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Feb 16, 2008 VH

 
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sat Feb 16, 2008 4:17 am    Post subject: Feb 16, 2008 VH Reply with quote

Code:
   |---c1--|---c2--|---c3--||---c4--|---c5--|---c6--||---c7--|---c8--|---c9--
-----------------------------------------------------------------------------
r1 |     7 |     1 |     9 ||    46 |     5 |   346 ||     8 |     2 |   346
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r2 |     8 |     2 |    34 ||     1 |   346 |     9 ||    56 |   345 |     7
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r3 |     6 |     5 |    34 ||     2 |     7 |     8 ||     1 |     9 |    34
===========================||=======================||=======================
r4 |     9 |     4 |    27 ||    78 |    28 |     1 ||     3 |     6 |     5
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r5 |     1 |     8 |    67 ||     3 |    46 |     5 ||     9 |    47 |     2
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r6 |     5 |     3 |   267 ||     9 |   246 |   467 ||    47 |     1 |     8
===========================||=======================||=======================
r7 |     2 |     6 |     5 ||   478 |     1 |   347 ||    47 |  3478 |     9
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r8 |     4 |     9 |     1 ||   578 |    38 |     2 ||    56 |  3578 |    36
---+-------+-------+-------||-------+-------+-------||-------+-------+-------
r9 |     3 |     7 |     8 ||   456 |     9 |    46 ||     2 |    45 |     1
.............................................................................



I can see a difference in approaches already with this one.

the ones that favor wings will go with an x-wing on 7
xyz-wing on r6c5 {2,4,6}

the ones that color first will fall in love with the number 3, it makes two eliminations and solves the puzzle.
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Johan



Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium

PostPosted: Sat Feb 16, 2008 9:18 am    Post subject: Reply with quote

A Finned x-wing takes out <3> in R8C9, either the fin(F) is true or the x-wing@, in both cases they eliminate <3> in R8C9.

Code:
+--------------------------+--------------------------+--------------------------+
| 7          1        9    | 46        5         346  | 8        2          346  |
| 8          2        34   | 1       @ 346       9    | 56     @ 35         7    |
| 6          5        34   | 2         7         8    | 1        9          34   |
+--------------------------+--------------------------+--------------------------+
| 9          4        27   | 78        28        1    | 3        6          5    |
| 1          8        67   | 3         46        5    | 9        47         2    |
| 5          3        267  | 9         246       467  | 47       1          8    |
+--------------------------+--------------------------+--------------------------+
| 2          6        5    | 478       1         347  | 47     F 3478       9    |
| 4          9        1    | 578     @ 38        2    | 56     @ 3578     -[3]6  |
| 3          7        8    | 456       9         46   | 2        45         1    |
+--------------------------+--------------------------+--------------------------+
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sat Feb 16, 2008 9:34 am    Post subject: Reply with quote

Code:
+--------------------------+--------------------------+--------------------------+
| 7          1        9    | 46        5        R346  | 8        2         G346  |
| 8          2        34   | 1        G346       9    | 56     -[3]5        7    |
| 6          5        34   | 2         7         8    | 1        9          34   |
+--------------------------+--------------------------+--------------------------+
| 9          4        27   | 78        28        1    | 3        6          5    |
| 1          8        67   | 3         46        5    | 9        47         2    |
| 5          3        267  | 9         246       467  | 47       1          8    |
+--------------------------+--------------------------+--------------------------+
| 2          6        5    | 478       1        G347  | 47      R3478       9    |
| 4          9        1    | 578      R38        2    | 56       3578     -[3]6  |
| 3          7        8    | 456       9         46   | 2        45         1    |
+--------------------------+--------------------------+--------------------------+


this is Johan's grid with the coloring on 3 in it.

it does the same thing that the finned creature did and it eliminates the 3 in r2c8 and r8c9 because they both see a red and a green 3
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andras



Joined: 31 Oct 2007
Posts: 56
Location: Mid Wales

PostPosted: Sat Feb 16, 2008 10:38 am    Post subject: Reply with quote

A very interesting one, but I'm glad it was a Saturday puzzle, as it kept me going for quite a while!

John
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Asellus



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

PostPosted: Sat Feb 16, 2008 11:08 am    Post subject: Reply with quote

That coloring on <3> (ignoring c5, which doesn't really add anything) is also called a Skyscraper, it so happens.

The Finned X-Wing has the same effect due to the resulting locked candidates. (r28 is also a Finned X-Wing with the same overall result.)

Or, if you prefer, the b9/r2 ER eliminates <3> in r8c5 as yet another path to the same place.

So, at least 5 ways to see it.
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Sat Feb 16, 2008 11:50 am    Post subject: Reply with quote

For me, it was the skyscraper (the one that takes out 3 in r2c8).

Very straightforward, this one. There were so few multi-value (more than 2) cells left after basics that I spent most of the time trying to find a xy(z) wing (and failed to see the one that was present !!!) and only then turned to the coloring approach.

