User *find_user(const char *name, const User *head) {
    for (User *ptr = (User *)head; ptr != NULL; ptr = ptr->next) {
        if (strcmp(ptr->name, name) == 0) {
            return ptr;
        }
    }

    return NULL;
}
/*
 * Return a pointer to the user with this name in
 * the list starting with head. Return NULL if no such user exists.
 *
 * NOTE: You'll likely need to cast a (const User *) to a (User *)
 * to satisfy the prototype without warnings.
 */