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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Mon Nov 16, 2009 9:25 am Post subject: Puzzle NR 09/11/16 (A) |
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| Code: | +-----------------------+
| 4 . 8 | 2 7 . | . 3 9 |
| . . 3 | . . . | 4 . . |
| 7 5 9 | . . 3 | . 1 8 |
|-------+-------+-------|
| 1 . . | 8 3 . | . . . |
| 5 . . | 1 . . | . . 3 |
| . . 6 | . . . | . . . |
|-------+-------+-------|
| . 2 . | . . . | 3 . 4 |
| 8 . 4 | . . . | . 2 . |
| 3 . 1 | . 4 . | 8 . . |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Mon Nov 16, 2009 2:32 pm Post subject: |
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After basics, I had the following code:
| Code: | *-----------------------------------------------------------*
| 4 16 8 | 2 7 15 | 56 3 9 |
| 2 16 3 | 59 18 1589 | 4 567 567 |
| 7 5 9 | 4 6 3 | 2 1 8 |
|-------------------+-------------------+-------------------|
| 1 4 27 | 8 3 5679 | 5679 56 256 |
| 5 8 27 | 1 29 679 | 679 4 3 |
| 9 3 6 | 57 25 4 | 157 8 125 |
|-------------------+-------------------+-------------------|
| 6 2 5 |@79 18 18 | 3 @79 4 |
| 8 @79 4 | 3 59 @579 | 16 2 16 |
| 3 @79 1 | 6 4 2 | 8 @579 57 |
*-----------------------------------------------------------* |
Notice the pattern for the bivalue 79 in boxes 789 marked @. I was unable to readily find Myth's post to verify that this is a valid DP pattern, but by simply walking the sequence it is a deadly pattern. Thus either r8c6=5 or r9c8=5; both force r9c2=9 to complete the puzzle.
Ted |
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arkietech
Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA
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| Posted: Mon Nov 16, 2009 2:51 pm Post subject: |
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| two w-wings 57 the 95 solve it |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Mon Nov 16, 2009 10:40 pm Post subject: |
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| XY-Wing (795), Kite (5) and BUG+1. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Tue Nov 17, 2009 5:16 am Post subject: |
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Kraken row 6 on candidate 5... => r7c4 <> 9
as a diagram...
(5)r6c4 - (5=9)r2c4
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(5)r6c5 - (5=9)r8c5
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(5)r6c7 - (5)r1c7 = (5)r1c6 - (5=9)r2c4
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(5)r6c9 - (5=7)r9c9 - (7=9)r7c8
the way I noticed this was I imagined that if the 5's in r6c79 were false, the 5's in r6c45 were strongly linked then I would have a w-wing {5,9}, pincers in r8c5 and r2c4.
so the w-wing would make a node.
(9=5)r2c4 - (5)r6c4 = (5)r6c5 - (5=9)r8c5; is node #1
then if that w-wing is false, you get a strong inference on the 5's that are left in row 6 in box 6. those 5's help create another chain which will be node #2
(9=5)r2c4 - (5)r1c6 = (5)r1c7 - (5)r6c7 = (5)r6c9 - (5=7)r9c9 - (7=9)r7c8
notice how both of these chains eliminate the 9 in r7c4
[(9=5)r2c4 - (5)r6c4 = (5)r6c5 - (5=9)r8c5] = [(9=5)r2c4 - (5)r1c6 = (5)r1c7 - (5)r6c7 = (5)r6c9 - (5=7)r9c9 - (7=9)r7c8]; r7c4 <> 9
makes for a massive chain. these chains are strongly linked. if they were both false then there wouldn't be any 5's in row 6. since one or the other has to be true, either one says the 9 can't exist in r7c4.
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Using the W-wing as a node isn't any different than using a naked pair/ALS or a hidden pair (or naked tripe/naked quad and their equivelant hiddent counterparts) as a node in a chain.
AND it isn't any different than using just one candidate as a node.
the important thing to notice about the above massive chain is that all the inferences are there for the reader to see. there isn't any questions as to what candidates are strongly or weakly linked. |
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