单链表C++

#include <iostream>

using namespace std;

template<typename T>

class List
{
public:
    struct Node
    {
        T data;
        Node *next;
    };
    int theSize;
    List()
    {
        head = new Node;
        int theSize = 0;
    }

    ~List()
    {
        if(theSize == 0)
        {
            delete head;
            head = NULL;
            cout<<endl;
            cout<<"SIZE=0析构"<<endl;
        }
        else
        {
            while(head->next != NULL)
            {
                Node *ptemp = head;
                head = head->next;
                delete ptemp;
            }
            delete head;
            head = NULL;
            cout<<endl;
            cout<<"清除链表析构"<<endl;
        }
        cout<<endl;
        cout<<"*************析构函数***************";
    }

    void CreateList(int n)   //创建链表
    {
        int i = n;
        theSize = n;
        if(n<0)
            cout<<"输入错误结点个数:"<<endl;
        Node *p = head;
        while(n-->0)
        {
            cout<<"输入第"<<i-n<<"个结点的值:"<<endl;
            Node *ptemp = new Node;
            cin>>ptemp->data;
            p->data = ptemp->data;
            p->next = ptemp;
            p = ptemp;
        }
    }

    void erasePos(int pos)  //删除链表某个位置的值
    {
        if(this->theSize == 0)
            cout<<"链表为空！"<<endl;
        if(pos > theSize)
            cout<<"输入位置超出链表长度！"<<endl;
        else
        {
            Node *p = head;
            for(int i = 1; i < pos-1; i++)
                p = p->next;
            p->next = p->next->next;
            theSize--;
        }
    }

    void eraseAll()    //删除链表
    {
        if(theSize > 0)
        {
            Node *cur = head;
            while(theSize>0)
            {
                Node *p = new Node;
                p = cur->next;
                cur = p;
                delete p;
                theSize--;
            }
            delete cur;
            cout<<"链表清除成功！";
            cout<<"*******"<<"链表一共有"<<theSize<<"个结点！"<<endl;
        }
        else
            cout<<"链表本身为空！"<<endl;
    }

    void push_back()   //在链表尾部插入值
    {
        Node *p = head;
        if(theSize >= 0)
        {
            T dd;
            cout<<"插入的值为：";
            cin>>dd;
            int i = theSize;
            for(; i>1; --i)
                p = p->next;
            Node *ptemp = new Node;
            ptemp->data = dd;
            ptemp->next= NULL;
            p->next = ptemp;
            theSize++;
            cout<<"成功在尾部添加："<<dd<<endl;
        }
        else
            cout<<"结点数有误！"<<endl;
        this->Show();
    }

    void findNode(int k)     //查找第k个结点
    {
        if(theSize ==0)
        {
            cout<<"链表为空！"<<endl;
        }
        if(k > theSize || k <= 0)
        {
            cout<<"输入的结点数有误！"<<endl;
        }
        else
        {
            Node *p = head;
            for(int i = 1; i<k; i++)
                p = p->next;
            cout<<"第"<<k<<"个结点为："<<p->data<<endl;
        }
    }

    void insertPos(int pos)   //指定位置插入结点
    {
        T d;
        if(pos<0 || pos>theSize+1)
            cout<<"输入的结点数有误！"<<endl;
        if(pos == (theSize+1))
        {
            this->push_back();
        }
        else
        {
            Node *p = head;
            for(int i = 1; i<pos-1; i++)
                p = p->next;
            cout<<"在第"<<pos<<"个结点插入：";
            cin>>d;
            Node *ptemp = new Node;
            ptemp->next = p->next;
            ptemp->data = d;
            p->next = ptemp;
            p = ptemp;
            theSize++;
            cout<<"插入结点后的链表为：";
            this->Show();
        }
    }

    void isExist()    //查找某个值是否存在
    {
        if(theSize == 0)
            cout<<"链表为空！"<<endl;
        else
        {
            cout<<"你所要查找的元素为：";
            T d;
            cin>>d;
            Node *p = head;
            int Num = 0;
            for(int i = 1; i <= theSize; i++)
            {
                Num += p->data == d?1:0;
                p = p->next;
            }
            if(Num>0)
                cout<<"值为"<<d<<"的结点"<<"有"<<Num<<"个！"<<endl;
            else
                cout<<"不存在值为"<<d<<"的结点！"<<endl;
        }
    }

    void inverseList()    //逆序链表
    {
        if(theSize == 0)
            cout<<"链表为空！"<<endl;
        else
        {
            int n = theSize;
            for(; n>=1; n--)
            {
                Node *p = head;
                for(int i=1; i<n; i++)
                    p = p->next;
                cout<<p->data<<" ; ";
            }
            cout<<"*******"<<"链表一共有"<<theSize<<"个结点！"<<endl;
        }
    }

    void Show()    //显示链表信息
    {
        Node *p = head;
        for(int i = 1; i <= theSize; i++)
        {
            cout<<p->data<<" ; ";
            p = p->next;
        }
        cout<<"*******"<<"链表一共有"<<theSize<<"个结点！"<<endl;
    }
private:
    Node *head;
};

#include "List.h"

int main()
{
    List<double> ln1;
    int n;
    cout<<"一：确定建立链表的结点数：";
    cin>>n;
    ln1.CreateList(n);
    ln1.Show();
    cout<<endl;

    cout<<"二：在链表结尾插入：";
    ln1.push_back();
    cout<<endl;

    cout<<"三：所要查询的结点位置：";
    int k;
    cin>>k;
    ln1.findNode(k);
    cout<<endl;

    cout<<"四：插入结点的位置：";
    int t;
    cin>>t;
    ln1.insertPos(t);
    cout<<endl;

    cout<<"五：判断你所要查找的元素是否存在。"<<endl;
    ln1.isExist();
    cout<<endl;

    cout<<"六：要删除的结点：";
    int h;
    cin>>h;
    ln1.erasePos(h);
    ln1.Show();
    cout<<endl;

    cout<<"七：逆序链表：";
    ln1.inverseList();
    cout<<endl;

    cout<<"八：删除链表"<<endl;
    ln1.eraseAll();

    return 0;
}