优先队列(priority queue)

        普通的队列是一种先进先出的数据结构，元素在队列尾追加，而从队列头删除。在优先队列中，元素被赋予优先级。当访问元素时，具有最高优先级的元素最先删除。优先队列具有最高进先出 （largest-in，first-out）的行为特征。

        例如下图：任务的优先权及执行顺序的关系
        

        优先队列是0个或多个元素的集合,每个元素都有一个优先权或值

时间复杂度

        Push时进行排序
                有序链表（即顺序存储结构），则插入时找插入点的时间复杂度为O(n)
                直接出链表表头（也就是队头元素）的时间复杂度为O(1)

        Pop时进行遍历
                有序链表（即顺序存储结构），则插入时找插入点的时间复杂度为O(1)
                遍历出优先级最高的链表表头（也就是队头元素）的时间复杂度为O(n)

======================================================================================================

        队列是一种特殊的线性表，特殊之处在于它只允许在表的前端（front）进行删除操作，而在表的后端（rear）进行插入操作，和栈一样，队列是一种操作受限制的线性表。进行插入操作的端称为队尾，进行删除操作的端称为队头。队列中没有元素时，称为空队列。

        在队列这种数据结构中，最先插入的元素将是最先被删除的元素；反之最后插入的元素将是最后被删除的元素，因此队列又称为“先进先出”（FIFO—first in first out）的线性表。

队列（Queue）是只允许在一端进行插入，而在另一端进行删除的运算受限的线性表
        （1）允许删除的一端称为队头（Front）。
        （2）允许插入的一端称为队尾（Rear）。
        （3）当队列中没有元素时称为空队列。
        （4）队列亦称作先进先出（First In First Out）的线性表，简称为FIFO表。
       

        队列的修改是依先进先出的原则进行的。新来的成员总是加入队尾（即不允许"加塞"），每次离开的成员总是队列头上的（不允许中途离队），即当前"最老的"成员离队。

链式存储结构
        在计算机中用一组任意的存储单元存储线性表的数据元素(这组存储单元可以是连续的,也可以是不连续的).
        它不要求逻辑上相邻的元素在物理位置上也相邻.因此它没有顺序存储结构所具有的弱点,但也同时失去了顺序表可随机存取的优点.


        链式存储结构特点：
                1、比顺序存储结构的存储密度小 (每个节点都由数据域和指针域组成，所以相同空间内假设全存满的话顺序比链式存储更多)。
                2、逻辑上相邻的节点物理上不必相邻。
                3、插入、删除灵活 (不必移动节点，只要改变节点中的指针)。
                4、查找结点时链式存储要比顺序存储慢。
                5、每个结点是由数据域和指针域组成。

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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       C++完整个代码示例（代码在VS2005下测试可运行）

AL_QueuePriorityList.h

/**
  @(#)$Id: AL_QueuePriorityList.h 40 2013-09-10 09:14:44Z xiaoting $
  @brief   
  ////////////////////////////////Priority queue (priority queue)e//////////////////////////////////////////
  Common queue is a FIFO data structure, the end of an additional element in the queue, and the head removed from the queue. In the 
  priority queue element is given priority. When accessing the element, the element with the highest priority first removed. Priority 
  queue with the highest first-out (largest-in, first-out) the behavioral characteristics.
  
  Priority queue is 0 or more elements of the collection, each element has a priority or value of the operations performed on the 
  priority queue with a) Find; 2) Insert a new element; 3) Delete in the minimum priority queue (min priorityq ueue), the lookup 
  operation to search for smallest element priority, delete operation to remove the element; for maximum priority queue (max priority 
  queue), lookup to search for the largest element of the priority, delete operation is used remove the element. priority queue 
  element can have the same priority, find and delete operations can be carried out according to any priority.

  A queue is a special linear form, so special is that it only allows the front end of the table (front) delete operation, 
  and the rear end of the table (rear) for insertion, and the stack, as the queue is an operating by restricted linear form. Insert 
  operation is called the tail end, the end delete operation called HOL. No element in the queue, it is called an empty queue.
  
