线性表——（3）双向链表

#include"ListNode.h"

template<class T>
class DoubleList
{
public:
    DoubleList() {
        head = new ListNode<T>();
        head->p_prior = head;
        head->p_next = head;
    }
    ~DoubleList() {
        Clear();
        delete head;
    }
    void Clear();   // 清空
    int Length() const; // length
    ListNode<T>* Find(T item);  // 查找item，返回指针，找不到返回空
    int GetItem(int n, T &targ);    // 查找n号元素，存入targ
    int Insert(int n, const T targ);    //  将targ插入n号前
    int Delete(int n);  // 删除n号

private:
    ListNode<T>* head;
};

template<class T>
inline void DoubleList<T>::Clear()
{
    ListNode<T>* p = head->p_next;
    ListNode<T>* pdel;
    while (p != head) {
        pdel = p;
        p = pdel->p_next;
        delete pdel;
    }
    p->p_prior = head;
    p->p_next = head;
}

template<class T>
inline int DoubleList<T>::Length() const
{
    int count = 0;
    ListNode<T>* p = head->p_next;
    while (p != head) {
        ++count;
        p = p->p_next;
    }
    return count;
}

template<class T>
inline ListNode<T>* DoubleList<T>::Find(T item)
{
    ListNode<T>* prior = head->p_prior;
    ListNode<T>* next = head->p_next;
    while (prior->p_next != next && prior != p_next) {
        if (prior->data == item)
            return prior;
        if (next->data == item)
            return next;
        prior = prior->p_prior;
        next = next->p_next;
    }
    return NULL;
}

template<class T>
inline int DoubleList<class T>::GetItem(int n, T & targ)
{
    if (n < 0)
        return 0;
    ListNode<T>* p = head;
    for (int i = 0; i < n; ++i) {
        p = p->p_next;
        if (p == head)
            return 0;
        T data = p->data;
        return data;
    }
}

template<class T>
inline int DoubleList<T>::Insert(int n, const T targ)
{
    if (n < 0)
        return 0;
    ListNode<T>* p_newnode = new ListNode<T>(targ);
    ListNode<T>* p = head;
    for (int i = 0; i < n; ++i) {
        p = p->p_next;
        if (p == head)
            return 0;
    }
    p_newnode->p_next = p->p_next;
    p_newnode->p_prior = p;
    p->p_next = p_newnode;
    p->p_next->p_prior = p_newnode;
    return 1;
}

template<class T>
inline int DoubleList<T>::Delete(int n)
{
    if (n < 0)
        return 0;
    ListNode<T>* p = head;
    ListNode<T>* pdel;
    for (int i = 0; i < n; ++i) {
        p = p->p_next;
        if (p == head)
            return 0;
    }
    pdel = p;
    p->p_prior->p_next = p->p_next;
    p->p_next->p_prior = p->p_prior;
    delete pdel;
    return 1;
}