Hi David,
The trouble with BUG is that it is usually the last step before the final cascade of singles. Sudokus as complex as the Daily Nightmares can be solved in many ways, and I can only hope that the solving path you choose leads to to the BUG. Since DIC's are not on my list, using them will lead you away from the BUG.
About todays Nightmare:
Singles and intersections bring you here:
Code: Select all
.------------------.------------------.------------------.
| 456 259 3 | 1 24679 2479 | 479 249 8 |
| 1 289 24 | 278 24679 3 | 5 249 4679 |
| 46 289 7 | 28 2469 5 | 1 3 469 |
:------------------+------------------+------------------:
| 89 3 6 | 27 2479 24789| 49 1 5 |
| 89 4 5 | 6 1 89 | 3 7 2 |
| 2 7 1 | 3 5 49 | 6 8 49 |
:------------------+------------------+------------------:
| 7 6 9 | 4 8 1 | 2 5 3 |
| 45 25 8 | 9 3 27 | 47 6 1 |
| 3 1 24 | 5 27 6 | 8 49 479 |
'------------------'------------------'------------------'
My solver now continues:
finned X-Wing removes 2 from R1C6
finned X-Wing removes 4 from R2C9
finned X-Wing removes 7 from R1C5
X-Wing removes 7 from R4C6
finned X-Wing removes 9 from R1C6
intersection removes 9 from R4C5
uniqueness 1 removes 89 from R4C6
a few singles
naked pair 47 in row 1
X-Wing removes 4 from R2C5
XY-Wing removes 7 from R2C4
single and intersection
hidden pair 67 in row 2
hidden pair 28 in row 3
uniqueness 1 removes 28 from R2C2 (leaves single 9)
a few singles
brings us to da BUG:
Code: Select all
.------------.------------.------------.
| 56 25 3 | 1 69 47 | 47 29 8 |
| 1 9 24 | 8 67 3 | 5 24 67 |
| 46 8 7 | 2 469 5 | 1 3 69 |
:------------+------------+------------:
| 8 3 6 | 7 24 24 | 9 1 5 |
| 9 4 5 | 6 1 8 | 3 7 2 |
| 2 7 1 | 3 5 9 | 6 8 4 |
:------------+------------+------------:
| 7 6 9 | 4 8 1 | 2 5 3 |
| 45 25 8 | 9 3 27 | 47 6 1 |
| 3 1 24 | 5 27 6 | 8 49 79 |
'------------'------------'------------'
You see how many things you could have missed or done differently?
cheers,
Ruud