The more general version of Grover's algorithm searches for one of $M$ entries that match a criterion, out of $N$ total entries.
I have seen it written that this takes $O(\sqrt{N/M})$ iterations, to find one of the $M$ matching entries, with good probability. (e.g. on wikipedia )
Is this still valid when $M$ is large, say $M=N/2$ ? In that case we get $O(1)$ iterations?