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Dec 11 VH

 
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yeoks



Joined: 16 May 2010
Posts: 17

PostPosted: Tue Dec 11, 2012 10:15 am    Post subject: Dec 11 VH Reply with quote

After basics
Code:

+------------+----------------------+---------------+
| 37  36  8  | 3579   1      3579   | 257 269  4    |
| 1   46  59 | 45789  4579   2      | 578 3    69   |
| 347 2   59 | 6      34579  345789 | 578 189  19   |
+------------+----------------------+---------------+
| 25  179 4  | 2579   25679  1579   | 3   267  8    |
| 25  17  3  | 24578  24567  14578  | 9   2467 256  |
| 8   79  6  | 234579 234579 34579  | 1   247  25   |
+------------+----------------------+---------------+
| 34  8   17 | 2479   2479   6      | 24  5    1239 |
| 6   5   2  | 1      349    349    | 48  89   7    |
| 9   34  17 | 2457   8      457    | 6   12   123  |
+------------+----------------------+---------------+


I need 2 steps to solve.
XYZ Wing 189 pivoted at r3c8; r1c8 <>9 followed by
XY Wing 23-4 pivoted at r9c9; r7c1<>4
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George Woods



Joined: 28 Mar 2006
Posts: 232
Location: Dorset UK

PostPosted: Tue Dec 11, 2012 11:23 am    Post subject: another almost xy Reply with quote

this is a 1 stepper after only3 numbers have been entered!
If r9c9 <>1 then xy 234 pivoted at r7c7 sets r9c2 =4 else if r9c9 =1 simple eliminations lead to r9c2 =4

so r9c2 = 4 and this solves it
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arkietech



Joined: 31 Jul 2008
Posts: 1708
Location: Northwest Arkansas USA

PostPosted: Tue Dec 11, 2012 12:36 pm    Post subject: Reply with quote

The first step solves it.

Code:
 
 *-----------------------------------------------------------------------------*
 | 37      36      8       | 3579    1       3579    | 257     269     4       |
 | 1       46      59      | 45789   4579    2       | 578     3       69      |
 | 347     2       59      | 6       34579   345789  | 578     189     19      |
 |-------------------------+-------------------------+-------------------------|
 | 25      179     4       | 2579    25679   1579    | 3       267     8       |
 | 25      17      3       | 24578   24567   14578   | 9       2467    256     |
 | 8       79      6       | 234579  234579  34579   | 1       247     25      |
 |-------------------------+-------------------------+-------------------------|
 |a34      8       17      | 2479    2479    6       |b24      5       129-3   |
 | 6       5       2       | 1       349     349     | 48      89      7       |
 | 9       4-3     17      | 2457    8       457     | 6      c12     c123     |
 *-----------------------------------------------------------------------------*
(3=4)r7c1-(4=2)r7c7-(2=3)r9c89 => -3r7c9,r9c2; stte
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hughwill



Joined: 05 Apr 2010
Posts: 166
Location: Birmingham UK

PostPosted: Tue Dec 11, 2012 12:50 pm    Post subject: Dec 11 VH Reply with quote

Quote:
if r9c9 =1 simple eliminations lead to r9c2 =4


George- If r9c9=1 then surely r9c2 has the only remaining 3 on the row....or
have I as usual misunderstood?

Dan- Is there a name for your pseudo XY wing?



Hugh
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arkietech



Joined: 31 Jul 2008
Posts: 1708
Location: Northwest Arkansas USA

PostPosted: Tue Dec 11, 2012 1:50 pm    Post subject: Re: Dec 11 VH Reply with quote

hughwill wrote:
Dan- Is there a name for your pseudo XY wing?


Yes it is an als xy-wing -- remove the 2 from column 89 of row 9 and it forces r9c8 =1 and r9c9=3.
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George Woods



Joined: 28 Mar 2006
Posts: 232
Location: Dorset UK

PostPosted: Tue Dec 11, 2012 2:22 pm    Post subject: Re: Dec 11 VH Reply with quote

hughwill wrote:
Quote:
if r9c9 =1 simple eliminations lead to r9c2 =4


George- If r9c9=1 then surely r9c2 has the only remaining 3 on the row....or
have I as usual misunderstood?

Dan- Is there a name for your pseudo XY wing?



Hugh

No not quite a misunderstanding but the reasoning below that denies the 1 smacks of "trial and error"

If r9 is 1 then as you say r9c2 is 3 BUT also it must be a 4 since solving 124 in Block 9 forces r9c2 to be 4 so this shows that it can't be 1 and the simple xy wing now says that r9c2 is 4 .......
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Marty R.



