To find the correct switch (1, 2, or 3), turn switch 1 to 'on' and leave it like that for a few minutes.
After that, you turn switch 1 back to 'off', and turn switch 2 to 'on'. Now enter the room.
If the light bulb is lit, then you know that switch 2 is connected to it.
If the bulb is not lit, then it has to be switch 1 or 3.
Now touching for short the light bulb, will give you the answer: if the bulb is still hot,
then switch 1 was the correct one; if the bulb is cold, then it has to be switch 3.
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