- Code: Select all
+---------------------------+-------------------------+----------------------------+
| 24589 12689 14689 | 349 345689 7 | 12389 2489 1389 |
| 24589 12689 14689 | 349 345689 5689 | 123789 24789 13789 |
| 489* 7 3 | 2 489* 1 | 89* 5 6 |
+---------------------------+-------------------------+----------------------------+
| 789* 3 5 | 79* 2 4 | 6 1 789* |
| 1 89* 2 | 6 7-89* 3 | 5 789* 4 |
| 6 4 789* | 5 1 89* | 789* 3 2 |
+---------------------------+-------------------------+----------------------------+
| 3 5 789* | 1 79* 2 | 4 6 789* |
| 24789 12689 146789 | 3479 345679 569 | 123789 2789 135789 |
| 2479 1269 14679 | 8 345679 569 | 12379 279 13579 |
+---------------------------+-------------------------+----------------------------+
Look at cells marked (*): r34567
15 cells, 4 digits (4,7,8,9)
Digit 4 can be there at most once (r4), digit 7 can be there at most four times (r4567) => digits 8 and 9 must be there five times each.
This is impossible if 8 or 9 is at the central position r5c5:
- Code: Select all
8 | | 8
-------------------------
x | | x
x | 8 | x
x | | x
-------------------------
8 | | 8
If r5c5 is 8, in r3 and r7, 8 cannot be in the same stack (=> b4 or b6 void of 8); and 8 cannot be in diagonal boxes (=> r4 or r6 void of 8)
Same rationale for digit 9.
=> -89 r5c5; lclste