单链表模板类

链表是最基本的数据结构，是一组不连续的数据的集合，链表中每个结点除包含结点元素外，还包含下一结点的地址。对链表可以实现插入、删除、查找以及显示等操作。

/* * 单链表模板类List.h */ #ifndef _LIST_H_#define _LIST_H_#include <iostream>using namespace std;template <class TYPE>class List{public:    List();    List(TYPE x[], int n);    List(const List<TYPE> *l);    ~List();    void insert(const TYPE &x);    bool remove(const TYPE &x);    void display() const;    int size() const;    int at(int x, TYPE &k) const;private:    struct ListNode    {        TYPE data;        ListNode *next;    };    ListNode *list;    void insert(ListNode *&l, const TYPE &x);    bool remove(ListNode *&l, const TYPE &x);    void display(ListNode *l) const;    int size(ListNode *l) const;    int at(ListNode *l, int x, TYPE &k) const;};#endif// 构造函数template <class TYPE>List<TYPE>::List(){    list = new ListNode;    list->next = NULL;}// 利用数组初始化链表template <class TYPE>List<TYPE>::List(TYPE x[], int n){    list = new ListNode;    list->next = NULL;    for(int i = 0; i < n; ++i)    {        insert(list, x[i]);    }}// 利用链表初始化链表template <class TYPE>List<TYPE>::List(const List<TYPE> *l){    if(l->list == NULL)        list = NULL;    else    {        ListNode *p = l->list->next;        ListNode *pt = list = new ListNode;        while(p)        {            ListNode *q = new ListNode;            q->data = p->data;            q->next = NULL;            pt->next = q;            pt = q;            p = p->next;        }    }}// 析构函数template <class TYPE>List<TYPE>::~List(){    List *p = list->next;    while(p)    {        list->next = p->next;        free(p);        p = list->next;    }}// 外部调用插入数据方法template <class TYPE>void List<TYPE>::insert(const TYPE &x){    insert(list, x);}// 内部调用向List插入数据template <class TYPE>void List<TYPE>::insert(ListNode *&l, const TYPE &x){    ListNode *node = new ListNode;    node->data = x;    node->next = l->next;    l->next = node;}// 删除值为x的，删除成功返回true，失败返回falsetemplate <class TYPE>bool List<TYPE>::remove(const TYPE &x){    remove(list, x);}template <class TYPE>bool List<TYPE>::remove(ListNode *&l, const TYPE &x){    if(l == NULL)        return false;    ListNode *p = l->next;    ListNode *pre = l;    while(p && p->data != x)    {        pre = p;        p = p->next;    }    if(p)    {        pre->next = p->next;        delete p;    }    return true;}// 打印链表元素template <class TYPE>void List<TYPE>::display() const{    display(list);}template <class TYPE>void List<TYPE>::display(ListNode *l) const{    if(l != NULL)    {        ListNode *p = l->next;        if(p == NULL)        {            cout << "链表为空！" << endl;            return;        }        while(p)        {            cout << p->data << " ";            p = p->next;        }    }    else        cout << "链表不存在！" << endl;}// 返回链表中元素个数template <class TYPE>int List<TYPE>::size() const{    size(list);}template <class TYPE>int List<TYPE>::size(ListNode *l) const{    int s = 0;    if(l != NULL)    {        ListNode *p = l->next;        while(p)        {            s++;            p = p->next;        }    }    return s;}/* * 根据索引值取链表中的元素 * 如果索引值大于链表的大小返回-1 * 否则将索引值处结点的值保存在k中并返回1 */template <class TYPE>int List<TYPE>::at(int x, TYPE &k) const{    return at(list, x, k);}template <class TYPE>int List<TYPE>::at(ListNode *l, int x, TYPE &k) const{    if(size(l) < x || x <= 0)    {        return -1;    }    else    {        int i = 0;        ListNode *p = l->next;        while(p && i < x)        {            p = p->next;            i++;        }        k = p->data;    }    return 1;}