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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Wed Sep 15, 2010 4:38 am Post subject: Puzzle 10/09/15: C |
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| Code: | +-----------------------+
| 3 . 6 | . . . | . . 4 |
| . . . | . . . | . . . |
| 7 . . | . . . | 5 8 3 |
|-------+-------+-------|
| . . . | 4 . . | . . . |
| . . . | . 1 6 | . 4 . |
| . . . | . 8 7 | 3 . 6 |
|-------+-------+-------|
| . . 7 | . . 4 | . 5 1 |
| . . 4 | . 7 . | 2 . 8 |
| 6 . 2 | . . 3 | . . . |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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JC Van Hay
Joined: 13 Jun 2010
Posts: 494
Location: Charleroi, Belgium
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| Posted: Wed Sep 15, 2010 5:13 pm Post subject: |
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| Quote: | Skyscraper (9)C26 : => r4c1,r6c4<>9
4-SIS XY Chain or ALS XY Wing (12-9) : (92)R4C6 [(25)R6C14 (51)R6C1] (19)R6C8 : (9)r4c6=(9)r6c8 : => r4c78<>9 ... or ... Unique Loop of length 8 (79)R249 : => r4c78<>9
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Wed Sep 15, 2010 8:34 pm Post subject: |
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A wing+ ..
| Quote: | | m-wing(29) pseudocell ; (2=1)r3c6-(1=9)r8c6 - r8c2=(9-2)r6c2=r6c4 ; r3c4<>2, r4c6<>2 |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Thu Sep 16, 2010 1:15 pm Post subject: |
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6-cell ADP(79)r249c789
Internal SIS: r4c7=8 and/or r4c8=1 AIC: (9=8)r5c7-ADP(79)r249c789[(8)r4c7=(1)r4c8]-(1=9)r6c8; r4c78<>9
Additional deletions are available using the interanl SIS: (9=1)r6c8-ADP(79)r249c789[(1)r4c8=(8)r4c7]-r4c13=r5c1-(8=9)r7c1-r8c2=(9)r6c2; r6c4<>9
Other deletions may be possible but, if so, they are not immediately obvious. These three deletions do not progress the solution much further.
However, looking at the external SIS we find: col78/box6 r5c7=9 and/or r6c8=9, which are essentially the same as the internal SIS employed.
Another external SIS is row4 r4c1=9 and/or r4c6=9. This SIS directly results in r4c78<>9 as did the internal conditions. But this SIS offers more: ADP(79)r249c789[(9)r4c1=(9)r4c6]-r8c6=(9)r7c4; r7c1<>9=8 to complete the puzzle in one step.
Ted |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Sep 16, 2010 3:17 pm Post subject: |
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What does SIS stand for? |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Sep 17, 2010 2:16 pm Post subject: |
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| Marty R. wrote: |
What does SIS stand for? |
SIS: "Strong Inference Set"
As an example, the set of free, extra digits form the internal SIS for an AUR
Ted. |
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