a 7-by-7 highly symmetric crossword grid with three across and three down lights, each of length 7, intersecting in all even-numbered positions; all odd-numbered positions are unchecked


  1. any of bcbbbccccbc ccbcbcccbcbcca ba ccca ca but none of a bcaa
  2. any of aaaaaaaaac aaaaaaaaaaaa a2aaaaaa a2ac but none of 2aaaac a2aaaacc a22ac
  3. any of 234cb 234b 23444444cb 234444444b but none of 24cb 24b 2cb 3cb 23cb 234ccb


  1. either of abb abbb but none of abbbb ab aabb
  2. either of ]abc ]abbbbc but none of ]ac ]bc ]ab abc ]]abc
  3. either of abca a but none of aa aba cba abba bcca
  • $\begingroup$ This is my first puzzle of this sort and I request critiques and ideas for improvement. $\endgroup$
    – msh210
    Commented Jan 12, 2020 at 23:51
  • 1
    $\begingroup$ Sounds like it belongs here, but not quite? :) $\endgroup$
    – Avi
    Commented Jan 12, 2020 at 23:59

1 Answer 1


I think I solved it

The strings of characters in the clues seem like they can be described by regular expressions.

  [   a   2
a b { 2 , 3 } 
  c   ?   4
( ] ) a b + c
  +   +   c
( a b c ) ? a
  ?   ?   b
1 [bc]+a? (at least one of b or c (or mixed), then optional a)
2 a2?a+c? (a, then optional 2, then at least one a, then optional c)
3 234+c?b (23, then at least one 4, optional c, then b)
4 ab{2,3} (a, then exactly 2 or 3 b's)
5 (])ab+c (], then a, then at least one b, then c)
6 (abc)?a (optional abc, then a)

The cell where 3 and 6 meet could also be a * and satisfy the conditions.

I liked this puzzle, I've never seen anything like it. The only improvement I can see is if you made it have only one solution (maybe by adding more negative test cases).

  • $\begingroup$ I fixed 5 across. Also I meant to say you could replace it with a * $\endgroup$ Commented Jan 13, 2020 at 0:51
  • $\begingroup$ Excellent. 5 Across was actually meant to be []]ab+c — which supports your point that I should've worked harder at making this have a unique solution. $\endgroup$
    – msh210
    Commented Jan 13, 2020 at 0:52
  • $\begingroup$ Just for curiosity, what are you using to test your regex? Using Javascript []] doesn't match ], whereas (]) (or even ]) does match. $\endgroup$ Commented Jan 13, 2020 at 0:54
  • $\begingroup$ Perl 5. []] matches just the character ] there. $\endgroup$
    – msh210
    Commented Jan 13, 2020 at 0:55
  • 2
    $\begingroup$ I'd hazard a guess that the title is also a clue: Re is a synonym for regarding and RE is the abbreviation for Regular Expression $\endgroup$
    – user40528
    Commented Jan 13, 2020 at 11:14

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