-1

我正在为一个应该是双向链表的类编写程序。它可以编译，但是当我尝试执行命令 addleft 或 addright 时，出现分段错误错误。我对 C++ 相当陌生，所以任何建议都会很棒。我发布了代码的相关部分。

列表头文件：

//list.h

#include <string>
using namespace std;

class List {
    friend class Node;
public:
    List();
    void addleft(int);
    void addright(int);
    int left();
    int right();
    void print();
    bool search(int);
    //Node *head;
    //Node *tail;
    //Node *n;
};

列出类文件：

#include <iostream>
#include <string>
#include <stdio.h>
#include "List.h"
#include "Node.h"
using namespace std;
Node *current;
Node *tail;
Node *head;
Node *n;

List::List() {

}

void List::addleft(int a) {
    n = new Node;                                                       //The pointer n points to a new Node
    n->number = a;                                                      //Set the value in the node
    n->next = head;                                                     //Point the node to the old head of the linked list
    head->prev = n;                                                     //Link the old head node to the new node
    head = n;                                                           //Set the new node as the new head of the linked list
    head->prev = NULL;                                                  //Make the new node's previous pointer point to nothing (NULL)
    if(current == NULL) {                                               //If the list is empty...
            current = n;                                                //Set the new node as the current node pointer
        }
}

void List::addright(int a) {
    n = new Node;                                                       //The pointer n points to a new Node
    n->number = a;                                                      //Set the value in the node
    n->prev = tail;                                                     //Point the node to the old head of the linked list
    tail->next = n;                                                     //Link the old tail node to the new node
    tail = n;                                                           //Set the new node as the new tail of the linked list
    tail->next = NULL;                                                  //Make the new node's next pointer point to nothing (NULL)
    if(current == NULL) {                                               //If the list is empty...
        current = n;                                                    //Set the new node as the current node pointer
    }
}

int List::left() {
    current = current->prev;
    return current->number;
}

int List::right() {
    current = current->next;
    return current->number;
}

void List::print() {

}

bool List::search(int a) {
    int search;
    //while(search != tail) {

    //}
}

节点头文件：

//node.h

using namespace std;

class Node {
    friend class List;
public:
    Node();
private:
    int number;
    Node *next;
    Node *prev;
};

节点类文件：

#include <iostream>
#include <string>
#include <stdio.h>
#include "List.h"
#include "Node.h"
using namespace std;

Node::Node() {
    next = NULL;
    prev = NULL;
}
4

1 回答 1

2

我猜想headandtail最初被初始化为空指针。这就是为什么第一次尝试添加任何东西会崩溃。如果是这种情况，您必须通过代码的特殊分支处理第一次添加。head该特殊分支必须专门针对和tail都为空的情况编写。

编辑：在查看更多代码后，我们可以得出结论，您的代码确实是这种情况。

但是，编写一个List类然后将 and 声明head为tail文件范围的变量（而不是使它们成为List类的成员）是没有任何意义的。看起来您最初将它们声明为类成员，但后来将这些成员注释掉了。为什么？？？

于 2013-11-05T01:28:04.803 回答