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Re: Lights out puzzle

by salva (Abbot)
on Nov 28, 2011 at 11:26 UTC ( #940355=note: print w/replies, xml ) Need Help??

in reply to Lights out puzzle

Perl may not be the right tool to solve that problem.

A generic solution using GNU-Prolog (that has a very fast finite domain constraint solver):

It solves any problem where N < 20 in a few seconds.

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Re^2: Lights out puzzle
by ambrus (Abbot) on Nov 29, 2011 at 14:52 UTC

    This is a nice solution.

    I too was thinking that perl might not be the best tool for solving this, but for an entirely different reason. I wasn't thinking of this puzzle as a constraint satisfaction problem. Of course not, since it's

    which is what my second solution uses.

    But once you mentioned it, viewing as a constraint satisfaction problem also makes sense. After all,

    Update: for reference, the last time salva has surprised me with a nice solution using a finite domain constraint solver was Re^4: Seven by seven farming puzzle.

    Update: I ran the solution for (20, 20, 2). Your prolog solution took two and a half minutes (I have modified the printing part somewhat, but used GNU prolog). My perl solution took 40 seconds. So my opinion is that this prolog+finite-domain solution is fast enough. (Update: the same solution ran in SWI prolog is riddiculously slow though.)

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