< T >::items.

◆ Remove()

template<class T >
void CBinaryHeapT< T >::Remove ( size_t  index)
inline

Remove item at given index from the priority queue.

Parameters
indexThe position of the item in the heap

Definition at line 233 of file binaryheap.hpp.

References CBinaryHeapT< T >::items.

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

◆ Shift()

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 210 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: