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Re: Lights out puzzle

by choroba (Chancellor)
on Nov 28, 2011 at 18:09 UTC ( #940423=note: print w/replies, xml ) Need Help??

in reply to Lights out puzzle

Here's a quick Monday morning puzzle.
Quick?? I spent several hours on it, not being able to come with anything better then this: It's a bit randomized, but usually runs under 2 seconds on my machine. Run it with a filename as an argument to check the solution saved in the file.
Update: Removed forgotten debugging line.
Update2: Readmore changed to spoiler.

Replies are listed 'Best First'.
Re^2: Lights out puzzle
by choroba (Chancellor) on Nov 30, 2011 at 10:06 UTC
    Here are some comments on how it works:
    The code clears all the lines except for the last one (clean) the simple way: if there is a light, click underneath. The last line (or, better to say, broken line, i.e. the last line plus the remaining half of the previous one) is then solved half-randomly. At the beginning, I cache how clicking on the top line influences the last line, but only for one click on the line (i.e. I only know what the last line will be after having one light lit). Therefore, I have to click randomly until I get a cached position that I can solve. This works well for size 14, but the time doubles for each +2 in size, so size 20 is already too slow. Caching more positions could be added easily (like clicking two times), but I am not sure how much time it would take to cache all possible combinations on the first line.
    Because the order of clicks is not important, I keep a separate map of the board with 0 for the even clicks and 1 for the odd ones. This separate board is the output of the program.
Re^2: Lights out puzzle
by ambrus (Abbot) on Dec 01, 2011 at 10:41 UTC

    I changed the definition of the show and toggle methods like this:

    sub show { my $board = shift; print "\e[H"; for my $row (@$board) { return unless defined $row; print map $_ ? '*' : defined $_ ? '.' : '', @$row; print "\e[K\n"; } print "\e[J"; use Time::HiRes "sleep"; sleep(6e-3); } # show sub toggle { my ($board, $x, $y) = @_; my $old = $board->[$y][$x]; return unless defined $old; $board->[$y][$x] = $old eq 1 ? 0 : 1; } # toggle
    and now I can see the lights being chased down to the bottom of the board. Looks nice.
      Yes, in fact, I did something similar for debugging :-)

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