  This data structure in the queue, the first element inserted will be the first element to be removed; otherwise the last inserted 
  element will be the last element to be removed, so the queue is also known as "first in first out" (FIFO-first in first out) linear 
  form.

  @Author $Author: xiaoting $
  @Date $Date: 2013-09-10 17:14:44 +0800 (周二, 10 九月 2013) $
  @Revision $Revision: 40 $
  @URL $URL: https://svn.code.sf.net/p/xiaoting/game/trunk/MyProject/AL_DataStructure/groupinc/AL_QueuePriorityList.h $
  @Header $Header: https://svn.code.sf.net/p/xiaoting/game/trunk/MyProject/AL_DataStructure/groupinc/AL_QueuePriorityList.h 40 2013-09-10 09:14:44Z xiaoting $
 */

#ifndef CXX_AL_QUEUEPRIORITYLIST_H
#define CXX_AL_QUEUEPRIORITYLIST_H

///////////////////////////////////////////////////////////////////////////
//			AL_QueuePriorityList
///////////////////////////////////////////////////////////////////////////

template<typename T>  
class AL_QueuePriorityList
{
public:
	/**
	* Construction Constructed using the default priority queue
	*
	* @param
	* @return
	* @note
	* @attention	The default precedence relations: big > small
	*/
	AL_QueuePriorityList();

	/**
	* Destruction
	*
	* @param
	* @return
	* @note
	* @attention
	*/
	~AL_QueuePriorityList();

	/**
	* IsEmpty
	*
	* @param	VOID
	* @return	BOOL
	* @note		Returns true queue is empty
	* @attention
	*/
	BOOL IsEmpty() const;

	/**
	* Front
	*
	* @param	VOID
	* @return	T
	* @note		Returns a reference to the first element at the front of the queue.
	* @attention
	*/
	T Front() const;

	/**
	* Back
	*
	* @param	VOID
	* @return	T
	* @note		Returns a reference to the last and most recently added element at the back of the queue.
	* @attention
	*/
	T Back() const;

	/**
	* Pop
	*
	* @param	VOID
	* @return	T
	* @note		Removes an element from the front of the queue.
	* @attention
	*/
	T Pop();

		
	/**
	* Push
	*
	* @param	const T& tTemplate
	* @return	BOOL
	* @note		Adds an element to the back of the queue.
	* @attention	
	*/
	BOOL Push(const T& tTemplate);

	/**
	* Size
	*
	* @param	VOID
	* @return	DWORD
	* @note		Returns the number of elements in the queue
	* @attention
	*/
	DWORD Size() const;

	/**
	* Clear
	*
	* @param	VOID
	* @return	VOID
	* @note		clear all data
	* @attention
	*/
	VOID Clear();
	
protected:
private:

public:
protected:
private: 
	AL_Node<T>*		m_pHeader;
	DWORD			m_dwSize;

	AL_Node<T>*		m_pFront;
	AL_Node<T>*		m_pRear;
};


/**
* Construction Constructed using the default priority queue
*
* @param
* @return
* @note
* @attention	The default precedence relations: big > small
*/
template<typename T> 
AL_QueuePriorityList<T>::AL_QueuePriorityList():
m_pHeader(NULL),
m_dwSize(0x00),
m_pFront(NULL),
m_pRear(NULL)
{
	m_pHeader = new AL_Node<T>;

}

/**
* Destruction
*
* @param
* @return
* @note
* @attention
*/
template<typename T> 
AL_QueuePriorityList<T>::~AL_QueuePriorityList()
{
	Clear();
	//delete the header
	if (NULL != m_pHeader) {
		delete m_pHeader;
		m_pHeader = NULL;
	}
}

/**
* IsEmpty
*
* @param	VOID
* @return	BOOL
* @note		Returns true queue is empty
* @attention
*/
template<typename T> BOOL 
AL_QueuePriorityList<T>::IsEmpty() const
{
	return (0x00 == m_pHeader->m_pNext) ? TRUE:FALSE;
}


