Three switches outside a closed room control one bulb inside.
Flip them as much as you like — but you may enter the room only ONCE.
How do you find which switch controls the bulb?

Question

Accepted Answer

Turn switch 1 ON for several minutes. Turn it OFF. Turn switch 2 ON. Walk in: glowing = 2, off-but-warm = 1, off-and-cold = 3. — On/off gives you 2 signals — not enough for 3 switches. So you steal a third: heat. The bulb keeps a memory of being lit, even after you flip it off. The rest is just listening to what the bulb has to say.

Three switches outside a closed room control one bulb inside. Flip them as much as you like — but you may enter the room only ONCE. How do you find which switch controls the bulb?