单链表c++实现

#include<iostream>
using namespace std;
//单链表
class point{//结点类
public:
    int data;
    point *next;
};

class line{//单链表
public:
    int length;
    point *head;

    line();
    void show();//输出元素
    void creat_line(int n);//创建单链表
    void insert_elem(int i,int n);//插入元素
    void delete_elem(int i);//删除元素
    void delete_line();//删除单链表
    void print_length();//打印单链表长度
};

line::line(){//建立一个空表
    head=new point; 
    length=0;
    head->data=0;
    head->next=NULL;
}

void line::creat_line(int n){//建立一个单链表
    if(n<0){
        cout<<"输入不合法"<<endl;
        return;
    }
    point *temp,*new_elem;
    temp=head;//从头指针开始增加元素
    for(int i=0;i<n;i++){
        int m=0;
        new_elem=new point;
        cout<<"请为第"<<i+1<<"个元素赋值:";
        cin>>m;
        new_elem->data=m;
        new_elem->next=NULL;
        temp->next=new_elem;
        temp=new_elem;
        length++;
    }
}
void line::show(){//遍历输出单链表中的元素
    if(head==NULL){
        cout<<"此表为一个空表"<<endl;
        return;
    }
    point *temp=head;
    while(temp->next != NULL){
        temp=temp->next;
        cout<<temp->data<<" ";
    }
}
void line::insert_elem(int i,int n){//把元素值为n的数据插入到第i个元素之前
    if(i<0||i>=length+1){
        cout<<"插入的位置不存在"<<endl;
        return;
    }
    point *temp,*new_elem;
    temp=head;
    for(int i1=1;i1<i;i1++){
        temp=temp->next;
    }
    new_elem=new point;
    new_elem->data=n;
    new_elem->next=temp->next;
    temp->next=new_elem;
    length++;
}
void line::delete_elem(int i){//删除第i个元素
    if(head==NULL){
        cout<<"此表已经是空表了"<<endl;
        return;
    }
    point *temp,*p;
    temp=head;
    for(int i1=1;i1<i;i1++){
        temp=temp->next;
    }

    p=temp->next;
    temp->next=temp->next->next;
    delete p;
    p=NULL;
    length--;
}
void line::delete_line(){//整表删除
    if(head==NULL){
        cout<<"此表为空表了"<<endl;
        return;
    }
    point *temp1,*tem;
    temp1=head->next;
    tem=new point;
    while(temp1!=NULL){
        tem=temp1;
        temp1=temp1->next;
        head->next=temp1;
        tem->next=NULL;
        delete tem;
    }
    head->next=NULL;
}
void line::print_length(){
    cout<<"表的长度为"<<length<<endl;
}

int main(){
    line l;
    l.creat_line(4);
    l.insert_elem(2,100);
    l.delete_elem(4);
    l.show();
    l.print_length();

    return 0;
}