A town was invaded by aliens, and some of its residents were kidnapped and replaced by shapeshifters. You're tasked with capturing one of the shapeshifters. Here's the setup:
- There are 7 residents of the town.
- At least 4 of the residents are humans, and the remainder are shapeshifters. Everyone knows everyone else's type.
- Humans always tell the truth. Shapeshifters can answer however they want.
- If you ask anyone (whether human or shapeshifter) a question that a human couldn't truthfully answer yes or no to (e.g., "is the answer to this question 'no'?"), their head explodes and you die in the resulting explosion.
You can only ask each resident a single yes-no question. Once you get answers from all 7 residents, you need to pick someone to capture. Is it possible to guarantee you'll capture a shapeshifter?
Bonus 1: What if the alien story was a hoax, and everyone in the town is a human? Will you realize this with your strategy, so that you don't accidentally capture a human?
Bonus 2: Can you adapt your answer to towns with arbitrary numbers of residents, as long as there's always a majority of humans?