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Daily Sudoku Competition for Apr 15

 
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sat Apr 16, 2011 5:28 pm    Post subject: Daily Sudoku Competition for Apr 15 Reply with quote

200010809008009000950020000040000060600007904010000050000080012000600000403090008

Code:

+-------+-------+-------+
| 2 . . | . 1 . | 8 . 9 |
| . . 8 | . . 9 | . . . |
| 9 5 . | . 2 . | . . . |
+-------+-------+-------+
| . 4 . | . . . | . 6 . |
| 6 . . | . . 7 | 9 . 4 |
| . 1 . | . . . | . 5 . |
+-------+-------+-------+
| . . . | . 8 . | . 1 2 |
| . . . | 6 . . | . . . |
| 4 . 3 | . 9 . | . . 8 |
+-------+-------+-------+

Play online
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tlanglet



Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills

PostPosted: Sun Apr 17, 2011 1:59 pm    Post subject: Reply with quote

I previously posted a solution only later to realize that I had made an error in basics; somehow I had r8c5=7.

In any case, I finally got around to working the puzzle again and found this one step solution.....

anp(57=1)r78c1-(1=3)r2c1-als(3=67)r12c2-(6)r9c2=(6)r7c3; r7c3<>57=6

Ted


Last edited by tlanglet on Mon Apr 18, 2011 2:31 pm; edited 1 time in total
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Sun Apr 17, 2011 2:25 pm    Post subject: Reply with quote

One step... and a fun example of how a hidden-set interpretation makes a chain appear shorter but makes your head hurt (at least mine!)
Quote:
(6)r7c2=hp(26)r9c2|r8c3 - (1)r8c3=hp(14)r13c2 ; r13c2<>6
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Sun Apr 17, 2011 11:29 pm    Post subject: Reply with quote

Peter,

Is your solution to this puzzle ... or the one Norm withdrew?
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Mon Apr 18, 2011 6:48 am    Post subject: Reply with quote

daj95376 wrote:
Is your solution to this puzzle ... or the one Norm withdrew?

Smile It's a solution to the puzzle in the first post - I think. Though it looks even more opaque this morning...
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Mon Apr 18, 2011 10:31 am    Post subject: Reply with quote

After basics:
Code:
+----------------+----------------+----------------+
| 2    367  46   | 357  1    356  | 8    34   9    |
| 13   367  8    | 347  467  9    | 157  2    1567 |
| 9    5    146  | 378  2    368  | 17   34   167  |
+----------------+----------------+----------------+
| 3578 4    579  | 289  35   28   | 1237 6    137  |
| 6    23   25   | 1    35   7    | 9    8    4    |
| 378  1    79   | 2489 46   2468 | 237  5    37   |
+----------------+----------------+----------------+
| 57   9    567  | 3457 8    345  | 3456 1    2    |
| 157  8    1257 | 6    47   2345 | 345  9    35   |
| 4    26   3    | 25   9    1    | 56   7    8    |
+----------------+----------------+----------------+
Keith
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Asellus



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

PostPosted: Tue Apr 19, 2011 2:58 am    Post subject: Reply with quote

A little coloring led quickly to:
(3=1)r2c1 - (1)r8c1=(1-2)r8c3=(2)r9c2 - (2=3)r5c2; r12c2|r46c1<>3
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Tue Apr 19, 2011 3:25 am    Post subject: Reply with quote

Asellus wrote:
A little coloring led quickly to:
(3=1)r2c1 - (1)r8c1=(1-2)r8c3=(2)r9c2 - (2=3)r5c2; r12c2|r46c1<>3

Although Asellus's chain is short and correct, it fails to show a secondary property that often accompanies this pattern ... and always catches my attention. The weak inference on <1> in [c1] is founded on a strong link. Similarly for the weak inference on <2> in [c2]. Maybe this is what Asellus meant by "a little coloring". These strong links caught his attention as well, maybe.
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Asellus



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

PostPosted: Tue Apr 19, 2011 3:13 pm    Post subject: Reply with quote

daj95376 wrote:
Maybe this is what Asellus meant by "a little coloring". These strong links caught his attention as well, maybe.

Actually, I meant coloring, starting with <2>s:
Code:
+-----------------+-----------------+----------------+
| 2    367  46    | 357  1    356   | 8    34   9    |
| 13   367  8     | 347  467  9     | 157  2    1567 |
| 9    5    146   | 378  2    368   | 17   34   167  |
+-----------------+-----------------+----------------+
| 3578 4    579   | 289  35   28    | 1237 6    137  |
| 6    2A3a 2a5A  | 1    35   7     | 9    8    4    |
| 378  1    79    | 2489 46   2468  | 237  5    37   |
+-----------------+-----------------+----------------+
| 57   9    567   | 3457 8    345   | 3456 1    2    |
| 157  8    12A57 | 6    47   2a345 | 345  9    35   |
| 4    2a6A 3     | 25   9    1     | 56   7    8    |
+-----------------+-----------------+----------------+

The conjugate pair I then noticed was that of the <1>s in b7. I could have started multi-coloring with them, but noted simply that "A" color could be transported to 1A in r8c1 and thence to 3A in r2c1, providing the <3> pincers. All that remained was to write down the AIC.

You will pretty much not find me using the term "strong link" any longer. I find it too easily confused with strong inference, thus getting in the way of understanding. I prefer to refer to conjugate pairs. It is easier to state that conjugate pairs possess both weak and strong inferences without the language getting in the way.
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ronk



Joined: 07 May 2006
Posts: 398

PostPosted: Tue Apr 19, 2011 5:34 pm    Post subject: Reply with quote

Asellus wrote:
The conjugate pair I then noticed was that of the <1>s in b7. I could have started multi-coloring with them, but noted simply that "A" color could be transported to 1A in r8c1 and thence to 3A in r2c1, providing the <3> pincers. All that remained was to write down the AIC.

It is multi-coloring for the overall AIC, so I find these statements confusing. IOW r8c3 might ultimately be neither <2> nor <1>.

Asellus wrote:
You will pretty much not find me using the term "strong link" any longer. I find it too easily confused with strong inference, thus getting in the way of understanding. I prefer to refer to conjugate pairs.

That's a very good practice.
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Asellus



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

PostPosted: Wed Apr 20, 2011 9:43 am    Post subject: Reply with quote

ronk wrote:
It is multi-coloring for the overall AIC, so I find these statements confusing. IOW r8c3 might ultimately be neither <2> nor <1>.

Yes, of course. (Or better, r8c3 cannot be BOTH <2> and <1>.) As noted, it can be considered as multi-coloring. However, once I have a color cluster I often look for short sequences of alternating inferences extending from the cluster. These often replicate simple multi-coloring, but not always. For instance, coloring does not accommodate the strong inferences of ALS or ER very readily. In any case, it is analogous to pincer or fin transport and, like those, done without any color marking. The transported "colors" are ephemeral and not marked. It is in effect a shorthand for keeping track of the propagated strong inferences. But so, too, is pincer transport.
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ronk



Joined: 07 May 2006
Posts: 398

PostPosted: Wed Apr 20, 2011 3:53 pm    Post subject: Reply with quote

Asellus wrote:
The transported "colors" are ephemeral and not marked. It is in effect a shorthand for keeping track of the propagated strong inferences. But so, too, is pincer transport.

OK, I understand now, thanks.
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