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Sudtyro
Hooked

Joined: 16 Jan 2007
Posts: 49

Posted: Tue Jan 16, 2007 9:36 pm    Post subject: 16 December 2006 Nightmare

Don’t have a solver, but got this far manually before stalling out. Can anyone offer a kick-start?

 Code: 1   2    567 |  49   3   49  |  56  67   8 8   69   356 |  2    1   7   |  45  36   469 379 79   4   |  6    5   8   |  1   237  29 -------------+---------------+-------------- 5   14   9   |  3    7   26  |  8   246  126 26  3    68  |  5    48  1   |  9   246  7  267 14   678 |  48   9   26  |  3   5    126 -------------+---------------+-------------- 69  5    1   |  7    2   49  |  46  8    3 367 678  367 |  1    48  5   |  2   9    46 4   89   2   |  89   6   3   |  7   1    5
Ruud
Site Owner

Joined: 30 Dec 2005
Posts: 601

 Posted: Wed Jan 17, 2007 10:22 pm    Post subject: Hi Sudtyro, welcome to the forum. This Nightmare can be advanced from this point by 3D coloring. However, there is also an ALS-XZ move that breaks the puzzle. Consider r3468c9 with candidates for digits 12469. Consider r7c17 with candidates for digits 469. Both sets have one one surplus digit, which makes them Almost Locked Sets. Both sets have a single candidate for digit 4 in box 9, so one of the sets will NOT contain digit 4 and must contain all remaining digits. Both sets have a single candidate for digit 9, since one of them must be true (previous rule), r3c1 cannot contain digit 9. This leads to several singles and your next advanced move. Ruud_________________“If the human brain were so simple that we could understand it, we would be so simple that we couldn't.” - Emerson M Pugh
Sudtyro
Hooked

Joined: 16 Jan 2007
Posts: 49

 Posted: Thu Jan 18, 2007 12:43 am    Post subject: Thanks for the quick response! I had tried the 3D coloring, but didn't see an immediate way forward. Let me look at the ALS approach...that's a new study area for me. Still much to learn...
unkx80
Hooked

Joined: 26 Aug 2006
Posts: 33
Location: Singapore

 Posted: Thu Jan 18, 2007 7:55 pm    Post subject: Ruud's ALS-XZ is so big. There is a smaller ALS-XZ, actually a Type 2 WXYZ-Wing. The cells involved are r2c8, r2c2, r3c1, r3c2, leading to r2c3<>3.
Sudtyro
Hooked

Joined: 16 Jan 2007
Posts: 49

Posted: Fri Jan 19, 2007 10:01 pm    Post subject:

 unkx80 wrote: There is a smaller ALS-XZ, actually a Type 2 WXYZ-Wing. The cells involved are r2c8, r2c2, r3c1, r3c2, leading to r2c3<>3.

Thanks for the tip...learning fast!
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