c - 我的功能之一是意外地从列表中删除元素

Question

我正在尝试创建一个“图书馆”，其中有按字母顺序排序的目录，并且每个目录中都有按字母顺序排列的书籍。作为deletebook函数的一部分(不包括在内，因为它还不存在)，我编写了查找书籍目录的函数。该功能有效，但它会在此过程中删除书籍(我认为)，这不好。如何更改它以免删除它们？

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

struct book
{
    char *title;
    int number;
    char *country;
    struct book* new;
};

struct catalog
{
    char *name;
    struct catalog* next;
    struct book* firstbook;
};

void printList(struct catalog *head)
{
    struct catalog *temp = head;

    while(temp != NULL)
    {
        struct book* book = temp->firstbook;
        if(book == NULL)
        {
            printf("%s\n", temp->name);
        }
        while(book != NULL)
        {
            printf("%s  ", temp->name);
            printf("%s  ", book->title);
            printf("%d  ", book->number);
            printf("%s\n", book->country);
            book = book->new;
        }
        temp = temp->next;
    }
}
struct catalog *newcatalog(char *new_name)
{
    struct catalog* new_node = (struct catalog*) malloc(sizeof(struct catalog));
    new_node->name = malloc(strlen(new_name)+1);
    strcpy(new_node->name, new_name);
    new_node->next =  NULL;
    new_node->firstbook = NULL;
    return new_node;
}

struct book *newbook(char *booktitle, int number, char *country)
{
    struct book* newbook = (struct book*) malloc(sizeof(struct book));
    newbook->title = malloc(strlen(booktitle)+1);
    newbook->country = malloc(strlen(country)+1);
    strcpy(newbook->title, booktitle);
    strcpy(newbook->country, country);
    newbook->number = number;
    newbook->new = NULL;
    return newbook;
}
struct catalog *findcatalog(struct catalog** head, char *catalogname)
{
    struct catalog* current;
    current = *head;
    while(current != NULL)
    {
        if(!strcmp(current->name,catalogname))
        {
            return current;
        }
        current = current->next;
    }
    return NULL;
}


struct catalog *findbookcatalog(struct catalog** head, int number) //function that deletes a book when used
{
    struct catalog* current;
    current = *head;
    while(current != NULL)
    {
        while(current->firstbook != NULL)
        {
            if(current->firstbook->number == number)
            {
                return current;
            }
            current->firstbook = current->firstbook->new;
        }
        current = current->next;
    }
    return NULL;
}
struct book *findbook(struct catalog** head, int number)
{
    struct catalog* current = findbookcatalog(head, number);
    struct book* booklocation;
    while(current->firstbook != NULL)
    {
        booklocation = current->firstbook;
        if(current->firstbook->number == number)
        {
            return booklocation;
        }
    current->firstbook = current->firstbook->new;
    }
    return NULL;
}

void sortedBookInsert(struct catalog** head, char *catalogname, char *booktitle, int number, char *country)
{
    struct catalog* searched;
    struct book* pom;
    struct book* ksiazka = newbook(booktitle, number, country);
    searched = findcatalog(head, catalogname);

    if(searched->firstbook == NULL || strcmp(searched->firstbook->title, ksiazka->title)>0)
    {
        ksiazka->new =searched->firstbook;
        searched->firstbook = ksiazka;
    }
    else
    { pom = searched->firstbook;
        while(pom->new!= NULL && strcmp(searched->firstbook->title, ksiazka->title)< 0)
        {
            pom = pom->new;
        }
        ksiazka->new = pom->new;
        pom->new = ksiazka;
    }
}
void sortedInsert(struct catalog** head,char *name)
{
    struct catalog* current;
    struct catalog* new_node = newcatalog(name);
    if(new_node == NULL)
    {
        return;
    }

    if (*head == NULL || strcmp((*head)->name, new_node->name) > 0)
    {
        new_node->next = *head;
        *head = new_node;
    }
    else
    {
        current = *head;
        while (current->next!=NULL && strcmp(current->next->name, new_node->name) < 0)
        {
            current = current->next;
        }
        new_node->next = current->next;
        current->next = new_node;
    }
}
int main()
{

    struct catalog* head = NULL;
    sortedInsert(&head, "Kappa");
    sortedInsert(&head, "Pxntry");
    sortedInsert(&head, "Sdafscx");
    sortedInsert(&head, "Saxzxc");
    sortedInsert(&head, "Zsdas");
    sortedInsert(&head, "Zzzzzzzz");
    sortedInsert(&head, "Country");
    sortedBookInsert(&head, "Country", "PKP", 11111, "Germany");
    sortedBookInsert(&head, "Country", "Polacy", 11112, "Italy");
    sortedBookInsert(&head, "Country", "Bus", 11234, "France");
    sortedBookInsert(&head, "Country", "Poltics", 14111, "Russia");
    printList(head);
    findbookcatalog(&head, 11112); // this will "eat" "Bus" and "PKP", so books that appear before Polacy
    printf("\n");
    printList(head);
    return 0;
}

它应该打印我的嵌套列表两次，两次相同，但它会删除搜索书籍之前的所有书籍。

结果:

Country  Bus  11234  France
Country  PKP  11111  Germany
Country  Polacy  11112  Italy
Country  Poltics  14111  Russia
Kappa
Pxntry
Saxzxc
Sdafscx
Zsdas
Zzzzzzzz

Country  Polacy  11112  Italy
Country  Poltics  14111  Russia
Kappa
Pxntry
Saxzxc
Sdafscx
Zsdas
Zzzzzzzz

Answer 1

此代码将从列表中删除书籍:

current->firstbook = current->firstbook->new;

你可能想使用这样的东西:

current_book = current->firstbook;
while (current_book) {
    if (current_book->number == number) {
        return current_book;
    }
    current_book = current_book->new;
}

我更改了此功能，解决了您当前的问题:

struct catalog *findbookcatalog(struct catalog** head, int number) //function that deletes a book when used
{
    struct catalog* current;
    current = *head;
    struct book *current_book;
    while(current != NULL)
    {
        current_book = current->firstbook;
        while(current_book != NULL)
        {
            if(current_book->number == number)
            {
                return current;
            }
            current_book = current_book->new;
        }
        current = current->next;
    }
    return NULL;
}

我也改变了这个功能。它有同样的问题，只是你还没有测试过。

struct book *findbook(struct catalog** head, int number)
{
    struct catalog* current = findbookcatalog(head, number);
    struct book* booklocation;
    if (current != NULL) {
        booklocation = current->firstbook;
        while(booklocation != NULL)
        {
            if(booklocation->number == number)
            {
                return booklocation;
            }
            booklocation = booklocation->new;
        }
    }
    return NULL;
}