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Oct 9 VH
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Wed Oct 08, 2008 11:10 pm    Post subject: Oct 9 VH Reply with quote

After a messy and laborious clean up, a simple X-wing solves it.
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crunched



Joined: 05 Feb 2008
Posts: 168

PostPosted: Thu Oct 09, 2008 2:07 am    Post subject: Reply with quote

Code:

+-----------------+--------------+---------------+
| 2348  248   1   | 6   39  7    | 248 5    2349 |
| 7     5     48  | 139 2   1349 | 148 3489 6    |
| 234   6     9   | 5   8   134  | 124 7    1234 |
+-----------------+--------------+---------------+
| 128   1278  5   | 4   137 6    | 9   238  237  |
| 6     9     478 | 38  37  2    | 478 1    5    |
| 1248  12478 3   | 189 179 5    | 6   248  247  |
+-----------------+--------------+---------------+
| 12489 3     248 | 7   6   189  | 5   249  1249 |
| 5     127   27  | 139 4   139  | 127 6    8    |
| 1489  1478  6   | 2   5   189  | 3   49   1479 |
+-----------------+--------------+---------------+

Play this puzzle online at the Daily Sudoku site

An X-wing of 7 in columns 3 & 7.
Is that all one has to find?
I had to find another x-wing to solve this.
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arkietech



Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

PostPosted: Thu Oct 09, 2008 3:21 am    Post subject: Reply with quote

Still waiting for the puzzle here in Arkansas
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nataraj



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

PostPosted: Thu Oct 09, 2008 5:51 am    Post subject: Reply with quote

crunched wrote:

An X-wing of 7 in columns 3 & 7.
Is that all one has to find?

crunched,
In your grid, there is a naked triple (1,2,7) in row 8, which leads to a few more cells being solved (1 in r2c4, 4 in r3c3), but yes, the x-wing 7 alone solves the puzzle (this seems to be one of the rare cases where there is exactly one possible "advanced" step)

There is also an x-wing (4) but that one is not effective: I did a quick computer check, and after an xyz wing it was xy-chains of at least 6 steps.

Not a puzzle for x-wing haters...
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keith



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

PostPosted: Thu Oct 09, 2008 8:14 am    Post subject: Reply with quote

After basics:
Code:
+-------------------+-------------------+-------------------+
| 2348  248   1     | 6     39    7     |2-48   5     2349  |
| 7     5     48@   | 1     2     39    | 48@   39    6     |
| 23    6     9     | 5     8     4     | 12    7     123   |
+-------------------+-------------------+-------------------+
| 128   1278  5     | 4     17    6     | 9     238   237   |
| 6     9     478@  | 38    37    2     | 47@   1     5     |
| 1248  12478 3     | 89    179   5     | 6     248   247   |
+-------------------+-------------------+-------------------+
| 1489  3    2-48   | 7     6     18    | 5     249   1249  |
| 5     17    27    | 39    4     39    | 127   6     8     |
| 1489  1478  6     | 2     5     18    | 3     49    1479  |
+-------------------+-------------------+-------------------+

The X-wing @ takes out <4> in R1C7 and R5C3.

Those two cells are now a double W-wing (Remote Naked Pair), connected by the strong links in R2 aA and R8 bB:
Code:
+-------------------+-------------------+-------------------+
| 2348  248   1     | 6     39    7     | 28a   5     2349  |
| 7     5     48a   | 1     2     39    | 48A   39    6     |
| 23    6     9     | 5     8     4     |1-2    7     123   |
+-------------------+-------------------+-------------------+
| 128   1278  5     | 4     17    6     | 9     238   237   |
| 6     9    47-8   | 38    37    2     | 47    1     5     |
| 1248  12478 3     | 89    179   5     | 6     248   247   |
+-------------------+-------------------+-------------------+
| 1489  3     28b   | 7     6     18    | 5     249   1249  |
| 5     17    27B   | 39    4     39    | 127b  6     8     |
| 1489  1478  6     | 2     5     18    | 3     49    1479  |
+-------------------+-------------------+-------------------+
With coloring (transporting), it takes out <2> in R3C7 and <8> in R5C3.

