public static SinglyLinkedListNode reverse(SinglyLinkedListNode llist) {
        SinglyLinkedListNode prev = null;
        SinglyLinkedListNode current = llist;
        SinglyLinkedListNode nextNode = null;

        while (current != null) {
            nextNode = current.next;
            current.next = prev;
            prev = current;
            current = nextNode;
        }
        return prev;
    }