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16 SEPT VH
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Johan



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

PostPosted: Sun Sep 16, 2007 12:16 am    Post subject: 16 SEPT VH Reply with quote

A double wing-move collapses the grid.
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Marty R.



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

PostPosted: Sun Sep 16, 2007 12:32 am    Post subject: Reply with quote

How do you already have the puzzle for the 16th when I click and still see the 15th? Question

Is Sam updating by time zones?
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Sun Sep 16, 2007 7:39 am    Post subject: Reply with quote

It appears that the puzzles load up according to your local time. I have been aware ever since I started doing my Daily Sudoku last year that we Aussies get to see the puzzle well before others. I always have to wait until the next day to have a look at any discussion that may have been generated.

If you want to get the earliest possible glimpse, then perhaps you should find a New Zealander or Fijian to copy and email it to you. Very Happy
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Sun Sep 16, 2007 7:43 am    Post subject: Reply with quote

By the way, I didn't need any higher tricks, not even locked candidates, for this VH. It was a Medium at best. Perhaps I was just lucky.
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Johan



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

PostPosted: Sun Sep 16, 2007 8:12 am    Post subject: Reply with quote

Quote:
How do you already have the puzzle for the 16th when I click and still see the 15th?


Marty,

The puzzle always appears between 11 and 12 pm local time on my screen, perhaps we have GWT+2 hours is the reason why.
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Sun Sep 16, 2007 10:08 am    Post subject: Re: 16 SEPT VH Reply with quote

Johan wrote:
A double wing-move collapses the grid.


Don't know what a double wing is but I needed two XYZ wings (maybe it could have ben done more simply!)
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Sun Sep 16, 2007 1:27 pm    Post subject: Reply with quote

Quote:
Is that an ER in Blocks 5 & 8.



CGordon
No it isn't - smarten up !!!

CGordon


Last edited by cgordon on Mon Sep 17, 2007 11:48 am; edited 1 time in total
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sdq_pete



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

PostPosted: Sun Sep 16, 2007 2:02 pm    Post subject: Reply with quote

I'm afraid my old brain got stuck on this one. Here's the position I reached:

Code:

+----------+------------+--------------+
| 9  4  1  | 5   6   38 | 238  237 37  |
| 3  7  8  | 4   2   1  | 5    9   6   |
| 6  2  5  | 9   7   38 | 1348 13  134 |
+----------+------------+--------------+
| 4  38 23 | 6   138 5  | 9    127 137 |
| 5  1  6  | 23  9   7  | 23   4   8   |
| 28 9  7  | 238 138 4  | 6    123 5   |
+----------+------------+--------------+
| 27 6  23 | 17  5   9  | 134  8   134 |
| 1  5  4  | 38  38  2  | 7    6   9   |
| 78 38 9  | 17  4   6  | 13   5   2   |
+----------+------------+--------------+

Play this puzzle online at the Daily Sudoku site

What am I missing? Or have I already gone wrong?

Peter
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Sep 16, 2007 2:16 pm    Post subject: Reply with quote

I ignored both XY-wings in Boxes 3&6, and used mostly W-wing's or W-wing's with coloring to reach this BUG+1.

Code:

 *--------------------------------------------------*
 | 9    4    1    | 5    6    38   | 28   27   37   |
 | 3    7    8    | 4    2    1    | 5    9    6    |
 | 6    2    5    | 9    7    38   | 48   13   134  |
 |----------------+----------------+----------------|
 | 4    38   23   | 6    18   5    | 9    27   17   |
 | 5    1    6    | 23   9    7    | 23   4    8    |
 | 28   9    7    | 28   13   4    | 6    13   5    |
 |----------------+----------------+----------------|
 | 27   6    23   | 17   5    9    | 14   8    34   |
 | 1    5    4    | 38   38   2    | 7    6    9    |
 | 78   38   9    | 17   4    6    | 13   5    2    |
 *--------------------------------------------------*
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Sep 16, 2007 2:21 pm    Post subject: Reply with quote

Peter,

Look at Box 4.
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Sun Sep 16, 2007 10:23 pm    Post subject: Reply with quote

Strange. After looking at Pete's grid I saw that I had missed a very basic step. I was consequently able to finish without a single "clever" step. Is Kragzy correct - is this not a VH or did me and him screw up.
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Sep 16, 2007 10:59 pm    Post subject: Reply with quote

There were at least a couple of points where an XY-wing was the simplest move (depending of course on how one ranks the various techniques).
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Sun Sep 16, 2007 11:22 pm    Post subject: Reply with quote

Pete - how did you get the 7 in R3C5.
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Mon Sep 17, 2007 2:13 am    Post subject: Reply with quote

I just re-did this puzzle to see if yesterday's attempt was a fluke. It was. I needed two XY wings this time. I must have made an error in my lazy Sunday afternoon approach that turned to be lucky.
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada

PostPosted: Mon Sep 17, 2007 12:40 pm    Post subject: Reply with quote

I also redid it - and used 2 xwings, one xyz wing and a skyscraper. Not an easy one eh.
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Marty R.



