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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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 Posted: Sun Feb 21, 2010 12:10 am Post subject: Vanhegan Extreme Feb 20 |
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I wanted to practice using ALSs, so I tried this Vanhegan Extreme. After a couple of hours work, I have a solution.
Maybe others would like to give it a go. I am heading for the Scotch 
| Code: |
+-------+-------+-------+
| . 4 9 | 8 . 5 | . . . |
| . . . | 2 . . | . . 5 |
| . . . | . 7 9 | . . 8 |
+-------+-------+-------+
| 6 . 3 | . . . | . 7 1 |
| . . 7 | . . . | 3 . . |
| 4 8 . | . . . | 2 . 6 |
+-------+-------+-------+
| 9 . . | 1 6 . | . . . |
| 5 . . | . . 8 | . . . |
| . . . | 5 . 3 | 6 4 . |
+-------+-------+-------+
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Play this puzzle online at the Daily Sudoku site
Ted |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Sun Feb 21, 2010 12:40 am Post subject: |
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This is not a solution to the puzzle. It's just my mentioning a pattern that recently caught my attention while investigating chains of three strong links with only two values.
| Code: | after basics and before the finned X-Wing results in r8c2<>2
+-----------------------------------------------------------------------+
| 123 4 9 | 8 13 5 | 17 6 237 |
| 78 167 168 | 2 134 146 | 9 13 5 |
| 123 #1256 #1256 | 36 7 9 | 4 123 8 |
|-----------------------+-----------------------+-----------------------|
| 6 259 3 | 49 24589 24 | 58 7 1 |
| 12 1259 7 | 69 12589 126 | 3 589 4 |
| 4 8 @15 | 379 1359 17 | 2 59 6 |
|-----------------------+-----------------------+-----------------------|
| 9 237 24 | 1 6 247 | 58 58 237 |
| 5 2367 246 | 479 249 8 | 17 123 2379 |
| 78 *127 *128 | 5 29 3 | 6 4 279 |
+-----------------------------------------------------------------------+
# 88 eliminations remain
*) strong link on <1> that aligns with ...
#) strong link on <5>
@) <15> bivalue cell that sees an enpoint of each strong link
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| Code: | * * @ # #
(1)r9c2 = r9c3 - (1=5)r6c3 - r3c3 = (5)r3c2 => r3c2<>1, r9c2<>5 (if present)
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Unfortunately, this doesn't advance the solution (to my knowledge).  |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Feb 21, 2010 2:32 am Post subject: |
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Danny,
its the cyclops move.
has the single bi-value cell in the middle of the chain.
-----------
on the not so typical side of things we have some BUG-lite logic.
| Code: | +-----------------+--------------------+-------------------+
| 123 4 9 | 8 13 5 | 17 6 237 |
| 78 167 168 | 2 134 146 | 9 13 5 |
| 123 1256 1256 | 36 7 9 | 4 123 8 |
+-----------------+--------------------+-------------------+
| 6 259 3 | 49 249(58) 24 | (58) 7 1 |
| 12 1259 7 | 69 129(58) 126 | 3 9(58) 4 |
| 4 8 1-5 | 379 139(5) 17 | 2 9(5) 6 |
+-----------------+--------------------+-------------------+
| 9 237 24 | 1 6 247 | (58) (58) 237 |
| 5 367 246 | 479 249 8 | 17 123 2379 |
| 78 127 128 | 5 29 3 | 6 4 279 |
+-----------------+--------------------+-------------------+ |
the candidates {5,8} are aligned in a BUG-lite pattern in cells r467c578.
if you look closely at the columns that the BUG-lite candidates exist in, you should notice that the only other BUG-lite candidates are the 5's in r6c5 and r6c8.
one of these two 5's has to be true, A.K.A. strong inference, in order to avoid the BUG-lite from being true (which of course yields more than one solution).
this eliminates the 5 in r6c3 and solves the puzzle.
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Tue Feb 23, 2010 2:09 pm Post subject: |
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As noted when I posted this puzzle, I was specifically looking for ALS steps to solve the puzzle. So I found three ALS steps but used other moves to complete the puzzle.
ALS 134 in r12c5 provides the strong inference between the 3 and 4s: ALS134[(4)r2c5 = (3)r12c5]r12c5 - (3=6)r3c4 - (6=9)r5c4 - (9=4)r4c4; r4c5<>4.
Next, is the ALS 479 in r48c4 that provides the strong inference between the 7 and 9s: (1=3)r1c5 - (3=6)r3c4 - (6=9)r5c4 - ALS479[(9)r48c4 = (7)r8c4]r48c4 - (7=1)r8c7; r1c7<>1.
ALS A: 369 in r35c4
ALS B: 12349 in r1289c5
The "shared exclusive" digit is 3 located in box2
The "shared common" digit is 9
The deleted 9s are in r456c5 & r8c4
At this point, all three ALSs that I found did not appear to have a useful impact on solving the puzzle so I started looking for other steps.
Flightless xyz-wing 247 in r7c6
(2)r7c6 - (2=4)r4c6 - r2c6 = r2c5; r8c5<>4,
(4)r7c6; r8c5<>4,
(7)r7c6 - (7=4)r8c4; r8c5<>4.
6-cell DP (or a BUG-lite per Norm) 58 in r457c578 provides a strong inference: DP58[(1)r5c5 = (9)r5c8]r457c578 - (9=5)r6c8 - (5=1)r6c3; r6c56<>1 to complete the puzzle.
I hindsight, the initial LAS, the flightless xyz-wing and the DP58 are sufficient to complete the puzzle.
Ted |
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