C++ language implements doubly linked list (an assignment in Guangzhou University)

The requirements are: design a doubly linked list to store the length and width of the rectangle, then save the area, and finally sort according to the area, to realize the IO of the file

#include<iostream>
#include <fstream>
using namespace std;
class Node          //组成双向链表的节点
{
 public:
     int lgth;  //长度
     int width;  //宽度
     int area;   //面积
     Node * pNext;
     Node * pLast;
};

class List
{
private:
    Node * pHead;
    Node * pTail;
    int length;
public:
    List(int length)
    {
        this->length=length;
        pHead=new Node();
        pHead->pLast=NULL;
        pTail=pHead;
        for(int i=0;i<length;i++)
        {
            Node * temp=new Node();
            cout<<"please enter the no"<<i+1<<" Node's data:";
            cin>>temp->lgth>>temp->width;
            temp->area = temp->lgth*temp->width;
            temp->pNext=NULL;
            temp->pLast=pTail;
            pTail->pNext=temp;
            pTail=temp;
        }
    }

    void traverseList()        //正向遍历
    {
        Node * p=pHead->pNext;
        while(p!=NULL)
        {
            cout<<p->area<<endl;
            p=p->pNext;
        }
    }

     void WriteListIntoFile()        //写进文件
    {
        ofstream fout( "f:\\mytest.txt" );
        if ( ! fout)
        {
            cout << "文件不能打开" <<endl;
        }
        else
        {
            Node * p=pHead->pNext;
            while(p!=NULL)
            {
                fout<<p->lgth<<" "<<p->width<<" "<<p->area<<endl;
                p=p->pNext;
            }
        }
    }

    void traverseListReturn()  //逆向遍历
    {
        Node * p=pTail;
        while(p->pLast!=NULL)
        {
            cout<<p->area<<endl;
            p=p->pLast;
        }
    }

    void sortList()     //冒泡排序，只是交换了某个信息，没有交换所有的信息
    {
        Node * p=new Node();
        Node * q=new Node();
        int temp;
        for(p=pHead->pNext;p->pNext!=NULL;p=p->pNext)
        {
            for(q=p->pNext;q!=NULL;q=q->pNext)
            {
                if(q->area<p->area)
                {
                    temp=q->area;
                    q->area=p->area;
                    p->area=temp;
                }
            }
        }
    }

    void sortListByInsertWay()        //插入排序
    {
        if(pHead->pNext==NULL||pHead->pNext->pNext==NULL)
        {
            return;
        }
        Node * p2=pHead->pNext->pNext;
        Node * p1=pHead;
        pHead->pNext->pNext=NULL;
        while(p2)
        {
            Node * pN=p2->pNext;
            while(p1->pNext)
            {
                if(p2->area<p1->pNext->area)
                {
                    p2->pNext=p1->pNext;
                    p2->pLast=p1;
                    p1->pNext->pLast=p2;
                    p1->pNext=p2;
                    break;
                }
                p1=p1->pNext;
            }
            if(p1->pNext==NULL)
            {
                p2->pNext=NULL;
                p2->pLast=p1;
                p1->pNext=p2;
            }
            p2=pN;
        }

        //重新查找pTail的位置
        Node * pt=pHead;
        while(pt->pNext)
        {
            pt=pt->pNext;
        }
        pTail=pt;
    }

    void changeList(int num,int position) //修改链表中指定位置的节点,修改面积信息
    {
        Node * p=pHead->pNext;
        if(position>length||position<=0)
        {
            cout<<"over stack !"<<endl;
            return;
        }
        for(int i=0;i<position-1;i++)
        {
            p=p->pNext;
        }
        p->area=num;
    }

    void insertList(int lgth,int width,int position) //插入数据
    {
        Node * p=pHead->pNext;
        if(position>length||position<=0)
        {
            cout<<"over stack !"<<endl;
            return;
        }
        for(int i=0;i<position-1;i++)
        {
            p=p->pNext;
        }
        Node * temp=new Node();
        temp->lgth=lgth;
        temp->width = width;
        temp->area = temp->lgth*temp->width;
        temp->pNext=p;
        temp->pLast=p->pLast;
        p->pLast->pNext=temp;
        p->pLast=temp;
        length++;
    }

    void clearList() //清空
    {
        Node * q;
        Node * p=pHead->pNext;
        while(p!=NULL)
        {
            q=p;
            p=p->pNext;
            delete q;
        }
        p=NULL;
        q=NULL;
    }

    void deleteList(int position) //删除指定位置的节点
    {
        Node * p=pHead->pNext;
        if(position>length||position<=0)
        {
            cout<<"over stack !"<<endl;
            return;
        }
        for(int i=0;i<position-1;i++)
        {
            p=p->pNext;
        }
        p->pLast->pNext=p->pNext;
        p->pNext->pLast=p->pLast;
        delete p;
        length--;
    }

    int getItemInList(int position)  //查找指定位置的节点 ,返回面积信息
    {
        Node * p=pHead->pNext;
        if(position>length||position<=0)
        {
            cout<<"over stack !"<<endl;
            return 0;
        }
        for(int i=0;i<position-1;i++)
        {
            p=p->pNext;
        }
        return p->area;
    }

    ~List()
    {
        Node * q;
        Node * p=pHead->pNext;
        while(p!=NULL)
        {
            q=p;
            p=p->pNext;
            delete q;
        }
        p=NULL;
        q=NULL;
    }

};

int main()
{
    int num = 0;
    printf("write in your list nums:");
    scanf("%d",&num);
    List l(num);
    l.traverseList();
    cout<<"AFTER SORT-------------------------------------------------------"<<endl;
    l.sortList();             //冒泡排序
    //l.sortListByInsertWay();    //插入排序
    l.traverseList();
    cout<<"AFTER INSERT-----------------------------------------------------"<<endl;
    l.insertList(55,20,1);
    l.traverseList();
    cout<<"AFTER DELETE-----------------------------------------------------"<<endl;
    l.deleteList(1);
    l.traverseList();
    cout<<"Return Traverse--------------------------------------------------"<<endl;
    l.traverseListReturn();
    cout<<"Write FILE-------------------------------------------------------"<<endl;
    l.WriteListIntoFile();
    cout<<"Find the Second Node's data:"<<l.getItemInList(2)<<endl;
    return 0;
}