/**
* Front
*
* @param	VOID
* @return	T
* @note		Returns a reference to the first element at the front of the queue.
* @attention
*/
template<typename T> T 
AL_QueuePriorityList<T>::Front() const
{
	T tTypeTemp;
	memset(&tTypeTemp, 0x00, sizeof(T));

	if (TRUE ==IsEmpty()) {
		return tTypeTemp;
	}

	return m_pFront->m_data;
}

/**
* Back
*
* @param	VOID
* @return	T
* @note		Returns a reference to the last and most recently added element at the back of the queue.
* @attention
*/
template<typename T> T 
AL_QueuePriorityList<T>::Back() const
{
	T tTypeTemp;
	memset(&tTypeTemp, 0x00, sizeof(T));

	if (TRUE ==IsEmpty()) {
		return tTypeTemp;
	}

	return m_pRear->m_data;
}

/**
* Pop
*
* @param	VOID
* @return	T
* @note		Removes an element from the front of the queue.
* @attention
*/
template<typename T> T 
AL_QueuePriorityList<T>::Pop()
{
	T tTypeTemp;
	memset(&tTypeTemp, 0x00, sizeof(T));

	if (TRUE ==IsEmpty()) {
		return tTypeTemp;
	}
	
	AL_Node<T>*	pPop = m_pFront;
	//get the previous node of m_pRear
	m_pHeader->m_pNext = m_pFront->m_pNext;
	m_pFront = m_pHeader->m_pNext;
	tTypeTemp = pPop->m_data;

	//delete the top
	delete pPop;
	pPop = NULL;

	m_dwSize--;
	return tTypeTemp;
}

	
/**
* Push
*
* @param	const T& tTemplate
* @return	BOOL
* @note		Adds an element to the back of the queue.
* @attention	
*/
template<typename T> BOOL 
AL_QueuePriorityList<T>::Push(const T& tTemplate)
{
	AL_Node<T>*	pPush = new AL_Node<T>;
	if (NULL == pPush) {
		//new error
		return FALSE;
	}
	pPush->m_data = tTemplate;

	if (TRUE == IsEmpty()) {
		//the first time Push, not need to ++
		m_pHeader->m_pNext = pPush;
		m_pFront = m_pHeader->m_pNext;
		m_pRear = pPush;
	}
	else {
		AL_Node<T>*	pMove = m_pFront;
		AL_Node<T>*	pMovePre = m_pFront;
		while(NULL != pMove) {
			if (tTemplate > pMove->m_data) {
				//bigger
				break;
			}
			pMovePre = pMove;
			pMove = pMove->m_pNext;
		}
		if (NULL == pMove) {
			//smallest in the queue
			m_pRear->m_pNext = pPush;
			m_pRear = pPush;
		}
		else {
			if (m_pFront == pMovePre) {
				//inset to the front
				pPush->m_pNext = m_pFront;
				m_pFront = pPush;
				m_pHeader->m_pNext = m_pFront;
			}
			else {
				pPush->m_pNext = pMovePre->m_pNext;
				pMovePre->m_pNext = pPush;
			}
		}
	}

	m_dwSize++;
	return TRUE;
}

/**
* Size
*
* @param	VOID
* @return	DWORD
* @note		Returns the number of elements in the queue
* @attention
*/
template<typename T> DWORD 
AL_QueuePriorityList<T>::Size() const
{
	return m_dwSize;
}

/**
* Clear
*
* @param	VOID
* @return	VOID
* @note		clear all data
* @attention
*/
template<typename T> VOID 
AL_QueuePriorityList<T>::Clear()
{
	AL_Node<T>* pDelete = NULL;
	while(NULL != m_pHeader->m_pNext){
		//get the node
		pDelete = m_pHeader->m_pNext;
		m_pHeader->m_pNext = pDelete->m_pNext;
		delete pDelete;
		pDelete = NULL;
	}
	m_dwSize = 0x00;
}

