Question

我正试图了解C中的链接列表，并最终让自己感到困惑。

我的问题是：这是否正确地在列表末尾插入了不同的people？或者只是在开头插入它们？

目前我正在尝试在链接列表的末尾插入新的person。我的结构定义如下：

struct person {
     char *name;
     int age;
     struct person *next;
};

我正在从预先分配的数组中访问数据：

#define HOW_MANY 7
char *names[HOW_MANY]= {"Simon", "Suzie", "Alfred", "Chip", "John","Tim","Harriet"};
int ages[HOW_MANY]= {22, 24, 106, 6, 18, 32, 24};

这是我在结尾函数中的插入：

static struct person * insert_end(struct person *people, char *name, int age)
{
    struct person *newPeople = (struct person*)malloc(sizeof(struct person));
    if (newPeople == NULL)
    {
        perror("Memory allocation failed");
        abort();
    }
    newPeople->name = name;
    newPeople->age = age;
    if (people == NULL)
    {
        newPeople->next = people;
        people = newPeople;
        return people;
    }
    else {
        while(newPeople->next != NULL)
        {
            newPeople->next = people;
        }
        people = newPeople;
        return people;
    }
}

我认为函数中的while循环没有被执行，我无法弄清楚为什么。谢谢！

Answer 1

您确实将新记录放在列表的开头。您必须意识到newPeople-＆gt; next将始终为null，因为它是新分配的。你需要遍历人，直到people-＆gt; next为NULL然后asign newPeople。

Answer 2

newPeople->next在读取之前未给出值，从而导致未定义的行为。因此代码在最后或开始时都没有正确插入。

while(newPeople->next != NULL)  // undefined behavior

以下不初始化newPeople指向的对象。

struct person *newPeople = (struct person*)malloc(sizeof(struct person));

代码似乎是使用以下内容制作循环链接列表。

 if (people == NULL) {
    newPeople->next = people;
    ...

虽然没关系，但更常见的是形成NULL已终止的列表，我认为这是您的目标。

static struct person * insert_end(struct person *people, char *name, int age) {

    // struct person *newPeople = (struct person*)malloc(sizeof(struct person));
    // No need for cast.  Recommend sizeof object rather than sizeof type
    struct person *newPeople = malloc(sizeof *newPeople);
    if (newPeople == NULL) {
        ...
    }

    // Best to initial all fields.
    newPeople->name = name;
    newPeople->age = age;
    newPeople->next = NULL; 

    if (people == NULL) {
        return newPeople;  // New head node
    }
    // else not needed
    // else {

    // Code was attempting to march down wrong list.  
    // Create `walker` instead.
    struct person *walker = people;
    while(walker->next != NULL) {
      walker = walker->next;
    }
    walker->next = newPeople;
    return people;
  }

如何将新项插入C中的链表（在列表的末尾）

2 个答案: