000001607908070010020000000036005000004060900000200460000000050090030108802700000
Applying the usual, plus an XY-wing and a Type 2 UR, you get here:
Code: Select all
+----------------------+----------------------+----------------------+
| 34 45 35 | 89 289 1 | 6 289 7 |
| 9 6 8 | 345 7 24 | 25 1 234 |
| 7 2 1 | 345689 4589 4689 | 58 3489 349 |
+----------------------+----------------------+----------------------+
| 12 3 6 | 49 49 5 | 78 78 12 |
| 125 78 4 | 18 6 37 | 9 23 1235 |
| 15 78 9 | 2 18 37 | 4 6 135 |
+----------------------+----------------------+----------------------+
| 346 14 37 | 14689 12489 24689 | 27 5 2469 |
| 46 9 57 | 456 3 246 | 1 247 8 |
| 8 15 2 | 7 15 469 | 3 49 469 |
+----------------------+----------------------+----------------------+
The pattern
Code: Select all
12 | 12
125 | 125
15 | 15
Code: Select all
1 | 2
2 | 5
5 | 1
and
2 | 1
5 | 2
1 | 5
So, in the position posted above, one of R56C9 must be <3>; R5C8 and R23C9 cannot be <3>.
These eliminations solve the puzzle. (Actually, eliminating <3> from only one of R5C8 or R2C9 solves the puzzle!)
Otherwise, it seems, the path to the solution is still quite difficult. Sudoku Susser needs four chains (with 6, 11, 4, and 5 links) and an XY-wing.
Keith