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!
You have identified the purpose of these questions. They are determining your mindset when dealing with novel circumstances. Do you make an effort to explore and understand the actual constraints, or do you impose your own, preconceived notions on the scenario? Do you limit yourself needlessly?
The worst you can do is to treat it as a riddle and immediately give the "correct" answer. An interview isn't a knowledge test. They aren't trying to determine if you've seen and retained the accepted solution. They ask this sort of question to gain some insight into your problem solving skills.
A better answer is to step in to the question, and treat it like a real world scenario. Acknowledge the stated constraints, then explore them.
How much effort should we put into this problem? How much time and treasure are we going to spend on this? Why are we even determining which switch controls the light in the first place? What are the consequences of a wrong answer? If we're going to get fired for a wrong answer, we should take our time and get it right. If the consequences are "go try again", let's just start flipping switches.
Do we have other resources available? Is there someone in the room? Can we put someone in the room? Is there someone else available who uses the switch regularly? Can we ask their assistance? (If the room isn't being used often enough for anybody to know how the switches work, should it be repurposed to something more useful?)
Do we know that these are normal, simple switches? If they are three-way switches, or installed upside down, we can't trust their position.
Is it safe to assume the bulb is functional? The "riddle" answer fails on this.
Is it safe to assume the bulb starts cold? Did they run this test with another candidate a minute earlier? Did they leave it in a "hot" state for us already?
Is the light accessible when we get into the room, or is it inside a ceiling fixture, 12-feet over our heads?
What are the other switches connected to? If they control fans or lights or other appliances that can be sensed outside the room, we don't even need to leave the first room.
What is the necessity of the specific, given constraints? If this is a real-world scenario, we're probably not going to have a limitation on entering the room only once. If we can eliminate that constraint, the problem is a lot easier to solve.
Get feedback from the interviewer: Have we adequately explored this scenario to their satisfaction? Is there some other aspect we need to address?
Oi, who let the bot in?