Solving the puzzle.

Keith
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keith



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

PostPosted: Thu Oct 09, 2008 8:25 am    Post subject: Reply with quote

arkietech wrote:
Still waiting for the puzzle here in Arkansas
Dan, you can get the puzzle by clicking on the current puzzle it to get the printable PDF version. Change the date in the URL to "tomorrow", and the puzzle will display.

This only works to get you the puzzle after it is made available in time zones like New Zealand, which is sometime in the morning here in the USA.

Keith
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arkietech



Joined: 31 Jul 2008
Posts: 1834
Location: Northwest Arkansas USA

PostPosted: Thu Oct 09, 2008 11:24 am    Post subject: Reply with quote

keith wrote:
[...Change the date in the URL to "tomorrow", and the puzzle will display...

Thanks I will try it.

Not many ways to go on this one. x-wing(7) solves it.
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crunched



Joined: 05 Feb 2008
Posts: 168

PostPosted: Thu Oct 09, 2008 3:32 pm    Post subject: Reply with quote

nataraj wrote:

In your grid, there is a naked triple (1,2,7) in row 8, which leads to a few more cells being solved (1 in r2c4, 4 in r3c3), but yes, the x-wing 7 alone solves the puzzle (this seems to be one of the rare cases where there is exactly one possible "advanced" step)

There is also an x-wing (4) but that one is not effective: I did a quick computer check, and after an xyz wing it was xy-chains of at least 6 steps.

Not a puzzle for x-wing haters...

Code:

+-----------------+-----------+---------------+
| 2348  248   1   | 6  9  7   | 248 5    234  |
| 7     5     48  | 13 2  134 | 148 3489 6    |
| 234   6     9   | 5  8  134 | 124 7    1234 |
+-----------------+-----------+---------------+
| 128   1278  5   | 4  17 6   | 9   238  237  |
| 6     9     47  | 8  3  2   | 47  1    5    |
| 1248  12478 3   | 9  17 5   | 6   248  247  |
+-----------------+-----------+---------------+
| 12489 3     248 | 7  6  189 | 5   249  1249 |
| 5     127   27  | 13 4  139 | 127 6    8    |
| 1489  1478  6   | 2  5  189 | 3   49   1479 |
+-----------------+-----------+---------------+

Play this puzzle online at the Daily Sudoku site

After a little cleanup from the 7 x-wing, a 9 x-wing (columns 1,9) really opened it up for me. (Or is the expression closed it up?). See grid above.
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Florida Bob



Joined: 25 Jul 2007
Posts: 12

PostPosted: Thu Oct 09, 2008 4:00 pm    Post subject: Reply with quote

I may be blind today but I don't see the x-wing in Col. 3 & 7. Could someone be more descriptive. Also, how did you eliminate the 8 in R5 C3?
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Marty R.



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

PostPosted: Thu Oct 09, 2008 4:52 pm    Post subject: Reply with quote

Florida Bob wrote:
I may be blind today but I don't see the x-wing in Col. 3 & 7. Could someone be more descriptive. Also, how did you eliminate the 8 in R5 C3?

Note that in both columns 3 and 7 that 7s appear in only rows 5 and 8, thus the X-Wing.

As to the elimination of the 8, see Keith's first post in this thread.
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Thu Oct 09, 2008 5:57 pm    Post subject: Reply with quote

Florida Bob wrote:
I may be blind today but I don't see the x-wing in Col. 3 & 7. Could someone be more descriptive. Also, how did you eliminate the 8 in R5 C3?

Original PM as posted by crunched.

