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July27 VH
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Marty R.



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

PostPosted: Sun Jul 27, 2008 5:13 am    Post subject: July27 VH Reply with quote

Looks like I'm first. Two strongly connected moves did it.

Quote:
XY-Wing on 56-59-69 and M-Wing on 69.
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Sun Jul 27, 2008 7:41 am    Post subject: Reply with quote

I did the usual "cleaning up" with the help of a couple of XY wings and then went back and found an X wing on 9. Possibly the same solution as yours Marty, just from a different angle.
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nataraj



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

PostPosted: Sun Jul 27, 2008 8:21 am    Post subject: Reply with quote

It's one of these puzzles again: Easy to mild - with a "vh" twist at the end.

There are many possibilities (including 2 xy-wings and a few m-wings), but I did it with multi-coloring on 4.

Code:

+--------------------------+--------------------------+--------------------------+
| 57      137     2        | 35      4       8        | 6       17      9        |
| 8       1379    59       | 35      19      6        | 24      17      24       |
| 69      169     4        | 7       19      2        | 3       8       5        |
+--------------------------+--------------------------+--------------------------+
| 469     5       69       | 2       8       7        | 1       3       46       |
| 2       46      7        | 1       3       5        | 9       46      8        |
| 3       8       1        | 4       6       9        | 5       2       7        |
+--------------------------+--------------------------+--------------------------+
| 1       69      3        | 8       25      4        | 7       569     26       |
| 4579    479     8        | 6       25      3        | 24      459     1        |
| 456     2       56       | 9       7       1        | 8       456     3        |
+--------------------------+--------------------------+--------------------------+


This is the plot of strong links in "4":
Code:

+·····+·····+·····+
·     ·     ·     ·
·     ·     ·     ·
·     ·     ·2---2·
·     ·     ·|   |·
·     ·     ·|   |·
+·····+·····+|···|+
·*---------------6·
· \   ·     ·|  / ·
·  6-----------6  ·
·  |  ·     ·|    ·
·  |  ·     ·|    ·
+··|··+·····+|····+
·  |  ·     ·|    ·
·  |  ·     ·|    ·
·o *  ·     ·2 o  ·
·     ·     ·     ·
·*-------------*  ·
+·····+·····+·····+


One of the many possibilities to make a strong/weak/.../strong chain:

start at r9c6.
strong link to r9c1
weak (r9c1 "sees") r4c1
strong to r4c9
weak (r4c9 sees) r2c9 - (the strong link r4c9=r2c9 stands in as a weak link)
strong to r2c7.

Both ends see r8c7 and that solves the puzzle.

Yes, I know that the skyscraper rows 5 and 9 would have been easier Smile ...

There is also a kite (row 5 and col 9) and a skyscraper (cols 3 and 9) in "6" ....
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keith



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

PostPosted: Sun Jul 27, 2008 11:10 am    Post subject: Reply with quote

In Nataraj' grid:

An XY-wing 56-59-69 takes out <6> in R9C1.

An extended XY-wing 24-26-46-46-46 takes out <4> in R8C2. This one solves it in one step.

Keith
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Florida Bob



Joined: 25 Jul 2007
Posts: 12

PostPosted: Sun Jul 27, 2008 3:25 pm    Post subject: Reply with quote

I used a short chain of "9s" in col. 1 & 3 which led to an xy wing in col. 1 that broke the puzzle for me. A nice Sunday exercise.
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Marty R.



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

PostPosted: Sun Jul 27, 2008 3:28 pm    Post subject: Reply with quote

Quote:
An extended XY-wing 24-26-46-46-46 takes out <4> in R8C2. This one solves it in one step.

How are you using the term "Extended XY-Wing"? I thought you used that term for the technique where three identical bivalue calls act as a single XY cell, the technique I learned as "XY-Wing Chain." In this case it seems you've described what I learned as "XY-Wing with pincer coloring.

This whole terminology thing can be very confusing.
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nataraj



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

PostPosted: Sun Jul 27, 2008 4:44 pm    Post subject: Reply with quote

I like the term "extended" xy-wing because I can imagine something like this:

Summer. Very hot. Luckily, I have a fan. But, alas, the bed (and thus the fan) is too far away from the socket... What now?

