[英]Implementing a Generic Double linked list in c++
I have implemented a fairly simple idea of a double linked list.我已经实现了一个相当简单的双链表概念。 I don't know what am I doing wrong.
我不知道我做错了什么。 I have tried making the member variables of the node as public but doesn't help.
我尝试将节点的成员变量设为公开,但没有帮助。 Friend class doesn't help either?
朋友 class 也没有帮助? What is the nonclass type here?
这里的非类类型是什么?
d_list.h
d_list.h
#include "node.h"
#ifndef NODE_H
#define NODE_H
template<class T>
class d_list{
private:
int list_size;
T* head;
T* tail;
public:
//parametrized Default constructor
d_list(T* h=nullptr, T* t=nullptr):head(h),tail(t){}
//get Head of the List
T* gethead(){return this->head;}
T* gettail(){return this->tail;}
void addnodeastail(T* new_node){
if(this->head==nullptr){
this->head=new_node;//this->head will point towards new_node
this->tail=this->head;
this->list_size=list_size+1;
}
else{
this->tail= new_node;
this->tail->next=new_node->previous;
}
}
};
#endif
''' '''
node.h
节点.h
template<class T>
class Node{
private:
Node* next;
Node* previous;
T data;
public:
Node()=default;
Node(T dta):data(dta){}
~Node(){}
};
main.cpp
主文件
#include<iostream>
#include"d_list.h"
using namespace std;
int main(){
d_list<int> d1;
cout<<d1.gethead()<<endl;
cout<<d1.gettail()<<endl;
int var=20;
int* n1= &var;
int var2 =40;
int* n2= &var2;
d1.addnodeastail(n1);
d1.addnodeastail(n2);
cout<<d1.gethead()<<endl;
cout<<d1.gettail()<<endl;
return 0;
}
Error which I am receiving is something like
我收到的错误类似于
In file included from main.cpp:2:
d_list.h: In instantiation of 'void d_list<T>::addnodeastail(T*) [with T = int]':
main.cpp:14:24: required from here
d_list.h:28:29: error: request for member 'next' in '*((d_list<int>*)this)->d_list<int>::tail', which is of non-class type 'int'
28 | this->tail->next=new_node->previous;
| ~~~~~~~~~~~~^~~~
d_list.h:28:44: error: request for member 'previous' in '* new_node', which is of non-class type 'int'
28 | this->tail->next=new_node->previous;
| ~~~~~~~~~~^~~~~~~~
With和
template<class T>
class d_list{
private:
int list_size;
T* head;
T* tail;
you declare that head
and tail
are pointers to the template type T
.您声明
head
和tail
是指向模板类型T
的指针。
That means for d_list<int>
you effectively have这意味着对于
d_list<int>
你实际上有
int* head;
int* tail;
That makes no sense, your head and tail pointers should be pointers to the first and last nodes in the list:这没有任何意义,你的头和尾指针应该是指向列表中第一个和最后一个节点的指针:
Node<T>* head;
Node<T>* tail;
And when adding elements to the list, you need to create new Node<T>
instances to hold the data, and add the nodes to the list.并且在向列表中添加元素时,您需要创建新的
Node<T>
实例来保存数据,并将节点添加到列表中。
The thing is that head
and tail
shouldn't be T
, but rather node<T>
:问题是
head
和tail
不应该是T
,而是node<T>
:
Node<T>* head;
Node<T>* tail;
Remember, T
is the type of object you want to hold in your list.请记住,
T
是您要在列表中保留的 object 的类型。 It has no link associated with it.它没有与之关联的链接。 So if you do a
d_list<int>
currently as written, the templated code will look something like this:因此,如果您按当前编写的方式执行
d_list<int>
,则模板化代码将如下所示:
int* head;
int* tail;
These are not linked to each other, this is just a pointer to an int
(or a list of int
s if you used something like new
).它们没有相互链接,这只是一个指向
int
的指针(如果您使用了类似new
的东西,则为int
的列表)。 To create a link, you need to use Node
so o matter where in memory they are stored, they will have a logical connection.要创建链接,您需要使用
Node
,因此无论它们存储在 memory 的哪个位置,它们都将具有逻辑连接。 That way, d_list<int>
would look something like this instead:那样的话,
d_list<int>
会变成这样:
Node<int>* head;
Node<int>* tail;
This will let you use nodes to develop a logically connected list of int
s, which is exactly what you want for a linked list.这将允许您使用节点来开发
int
的逻辑连接列表,这正是您想要的链表。
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