在 C 中创建一个单向链表 [英] Creating a singly linked list in C

问题描述

我正在尝试根据作业的输入文本文件创建单向链接列表.我正在尝试一次做一点，所以我知道我的代码不完整.我尝试创建头指针并只是打印出它的值，我什至无法让它工作，但我不知道为什么.我包括了结构、我的创建列表和打印列表功能.我没有包含打开的文件，因为该部分有效.

I'm trying to create a singly linked list from an input text file for an assignment. I'm trying to do it a little bit at a time so I know my code is not complete. I tried creating the head pointer and just printing out its value and I can't even get that to work, but I'm not sure why. I included the struct, my create list, and print list functions. I didn't include the open file since that part works.

typedef struct List
{
   struct List *next;   /* pointer to the next list node */
   char *str;           /* pointer to the string represented */
   int count;           /* # of occurrences of this string */
} LIST;

LIST *CreateList(FILE *fp) 
{
    char input[LINE_LEN];
    LIST *root;             /* contains root of list             */
    size_t strSize;         
    LIST *newList;          /* used to allocate new list members */

    while (fscanf(fp, BUFFMT"s", input) != EOF) {

        strSize = strlen(input) + 1;

        /* create root node if no current root node */
        if (root == NULL) {
            if ((newList = (LIST *)malloc(sizeof(LIST))) == NULL) {
                printf("Out of memory...");
                exit(EXIT_FAILURE);
            } 
            if ((char *)malloc(sizeof(strSize)) == NULL) {
                printf("Not enough memory for %s", input);
                exit(EXIT_FAILURE);
            }
                memcpy(newList->str, input, strSize);   /*copy string    */
                newList->count = START_COUNT;
                newList->next = NULL;
                root = newList;
        }
    }
        return root;
}

/* Prints sinly linked list and returns head pointer */
LIST *PrintList(const LIST *head) 
{
    int count;

    for (count = 1; head != NULL; head = head->next, head++) {
        printf("%s    %d", head->str, head->count);
    }                       
    return head;     /* does this actually return the start of head ptr, b/c I want to 
                            return the start of the head ptr. */
}

推荐答案

root 有一个未定义的值，所以它不会初始化.CreateList 的第二行应该是

root has an undefined value, so it won't initialize. The second line of CreateList should be

LIST *root = NULL;

此外，进一步向下显然是项目细节的分配，但是 a) 代码无法捕获分配并将其保存在任何地方，并且 b) 分配的大小应该是 strSize，不是变量本身的长度.有几种方法可以修复它，但最直接的方法是:

Also, further down there is allocation apparently for the details of the item, but a) the code fails to capture the allocation and save it anywhere, and b) the size of the allocation should be strSize, not the length of the variable itself. There are several ways to fix it, but the most straightforward would be:

newList->str = (char *)malloc(strSize);
if (newList->str == NULL)

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