The extension cord, of course!

The xy-wing keith described has both pincers in place: 46 in r5c2 and 42 in r8c7. Unfortunately, the middle cell (26 in r7c9) is too far away from the 46... Good thing there is an extension available: the 46-46 in box 6. It connects the 26 in r7c9 with the 46 in r5c2 and we can rest easy... Smile

I guess in this special case one can see it both ways:
useless 24-26-46 with coloring 46-46 tacked on,
or: 24- (26 - extension 46-46) - 46

Marty R. wrote:
This whole terminology thing can be very confusing.


Only if you take it serious enough Laughing Laughing Laughing
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Clement



Joined: 24 Apr 2006
Posts: 1111
Location: Dar es Salaam Tanzania

PostPosted: Sun Jul 27, 2008 5:07 pm    Post subject: Daily Sudoku: Sun 27- Jul-2008 VH Reply with quote

XY-Wing 569, Pivot [5,6]r9c3 with Pincers [6,9]r7c2 and [5,9]r2c3 eliminatng 9 in r23c2 solving the puzzle. Smile

Last edited by Clement on Sun Jul 27, 2008 5:28 pm; edited 1 time in total
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cgordon



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

PostPosted: Sun Jul 27, 2008 5:07 pm    Post subject: Reply with quote

Using the conjugal pairs of 6's in R57 we can remove the 6 from R9C8 with a Finned X-Wing or from R7C2 with an ER - the end result is the same. There's also an ER that removes 4 from R5C8.
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keith



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

PostPosted: Sun Jul 27, 2008 5:21 pm    Post subject: Reply with quote

I guess I've taken to using "extended" for a number of variations. I think various of us use "(pincer) coloring", "extending", and "transporting" to mean the same thing.

Keith
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tlanglet



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

PostPosted: Mon Jul 28, 2008 12:15 am    Post subject: Reply with quote

I missed all the fun! After basics my first find was a finned x-wing in r58c28 that deleted the <4> in r8c7 to finish off the puzzle before it really started.

Ted
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nataraj



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

PostPosted: Mon Jul 28, 2008 5:47 pm    Post subject: Reply with quote

tlanglet wrote:
I missed all the fun! After basics my first find was


Not to worry, Ted. You didn't miss anything. The fun of finding a finned x-wing isn't so bad, is it?

After basics, whatever the first find, it probably solved the puzzle. Why, my grid was so empty already I didn't even think there WOULD be a vh step at all...
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nataraj



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

PostPosted: Mon Jul 28, 2008 5:55 pm    Post subject: Reply with quote

cgordon wrote:
Using the conjugal pairs of 6's ...


Just a minor detail, but in sudoku (like in mathematics and chemistry), it's conjugate pairs. Les pairs conjugals, c'est une chose tout à fait différente ... Very Happy
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Tue Jul 29, 2008 1:54 am    Post subject: Reply with quote

... et vive la difference!
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cgordon



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

PostPosted: Tue Jul 29, 2008 11:22 am    Post subject: Reply with quote

Conjugal - Conjugate - I see the difference - but with the situation I often end up with in Sudokus - there is a similarity. Twisted Evil
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Deb



Joined: 30 Jun 2008
Posts: 8

PostPosted: Sun Aug 03, 2008 7:15 pm    Post subject: Can You See This Next Step? Reply with quote

This puzzle is giving me palpitations. This is where I got to. My gut kept telling me the next step was in rows 4 & 5 with that cozy mix of 46's but I couldn't figure it out. When I asked for a hint from the computer for the next step it did indeed go straight to row 5 and put a 4 in column 2. Okay. So what was the logic for this? Can anyone help me?
Thanks, Deb

Code:

