In this paper, we study the online class cover problem where a (finite or infinite) family $\cal F$ of geometric objects and a set ${ \cal P}_r$ of red points in $\mathbb{ R}^d$ are given a prior, and blue points from $\mathbb{ R}^d$ arrives one after another. Upon the arrival of a blue point, the online algorithm must make an irreversible decision to cover it with objects from $\cal F$ that do not cover any points of ${ \cal P}_r$. The objective of the problem is to place a minimum number of objects. When $\cal F$ consists of axis-parallel unit squares in $\mathbb{ R}^2$, we prove that the competitive ratio of any deterministic online algorithm is $\Omega(\log |{ \cal P}_r|)$, and also propose an $O(\log |{ \cal P}_r|)$-competitive deterministic algorithm for the problem.
Categories: cs.CG