set intersection - finding the smallest array that intersects with a set of arrays -

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say have 3 arrays - ['a', 'b'], ['b', 'c'] , ['d']. if create fourth array intersects these 3 arrays minimal number of elements array i'd ['b', 'd']. question is... how go finding array?

like ['a', 'b', 'c', 'd'] intersects arrays it's not minimal intersection - ['b', 'd'] is.

any ideas?

i don't have answer algorithm, true that, commenter amit wrote, np-complete problem. problem called hitting set problem, equivalent set cover problem.

if you're fine approximation, according wiki article, greedily picking elements hit arrays gets.


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