[Edit: I'm reposting these computer generated solutions for the unsolvables because of several requests to repost them. They were removed in order to stimulate alternative, human generated solutions. I still hope others post alternative solutions, but for those looking for examples of grouped nice loops and multi-inference nice loops, they are here. Also per David's request I've summarized all of the techniques used in order of the number of occurances. I've also included more PMs and have updated the solutions and comments based on my latest solver]
#25 uses two of the new techniques we've been developing over the last several weeks based in part on previous work including a Kraken Fish Exclusion and a Death Blossom (an Advanced Aligned Pair Exclusion - named from "The Last Starfighter" - I'm a Robert Preston fan).
My solver did not solve this puzzle without Death Blossom (refered to as Kraken Blossom in my updated solver which allows for more link possibilities including strong links and grouped strong links as well as multiple links). The most recent changes to my solver have been addition of grouped nice loops where cells of the loop can overlap at the beginning and ending nodes. Updates to grouped nice loops did not eliminate the need for the Death Blossom. I haven't determined a minimal set of techniques yet, but the Death Blossom was the most advanced technique used. To shorten things I'm not showing singles in the summary.
Since the primary purpose of these solutions is to show application of various techniques I left in Uniqueness Tests (I personally think they are an excellent solving technique in their own right).
The names are something I made up for the new techniques since something thats capable of solving an unsolvable puzzle deserves a better name than "Adanced Pair Exclusion" or "Almost X-wing" or "Advanced BUG elimination". As always I will probably revert to the more benign names in the future, but couldn't resist the temptation. On the other hand, there's still "Overlapping Nice Loop" which needs a little more spice!
1) Naked Single (42)
2) Hidden Single (15)
3) Locked Line/Box (5)
4) Naked Pair (2)
5) Nice Loops with 3 Strong Links/BV Cells (2)
6) Locked Box/Box (1)
7) Finned X-wing (1)
8) 4-node XY-chain (1)
9) UR+2K(X,D),UR+3K(X,D) (1)
10) Advanced BUG-Lite with 3 lines (1)
11) Advanced Colouring with 3 Links (1)
12) Advanced Colouring with 6 Links (1)
13) Grouped Nice Loops with 4 GSL/ALS (1)
14) B=1 cell ALS-xy rule (1)
15) 5-valued/1-link Kraken Blossom (1)
16) Bivalued/1-link Kraken X-wing (1)
- Code: Select all
Locked Column Line/Box: r46c3 => r123c3<>8
Naked Column Pair: r13c3 => r2c3<>39,r46c3<>3,r8c3<>9,r9c3<>39
Locked Column Line/Box: r13c2 => r5c2<>7
Locked Column Line/Box: r79c2 => r1235c2<>3
Locked Column Box/Box: r279c2|r29c3 => r46c3<>5
Naked Column Pair: r13c2 => r2c2<>8
3-element Nice Loop: r5c4=1=r6c4=6=r6c3-6-r5c2-1-r5c4 => r6c4=16
3-element Nice Loop: r6c5=8=r6c3=6=r5c2-6-r5c6~3~r6c5 => r6c5<>3
B=1 cell ALS xy-rule: r4c3569-3-r5c6-6-r6c14789 => r4c7<>2
UR+2KX (7,8): r13c28, r2c78 => r1c8<>8
Bivalued/1-element Kraken Row X-Wing (r37/c9, fins=r3c4|r7c27) (r3c4=4=r3c5-4-, r7c2-6-r8c3-4-, r7c7=4=r7c45-4-): r3c49|r7c279=6 => r8c5<>4
+-----------------+---------------------+--------------------+
| 4 78 39 | 368 1 3689 | 23679 2379 5 |
| 6 15 15 | 2 389 7 | 39 389 4 |
| 2 78 39 | 3468*b 3489b 5 | 1 3789 67* |
+-----------------+---------------------+--------------------+
| 357 4 18 | 9 2378 238 | 357 6 127 |
| 37 16 2 | 1367 5 36 | 8 4 9 |
| 357 9 168 | 16 278 4 | 2357 12357 127 |
+-----------------+---------------------+--------------------+
| 9 2356* 7 | 348d 2348d 238 | 2456*d 125 126* |
| 8 26 46c | 5 279-4 1 | 24679 279 3 |
| 1 235 45 | 347 6 239 | 24579 2579 8 |
+-----------------+---------------------+--------------------+
4-element Grouped Nice Loop: r2c7-3-ALS:r12389c8-5-r9c3-4-r8c3=4=r8c7~9~r2c7 => r8c7<>9
+-----------------+-------------------+---------------------+
| 4 78 39 | 368 1 3689 | 23679 2379*b 5 |
| 6 15 15 | 2 389 7 | 39* 389*b 4 |
| 2 78 39 | 3468 3489 5 | 1 3789*b 67 |
+-----------------+-------------------+---------------------+
| 357 4 18 | 9 2378 238 | 357 6 127 |
| 37 16 2 | 1367 5 36 | 8 4 9 |
| 357 9 168 | 16 278 4 | 2357 12357 127 |
+-----------------+-------------------+---------------------+
| 9 2356 7 | 348 2348 238 | 2456 125 126 |
| 8 26 46* | 5 279 1 | 2467-9* 279*b 3 |
| 1 235 45* | 347 6 239 | 24579 2579*b 8 |
+-----------------+-------------------+---------------------+
Row Finned X-Wing: r2c578|r8c58 => r13c8<>9
6-element Advanced Colouring: r2c8=8=r2c5-8-r6c5=8=r6c3=6=r5c2-6-r5c6=6=r1c6=9=r9c6-9-r8c5=9=r8c8~9~r2c8 => r2c8<>9
Locked Column Line/Box: r12c7 => r9c7<>9
Advanced 3-line BUG Lite (SL:r3c3=9=r3c5, ALS:r1c7-3-r2c8-3-r2c5): r1c37|r3c35|r2c57 => r1c7<>3
5-valued/1-element Kraken/Death Blossom (r8c5-2-r8c2-6-, r8c5-7-r46c5|r45c6-6-, r8c5-9-r4579c6-6-): r8c5=279 => r5c2<>6
+-----------------+-------------------+-------------------+
| 4 78 39 | 368 1 3689 | 2679 237 5 |
| 6 15 15 | 2 389 7 | 39 38 4 |
| 2 78 39 | 3468 3489 5 | 1 378 67 |
+-----------------+-------------------+-------------------+
| 357 4 18 | 9 2378c 238cd | 357 6 127 |
| 37 1-6 2 | 1367 5 36cd | 8 4 9 |
| 357 9 168 | 16 278c 4 | 2357 12357 127 |
+-----------------+-------------------+-------------------+
| 9 2356 7 | 348 2348 238d | 2456 125 126 |
| 8 26b 46 | 5 279* 1 | 2467 279 3 |
| 1 235 45 | 347 6 239d | 2457 2579 8 |
+-----------------+-------------------+-------------------+
Locked Column Line/Box: r46c7 => r2c7<>3
3-element Advanced Colouring: r1c8=2=r1c7-2-r6c7=2=r6c9=7=r3c9~7~r1c8 => r1c8<>7
4-node XY-chain (r1c8-3-r3c8-7-r3c9-6-r7c9-2-) => r89c8<>2