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//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
// $NoKeywords: $
//=============================================================================//
#ifndef UTLPRIORITYQUEUE_H
#define UTLPRIORITYQUEUE_H
#ifdef _WIN32
#pragma once
#endif
#include "utlvector.h"
// T is the type stored in the queue, it must include the priority
// The head of the list contains the element with GREATEST priority
// configure the LessFunc_t to get the desired queue order
template< class T >
class CUtlPriorityQueue
{
public:
// Less func typedef
// Returns true if the first parameter is "less priority" than the second
// Items that are "less priority" sort toward the tail of the queue
typedef bool (*LessFunc_t)( T const&, T const& );
typedef T ElemType_t;
// constructor: lessfunc is required, but may be set after the constructor with
// SetLessFunc
CUtlPriorityQueue( int growSize = 0, int initSize = 0, LessFunc_t lessfunc = 0 );
CUtlPriorityQueue( T *pMemory, int numElements, LessFunc_t lessfunc = 0 );
// gets particular elements
inline T const& ElementAtHead() const { return m_heap.Element(0); }
inline bool IsValidIndex(int index) { return m_heap.IsValidIndex(index); }
// O(lgn) to rebalance the heap
void RemoveAtHead();
void RemoveAt( int index );
// O(lgn) to rebalance heap
void Insert( T const &element );
// Sets the less func
void SetLessFunc( LessFunc_t func );
// Returns the count of elements in the queue
inline int Count() const { return m_heap.Count(); }
// doesn't deallocate memory
void RemoveAll() { m_heap.RemoveAll(); }
// Memory deallocation
void Purge() { m_heap.Purge(); }
inline const T & Element( int index ) const { return m_heap.Element(index); }
protected:
CUtlVector<T> m_heap;
void Swap( int index1, int index2 );
// Used for sorting.
LessFunc_t m_LessFunc;
};
template< class T >
inline CUtlPriorityQueue<T>::CUtlPriorityQueue( int growSize, int initSize, LessFunc_t lessfunc ) :
m_heap(growSize, initSize), m_LessFunc(lessfunc)
{
}
template< class T >
inline CUtlPriorityQueue<T>::CUtlPriorityQueue( T *pMemory, int numElements, LessFunc_t lessfunc ) :
m_heap(pMemory, numElements), m_LessFunc(lessfunc)
{
}
template <class T>
void CUtlPriorityQueue<T>::RemoveAtHead()
{
m_heap.FastRemove( 0 );
int index = 0;
int count = Count();
if ( !count )
return;
int half = count/2;
int larger = index;
while ( index < half )
{
int child = ((index+1) * 2) - 1; // if we wasted an element, this math would be more compact (1 based array)
if ( child < count )
{
// Item has been filtered down to its proper place, terminate.
if ( m_LessFunc( m_heap[index], m_heap[child] ) )
{
// mark the potential swap and check the other child
larger = child;
}
}
// go to sibling
child++;
if ( child < count )
{
// If this child is larger, swap it instead
if ( m_LessFunc( m_heap[larger], m_heap[child] ) )
larger = child;
}
if ( larger == index )
break;
// swap with the larger child
Swap( index, larger );
index = larger;
}
}
template <class T>
void CUtlPriorityQueue<T>::RemoveAt( int index )
{
Assert(m_heap.IsValidIndex(index));
m_heap.FastRemove( index );
int count = Count();
if ( !count )
return;
int half = count/2;
int larger = index;
while ( index < half )
{
int child = ((index+1) * 2) - 1; // if we wasted an element, this math would be more compact (1 based array)
if ( child < count )
{
// Item has been filtered down to its proper place, terminate.
if ( m_LessFunc( m_heap[index], m_heap[child] ) )
{
// mark the potential swap and check the other child
larger = child;
}
}
// go to sibling
child++;
if ( child < count )
{
// If this child is larger, swap it instead
if ( m_LessFunc( m_heap[larger], m_heap[child] ) )
larger = child;
}
if ( larger == index )
break;
// swap with the larger child
Swap( index, larger );
index = larger;
}
}
template <class T>
void CUtlPriorityQueue<T>::Insert( T const &element )
{
int index = m_heap.AddToTail();
m_heap[index] = element;
while ( index != 0 )
{
int parent = ((index+1) / 2) - 1;
if ( m_LessFunc( m_heap[index], m_heap[parent] ) )
break;
// swap with parent and repeat
Swap( parent, index );
index = parent;
}
}
template <class T>
void CUtlPriorityQueue<T>::Swap( int index1, int index2 )
{
T tmp = m_heap[index1];
m_heap[index1] = m_heap[index2];
m_heap[index2] = tmp;
}
template <class T>
void CUtlPriorityQueue<T>::SetLessFunc( LessFunc_t lessfunc )
{
m_LessFunc = lessfunc;
}
#endif // UTLPRIORITYQUEUE_H
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