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Op doesn't have time for interviews
(programming.dev)
Post:
You have three switches in one room and a single light bulb in another room. You are allowed to visit the room with the light bulb only once. How do you figure out which switch controls the bulb? Write your answer in the comments before looking at other answers.
Comment:
If this were an interview question, the correct response would be "Do you have any relevant questions for me? Because have a long list of things that more deserving of my precious time than to think about this!
LED bulbs do get warm, not as hot as incandescent bulbs but they do emit heat. You might have to run them longer than a minute to warm it up enough to be immediate about it.