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spot the square

 
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JV



Joined: 09 Jan 2011
Posts: 24
Location: Devon, England

PostPosted: Thu Feb 24, 2011 1:08 pm    Post subject: spot the square Reply with quote

When I joined a few weeks ago, I was embarrassingly crass (frustration perhaps, though that's a reason rather than an excuse). Anyway, it's been good fun catching up, doing old DAZ puzzles, etc.

Here's an oddity, a difficult looking puzzle that needs just one move.
Menneske 5816838 after a couple of straighforward moves:
Code:

+----------------+---------------+----------------+
| 235  359  1    | 6   79   8    | 479  459  279  |
| 2568 5689 7    | 25  3    4    | 689  1589 1289 |
| 4    5689 5689 | 257 1    579  | 6789 3    2789 |
+----------------+---------------+----------------+
| 1    7    36   | 48  2    36   | 489  489  5    |
| 568  2    4568 | 9   68   1    | 348  7    38   |
| 9    348  348  | 478 5    37   | 1    2    6    |
+----------------+---------------+----------------+
| 3578 1    3589 | 578 789  579  | 2    6    4    |
| 5678 5689 2    | 1   4    5679 | 379  89   3789 |
| 678  4689 489  | 3   6789 2    | 5    189  1789 |
+----------------+---------------+----------------+


I'll pose it like a puzzle from a Sunday paper: can you find cell X and candidate a such that X = a quickly produces an impossibility? No advanced techniques needed - just look at it.

(I'll leave it to somebody else to explain - maybe of the APE or ALS ilk?)

JV
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Fri Feb 25, 2011 12:28 pm    Post subject: Reply with quote

Code:
 +--------------------------------------------------------------+
 |  235   359   1     |  6     79    8     |  479   459   279   |
 |  2568  5689  7     |  25    3     4     |  689  1(5)89 1289  |
 |  4     5689  5689  |  257   1     579   |  6789  3     2789  |
 |--------------------+--------------------+--------------------|
 |  1     7     36    |  48    2     36    |  489   489   5     |
 |  568   2     4568  |  9     68    1     |  348   7     38    |
 |  9     348   348   |  478   5     37    |  1     2     6     |
 |--------------------+--------------------+--------------------|
 |  3578  1     3589  |  578   789   579   |  2     6     4     |
 |  5678  5689  2     |  1     4     5679  |  379   89    3789  |
 |  678   4689  489   |  3     6789  2     |  5     189   1789  |
 +--------------------------------------------------------------+
 # 107 eliminations remain

          | ************** AIC *************** |
(5)r2c8 - (5=2)r1c8579 - r1c1 = r2c1 - (2=5)r2c5 - (5)r2c8
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JV



Joined: 09 Jan 2011
Posts: 24
Location: Devon, England

PostPosted: Sat Feb 26, 2011 2:45 pm    Post subject: Reply with quote

Thanks: very neat! (I didn't think of using the ALS in r1, & indeed didn't notice it.)

Most of us would see this via the ALS in box1r23, because you can see without thought that r2c8 = 5 removes 2 & 5 from r2c12, & 5 from r3c23. Can one express this in Eureka? - i.e. restricting it to r23.
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Asellus



Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA

PostPosted: Sun Feb 27, 2011 2:24 am    Post subject: Reply with quote

Try this:
(5=2)r2c4 - ALS[(2)r2c1=(5)r2c12|r3c23] - (5)r1c12=(5)r1c8
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JV



Joined: 09 Jan 2011
Posts: 24
Location: Devon, England

PostPosted: Sun Feb 27, 2011 9:25 am    Post subject: Reply with quote

Thanks, Asellus: very neat. I didn't think of starting with r2c4, but wouldn't have had the confidence to do it anyway.
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