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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Sat Sep 26, 2009 2:52 pm Post subject: LAT/Freep sep-25-09 |
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000026009050000020061900700800010000070608050000090008007000230020000010605100000
| Code: |
+-------+-------+-------+
| . . . | . 2 6 | . . 9 |
| . 5 . | . . . | . 2 . |
| . 6 1 | 9 . . | 7 . . |
+-------+-------+-------+
| 8 . . | . 1 . | . . . |
| . 7 . | 6 . 8 | . 5 . |
| . . . | . 9 . | . . 8 |
+-------+-------+-------+
| . . 7 | . . . | 2 3 . |
| . 2 . | . . . | . 1 . |
| 6 . 5 | 1 . . | . . . |
+-------+-------+-------+
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open in draw/play
open in andrew stuarts online solver |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Sep 26, 2009 5:15 pm Post subject: |
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I had fun with this one, using a variety of steps.
| Quote: | | XYZ (348), ER (3, 3, 4), W (37), XY (493) and XY (478) with pincer transport |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Sat Sep 26, 2009 9:07 pm Post subject: |
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| Marty R. wrote: | I had fun with this one, using a variety of steps.
| Quote: | | XYZ (348), ER (3, 3, 4), W (37), XY (493) and XY (478) with pincer transport |
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| Quote: | Skyscraper on 3 in r8c14 and then the xy-wing 47-8 with pincer transport noted by Marty
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Ted |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Sun Sep 27, 2009 4:07 am Post subject: |
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There is an interesting one-step solution based upon a generalization of the W-Wing concept. The standard W-Wing idea is 2 non-peer matching bivalues which each see the opposite ends of an external strong inference. However, if you consider that bivalues are just the smallest sort of ALS, then the technique can be enlarged by considering multiple cell ALS in place of one or both bivalues. (It is easiest to spot when only one of the bivalues is so substitued, as here.)
| Code: | +----------------+-----------------+-------------+
| 7 348 348 | 5 2 6 | 1 48 9 |
|b49 5 b489 |#7-4 478 1 | 6 2 3 |
| 2 6 1 | 9 348 34 | 7 48 5 |
+----------------+-----------------+-------------+
| 8 349 3469 | 347 1 5 | 349 67 2 |
| 349 7 2 | 6 34 8 | 349 5 1 |
| 5 1 346 | 2 9 347 | 34 67 8 |
+----------------+-----------------+-------------+
| 1 c489 7 |a48 5 49 | 2 3 6 |
| 349 2 c3489 | 3478 6 3479 | 5 1 47 |
| 6 34 5 | 1 347 2 | 8 9 47 |
+----------------+-----------------+-------------+ |
Cell "a" is our usual bivalue and the external strong inference is the conjugate <8>s in b7, marked "c". On the other end is the 489 ALS marked "b". It functions exactly as a W-Wing to remove <4> from "#":
ALS[(4)r2c13=(8)r2c3] - (8)r8c3=(8)r7c2 - (8=4)r7c4; r2c4<>4
I recalled that I had seen an example of this recently and went looking. I found it here in a post by Norm. While Norm's AIC is different, I saw it in this W-Wing based way as:
ALS[(8)r2c2=(4)r23c2] - (4)r1c3=(4)r6c3 - (4=8)r6c4; r2c4<>8
I believe that these are easy enough to spot that you needn't be an AIC user to exploit them. |
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