Code:
+-----------------+--------------+---------------+
| 2348  248   1   | 6   39  7    | 248 5    2349 |
| 7     5     48  | 139 2   1349 | 148 3489 6    |
| 234   6     9   | 5   8   134  | 124 7    1234 |
+-----------------+--------------+---------------+
| 128   1278  5   | 4   137 6    | 9   238  237  |
| 6     9     478 | 38  37  2    | 478 1    5    |
| 1248  12478 3   | 189 179 5    | 6   248  247  |
+-----------------+--------------+---------------+
| 12489 3     248 | 7   6   189  | 5   249  1249 |
| 5     127   27  | 139 4   139  | 127 6    8    |
| 1489  1478  6   | 2   5   189  | 3   49   1479 |
+-----------------+--------------+---------------+

After basic techniques, there are two X-Wings exposed. One is for (4) and can be found in rows 2 & 5. The other is for (7) and can be found in columns 3 and 7.

Code:
 (4) X-Wing r25\c37  =>  [r1c7],r7c3]<>4
 *--------------------------------------------------------------------*
 | 2348   248    1      | 6      39     7      | 28-4   5      2349   |
 | 7      5     *48     | 1      2      39     |*48     39     6      |
 | 23     6      9      | 5      8      4      | 12     7      123    |
 |----------------------+----------------------+----------------------|
 | 128    1278   5      | 4      17     6      | 9      238    237    |
 | 6      9     *478    | 38     37     2      |*47     1      5      |
 | 1248   12478  3      | 89     179    5      | 6      248    247    |
 |----------------------+----------------------+----------------------|
 | 1489   3      28-4   | 7      6      18     | 5      249    1249   |
 | 5      17     27     | 39     4      39     | 127    6      8      |
 | 1489   1478   6      | 2      5      18     | 3      49     1479   |
 *--------------------------------------------------------------------*

Code:
 (7) X-Wing c37\r58  =>  [r5c5],[r8c2]<>7
 *--------------------------------------------------------------------*
 | 2348   248    1      | 6      39     7      | 248    5      2349   |
 | 7      5      48     | 1      2      39     | 48     39     6      |
 | 23     6      9      | 5      8      4      | 12     7      123    |
 |----------------------+----------------------+----------------------|
 | 128    1278   5      | 4      17     6      | 9      238    237    |
 | 6      9     *478    | 38     3-7    2      |*47     1      5      |
 | 1248   12478  3      | 89     179    5      | 6      248    247    |
 |----------------------+----------------------+----------------------|
 | 1489   3      248    | 7      6      18     | 5      249    1249   |
 | 5      1-7   *27     | 39     4      39     |*127    6      8      |
 | 1489   1478   6      | 2      5      18     | 3      49     1479   |
 *--------------------------------------------------------------------*

I'm not going to try and explain keith's elimination [r5c3]<>8. However, please note that cells [r5c3] & [r5c7] are in both X-Wings. If [r5c3]=8, then the X-Wing cells for (4) would force [r5c7]=4. At the same time, the X-Wing cells for (7) would force [r5c7]=7 -- a contradiction. Thus, we can conclude that [r5c3]<>8.
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Florida Bob



Joined: 25 Jul 2007
Posts: 12

PostPosted: Thu Oct 09, 2008 6:25 pm    Post subject: Reply with quote

Thanks for the replies.

I guess my problem was more an issue of definitions. I think of an X wing following an AB, BC, AC format. The elimination in row 5 was the results of small chains, which I did not see.
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keith



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

PostPosted: Thu Oct 09, 2008 7:18 pm    Post subject: Reply with quote

Florida Bob wrote:
Thanks for the replies.

I guess my problem was more an issue of definitions. I think of an X wing following an AB, BC, AC format. The elimination in row 5 was the results of small chains, which I did not see.


Bob,

An X-wing starts with the same candidate on four corners of a rectangle.

An XY-wing is XY, YZ, XZ, or AB, BC, AC.

