turn on one switch...go to the first room, if it's not on go to a second room, if it is then it is the one, however, if it is neither the first nor the second rooms then it has to be the third
so now you only have one room to look at left
turn on the second switch
go to one of the possible rooms
if the light is on in that room, then it is the switch for that room
if not then it is the other room that was that the one from the first room
(you don't have to go see it though because it has to be it)
Last, you don't have to check but the last switch goes to the remaining room
(i know i sound confusing; but it all makes sense up here (pointing to my brain))
is it right?