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Are those times for finding a solution, or for all solutions? If all, that is truly impressive!

Dancing links is a backtracking algorithm, just a nice way to optimize the backtracking.

It is for finding the first solution. Sorry that I didn't mention it.

No worries. I could have guessed, if I'd paid attention to how large of an N you looked at. :)

Also, I should explicitly say thanks for sharing! It is fun reading solutions to this puzzle. Also fun to read Erlang.