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public/tier1/utlpriorityqueue.h

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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