c - 第二次显示嵌套列表时丢失它们

Question

我正在尝试使用嵌套列表构建一个“库”。一切工作正常，我可以使用我的排序添加函数添加元素，直到我注意到，如果我连续显示列表两次，第一次一切都会好起来，但在第二次“书籍元素”添加到目录中不显示，就像它们不存在一样。

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)
    {
        if(temp->firstbook == NULL)
        {
            printf("%s\n", temp->name);

        }
        while(temp->firstbook != NULL)
        {   printf("%s  ", temp->name);
            printf("%s  ", temp->firstbook->title);
            printf("%d  ", temp->firstbook->number);
            printf("%s\n", temp->firstbook->country);
            temp->firstbook = temp->firstbook->new;
        }
        temp = temp->next;
    }
}

struct book *newbook(char *booktitle, int number, char *country)
{
    struct book* newbook = (struct book*) malloc(sizeof(struct book));
    newbook->title = malloc(sizeof(strlen(booktitle)+1));
    newbook->country = malloc(sizeof(strlen(country)+1));
    newbook->title = booktitle;
    newbook->country = country;
    newbook->number = number;
    newbook->new = NULL;
}

struct catalog *findcatalog(struct catalog** head, char *catalogname)
{
    struct catalog* current;
    current = *head;
    while(current != NULL)
    {
        if(current->name == catalogname)
        {
            return current;
        }
        current = current->next;
    }
}

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 (*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, "Aaaaaa");
sortedInsert(&head, "Sdafscx");
sortedInsert(&head, "Saxzxc");
sortedInsert(&head, "Asdas");
sortedInsert(&head, "Zzzzzzzz");
sortedInsert(&head, "Country");
sortedBookInsert(&head, "Country", "PKP", 11111, "Germany");
sortedBookInsert(&head, "Country", "Polacy", 11112, "Italy");
sortedBookInsert(&head, "Country", "Autobusy", 11234, "France");
sortedBookInsert(&head, "Country", "Polityka", 14111, "Russia");
printList(head);
printList(head);
return 0;

}

When I print my list for a second time, elements from SortedBookInsert just... are not there. I am very confused.

Answer 1

newbook 中缺少返回，必须

struct book *newbook(char *booktitle, int number, char *country)
{
    struct book* newbook = (struct book*) malloc(sizeof(struct book));
    newbook->title = malloc(sizeof(strlen(booktitle)+1));
    newbook->country = malloc(sizeof(strlen(country)+1));
    newbook->title = booktitle;
    newbook->country = country;
    newbook->number = number;
    newbook->new = NULL;

    return newbook;
}

如果没有返回，行为是未定义的。

另请注意，您执行以下操作会造成 2 次内存泄漏:

newbook->title = malloc(sizeof(strlen(booktitle)+1));
newbook->country = malloc(sizeof(strlen(country)+1));
newbook->title = booktitle;
newbook->country = country;

但由于sizeof，您也没有分配正确的长度，必须是

newbook->title = malloc(strlen(booktitle)+1);
newbook->country = malloc(strlen(country)+1);
strcpy(newbook->title, booktitle);
strcpy(newbook->country, country);

在findcatalog中，如果找不到目录，也不会返回

struct catalog *findcatalog(struct catalog** head, char *catalogname)
{
    struct catalog* current;
    current = *head;
    while(current != NULL)
    {
        if(current->name == catalogname)
        {
            return current;
        }
        current = current->next;
    }
    return NULL;
}

如果没有返回，行为是未定义的。

在sortedBookInsert中，您可能需要在执行searched->firstbook之前检查searched是否不为NULL，例如:

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 == NULL)
      return;
    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;
    }
}

但说实话我不确定

在查找目录

if(current->name == catalogname)

必须是

if(!strcmp(current->name, catalogname))

函数printList修改目录时执行temp->firstbook = temp->firstbook->new;，需要替换

   while(temp->firstbook != NULL)
   {   printf("%s  ", temp->name);
       printf("%s  ", temp->firstbook->title);
       printf("%d  ", temp->firstbook->number);
       printf("%s\n", temp->firstbook->country);
       temp->firstbook = temp->firstbook->new;
   }

例如:

struct book* firstbook = temp->firstbook;

    while(firstbook != NULL)
    {   printf("%s  ", temp->name);
        printf("%s  ", firstbook->title);
        printf("%d  ", firstbook->number);
        printf("%s\n", firstbook->country);
        firstbook = firstbook->new;
    }

如果我进行所有这些修改并使用此定义:

struct catalog* newcatalog(char *name)
{
  struct catalog* r = malloc(sizeof(struct catalog));

  r->name = malloc(strlen(name)+1);
  strcpy(r->name, name);
  r->next = NULL;
  r->firstbook = NULL;

  return r;
}

编译和执行:

pi@raspberrypi:/tmp $ gcc -g -pedantic -Wall -Wextra l.c
pi@raspberrypi:/tmp $ ./a.out
one
Aaaaaa
Asdas
Country  Autobusy  11234  France
Country  PKP  11111  Germany
Country  Polacy  11112  Italy
Country  Polityka  14111  Russia
Kappa
Saxzxc
Sdafscx
Zzzzzzzz
two
Aaaaaa
Asdas
Country  Autobusy  11234  France
Country  PKP  11111  Germany
Country  Polacy  11112  Italy
Country  Polityka  14111  Russia
Kappa
Saxzxc
Sdafscx
Zzzzzzzz
pi@raspberrypi:/tmp $ 

在valgrind下执行

pi@raspberrypi:/tmp $ valgrind ./a.out
==7575== Memcheck, a memory error detector
==7575== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==7575== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==7575== Command: ./a.out
==7575== 
one
Aaaaaa
Asdas
Country  Autobusy  11234  France
Country  PKP  11111  Germany
Country  Polacy  11112  Italy
Country  Polityka  14111  Russia
Kappa
Saxzxc
Sdafscx
Zzzzzzzz
two
Aaaaaa
Asdas
Country  Autobusy  11234  France
Country  PKP  11111  Germany
Country  Polacy  11112  Italy
Country  Polityka  14111  Russia
Kappa
Saxzxc
Sdafscx
Zzzzzzzz
==7575== 
==7575== HEAP SUMMARY:
==7575==     in use at exit: 148 bytes in 11 blocks
==7575==   total heap usage: 12 allocs, 1 frees, 1,172 bytes allocated
==7575== 
==7575== LEAK SUMMARY:
==7575==    definitely lost: 12 bytes in 1 blocks
==7575==    indirectly lost: 136 bytes in 10 blocks
==7575==      possibly lost: 0 bytes in 0 blocks
==7575==    still reachable: 0 bytes in 0 blocks
==7575==         suppressed: 0 bytes in 0 blocks
==7575== Rerun with --leak-check=full to see details of leaked memory
==7575== 
==7575== For counts of detected and suppressed errors, rerun with: -v
==7575== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 6 from

<小时/>

请注意，在您的代码中，您为名称/书名/国家/地区提供了文字字符串，因此它们永远不会消失/更改，因此复制它们是没有用的，但在重用同一数组的“真实”情况下，情况并非如此或字符从文件中获取它们或在标准输入上读取它们等，所以我建议您按照我的建议复制它们