Inserting a new node at the end of a linked-list

Hi everyone!

I'm trying to write a program that lets the user append nodes at the end of a linked list. It kinda works but the main problem is that it doesn't actually create any new nodes later on, the function I've written creates one new node and then just keeps on changing its values over and over again.

Code:

---

static void append(Node *_tail, unsigned _id) {
    Node temp = { .id = _id, .next = NULL };


    if (_tail == NULL) {
        _tail = &temp;
    } else {
        _tail->next = &temp;
        _tail = &temp;
    }
}

---

I've also tried dynamically allocating memory for the nodes with malloc() and calloc() but that gave me the same results. What am I doing wrong?

Here's the main() function if you were wondering.

Code:

---

int main(void) {
    unsigned input;
    Node n3 = { .id = 3, .next = NULL };
    Node n2 = { .id = 2, .next = &n3 };
    Node n1 = { .id = 1, .next = &n2 };
    Node *head = &n1, *tail = &n3;


    for (;;) {
        printf("Enter an ID: "), scanf("%u", &input);


        append(tail, input);


        for (Node *i = head; i != NULL; i = i->next) {
            printf("ID: %u\n", i->id);
        }
    }


    return 0;
}

---

This is wrong because you have a local variable for the new local: that variable ceases to exist after the function returns. You could make it static, but then all you'll ever have is one variable, so you'll never be able to grow the linked list.

A common solution is to use dynamic memory allocation, i.e., your attempt with malloc and free, but you probably just used it wrongly. I suggest posting your attempt for that.

Quote:

---

Originally Posted by laserlight

I suggest posting your attempt for that.

---

I'm sorry for the delayed reply. Anyways, here it is!

Code:

---

static Node *getLast(Node *_head) {
    Node *i = NULL;


    for (i = _head; i != NULL; i = i->next);


    return i;
}


static void append(Node *_head, unsigned _id) {
    Node *temp = (Node*)calloc(1, sizeof(Node));
    temp->id = _id;
    temp->next = NULL;


    if (_head == NULL) {
        _head = temp;
    } else {
        _head = getLast(_head);
        _head->next = temp;
    }
}

---

And here's main()

Code:

---

int main(void) {
    unsigned input;
    Node *head = NULL;


    for (;;) {
        printf("Enter an ID: "), scanf("%u", &input);


        append(head, input);


        for (Node *i = head; i != NULL; i = i->next) {
            printf("ID: %u\n", i->id);
        }
    }


    return 0;
}

---

This program doesn't even print the list. I might be iterating over the list wrongly, but I dunno.

Your append function cannot modify main's local copy of head.
Also, your getLast always returns NULL.

For append, you can return head from it and call it like:

Code:

---

    head = append(head, id);  // Node *append(Node *head, int id);

---

Or you can pass in a pointer to head so it can be directly manipulated.

Code:

---

    append(&head, id);        // void append(Node **phead, int id);

---

For getLast,

Code:

---

Node *getLast(Node *nd) {
    if (nd) for ( ; nd->next; nd = nd->next) ;
    return nd;
}

---