As I traveled across the web, searching far and wide, I came across an odd puzzle that made me feel awry. It foretold the future's path and predicted no tie. How could this puzzle work, and what was the answer it told me. I know it's my destiny.

Mysterious Grid

Note: Please ignore the messiness, it should be a straightforward grid, but I ran into issues collecting images large enough.

  • $\begingroup$ Pretty simple, but you hid it cleverly enough that it took me a while to notice the solution words. Fun puzzle! $\endgroup$ – Deusovi Nov 7 '16 at 5:18

This is a

regex crossword! A "regular expression" (or "regex") is a programming tool to specify types of string. A regex crossword is a type of puzzle, invented at the 2013 Mystery Hunt and now available online at all types of difficulty levels, where each row and column must match a specific regex.

How it works:

Brackets give options for characters. \s is a space. Parentheses also give options, but for longer strings. (With brackets, you can pick any character inside. With parentheses, you have to choose a full string, delimited by any of (|).) Braces give the number of times anything in brackets is repeated. Stars mean "the previous thing is done 0 or more times", plus signs mean "the previous thing is done 1 or more times", and question marks mean "the previous thing may or may not be done at all".

The solution to this is

ambiguous! There are actually two solutions.

and the other solution...


  • $\begingroup$ That MIT puzzle is probably one of my favourite puzzles. Was always surprised I'd never seen any equivalent ones posted here (and never got around to doing it myself). $\endgroup$ – Alconja Nov 7 '16 at 5:23
  • $\begingroup$ "WHO WILL WIN" does not match. :) $\endgroup$ – Rubio Nov 7 '16 at 5:29
  • 8
    $\begingroup$ ...forgot to add. This puzzle is also likely a nod to this famous one (spoilers). $\endgroup$ – Alconja Nov 7 '16 at 5:41

There's actually two errors in the puzzle at the moment

The intended solution was posted by Deusovi.
The actual solution is
WHO WILLWIN     (i.e. no space)
and then either of the two choices,

This only works if the regex has to match the string at all, but not necessarily match it in its entirety. If the regex is required to implicitly begin with ^ and end with $ so that it must match the entirety of the row or column entry then there is, as posted, no solution possible.

The intended solution would work if the first row instead said
i.e. adding a dot after the +
There are other ways to fix as well, but that way seems straightforward enough.

To meet the condition mentioned in the spoiler above, which I suspect is required, there's a second error which must be fixed for any solution to work. The 7th column is missing a final +, and must be
to satisfy the additional constraint.

  • $\begingroup$ Hm? That's not possible - it doesn't line up with the columns. $\endgroup$ – Deusovi Nov 7 '16 at 6:28
  • $\begingroup$ Hm, then how does it even fit in the columns? Which character fits which column regex? Do you just skip a column? $\endgroup$ – Deusovi Nov 7 '16 at 6:37
  • $\begingroup$ i'm sure it's supposed to have the space, but right now it doesn't actually match the row pattern if the space is included. on further review I see i didn't quite understand how the columns worked, but I do now, and have fixed my code ... by sheer happenstance, the solution with the missing space still works, if you only use the two characters from the two lines with a 12th character as the string to match against the pattern. see pastebin.com/q4nD3Vkf for details. $\endgroup$ – Rubio Nov 7 '16 at 7:06
  • $\begingroup$ Good points on the mistakes, sorry about that, I guess I jumped the gun on posting. Deusovi has the intended answer, and I'll work on getting a more fixed version edited in. $\endgroup$ – Sconibulus Nov 7 '16 at 12:41

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