I finally got around to watching last week’s Futurama late last night, and there’s an interesting permutations puzzle involved. The puzzle itself is a minor SPOILER, so stop now if 5 days isn’t enough time for you.

Puzzle: There’s a machine that can swap minds between bodies, but can’t swap two people if it’s already swapped that pair of bodies. A group of people use the machine to perform an arbitrary sequence of swaps among themselves. How can this group and two outsiders use the machine to restore everyone’s mind and body?

My solution is here.

I wonder if this is a recasting of a classic swapping puzzle I’m not familiar with.