链表char指针scanf输入

Question

I'm attempting to input multiple times to a char pointer in linked list using scanf . but every time I enter new input the name changes in all the fields.

here is my linked list:

struct node {
struct node *next;
int level;
char *name;
};

here is my main function:

struct node *root = NULL;
while (1) {
    char arrays[12];
    char *n;
    n = arrays;
    int i = NULL;
    printf("Enter level: ");
    scanf("%i", &i);
    printf("\nEnter name: ");
    scanf("%s", arrays);
    insert(&root, i, n, compare);
    display(root);
    }

insert function:

void insert(struct node **head, const int level, char *name, int(*cmp)(struct node *l, struct node *r))
{
    struct node *new;
    new = malloc(sizeof *new);
    new->level = level;
    new->name = name;

    /* Find the insertion point */
    for (; *head != NULL; head = &(*head)->next)
    {
        if ((*head)->level > level || (*head)->level == level && cmp(*head, new) > 0) { break; }
    }
    new->next = *head;
    *head = new;
}

basically if I input:

input:        |   expected output:    |    actual output:
1     smith   |   1     john          |    1     alice
1     john    |   1     smith         |    1     alice
3     malek   |   2     alice         |    2     alice
2     alice   |   3     malek         |    3     alice

note: the functions are working as expected when I'm entering data manually without scanf eg:

insert(&root, 1, "Abbas", compare);
insert(&root, 1, "Calbass", compare);

Answer 1

This line:

new->name = name;

just change the value of pointer - it does not copy a string. So all elements in the linked list will point to arrays . So changing the contents of arrays will make it look as if all elements in the list was changed (but they wasn't).

You probably need:

strcpy(new->name, name);

and then you need to malloc memory for the string as well.

Something like:

new = malloc(sizeof *new);
new->level = level;
new->name = malloc(12 * sizeof(char));  // Memory for the string
strcpy(new->name, name);                // Copy the input string

BTW:

Change

    insert(&root, i, n, compare);

to

    insert(&root, i, arrays, compare);

and remove the n variable. The functionality is the same but the coder is easier to read and understand.

Answer 2

Look like you're inserting a pointer to arrays into the list. When you write:

insert(&root, 1, "Abbas", compare);

it's work because nothing modify the string literal "Abbas", but arrays 's content is overwritten every time the scanf("%s", arrays); is executed. Consider changing char* name to char name[12] and reading input directly into the node.