An even more trivial example is a singly-linked list with a sentinel node (the last node points back to it).<p>But that&#x27;s not really the question here.  Any linked list is not an algorithm, it&#x27;s a data structure.<p>The question is what operations can you do using circular references cannot be done without.  I think otabdeveloper1 is right, because you can use a garbage collection type process to &#x27;run&#x27; any other algorithm on a graph with cycles in it, using temporary lists and stacks to do whatever the algorithm would use circular references for.