In the comments a couple entries ago, someone mentioned a lightbulb-centric riddle I solved during one of the interviews I did for my current job. Many of you have probably already heard it, but for those that haven’t heard this one yet, it does make you feel good when you figure it out. In that spirit, the riddle:
There are two windowless rooms, connected to each other by a door. In one room are three lightswitches, and in the other room are three lightbulbs. Each switch controls one of the three lightbulbs. You are in the room with the lightswitches, and the door is closed. You are allowed to open the door after manipulating the switches and go into the lightbulbs room, but you are not allowed to re-enter the lightswitches room once you leave it.
Which switch controls each bulb?
Rules and suggestions while wrestling with this one:
- If you already know the answer, for Pete’s sake, don’t post it in the comments!
- If you’re trying to figure out the answer, it’s probably best to not read the comments.
- If you figure it out and leave a comment, please type something obvious in ALL CAPS letting people know you’re about to answer it so they don’t read your comment if they don’t want to know the answer yet.
- You have no additional supplies with you in the rooms. The answer isn’t a dumb “gotcha” kind of answer like, “See light under the door, blah blah.” It’s straightforward. I’m not sure if my riddlers told me that when they asked this of me, but I think it makes the riddle less frustrating, while still allowing it to be challenging.
Go for it!