This is a nice little puzzle by the Grabarchuk family of puzzle designers. Your problem should you choose to tackle it is, using normal chess knight’s jumps, swap the white and black knights in the fewest jumps.

Here’s how I did it. Of course don’t read on if you want to try and solve it yourself.

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First index the squares 1–8 and translate all possible moves into a graph.

Then start sliding the knights (yellow and blue in the animation below) along the graph edges in an intuitive way and eventually swap the two occupied sets in 18 jumps at least.

Could you solve this one now?

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