A linked list in which following successors returns to the starting node rather than reaching null. A common non-dummy representation uses a null tail pointer for the empty case and a finite simple cycle for the nonempty case;
tail.next is the first node. A traversal stops after one complete turn, comparing object identity with its remembered start. Appending is constant-time once the insertion point and absence of duplicate keys are established. New to topics? Read the docs here!