The “correct” answer doesnt work for led bulbs. A more modern answer would be why the hell can i only go to the room once!? Or you could get a friend/coworker to go to the room and just observe the bulb. One blink switch one, two blinks switch two etc. Lastly if you know a random switch is controlling a light in another room, why the hell is that switch not labeled if you already knew about it. Like how did this problem even arise in the first place. Also if you just want light in the room right now just turn all 3 on and go to the room.








I think of the interviewer ask this specific question they aren’t sophisticated enough to expect anything else than the “correct” answer. The question is so old, stupid, and irrelevant that anyone smart enough to ask actual good interview questions would never lead with this.