#endif // CXX_AL_QUEUEPRIORITYLIST_H
/* EOF */

测试代码

#ifdef TEST_AL_QUEUEPRIORITYLIST
	AL_QueuePriorityList<DWORD> cQueuePriorityList;
	BOOL bEmpty = cQueuePriorityList.IsEmpty();
	std::cout<<bEmpty<<std::endl;
	DWORD dwSize = cQueuePriorityList.Size();
	std::cout<<dwSize<<std::endl;
	DWORD dwFront = cQueuePriorityList.Front();
	std::cout<<dwFront<<std::endl;
	DWORD dwBack = cQueuePriorityList.Back();
	std::cout<<dwBack<<std::endl;
	DWORD dwPop = cQueuePriorityList.Pop();
	std::cout<<dwPop<<std::endl;

	cQueuePriorityList.Push(999);
	bEmpty = cQueuePriorityList.IsEmpty();
	std::cout<<bEmpty<<std::endl;
	dwSize = cQueuePriorityList.Size();
	std::cout<<dwSize<<std::endl;
	dwFront = cQueuePriorityList.Front();
	std::cout<<dwFront<<std::endl;
	dwBack = cQueuePriorityList.Back();
	std::cout<<dwBack<<std::endl;
	dwPop = cQueuePriorityList.Pop();
	std::cout<<dwPop<<std::endl;

	DWORD dwTestNum[]={14,10,56,7,83,22,36,91,3,47,72,0,91,100,7};
	for (DWORD dwCnt=0; dwCnt<(sizeof(dwTestNum)/sizeof(DWORD)); dwCnt++) {
		cQueuePriorityList.Push(dwTestNum[dwCnt]);
		dwBack = cQueuePriorityList.Back();
		std::cout<<dwTestNum[dwCnt]<<std::endl;
	}

	dwSize = cQueuePriorityList.Size();
	std::cout<<dwSize<<std::endl;
	for (DWORD dwCount=0; dwCount<dwSize; dwCount++) {
		dwPop = cQueuePriorityList.Pop();
		std::cout<<dwPop<<std::endl;
	}
	struct sMySelfData {
		BOOL operator > (sMySelfData sData) const{
			return this->dwPriority > sData.dwPriority;
		}
		DWORD dwPriority;
		DWORD dwValue;
	};
	// 	class sMySelfData {
	// 	public:
	// 		BOOL operator > (sMySelfData sData) const{
	// 			return this->dwPriority > sData.dwPriority;
	// 		}
	// 		DWORD dwPriority;
	// 		DWORD dwValue;
	// 	};
	bEmpty = cQueuePriorityList.IsEmpty();
	std::cout<<bEmpty<<std::endl;
	dwSize = cQueuePriorityList.Size();
	std::cout<<dwSize<<std::endl;
	dwFront = cQueuePriorityList.Front();
	std::cout<<dwFront<<std::endl;
	dwBack = cQueuePriorityList.Back();
	std::cout<<dwBack<<std::endl;
	dwPop = cQueuePriorityList.Pop();
	std::cout<<dwPop<<std::endl;

	//test myself data
	sMySelfData sData1;
	memset(&sData1, 0x00, sizeof(sMySelfData));
	sMySelfData sData2;
	memset(&sData1, 0x00, sizeof(sMySelfData));
	sMySelfData sData3;
	memset(&sData1, 0x00, sizeof(sMySelfData));
	sMySelfData sData4;
	memset(&sData1, 0x00, sizeof(sMySelfData));
	sData1.dwPriority = 1;
	sData1.dwValue = 1;
	sData2.dwPriority = 2;
	sData2.dwValue = 2;
	sData3.dwPriority = 3;
	sData3.dwValue = 3;
	sData4.dwPriority = 2;
	sData4.dwValue = 4;
	sMySelfData sData5;

	AL_QueuePriorityList<sMySelfData> cQueuePriorityListMy;
	cQueuePriorityListMy.Push(sData1);
	cQueuePriorityListMy.Push(sData2);
	cQueuePriorityListMy.Push(sData3);
	cQueuePriorityListMy.Push(sData4);

	dwSize = cQueuePriorityListMy.Size();
	std::cout<<dwSize<<std::endl;

	sMySelfData sData;
	memset(&sData, 0x00, sizeof(sMySelfData));
	for (DWORD dwCount=0; dwCount<dwSize; dwCount++) {
		memset(&sData, 0x00, sizeof(sMySelfData));
		sData = cQueuePriorityListMy.Pop();
		std::cout<<sData.dwPriority<<" "<<sData.dwValue<<std::endl;
	}
#endif