Let L be a list of lists, like [[1,2], [2,3,4], [4,5]].
Is there a function to list minimal sets S such that for every (sub)list of L there is at least one element in S? For example {1, 3, 5} would be one "cover" that I am looking for. It is minimal, i.e. {1, 3}, {1, 5} and {3, 5} would not cover all (sub)lists of L, even if it is not minimun ({2, 4} and {2, 5} are).
I suppose that this is NP-complete but can be done in small cases. Might be that this could be formulated as a graph theory problem.
-- Jori Mäntysalo
