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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Fri Aug 21, 2009 3:55 pm Post subject: Set XY_03 Puzzle 038 |
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My workaround to the XY-Chain was very unexpected ... and not found the first few tries.
| Code: | +-----------------------+
| 2 . . | . 1 . | 8 . 4 |
| . 7 . | . . . | . . . |
| . . 4 | 7 . . | . . 1 |
|-------+-------+-------|
| . . 8 | 2 . . | . . 7 |
| 7 . . | . 5 1 | 2 8 . |
| . . . | . 6 . | . . 9 |
|-------+-------+-------|
| 5 . . | . 3 . | . . 6 |
| . . . | . 7 . | . 9 . |
| 3 . 7 | 6 . 2 | 4 . . |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Fri Aug 21, 2009 7:31 pm Post subject: |
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here is a path around the puzzle devastating xy-chain.
| Code: | .---------------------.---------------------.---------------------.
| 2 369 5 | 39 1 69 | 8 7 4 |
|U689 7 1 | 3459 2489 45689 |U569 2356 25 |
|U689 3689 4 | 7 289 5689 |U569 2356 1 |
:---------------------+---------------------+---------------------:
| 149 5 8 | 2 49 3 | 16 46 7 |
| 7 469 69 | 49 5 1 | 2 8 3 |
| 14 2 3 | 8 6 7 | 15 45 9 |
:---------------------+---------------------+---------------------:
| 5 1489 29 | 149 3 489 | 7 12 6 |
| 468 1468 26 | 145 7 458 | 3 9 28 |
| 3 189 7 | 6 89 2 | 4 15 58 |
'---------------------'---------------------'---------------------' |
the marked UR69 has strong inferences on the 8's in r23c1 and the 5's in r23c7
1...AUR inference...UR69[(8)r23c1 = (5)r23c7] - (5=2)r2c3 - (2=8)r8c9; r8c1 <> 8
2...Discontinuous nice loop...(9=4)r5c4 - (4)r5c2 = (4)r46c1 - (4=6)r8c1 - (6)r8c3 = (6)r5c3; r5c3 <> 9
or if you just want the non-xy-chain one stepper and be done with it.
(1=5)r9c8 - (5)r9c9 = (5)r2c9 - (5)r2c4 = (5-1)r8c4 = (1)r7c4; r7c8 <> 1
[Edit: corrected typo, daj95376] |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Fri Aug 21, 2009 10:36 pm Post subject: |
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storm_norm: Nice find on the <68> UR. I failed to catch it.
| storm_norm wrote: | or if you just want the non-xy-chain one stepper and be done with it.
(1=5)r9c8 - (5)r9c9 = (5)r2c9 - (5)r2c4 = (5-1)r8c4 = (1)r7c4; r7c8 <> 1
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aka: 6-cell gM-Wing ... or a non-productive Skyscraper w/extensions
Note #1: If you perform an Empty Rectangle for [r8c4] <> 4 first, then [r8c4] is a bivalue identical to [r9c8].
Note #2: Instead of (1)r7c4; r7c8 <> 1, there's also (1)r8c2; r9c2 <> 1.
Last edited by daj95376 on Fri Aug 21, 2009 11:09 pm; edited 1 time in total |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Fri Aug 21, 2009 11:08 pm Post subject: |
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| daj95376 wrote: | | storm_norm wrote: | or if you just want the non-xy-chain one stepper and be done with it.
(1=5)r9c8 - (5)r9c9 = (5)r2c9 - (5)r2c4 = (5-1)r8c4 = (1)r7c4; r7c8 <> 1
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aka: 6-cell gM-Wing ... or a non-productive Skyscraper w/extensions
Note #1: If you perform an Empty Rectangle for [r8c4] <> 4 first, then [r8c4] is a bivalue identical to [r9c8].
Note #2: Instead of (1)r7c4; r7c8 <> 1, there's also (1)r8c2; r9c2 <> 1. |
yep yep
the skyscraper on 5's is the key to that chain.
nice one. |
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