C++模版技术实现简单双向链表

//
// C++ 模版技术实现简单双向链表示例. 
// 
 
#include <cstdlib>
#include <iostream>
#include <iomanip>
#include <stdexcept>
 
// 双向链表类模版前置声明
template <typename T> class DoublyLinkedList; 
 
//
// 双向链表节点类模版. 
// 
template <typename T>
class Node
{
        friend class DoublyLinkedList<T>;
        
private:
        T _value;
        Node<T> *_pPrior, *_pNext;

public:
        Node(void)
                : _pPrior(NULL)
                , _pNext(NULL)
        { NULL; }
        
        explicit Node(const T &val)
                : _value(val)
                , _pPrior(NULL)
                , _pNext(NULL)  
        { NULL; }
        
        T& getValue(void)
        { return _value; }
        
        Node<T>* getPrior(void)
        { return _pPrior; }
        
        Node<T>* getNext(void)
        { return _pNext; }      
};
 
//
// 双向链表类模版 
//
template <typename T>
class DoublyLinkedList 
{
private:
        Node<T> *_pHead;
        
public:
        DoublyLinkedList(void);
        ~DoublyLinkedList(void);
        void clear(void);
        size_t length(void) const;
        T& visit(const size_t pos);
        Node<T>* add(const T &val);
        Node<T>* insert(const size_t pos, const T &val);
        Node<T>* search(const T &val) const;
        Node<T>* remove(const size_t pos);        
};
 
 
template <typename T>
DoublyLinkedList<T>::DoublyLinkedList(void)
{
        _pHead = new Node<T>();
} 
 
 
template <typename T>
DoublyLinkedList<T>::~DoublyLinkedList(void)
{
        clear();
        delete _pHead;
} 
 
//
// 清空链表中插入的所有节点，头节点除外. 
//
template <typename T> 
void DoublyLinkedList<T>::clear(void)
{
        for (Node<T> *pDel = _pHead->_pNext; NULL != pDel; pDel = pDel->_pNext)
        {
                _pHead->_pNext = pDel->_pNext;
#if !defined(NDEBUG)
                std::cout << "删除值：" << pDel->_value << std::endl; 
#endif  
                delete pDel;
        }
} 
 
//
// 求节点总数，排除头结点.
// 
template <typename T> 
size_t DoublyLinkedList<T>::length(void) const
{
        size_t len = 0;

        for (Node<T> *pTemp = _pHead->_pNext; NULL != pTemp; ++len)
        { pTemp = pTemp->_pNext; }
        
        return len;     
} 
 
//
// 在指定位置 pos 插入节点，若 pos 过大，则在表尾插入.返回插入节点指针. 
// 
template <typename T> 
T& DoublyLinkedList<T>::visit(const size_t pos)
{
        Node<T> *pVisit = _pHead->_pNext;
        
        for (size_t i = 0; NULL != pVisit && i < pos; ++i, pVisit = pVisit->_pNext)
        { NULL; }
        
        if (NULL == pVisit)
        {
                throw std::overflow_error("访问链表节点越界 !");
        }
        
        return pVisit->_value;
}
 
//
// 在链表头节点后插入新节点.
//
template <typename T> 
Node<T>* DoublyLinkedList<T>::add(const T &val)
{
        Node<T> *pNew = new Node<T>(val);
        
        pNew->_pNext = _pHead->_pNext;
        _pHead->_pNext = pNew;
        
        return pNew;
} 
 
//
// 在指定位置 pos 插入节点，若 pos 过大，则在表尾插入.返回插入节点指针. 
// 
template <typename T> 
Node<T>* DoublyLinkedList<T>::insert(const size_t pos, const T &val)
{
        Node<T> *pPrev = _pHead;
        
        for (size_t i = 0; NULL != pPrev->_pNext && i < pos; ++i)
        { pPrev = pPrev->_pNext; }
        
        Node<T> *pNew = new Node<T>(val);
        pNew->_pNext = pPrev->_pNext;
        pPrev->_pNext = pNew;
        
#if !defined(NDEBUG)
        std::cout << "插入节点：" << pNew->_value << std::endl; 
#endif

        return pNew;
}
 
//
// 根据指定的数据值查找节点，找到返回节点指针，否则返回 NULL. 
// 
template <typename T> 
Node<T>* DoublyLinkedList<T>::search(const T &val) const
{
        Node<T> *pTemp = _pHead->_pNext;
        
        for (NULL; NULL != pTemp && val != pTemp->_value; pTemp = pTemp->_pNext)
        { NULL; } 
        
        return pTemp;
}
 
//
// 删除指定位置节点，并返回前一节点指针，
// 若 pos 过大则不删除，返回最后一个节点指针.
//
template <typename T>
Node<T>* DoublyLinkedList<T>::remove(const size_t pos)
{
        Node<T> *pPrev = _pHead;
        
        for (size_t i = 0; NULL != pPrev->_pNext && i < pos; ++i)
        {
                pPrev = pPrev->_pNext;
        }
        
        if (NULL != pPrev->_pNext)
        {
                Node<T> *pDel = pPrev->_pNext;
                pPrev->_pNext = pDel->_pNext;
#if !defined(NDEBUG)
                std::cout << "删除节点：" << pDel->_value << std::endl; 
#endif
                delete pDel;
        }
        
        return pPrev; 
}
 
//
// 在 main 函数结束后调用，防止控制台一闪而过. 
//
void calledAfterMain(void)
{
        system("pause");
}
 
//
// 测试链表 
// 
int main(void)
{
        const size_t MAX_LIST_SIZE = 10;
        DoublyLinkedList<int> linkedList;
        
        for (size_t i = 0; i < MAX_LIST_SIZE; ++i)
        {
                // linkedList.insert(i, i);
                linkedList.add(i);
        }
        
        std::cout << "链表长度: " << linkedList.length() << std::endl; 
        
        try
        {
                for (size_t i = 0; i < MAX_LIST_SIZE + 1; ++i)
                {
                        std::cout << std::setw(3) << linkedList.visit(i);
                }
                std::cout << std::endl;
        }
        catch (const std::exception &e)
        {
                std::cout << std::endl << e.what() << std::endl;
        }
        
        atexit(calledAfterMain);
        return EXIT_SUCCESS;
}