A Colorful Verification Creams Wex 427

The second Weekly Extreme review puzzle, 427 is prey of a Sue de Coq verification trial, but I had to get out the crayons to do it.

Non WECers, did you like your first Weekly Extreme Competition puzzle? If you like the review puzzles, the entire line up of puzzles and solutions to date is found at

www.sudoku.org.uk/WeeklySudoku.asp . The large print puzzle for the current week is at

www.sudoku.org.uk/PrintWeeklySudoku.asp .

Wex 427 offered a fairly moderate slink marking bypass and box marking, followed by a very tough line marking:

wex 427 LM

wex 427 basic trSysudokies, look at the size of those fill strings. What did I miss?

Anyway, there’s a couple of remotely possible unique rectangles, but following my own advice on #426, I was looking over the chutes for a Sue de Coq.


I found one right in the middle, Cr5 = 5(3+9)(7+8)+875 . I’m hoping for a removal of 3r6c4. The verification does not go well, however, as the marking doesn’t reach resolution.

wex 427 sdctrwex 427 coloringThere are many slinks and bv, so I get out the crayons to continue the trial. After extending the blue/green cluster as far as I can, I have related bv left, so I throw in a red/orange. Now we look for interactions.

We have cell r1c7 asserting

not (green & orange),

and cell r9c5 asserting

not(green & red)


So that means: (blue or red) and (blue or orange) = blue and (red or orange) = blue

wex 427 blue to redThe distributive law of Boolean logic helps our Sue de Coq verifying trial along, particularly when S4 hands the gavel to red.   It’s a small step to the solution. WEC 427 is not admitted into the Sysudoku Extreme Club.

I admit to missing the above Sue de Coq on my first encounter with 427. I finally saw it on my scan through the slides before putting the final post together. That sneaky verification buried a finned swordfish and a freeform reduction of 2-patterns to one pink and two olive, with a subsequent pattern trial. #*&@%^!:(

It would be great to have some WECer commentary on SdC verification trials, to go along with this post. I believe SdC verification meets the “logic” criteria outlined in the previous post. Do you believe they are a form of trial-and-error? Does either the prior identification of removed candidates, or the reproducible evidence of the 2-D trial trace, reduce T & E concerns? Has anyone else employed the single alternate form of Sue deCoq with a verification or a solution by verification trial?

We’re still looking for a sysudokie extreme level WEC. Next time, the applicant is Wex 428.

About Sudent

I'm John Welch, a retired engineering professor, father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. Sudoku analysis and illustration is a great hobby and a healthy mental challenge.
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