Given a graph with $V$ vertices and $k$, find a set $K$ of $k$ vertices of $G$. Let $c(v)$ be the distance (in BFS-like) of the vertex $v \in V$ to the closest vertex $u \in K$. How to choose the set $K$ such that the maximum $c(v) \forall v \in V$ is minimized?
This is like a dominating set, but each vertex covers a range of vertices, and we are interested in minimizing this range.