Joined: 12 Feb 2006
Posts: 5121
Location: Rochester, NY, USA

PostPosted: Tue Dec 11, 2012 3:17 pm    Post subject: Reply with quote

It's my personal preference to limit myself to the standard VH moves on these puzzle and I needed two of them: XYZ-Wing on 189 pivoted in r3c8 and the XY-Wing on 243 pivoted in r7c7. Interesting puzzle, as the large number of polyvalue cells required care as well.
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Marty R.



Joined: 12 Feb 2006
Posts: 5121
Location: Rochester, NY, USA

PostPosted: Tue Dec 11, 2012 4:05 pm    Post subject: Reply with quote

Quote:
If r9 is 1 then as you say r9c2 is 3 BUT also it must be a 4 since solving 124 in Block 9 forces r9c2 to be 4 so this shows that it can't be 1 and the simple xy wing now says that r9c2 is 4 .......


By the way, Ted uses this type of move and calls it an Almost XY-Wing, or AXY.
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keith



Joined: 19 Sep 2005
Posts: 3150
Location: near Detroit, Michigan, USA

PostPosted: Tue Dec 11, 2012 6:37 pm    Post subject: Reply with quote

Marty R. wrote:
Quote:
If r9 is 1 then as you say r9c2 is 3 BUT also it must be a 4 since solving 124 in Block 9 forces r9c2 to be 4 so this shows that it can't be 1 and the simple xy wing now says that r9c2 is 4 .......


By the way, Ted uses this type of move and calls it an Almost XY-Wing, or AXY.

A while ago we played with this and called it a finned XY-wing, the idea being that an extra digit in an XY-wing is a fin.

I would prefer "almost" since the fish people have their definition of what a fin is.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5121
Location: Rochester, NY, USA

PostPosted: Tue Dec 11, 2012 7:16 pm    Post subject: Reply with quote

keith wrote:

A while ago we played with this and called it a finned XY-wing, the idea being that an extra digit in an XY-wing is a fin.

I would prefer "almost" since the fish people have their definition of what a fin is.

Keith


I remember it well, the first example of what was called a "Finned" XY-Wing, which seems appropriate. However, Ted is the leading user and he uses "Almost", so that's how I now refer to it.
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keith



Joined: 19 Sep 2005
Posts: 3150
Location: near Detroit, Michigan, USA

PostPosted: Tue Dec 11, 2012 8:46 pm    Post subject: Reply with quote

Marty R. wrote:
keith wrote:

A while ago we played with this and called it a finned XY-wing, the idea being that an extra digit in an XY-wing is a fin.

I would prefer "almost" since the fish people have their definition of what a fin is.

Keith


I remember it well, the first example of what was called a "Finned" XY-Wing, which seems appropriate. However, Ted is the leading user and he uses "Almost", so that's how I now refer to it.


Here is the original thread, which refers to others:

http://www.dailysudoku.com/sudoku/forums/viewtopic.php?p=12552

Very interesting reading!

No offense to current participants, but I miss Asellus and Nataraj!

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5121
Location: Rochester, NY, USA

PostPosted: Wed Dec 12, 2012 1:40 am    Post subject: Reply with quote

Quote:
Very interesting reading!

No offense to current participants, but I miss Asellus and Nataraj!


Interesting indeed.

I miss those two guys as well. I've been active on various forums ever since I got my first computer 13 years ago and if there's one constant, it's that people come and go.

When I first joined here almost seven years ago the cast of characters was different; you might be the only one still left. There was David Bryant of DIC fame who was the most prolific poster until he dropped out and I eventually took over that unfortunate "honor."

There was Tracy, Ravel, Steve, and dozens of others who don't come to mind. Sam even posted in those days!

Nothing stays the same.
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hughwill



Joined: 05 Apr 2010
Posts: 166
Location: Birmingham UK

PostPosted: Wed Dec 12, 2012 4:44 pm    Post subject: Dec 11 VH Reply with quote

Quote:
I miss those two guys as well. I've been active on various forums ever since I got my first computer 13 years ago and if there's one constant, it's that people come and go.


If it's any solace, Nataraj posted on 'other puzzles' today (to celebrate 12.12.12). However Assellus stopped suddenly(?) just over a year ago...
Tout ca change, tout c'est la meme chose.
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