Wikipedia lists exactly two problems as $\mathsf{NL}$-complete - 2-satisfiability and St-connectivity (although stating that there are "several"):


My old literature on complexity (from study) also has no additional examples. And the complexity zoo also lists the graph reachability problem as sole example:


So, are there any other problems known to be $\mathsf{NL}$-complete?


Here are three more examples, taken from an assignment by Trevisan:

  1. Given an NFA and a word, determining whether the NFA accepts the word.

  2. Reachability in DAGs.

  3. Determining whether a digraph is strongly connected.

Planken shows that the Simple Temporal Problem with bounded weights is NL-complete (see the link for definitions).

There are likely many others. Schaefer's dichotomy theorem, in particular, gives many examples.


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