554
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!
The official answer to this riddle is turn switch 1 on for a minute or so, switch it off then switch 2 on. if the bulb is hot but dark, its 1, if it's lit it's 2 and if it's out and cold its 3.
the adult answer is why do I have only one chance to walk in the room?
8 lightswitch states. Smack em all on, and smack em all off. If there's no change, that's a bad lightswitch
if hot they're using out of date lighting, who the fuck uses incandescent bulbs this far into the 21st century? they have failed their interview with me.
The image does depict an incandescent filament bulb.
LED do not have a 100% efficiency, and do produce waste heat. A lot less than an incandescence one, sure, but enough for that answer to be valid.
Well, maybe you'd better wait 10min instead of one, to make sure the led lightbulb heats enough, but still...
I tested this with a 5W IKEA LED light-bulb, since I was just doom scrolling, anyway:
This means that the solution either breaks down entirely, or is unreliable, since you are not (reliably) able to tell the first two buttons apart
Highly arguable. Especially without specifications on the lamp. It could be a rather dim and small one. Then, you either need special equipment or supersenses.
note the premise specifies HOT.
none of my LED bulbs get hot even after hours. they do warm up from 'cold' but HOT?
ymmv.
The "premise" is detecting that a now dark light was recently turned on by feeling for residual heat. "Hot" is a relative term.
actually not really - hot specifies HOT; if it were room temp, warm, warmer than another that sat unused - sure. but you're only flipping it on for a short time. HOT?
it's pedantic, but parsing is important here because some HR shitwad decided these silly stupid games were a valid hiring method on filtering pedants apparently
The question is outdated as fuck too. It's not a new riddle.
You know, we're talking about how pointless a riddle it is. "Why can't I walk into the room more than once?" I've heard similar hiring riddles about things like "You've got ten ethernet cables that run the length of a long hallway. They're not marked at either end, what's the most efficient way of finding out which is which?"
And you know what? If I'm hiring a networking guy, I don't want him to deliver me an "ooh I know this one" answer to that, I want him to tell me he's got a cable tester with several remote probes so he can figure that out in a small number of trips. Maybe show me how he can hook a couple together with a coupler and use the cable length function to shave a couple of trips off. Not recite a memorized brain teaser answer.
Thr difference in phrasing is that your question presents a reasonable objective rather than an unreasonable constraint. You're also asking something subject-specific from someone who ought to be versed in that subject. That's not a riddle, it's a task you're expecting your hire to be capable of.
That's kind of my point. Google started that nonsense of making job interviews into lateral thinking puzzles, then all managers latched onto that to make themselves look hip.
I want to see competence and practical problem solving skills.
yeah silly games for bored hiring managers
this is the classic answer but it also fails pure logic because the question only implies one of them actually works, and even then, it's only one of them. the truth is any number of them could work, or a specific combination, or a number of combinations, or it might be none. the bulb itself to could be busted. my point is not to be an uncooperative asshole but that a logic puzzle that relies on real world properties should cover its bases.
So I can't go to the other room to set up a camera?
What if it's a LED bulb?
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.
The actual adult answer is questioning why the switch is in a different room and if it's because of safety, demand for safety protocol