Code: Select all
.-------------------.---------------------.------------------.
| 1 8 49 | 349 349 5 | 2 6 7 |
|#49 7 2 | 1 6 49 | 58 358 38 |
| 3 6 5 | 8 27 27 | 1 9 4 |
:-------------------+---------------------+------------------:
|#249 5 1 | 7 2349 249 | 6 38 389 |
|#2469 2349 8 | 234-69 1 24-69 | 57 57 39 |
|*67+9 ^39 *67+3 |^369 5 8 | 4 2 1 |
:-------------------+---------------------+------------------:
| 5 1 49 | 249 2479 3 | 789 78 6 |
|*67+29 29 *67 | 69 8 1 | 3 4 5 |
| 8 349 36 | 5 479 4679 | 79 1 2 |
'-------------------'---------------------'------------------'
In the jargon of the Solving Guide, there are two "unique subset" possibilities here, one of which must hold, but I'll state the argument in equivalent terms of Almost Locked Sets (ALS's). If the UR pattern is avoided by choosing one of the surplus candidates in row 6, either (9)r6c1 or (3)r6c3, the ALS r6c24 (marked with "^") becomes locked with "6" forced into r6c4. On the other hand, if the UR pattern is avoided by choosing one of (2or9)r8c1, then the ALS r245c1 (marked with "#") becomes locked with "6" forced into r5c1. In either case, both of r5c46 see a "6" (and for that matter, so do cells r6c13). In AIC form:
(6=39)r6c24 - ((3or9)=67)r6c13 - UR - (67=(2or9))r8c13 - (249=6)r245c1 => r5c46, r6c13 <> 6