regarding Example 6:
- Code: Select all
+-------------------+-------------------+-------------------+
| 7 *16 45 | 2 8 16 | 3 45 9 |
|*19 3 45 | 45 7 19 | 2 8 6 |
|*269 29 8 | 3 45 69 | 14 7 15 |
+-------------------+-------------------+-------------------+
| 3 2678 267 | 17 9 4 | 5 26 128 |
|-689 4 679 | 157 25 27 | 169 3 18 |
|*29 5 1 | 8 6 3 | 49 249 7 |
+-------------------+-------------------+-------------------+
|-1689 189 269 | 49 24 5 | 7 1269 3 |
| 4 679 3 | 69 1 27 | 8 59 25 |
| 5 12679 2679 | 679 3 8 | 69 1269 4 |
+-------------------+-------------------+-------------------+
An alternative analysis is by using almost-locked sets:
r5c1 ISN'T 9: weak link to almost-locked sets r1c2 and r2c1 r3c1 r6c1 mutually doubly-linked by 1,6
r7c1 ISN'T 9: weak link to almost-locked sets r1c2 and r2c1 r3c1 r6c1 mutually doubly-linked by 1,6
that is,
- Code: Select all
.1
. \
1 6
| .
2---+--6
|
9....9*
9* may be eliminated
But now I have a different problem.
I've added "strong sets" to Sudoku Assistant to advance Exercise 6.
This involves recognizing that strong chains might have "nodes" that
involve more than one mark. But now it's stuck at:
- Code: Select all
|---c1--|---c2--|---c3--||---c4--|---c5--|---c6--||---c7--|---c8--|---c9--
-----------------------------------------------------------------------------
r1 | 7 | 156 | 456 || 2 | 48 | 16 || 3 | 458 | 9
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r2 | 19 | 3 | 45 || 1458 | 7 | 149 || 2 | 58 | 6
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r3 | 269 | 269 | 8 || 3 | 45 | 69 || 14 | 7 | 15
===========================||=======================||=======================
r4 | 3 | 2678 | 267 || 1478 | 9 | 1247 || 5 | 126 | 128
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r5 | 2689 | 4 | 25679 || 1578 | 258 | 127 || 169 | 3 | 128
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r6 | 289 | 258 | 1 || 58 | 6 | 3 || 49 | 249 | 7
===========================||=======================||=======================
r7 | 1689 | 1689 | 269 || 469 | 24 | 5 || 7 | 1269 | 3
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r8 | 4 | 679 | 3 || 679 | 1 | 27 || 8 | 2569 | 25
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r9 | 5 | 12679 | 2679 || 679 | 3 | 8 || 169 | 1269 | 4
-----------------------------------------------------------------------------
...............................................................................................
I think I've only partially impemented "strong sets".
So what is the next "nice loop" here? Does a nice loop, for example,
take out r2c4#8 due to a problem then with the placement of 2 in row 5?
Thanks.