建立专门的链表类处理有关动态链表的操作 扩展二

#include<iostream>using namespace std;template <class TT,class PP>class Student  //结点类{public:    Student(TT n,PP s){num=n;score=s;next=NULL;}    ~Student(){};    Student *next;   //指向下一个结点    TT num;    PP score;};class MyList  //链表类{public:    MyList(){head=NULL;}    MyList(int n,double s); //以Student(n,s)作为单结点的链表    ~MyList();    int display();  //输出链表，返回值为链表中的结点数    void insert(int n,double s);  //插入一系列结点：将Student(n,s)结点插入链表，该结点作为第一个结点    void append(int n,double s);  //追加：将Student(n,s)结点插入链表，该结点作为最后一个结点    void cat(MyList &il); //将链表il连接到当前对象的后面    int length();  //返回链表中的结点数private:    Student<int,double> *head;   //链表的头结点};//以下为类成员函数的定义MyList::MyList(int n,double s){    head=new  Student<int,double>(n,s);}MyList::~MyList(){    while(head!=NULL)    {        Student<int,double> *p=head;        head=head->next;        delete p;    }    head=NULL;}int MyList::display(){    int i=0;    Student<int,double> *head1=head;    while(head1!=NULL)    {        cout<<"num:"<<head1->num<<"\t"<<"score:"<<head1->score<<endl;        head1=head1->next;        ++i;    }    head1=NULL;    return i;}void MyList::insert (int n,double s)//熟练运用点的两种顺序插入{    Student<int,double> *pt=new Student<int,double>(n,s);    pt->next=head;    head=pt;}void MyList::append(int n,double s)//关键点在于如何遍历到最后一点{    Student<int,double> *head2=head;    if(head==NULL)head=new Student<int,double>(n,s);    else    {    while(head2->next!=NULL)head2=head2->next;    head2->next=new Student<int,double>(n,s);    }//  head2->next->num=n;//之前的错误写法，没有分配空间就赋值//  head2->next->score=s;//  head2->next->next=NULL;}//void MyList::cat(MyList &il)//错误在于将一个链表直接附加到另外的链表后，导致析构时附加的链表被析构两次//{                                                  //在函数尾部将附加的链表头置为NULL，就不会出错//                                                   //但是这样貌似也不是很好//  Student *pt=head;//  while(pt->next!=NULL)pt=pt->next;//  pt->next=il.head;//  il.head=NULL;//}void MyList::cat(MyList& il){    Student<int,double> *pt=il.head;    while(pt)    {        append(pt->num,pt->score);        pt=pt->next;    }}int MyList::length(){    int i=0;    Student<int,double> *head1=head;    while(head1!=NULL)    {        head1=head1->next;        ++i;    }    head1=NULL;    return i;}//测试函数int main(){    int n;    double s;    MyList head1;    cout<<"input head1: "<<endl;  //输入head1链表    for(int i=0;i<2;i++)    {        cin>>n>>s;        head1.insert(n,s);  //通过“插入”的方式    }    cout<<"head1: "<<endl; //输出head1    head1.display();    MyList head2(1001,98.4);  //建立head2链表    head2.append(1002,73.5);  //通过“追加”的方式增加结点    head2.append(1003,92.8);    head2.append(1004,99.7);    cout<<"head2: "<<endl;   //输出head2    head2.display();    head2.cat(head1);   //把head1追加到head2后面    cout<<"length of head2 after cat: "<<head2.length()<<endl;    cout<<"head2 after cat: "<<endl;   //显示追加后的结果    head2.display();    return 0;}