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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Thu Feb 17, 2011 6:34 pm Post subject: Puzzle 11/02/17 |
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| Code: | +-----------------------+
| 2 . . | 8 . 1 | . . 3 |
| . 8 1 | 4 . 3 | 2 5 . |
| . 3 4 | . . 5 | . . . |
|-------+-------+-------|
| 7 4 . | . 1 2 | . . . |
| . . . | 3 8 . | . . . |
| 8 2 3 | 6 . 4 | . 1 . |
|-------+-------+-------|
| . 6 . | . . . | 1 . . |
| . 1 . | . . 9 | . 3 . |
| 3 . . | . . . | . . 9 |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Thu Feb 17, 2011 7:34 pm Post subject: |
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Two steps
| Quote: | xy-wing-like(59-7) ; (7=69)r21c5 - (9=5)r6c5 - (5=7)r6c9 ; r2c9<>7
finned x-wing(5) r6, r9 ; r5c7<>5 |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Thu Feb 17, 2011 8:36 pm Post subject: |
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| I definitely need to expand my chain logic!!! |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Feb 18, 2011 2:29 am Post subject: |
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I threw in the towel. I'm not ashamed to say that I couldn't complete the puzzle, but I'm definitely ashamed to say that I used the abomination known as a Finned or Almost XY-Wing.   While it made a couple of eliminations, it didn't open anything up that I could see. |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Fri Feb 18, 2011 9:57 am Post subject: |
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I kept thinking about Peter's first step in terms of adding something similar to my solver. However, my solver currently needs strong links/inferences to only use two values. Then I realized that Peter's chain could be altered to meet this objective:
| Code: | ALS(7=5)r216c5 - (5=7)r6c9 ; r2c9<>7
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As for my solver's solution:
| Code: | r69\c57 finned X-Wing <> 5 r5c7 (needed Marty!)
r6c4 2-String Kite <> 9 r3c7 extraneous
+--------------------------------------------------------------------------------+
| 2 5 7 | 8 a69 1 | 49-6 49-6 3 |
| 69 8 1 | 4 79-6 3 | 2 5 d67 |
| 69 3 4 | 279 2679 5 | 678 6789 1 |
|--------------------------+--------------------------+--------------------------|
| 7 4 56 | 59 1 2 | 3 689 568 |
| 1 9 56 | 3 8 7 | 46 246 2456 |
| 8 2 3 | 6 b59 4 | 579 1 c57 |
|--------------------------+--------------------------+--------------------------|
| 45 6 9 | 257 3 8 | 1 247 2457 |
| 45 1 28 | 257 2457 9 | 45678 3 245678 |
| 3 7 28 | 1 245 6 | 458 248 9 |
+--------------------------------------------------------------------------------+
# 68 eliminations remain
XY-Chain: (6=9)r1c5 =5r6c5 =7r6c9 =6r2c9 => r1c78,r2c5<>6
<59+7> XY-Wing r6c5/r2c5+r6c9 <> 7 r2c9
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Fri Feb 18, 2011 10:53 am Post subject: |
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| daj95376 wrote: | | Then I realized that Peter's chain could be altered to meet this objective |
I think that will always be the case if the next "term" in the chain is a strong link on a bivalue - you can always upgrade the als from an ANP, to an ANT or ANQ etc.? |
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