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

PostPosted: Mon Sep 17, 2007 3:41 pm    Post subject: Reply with quote

I had a heck of a time with this; obviously missed something based on other posts. Two XYZ-Wings, three rectangles, a W-Wing and an XY-Wing with coloring finished it off.
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sdq_pete



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

PostPosted: Mon Sep 17, 2007 3:48 pm    Post subject: Reply with quote

cgordon wrote:
Pete - how did you get the 7 in R3C5.

Don't know if it's still relevant - actually I can't remember. Sorry!
I found this one tough somehow - maybe sometimes you just don't spot the intended XY wings and such. Of course, Tracy pointed out that I had failed to eliminate some 3's in Row 4, but even after that I was rather stuck. Ultimately there was an XY wing with pivot at R1C9.

Peter
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George Woods



Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK

PostPosted: Mon Sep 17, 2007 8:30 pm    Post subject: retraction of previous claim Reply with quote

Having looked at sdq_pete's grid I realised I had erroneously claimed an XYZ wing based on r3c8 being 12 - eliminating the 2 at r4c8 - but of course I had misread 12 - and it really is 13 so the xyz wing removes the 3 from r4c8 as recognised by sdq_pete, but doesn't seem to lead anywhere. Further I couldn't see any obvious answer to sdq_pete's grid, via the discussion. The position is pretty much where I got to (after an XY wing and an XYZ wing plus the "useless" XYZ wing mentined above)

So for me the puzzle had to be solved again properly, 'cos my lucky mistaken elimination of the 2 from r4c8 is not valid on this argument. -- But hang on!!
If r4c8 is 2 then r5c7 is 3 and r4c9 is 7 making r1c9 3 and no room for a 3 in col 8! So yes the 2 at r4c8 can be removed giving a straightforward solution.

So this solution will be classed as a forcing chain- but it so short and the argument doesn't need pencil and paper - so I claim it is logical -albeit not one beloved of those that use rules that might be built into a computer program!!!!!

Can someone transform this solution into a more "acceptable" form?
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Asellus



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

PostPosted: Mon Sep 17, 2007 10:58 pm    Post subject: Reply with quote

George,

I don't know how "acceptable" this is, but perhaps the easiest way to see it consistent with common techniques is as the overlap of an X-Wing with a W-Wing-like structure.

First, the X-Wing is on <7> in R14C89.

The "not quite W-Wing" involves the bivalue cells at R5C7 and R1C9, {23} and {37} respectively. Note that there is an external strong link on <3> in Box 9 between C7 and C9. This means that one or both of the bivalues cannot be <3>. Thus, R5C7 is <2> and/or R1C9 is <7>.

If R5C7 is <2>, R4C8 cannot be. If R1C9 is <7>, then so must be R4C8, due to the X-Wing. So, again, it cannot be <2>. So, <2> is eliminated.

(It is of course possible to construct a chain notation; but, I believe it would be a bit messy.)

Maybe someone can see some other angle on it. I tried without success to see it as an ALS or Sue de Coq type of elimination.
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Jeff



Joined: 06 May 2007
Posts: 40

PostPosted: Tue Sep 18, 2007 1:22 am    Post subject: Sept 16 VH Reply with quote

I have read all the posts on this puzzle and I simply can't figure out what to do next. Here is my current progress.
Code:

+----------+------------+--------------+
| 9  4  1  | 5   6   38 | 238  237 37  |
| 3  7  8  | 4   2   1  | 5    9   6   |
| 6  2  5  | 9   7   38 | 1348 13  34  |
+----------+------------+--------------+
| 4  38 23 | 6   18  5  | 9    127 17  |
| 5  1  6  | 23  9   7  | 23   4   8   |
| 28 9  7  | 238 138 4  | 6    123 5   |
+----------+------------+--------------+
| 27 6  23 | 17  5   9  | 134  8   134 |
| 1  5  4  | 38  38  2  | 7    6   9   |
| 78 38 9  | 17  4   6  | 13   5   2   |
+----------+------------+--------------+


I can't figure out what to do next. I would appreciate some real specific suggestions. I don't know what a w-wing is and I haven't been able to find a nice clear explanation of it with a good example. I hope I don't have to use a w-wing to solve this one. I have somewhat mastered the x, xy, and xyz patterns and a few other techniques.

Many thanks to all of you on this web site.
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