// List implementation
typedef struct ListNode {
    void* data;
    struct ListNode* next;
    struct ListNode* prev;
} ListNode;

typedef struct List {
    int size;
    ListNode* head;
    ListNode* tail;
    size_t type;
} List;
List* list_init() {
    List* list = malloc(sizeof(List));
    assert(list);

    list->size = 0;
    list->head = NULL;
    list->tail = NULL;

    return list;
}

void list_cleanup(List* list) {
    ListNode* current = list->head;
    while (current != NULL) {
        ListNode* next = current->next;
        free(current);
        current = next;
    }
    free(list);
}

void list_push(List* list, void* data) {
    ListNode* node = malloc(sizeof(ListNode));
    assert(node);

    node->data = data;
    node->next = list->head;
    node->prev = NULL;

    if (list->head != NULL) {
        list->head->prev = node;
    } else {
        list->tail = node;
    }
    list->head = node;

    list->size++;
}

void list_remove_nth(List* list, int n) {
    assert(n >= 0 && n < list->size);
    ListNode* cur = list->head;
    for (int i = 0; i < n && cur != NULL; i++)
        cur = cur->next;

    if (cur == list->head) {
        list->head = cur->next;
        if (list->head != NULL)
            list->head->prev = NULL;
        else
            list->tail = NULL;
    } else if (cur == list->tail) {
        list->tail = cur->prev;
        list->tail->next = NULL;
    } else {
        cur->prev->next = cur->next;
        cur->next->prev = cur->prev;
    }

    free(cur);
    list->size--;
}

void* list_get_nth(List* list, int n) {
    assert(n >= 0 && n < list->size);
    ListNode* cur = list->head;
    for (int i = 0; i < n; i++) {
        cur = cur->next;
    }

    return cur->data;
}

// Main function
    List* li = list_init();
    int x = 4;
    int y = 8;
    list_push(li, &x);
    list_push(li, &x);
    list_push(li, &y);
    list_push(li, &x);

    printf("List size is: %d\n", li->size);

    ListNode* cur = li->head;
    printf("Getting list elements with while loop:\n");
    while (cur != NULL) {
        printf("%d\n", *(int*)cur->data);
        cur = cur->next;
    }

    printf("Getting list elements with for loop (list_get_nth):\n");
    for (int i = 0; i < li->size - 1; i++) {
        printf("%d: %d\n", i, *(int*)list_get_nth(li, i));
    }

    list_remove_nth(li, 0);
    list_remove_nth(li, 3);
    printf("List size after removing elements: %d\n", li->size);

    printf("New List elements (using for loop):\n");
    for (int i = 0; i < li->size - 1; i++) {
        printf("%d\n", *(int*)list_get_nth(li, i));
    }

    list_cleanup(li);