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AHS-ALS Logic Example

 
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Bud



Joined: 06 May 2010
Posts: 47
Location: Tampa, Florida

PostPosted: Thu Oct 14, 2010 3:41 pm    Post subject: AHS-ALS Logic Example Reply with quote

I learned AHS=ALS logic from Allan Barker. This is an excellent example of one of these techniques. The (16)AHS cells are labeled B and the (125) ALS cells are labeled A in the puzzle grid. Each of these is contolled by a single digit ! in the cell labeled C. If C<>1 the AHS becomes a locked set 16 and if C=1 the ALS becomes a locked set 25. In either case 5 cannot be in r4c4.

AHS-ALS Logic Example
Code:

+------------------+-------------------+----------------+
| 2578  359  23578 | 12359  6    12359 | 1279  4   1379 |
| 27    39   4     | 8      39   12A   | 127   6   5    |
| 256   1    2356  | 23459  7    23459 | 29    8   39   |
+------------------+-------------------+----------------+
| 4     35   1356B | 13-569B 359 13579C| 789   2   789  |
| 56    7    9     | 256    8    25A   | 3     1   4    |
| 18    2    138   | 13     4    79    | 579   59  6    |
+------------------+-------------------+----------------+
| 159   6    15    | 34     2    34    | 1589  7   189  |
| 3     8    12    | 7      59   6     | 4     59  12   |
| 2579  4    257   | 59     1    8     | 6     3   29   |
+------------------+-------------------+----------------+


The original puzzle is the 9-26-10 tough at sudoku.com.au.
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Thu Oct 14, 2010 5:18 pm    Post subject: Reply with quote

Nice find! An alternate perspective similar to what's done in this forum:

Code:
ALS(5=21)r52c6 - AHS(1=16)r4c634  =>  r4c4<>5


[Edit: several attempts to properly present information.]


Last edited by daj95376 on Thu Oct 14, 2010 9:54 pm; edited 3 times in total
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ronk



Joined: 07 May 2006
Posts: 397

PostPosted: Thu Oct 14, 2010 7:56 pm    Post subject: Reply with quote

daj95376 wrote:
Nice find! An alternate perspective similar to what's done in this forum:

Code:
     A           A               CBB
(5=2)r5c6 - (2=1)r2c6 - (1=16)r4c634  =>  r4c4<>5

I don't actually recall seeing almost-hidden-sets in an AIC on this forum. In any case, it would be clearer if the set were identified as hidden, for example ...

(5=2)r5c6 - (2=1)r2c6 - (1)r4c6 = (hp16)r4c34 => r4c4<>5
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Thu Oct 14, 2010 8:30 pm    Post subject: Reply with quote

ronk wrote:
(5=2)r5c6 - (2=1)r2c6 - (1)r4c6 = (hp16)r4c34 => r4c4<>5

Considering the fact that I didn't properly identify the ALS as (5=21)r52c6, then partitioning the AHS term seems appropriate.

I prefer your notation because it shows that "almost" isn't needed. It's simply an AIC with a hidden pair term.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sat Oct 16, 2010 9:04 am    Post subject: Reply with quote

Quote:
I don't actually recall seeing almost-hidden-sets in an AIC on this forum


might want to look a little closer. I and several others have posted AHS in AIC's in this forum.
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ronk



Joined: 07 May 2006
Posts: 397

PostPosted: Sat Oct 16, 2010 9:33 am    Post subject: Reply with quote

storm_norm wrote:
Quote:
I don't actually recall seeing almost-hidden-sets in an AIC on this forum

might want to look a little closer. I and several others have posted AHS in AIC's in this forum.

Thanks for the links.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sat Oct 16, 2010 7:12 pm    Post subject: Reply with quote

ha. sorry.

http://www.dailysudoku.com/sudoku/forums/viewtopic.php?t=5030&highlight=&sid=576bed82a733e99dca13668af10f3d1f

http://www.dailysudoku.com/sudoku/forums/viewtopic.php?t=4431&highlight=&sid=489774e9f17b598d46cf7b524573bc4a
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