This question concerns the time complexity of outputting the unions of subsets of a given set.
Given $m$ subsets of an $k$-element set, can the union of those sets be computed in linear time with respect to $m+k$? Or $(m+k)p(\log (m+k))$, where $p(x)$ is some polynomial? Or at least known is there a subquadratic algorithm (with respect to $m+k$)?
Any direction on this would be much appreciated.