製作鏈表：獲取分段錯誤

Question

我正在練習如何在C++中創建鏈接列表，代碼如下。我是否分配錯誤？我不確定它是否是我的構造函數，用於導致錯誤的節點或列表，但我不斷收到分段錯誤。我是一名初學者，我真的很想理解內存分配。

main.cpp中：

#include <iostream> 
#include <cstdio> 
#include <cstdlib> 
#include <string> 
#include "list.h" 
using namespace std; 


int main(void) 
{ 

int option; 
list *linked; 
linked = new list; 




while(1) 
{ 
// menu 
cout<<"********************************************"<<endl; 
cout<<" what option would you like to use "<<endl; 
cout<<" 1.add a node"<<endl; 
cout<<" 2.show list"<<endl; 
cout<<" 3.delete node"<<endl; 
cout<<"********************************************"<<endl; 
cin>>option; 
//switch for option 
    switch(option) 
    { 
    case 1 : 
    cout<<"you picked add a node"<<endl; 
    (*linked).add_node(); 
    break; 
    case 2 : 
    cout<<"you picked show list"<<endl; 
    break; 
    case 3 : 
    cout<<"you picked delete node"<<endl; 
    break; 
    default: 
    cout<<"thats not a valid option"<<endl; 
    break; 
    } 
} 

return 0; 

} 

list.h：

#include <iostream> 
#include <cstdio> 
#include <cstdlib> 
#include <string> 

using namespace std; 
class node 
{ 
private: 
node *next; 
node *prev; 
string note; 

public: 
// constructor 
node(); 
//gets 
node* get_next(void) 
{return next;} 
node* get_prev(void) 
{return prev;} 
// setts 
void set_next(node* x) 
{next=x;} 
void set_prev(node* x) 
{prev=x;} 
}; 
class list 
{ 
private: 
node *head, *current, *tail; 


public: 
//constructor 
list(); 

void add_node(void); 
}; 

node::node(void) 
{ 
string x; 
cout<<"hi"<<endl; 
//set front and back null 
next=NULL; 
prev=NULL; 

//write the note 
cout<<" what note would you like to write in the node"<<endl; 
cin>>x; 
note=x; 
} 
list::list(void){ 
//start the list pointing to null 
head = tail = NULL; 
} 
void list::add_node(void) 
{ 


//make first node 
    if(head=0){ 
head = new node; 
cout<<"1"<<endl; 
} 
//make 2nd node 
else if((*head).get_next()==0){ 
cout<<"2"<<endl; 
node* temp;// buffer 
temp= new node; 
(*head).set_next(temp); 
(*head).set_prev(temp); 
(*tail).set_next(head); 
(*tail).set_prev(head); 

} 





} 

---

Answer 1

我相信添加節點時，你所得到的故障。

我看到的問題是，第一次插入後，你已經正確地分配了一個頭，但沒有做任何事情的尾巴。在下一個插入中，因爲你的頭部有效，你進入'make second node'代碼塊，在這裏你試圖去引用尚未初始化的tail成員。