Keith
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keith



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

PostPosted: Thu Oct 09, 2008 7:33 pm    Post subject: Reply with quote

daj95376 wrote:

I'm not going to try and explain keith's elimination [r5c3]<>8.
Let me do it again:
Code:
+-------------------+-------------------+-------------------+
| 2348  248   1     | 6     39    7     | 28a   5     2349  |
| 7     5     48c   | 1     2     39    | 48b   39    6     |
| 23    6     9     | 5     8     4     | 12    7     123   |
+-------------------+-------------------+-------------------+
| 128   1278  5     | 4     17    6     | 9     238   237   |
| 6     9    47-8   | 38    37    2     | 47    1     5     |
| 1248  12478 3     | 89    179   5     | 6     248   247   |
+-------------------+-------------------+-------------------+
| 1489  3     28d   | 7     6     18    | 5     249   1249  |
| 5     17    27@   | 39    4     39    | 127@  6     8     |
| 1489  1478  6     | 2     5     18    | 3     49    1479  |
+-------------------+-------------------+-------------------+
Cells a and d are a pair, <28>. They are connected by the strong link on <2>, @ in R8. This is a W-wing: Any cell that sees both a and d cannot be <8>. One or both of a and d is <8>. There are no direct eliminations to make.

Now, the coloring, or transporting part: Note the strong links on <8> ab in C7, and bc in R2. If a is <8>, b is not <8>, c is <8>. Any cell that sees both c and d is not <8>, and you can eliminate <8> from R5C3 as shown.

Keith
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cgordon



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

PostPosted: Thu Oct 09, 2008 9:28 pm    Post subject: Reply with quote

Quote:
After a messy and laborious clean up, a simple X-wing solves it.

This first post says it all. It was more challenging to find the naked 2's and 9's in the basics than some mickey mouse x-wing. That's my gripe for the day! Good Day Bruce.
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daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Thu Oct 09, 2008 10:31 pm    Post subject: Reply with quote

keith wrote:
daj95376 wrote:
I'm not going to try and explain keith's elimination [r5c3]<>8.

Let me do it again: ...

I hope this wasn't for my benefit. I understood ... I just refused to re-explain it -- especially when I had a short loop for the same elimination.

Code:
[cloop__3]: -4r5c3  4-7r5c7  7r8c7 -7r8c3  7r5c3  =>  [r5c3]<>8

However, since the (manual) solutions in this forum shy away from (many) chains, fish, and a few other techniques, I spotted the overlapping X-Wings explanation and thought it was perfect.
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kragzy



Joined: 01 May 2007
Posts: 112
Location: Australia

PostPosted: Thu Oct 09, 2008 10:44 pm    Post subject: Reply with quote

cgordon wrote:
Quote:
After a messy and laborious clean up, a simple X-wing solves it.

This first post says it all. It was more challenging to find the naked 2's and 9's in the basics than some mickey mouse x-wing. That's my gripe for the day! Good Day Bruce.


G'day polite American.
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cgordon



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

PostPosted: Thu Oct 09, 2008 11:05 pm    Post subject: Reply with quote

Quote:
G'day polite American.

American?? We're still part of the Empire mate.
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keith



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

PostPosted: Fri Oct 10, 2008 1:16 am    Post subject: Reply with quote

>> hope this wasn't for my benefit. I understood ...

No, in my quest to be a teacher, I will explain it again.

Keith
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nataraj



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

PostPosted: Fri Oct 10, 2008 6:24 am    Post subject: Reply with quote

nataraj wrote:

this seems to be one of the rare cases where there is exactly one possible "advanced" step



keith wrote:
The X-wing @ takes out <4> in R1C7 and R5C3.

Those two cells are now a double W-wing (Remote Naked Pair), connected by the strong links in R2 aA and R8 bB: [...] With coloring (transporting), it takes out <2> in R3C7 and <8> in R5C3.

Solving the puzzle.

Keith


I stand corrected - as I knew I would Very Happy

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