Guess there are more chains than wings in my nature...
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Sat Feb 16, 2008 3:56 pm    Post subject: Reply with quote

I couldn't see a solution using the built-in techniques needed to solve these. I did have an X-Wing and XY-Wing, but it was an ER on 3 that broke it open.
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keith



Joined: 19 Sep 2005
Posts: 3340
Location: near Detroit, Michigan, USA

PostPosted: Sat Feb 16, 2008 4:35 pm    Post subject: Reply with quote

Marty R. wrote:
I couldn't see a solution using the built-in techniques needed to solve these. I did have an X-Wing and XY-Wing, but it was an ER on 3 that broke it open.


This, after basics:
Code:
+----------------+----------------+----------------+
| 7    1    9    | 46   5    346  | 8    2    346  |
| 8    2    34   | 1    346  9    | 56   35   7    |
| 6    5    34   | 2    7    8    | 1    9    34   |
+----------------+----------------+----------------+
| 9    4    27   | 78   28   1    | 3    6    5    |
| 1    8    67   | 3    46   5    | 9    47   2    |
| 5    3    267  | 9    246  467  | 47   1    8    |
+----------------+----------------+----------------+
| 2    6    5    | 478  1    347  | 47   3478 9    |
| 4    9    1    | 578  38   2    | 56   3578 36   |
| 3    7    8    | 456  9    46   | 2    45   1    |
+----------------+----------------+----------------+

There is an XYZ-wing <46> that takes out <4> in R6C5.
An X-wing in R67C67 that talkes out <7> in three cells in R67.

Then, some cleaning up lets you solve R2C7, and the puzzle is done.

Not quite how I did it. After the above wings, there turns out to be an X-wing that takes out <6> in R1C9, which also solves it.

Keith
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Sun Feb 17, 2008 9:58 am    Post subject: Reply with quote

I know this really isn't the place to discuss this, but if you have been watching the Blu-Ray vs HD DVD war... Blu-Ray got a big boost this past week when toshiba won't be making any devices that read HD DVDs, and wal-mart is not selling HD DVDs, and Netflix is not going to offer HD-DVDs. its all Blu-Ray for those companies.

any picks for the Daytona?
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sdq_pete



Joined: 30 Apr 2007
Posts: 119
Location: Rotterdam, NL

PostPosted: Sun Feb 17, 2008 12:02 pm    Post subject: Reply with quote

Summarising the X moves, I had:
Code:
XYZ 467 R6C6
X    7  C67
XY  478 R4C4
A UR also arose in that little 47 square (R67 C67) though I didn't need it.
Strangely, recognising X-wings is my Achilles heel, even though from a logical point of view it is the simplest of the "advanced" techniques. In this case, I recognised the square of 4's as potential X-wing but for some reason missed the 7's... Weird! Just thought I'd get that off my chest.

Peter
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Mon Feb 18, 2008 8:52 pm    Post subject: Reply with quote

Quote:
Strangely, recognising X-wings is my Achilles heel, even though from a logical point of view it is the simplest of the "advanced" techniques


hi Peter,

I'd also like to throw the type 1 UR in there as the easiest to see visually. and probably just as easy to understand logically as the x-wing. for my two cents.
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Wed Feb 20, 2008 9:43 pm    Post subject: Reply with quote

sdq_pete wrote:
A UR also arose in that little 47 square (R67 C67) though I didn't need it.


Peter, I just don't get it (and bear in mind MY Achilles' heel is URs) - how can a rectangle covering four boxes ever be part of a DP? Your square has one foot in each of the four boxes. How does that work?

storm_norm wrote:
and probably just as easy to understand logically as the x-wing. for my two cents

Sorry, Norm, I don't (understand it as easily). I would appreciate it if you'd explain. Or maybe you guys are referring to something different. Please - help me. I seriously do not know what you are talking about.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Wed Feb 20, 2008 11:32 pm    Post subject: Reply with quote

nataraj,

sorry, I didn't know the UR was happening over 4 boxes. if it is then its not a UR.

I was merely stating that the type 1 UR is visually easy to see.

and you are right. a UR can only happen in 2 boxes.
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Thu Feb 21, 2008 6:21 am    Post subject: Reply with quote

Thanks, Norm! While I do agree that possible URs attract attention much more than possible x-wings (I mean, they are practically jumping out of the grid and wave a flag saying "here I am, do something!" Very Happy), I find it much easier to grasp and immediately apply x-wing logic than the logic behind UR types above 1 or non-rectangular DPs. I continue to be amazed at what ravel and others can do with those patterns, but when I encounter them myself it takes me forever to develop the reasoning and convince myself that, yes, in this case x can be removed because of ... [insert whatever type logic applies]

keith's guide helps a lot but I guess it takes a lot of practice to really feel comfortable with those URs. Confused
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