+--------------+---------+-----------+
| 57   137  2  | 35 4  8 | 6  17  9  |
| 8    1379 59 | 35 19 6 | 24 17  24 |
| 69   169  4  | 7  19 2 | 3  8   5  |
+--------------+---------+-----------+
| 469  5    69 | 2  8  7 | 1  3   46 |
| 2    46   7  | 1  3  5 | 9  46  8  |
| 3    8    1  | 4  6  9 | 5  2   7  |
+--------------+---------+-----------+
| 1    69   3  | 8  25 4 | 7  569 26 |
| 4579 479  8  | 6  25 3 | 24 459 1  |
| 456  2    56 | 9  7  1 | 8  456 3  |
+--------------+---------+-----------+
[/code]
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nataraj



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

PostPosted: Sun Aug 03, 2008 7:45 pm    Post subject: Re: Can You See This Next Step? Reply with quote

Deb wrote:
This is where I got to. ... it did indeed go straight to row 5 and put a 4 in column 2. Okay. So what was the logic for this? Can anyone help me?
Thanks, Deb

Code:

+--------------+---------+-----------+
| 57   137  2  | 35 4  8 | 6  17  9  |
| 8    1379 59 | 35 19 6 | 24 17  24 |
| 69   169  4  | 7  19 2 | 3  8   5  |
+--------------+---------+-----------+
| -469  5   69 | 2  8  7 | 1  3   46 |
| 2    4*6  7  | 1  3  5 | 9  4*6 8  |
| 3    8    1  | 4  6  9 | 5  2   7  |
+--------------+---------+-----------+
| 1    69   3  | 8  25 4 | 7  569 26 |
| 4579 479  8  | 6  25 3 | 24 459 1  |
| 4*56 2    56 | 9  7  1 | 8  4*56 3  |
+--------------+---------+-----------+


Deb, I cannot see a move that immediately takes out the 6 from r5c2.
But there is a skyscraper (4) in rows 5 and 9 that removes 4 from r4c1. That leaves a naked single 4 in r5c2.

----

Since the program cannot do skyscrapers, I really don't know why it gave that hint. Probably a whole series of eliminations ... There is an xy-wing takes out 6 in r9c1, another one takes out 9 in r23c2. A box-line in box 7/col 2 removes 9 from r8c1, which in turn reveals a naked triple 4,5,7 in col 1. This removes 4 from r4c1 and we get that naked single again. Really, the hints are not that obvious sometimes Twisted Evil
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Deb



Joined: 30 Jun 2008
Posts: 8

PostPosted: Sun Aug 03, 2008 8:50 pm    Post subject: Thanks for trying Reply with quote

nataraj, thanks for trying. I guess since I put so much time into trying to find some solution from rows 4 & 5, and since the computer seemed to agree, I was tearing my hair out trying to see it. But I'll look up "skyscraper". Thanks. Deb
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nataraj



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

PostPosted: Sun Aug 03, 2008 9:37 pm    Post subject: Reply with quote

Deb wrote:
... since the computer seemed to agree ...


Deb, one thing to remember about the computer's hints: the program does NOT tell you the next step, but the next solved cell!
It might be that several steps are needed before the next cell is solved.

In contrast to that electronic behaviour, humans usually give the next step (i.e. the next elimination) as a hint.
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Marty R.



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

PostPosted: Sun Aug 03, 2008 9:45 pm    Post subject: Reply with quote

I have no idea of what logic the hint used.

Code:
+--------------+---------+--------------+
| 57   137   2  | 35 4  8 | 6  17  9    |
| 8    1379  59 | 35 19 6 | 24 17  24   |
| 69   169   4  | 7  19 2 | 3  8   5    |
+--------------+---------+--------------+
| 469  5     69 | 2  8  7 | 1   3   46b |
| 2    46e   7  | 1  3  5 | 9   46d 8   |
| 3    8     1  | 4  6  9 | 5   2   7   |
+--------------+---------+--------------+
| 1    69    3  | 8  25 4 | 7   569 26a |
| 4579 479   8  | 6  25 3 | 24c 459 1   |
| 456  2     56 | 9  7  1 | 8   456 3   |
+--------------+---------+--------------+


A, b and c are an XY-Wing which removes nothing directly. But color pincer b to d and e and the new pincers e and c take out the 4 from r8c2, leaving r5c2 as the only remaining 4 in that column. This is just another way of removing the 4 in r8c2 as the aforementioned skyscraper.
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