Nyttigt regexp :-)
On Thursday 20 April 2006 16:03, Ilmari Karonen wrote:
> Sudoku solvers are old hat, of course, but this one is a bit different:
> it's a regexp. I suppose someone may have done this before, but if so,
> I haven't seen it. It's grossly inefficient, of course, solving the
> puzzle entirely by guesswork and backtracking, but that's not really the
> point. (It could be made quite a bit faster by hardcoding the givens in
> the regexp, but that would make the regexp non-generic.)
>
> #!/usr/bin/perl -w
> use strict;
>
> my $sudoku = ("^.*" .
> (join ".*\n.*", "(.)",
> map {
> my $n = $_;
> ("(?!" .
> (join "|",
> (map "\\" . ($_+1),
> (grep $_ < $n &&
> (int($_ % 9) == int($n % 9) ||
> int($_ / 9) == int($n / 9) ||
> int($_ / 27) == int($n / 27) &&
> int($_ / 3 % 3) == int($n / 3 % 3)),
> 0..80))) .
> ")(.)");
> } 1..80) .
> ".*\$"
> );
>
> while (<>) {
> chomp;
> length != 81 || tr/1-9_//c and (print("Bad input.\n"), next);
> s/(.)/$1 eq "_" ? "123456789\n" : "$1\n"/eg;
> print((join("", /$sudoku/) || "No solution."), "\n");
> }
>
>
> __END__
>
> Input, in case it's not obvious from the code, is an 81-character string
> listing the numbers in left-right, top-down order, with "_" for blanks.
> The while loop mangles it into the proper format for the regexp (81
> lines, each listing the allowed numbers for the corresponding cell) and
> outputs the solution in the same format as the input.
