static bool hasCycle(SinglyLinkedListNode head) {

        List<SinglyLinkedListNode> list = new List<SinglyLinkedListNode>();
        while(head!=null) 
        {
            if (list.Contains(head)) 
            {
                return true;
            } 
            else 
            {
                list.Add(head);
                head = head.next;
            }
        }
        return false;
    }