[callahad]

> once the leader has seen the light be on a sufficient number of times he can definitively say that they have all been in the room.

Ah, but what's a sufficient number of times? The unknown initial state is what tripped me for a bit. :)

[gberger]

n-1, where n is the number of prisoners. -1 to account for the leader.

[evanb]

It's actually 2(n-1), because the designated switch can start in either state.