Question

`你好我刚刚在代码块中编写了这段代码，在构建和运行之后，它说程序已停止工作。我无法找到我做错了什么。我不知道问题是否与我的代码有关，或者与我正在使用的编译器有什么关系。请帮忙

Library.h：

#ifndef LIBRARY_H
#define LIBRARY_H
#include <iostream>
#include <string>
using namespace std;
class Library
{
public:
    struct book
    {

        string tittle;
        int number;
        struct book* next;
    }* head, *tail, *ptr;

    Library();
    ~Library();
    book* searchName(book *, string);
    void addNode(book *);
    book *initNode(string s, int i);
    void displayNode(book *ptr) const;
    void displayList(book *ptr) const;
protected:
};

#endif

Library.cpp

#include "Library.h"

Library::Library() :
        head(NULL), tail(NULL)
{
}

Library::~Library()
{
    book *current, *temp;

    current = head;

    temp = head;
    while (current != NULL)
    {
        current = current->next;
        delete temp;
        temp = current;
    }
}

Library::book * Library::searchName(Library::book* ptr, string name)
{
    while (name != ptr->tittle)
    {
        ptr = ptr->next;
        if (ptr == NULL)
            break;
    }
    return ptr;
}

void Library::addNode(book *newNode)
{
    if (head == NULL)
    {
        head = newNode;
        head = newNode;
    }
    tail->next = newNode;
    newNode->next = NULL;
    tail = newNode;
}

Library::book *Library::initNode(string s, int i)
{
    book *ptr = new book;
    if (ptr == NULL)
        return static_cast<book *>(NULL);
    else
    {
        ptr->tittle = s;
        ptr->number = i;
        return ptr;
    }
}

void Library::displayNode(book *ptr) const
{

    cout << ptr->number << ": " << ptr->tittle << endl;
}

void Library::displayList(book *ptr) const
{
    if (!ptr)
        cout << "Nothing to display" << endl;
    while (ptr)
    {
        displayNode(ptr);
        ptr = ptr->next;
    }
}

main.cpp

#include "Library.h"
#include <iostream>
using namespace std;

int main()
{
    Library a;
    Library::book *ptrr;
    ptrr = a.initNode("s1", 1);
    a.addNode(ptrr);
    ptrr = a.initNode("s2", 2);
    a.addNode(ptrr);
    a.displayList(a.head);
}

Answer 1

当您从a.addNode(ptrr)拨打第一个main时，它会tail->next = newNode;（Library::addNode内），但tail为NULL（它没有分配），它崩溃....

现在，代码中可能还有其他问题，但这很可能是第一个让程序停止工作的问题......

请注意，代码中的某些内容可以简化。

像：

Library::book *Library::initNode(string s, int i)
{
    book *ptr = new book;
    if (ptr == NULL)
        return static_cast<book *>(NULL);
    else
    {
        ptr->tittle = s;
        ptr->number = i;
        return ptr;
    }
}

可能只是：

Library::book *Library::initNode(string s, int i)
{
    book *ptr = new book;
    if (ptr != NULL)
    {
        ptr->tittle = s;
        ptr->number = i;
    }
    return ptr;
}

和

void Library::addNode(book *newNode)
{
    if (head == NULL)
    {
        head = newNode;
        head = newNode;
    }
    tail->next = newNode;
    newNode->next = NULL;
    tail = newNode;
}

应该是：

void Library::addNode(book *newNode)
{
    if ( newNode != NULL ) // just in case
    {
        if (head == NULL)
        {
            head = newNode; // one is enough
        }
        if ( tail != NULL ) // to fix your crash
            tail->next = newNode;
        newNode->next = NULL;
        tail = newNode;
    }
}

另外，请参阅user4581301注释，析构函数代码甚至不编译....

.exe已经停止工作代码块cpp

1 个答案: