Discuss the <a href="http://www.sudocue.net/daily.php">Daily Sudoku Nightmare</a> here
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Ron Moore
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Post
by Ron Moore »
This is the position in the 28 Dec 2006 Nightmare, after initial eliminations from basic techniques:
Code: Select all
.------------------.-------------------.------------------.
| 1237 4 *236 | 9 56 8 | 567 27 137 |
| 237 *267 9 | 56 4 1 | 5678 278 378 |
| 5 *16 8 | 3 2 7 | 69 4 19 |
:------------------+-------------------+------------------:
| 18 *156 4 | 56 13567 35 | 78 9 2 |
|-289 *256 *26 |-24 5679 -2459 | 3 1 78 |
| 1-29 3 7 | 8 19 29 | 4 56 56 |
:------------------+-------------------+------------------:
| 4 8 1 | 7 59 6 | 2 3 59 |
| 6 27 5 | 1 389 2349 | 789 78 4789 |
| 237 9 23 | 24 58 245 | 1 5678 45678|
'------------------'-------------------'------------------'
After eliminations from the following chain (cells marked with "*" in the diagram), the solution is completed with singles only:
- (2=6)r5c3 - (6)r1c3 = (6)r2c2 - (6=152)r345c2 => r5c146, r6c1 <> 2
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Myth Jellies
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Post
by Myth Jellies »
Hate to spoil your fun, Ron; but if your grid is correct, there is no obvious (6)r1c3 = (6)r2c2 strong link. The 6 in r3c2 messes you up.
There is a nice little 56-UR in r69c89 which can only be escaped via the 5 in r7c9. Might as well hit the low hanging fruit.
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Ron Moore
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by Ron Moore »
Ugh! No excuse for that. I think I had one too many (puzzles at one stretch).
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rcbroughton
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by rcbroughton »
Once you do the simple eliminations from the UR, there is a strong chain on 7 at r9c9->r9c1->r8c2->r2c2 that eliminates 7 from r2c9
followed by a strong/weak chain on value 2 at r5c2->r5c4->r9c4->r8c6->r8c2 eliminating 2 from r5c2
after another cople of simple steps there's a strong/weak chain on 5 at r1c5->r2c4->r2c7->r3c7->r3c9->r3c2->r5c2 removing 5 from r5c5
There are then a couple of real tricky to spot chains
r5c9->r4c7->r4c1->r4c2->r3c2->r3c9->r3c7->r2c7->r2c4->r1c5->r9c5 removing 8 from r9c9
then (1)r1c1->(1)r1c9->(3)r1c9->(3)r2c9->(8)r2c9->(8)r2c8->(2)r2c8->(2)r1c8 removing 2 from r1c1 and 1 from r1c8
then (1)r1c1->(1)r1c9->(3)r1c9->(3)r2c9->(8)r2c9->(8)r2c8->(8)r8c8->(7)r8c8->(7)r8c2->(7)r2c2 removing 7 from r1c1 and 1 from r2c2
finally r1c1->r3c2->r4c2->r4c1->r4c7->r5c9->r2c9 3 from r1c9 r2c1
after that, it's singles