C语言单链表的释放内存空间问题
本帖最后由 萝卜luobo 于 2018-11-17 11:23 编辑#include <stdio.h>
#include <stdlib.h>
struct Book
{
char title;
char author;
struct Book *next;
};
void getInput(struct Book *book);
void addBook(struct Book **library);
void printLibrary(struct Book *library);
void releaseLibrary(struct Book *library);
void getInput(struct Book *book)
{
printf("请输入书名：");
scanf("%s", book->title);
printf("请输入作者：");
scanf("%s", book->author);
}
void addBook(struct Book **library)
{
struct Book *book, *temp;
book = (struct Book *)malloc(sizeof(struct Book));
if (book == NULL)
{
printf("内存分配失败了!\n");
exit(1);
}
getInput(book);
if (*library != NULL)
{
temp = *library;
*library = book;
book->next = temp;
}
else
{
*library = book;
book->next = NULL;
}
}
void printLibrary(struct Book *library)
{
struct Book *book;
int count = 1;
book = library;
while (book != NULL)
{
printf("Book%d: ", count);
printf("书名: %s\n", book->title);
printf("作者: %s\n", book->author);
book = book->next;
count++;
}
}
void releaseLibrary(struct Book *library)
{
while (library != NULL)
{
free(library);
library = library->next;
}
}
int main(void)
{
struct Book *library = NULL;
int ch;
while (1)
{
printf("请问是否需要录入书籍信息(Y/N)：");
do
{
ch = getchar();
} while (ch != 'Y' && ch != 'N');
if (ch == 'Y')
{
addBook(&library);
}
else
{
break;
}
}
printf("请问是否需要打印图书信息(Y/N)：");
do
{
ch = getchar();
} while (ch != 'Y' && ch != 'N');
if (ch == 'Y')
{
printLibrary(library);
}
releaseLibrary(library);
return 0;
}
这是小甲鱼老师的代码
为什么
void releaseLibrary(struct Book *library)
{
while (library != NULL)
{
library = library->next;
free(library);
}
}
这样不可以，而是要这样
void releaseLibrary(struct Book **library)
{
struct Book *temp;
while(*library != NULL)
{
temp = *library;
*library =(*library)-> next;
free(temp);
}
}
第一张图里，执行完free(library)后library指向的空间的内容就不存在了，虽然library指针的值没变。但library的next找不到了 用后面那短代码的时候需要，releaseLibrary(&library);加个取地址；
第一段是，你都把library指向的内存空间释放掉啦，而在接下来的程序中你还在使用它，肯定会出错啊；
像这样先缓存下来就可以
void releaseLibrary(struct Book *library)
{
struct Book *temp;
while (library != NULL)
{
temp = library->next;
free(library);
library = temp;
}
}
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