JPF wrote:Could it be qualified ?
- Code: Select all
*--------------------------------------------------------------------*
| 2589 56 28 | 13 7 13 | 25 24569 24589 |
| 567 1 4 | 89 2 89 | 567 3 57 |
| 23789 289 238 | 4 5 6 | 127 279 12789 |
|----------------------+----------------------+----------------------|
| 1249 249 7 | 1259 6 1249 | 8 25 3 |
| 24 3 5 | 27 8 247 | 9 1 6 |
| 1289 289 6 | 1259 3 129 | 4 257 257 |
|----------------------+----------------------+----------------------|
| 2348 248 1238 | 6 9 5 | 1237 247 1247 |
| 456 7 9 | 23 1 23 | 56 8 45 |
| 235 56 123 | 78 4 78 | 1235 2569 1259 |
*--------------------------------------------------------------------*
where a Y-wing style (though I would like it we changed the name of this technique to something that does not refer to xy-wings and which correlates to what it really looks like, namely remote naked pairs...perhaps
semi-remote naked pairs) between r1c2,r8c7<56> implies r1c7<>5 (there is also an xyz-wing that will make this same exclusion). After cleaning up the grid a bit, we get
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*-----------------------------------------------------------*
| 59 56A 8 | 13 7 13 | 2 456a9 459 |
| 56a7B 1 4 | 89 2 89 | 567 3 57 |
| 237b9 29 23 | 4 5 6 | 1 7B9b 8 |
|-------------------+-------------------+-------------------|
| 1249 249 7 | 1259 6 1249 | 8 25 3 |
| 24 3 5 | 27 8 247 | 9 1 6 |
| 1289 289 6 | 1259 3 129 | 4 257 257 |
|-------------------+-------------------+-------------------|
| 2348 248 123 | 6 9 5 | 37 247 1247 |
| 456 7 9 | 23 1 23 | 56 8 45 |
| 235 56 123 | 78 4 78 | 35 256A9- 1259 |
*-----------------------------------------------------------*
Now a little 3D-coloring implies r9c8<>9, which solves the puzzle.
[r9c8]-9-[r3c8]-7-[r3c1]=7=[r2c1]=6=[r1c2]-6-[r1c8]=6=[r9c8]
I can find a few bidirectional cycles, but none yet that really crack the puzzle open.