Nice! Passes my basket case:

C:\test>1118262
 3 swaps => 1 2 3 a b c
 4 swaps => 1 2 a b c d
 5 swaps => 1 a b c d e
16 swaps => 1 2 3 4 5 6 7 8 a b c d e f g h i j
 6 swaps => 1 2 3 a b c d e f
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I took out the shorter/longer tests as that's never going to be a requirement. (Cool that it doesn't matter to the algorithm though!)

It'll take me a while to wrap my brain around it -- recursion always does -- but so far it ticks all the boxes. Thank you.