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Truly VH

 
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Earl



Joined: 30 May 2007
Posts: 546
Location: St Louis MO

PostPosted: Mon Jul 23, 2007 2:37 am    Post subject: Truly VH Reply with quote

Since todays VH went too smoothly, I found one that was truly VH.
Any one see the next move?

I see forcing chains, but prefer a cleaner solution path.
Earl

Code:

+-------------+--------------+-----------+
| 3  9    1   | 8    27  4   | 67  267 5 |
| 5  4    8   | 67   3   26  | 1   27  9 |
| 2  7    6   | 1    5   9   | 4   3   8 |
+-------------+--------------+-----------+
| 1  56   4   | 9    8   7   | 2   56  3 |
| 8  2356 35  | 4    12  123 | 569 569 7 |
| 7  23   9   | 5    6   23  | 8   4   1 |
+-------------+--------------+-----------+
| 49 8    357 | 3467 47  356 | 579 1   2 |
| 6  135  2   | 37   9   135 | 57  8   4 |
| 49 15   57  | 2    147 8   | 3   579 6 |
+-------------+--------------+-----------+

Play this puzzle online at the Daily Sudoku site


Last edited by Earl on Mon Jul 23, 2007 9:40 pm; edited 3 times in total
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Marty R.



Joined: 12 Feb 2006
Posts: 5165
Location: Rochester, NY, USA

PostPosted: Mon Jul 23, 2007 4:09 am    Post subject: Reply with quote

XY-Wing based in box 8, but don't know how far it takes you.
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Mon Jul 23, 2007 2:19 pm    Post subject: Re: Truly VH Reply with quote

Earl wrote:
Since todays VH went too smoothly, I found one that was truly VH.
Any one see the next move?



How did you eliminate 5 for R5C8?
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Earl



Joined: 30 May 2007
Posts: 546
Location: St Louis MO

PostPosted: Mon Jul 23, 2007 2:32 pm    Post subject: Truly VH Reply with quote

Oops!
That makes it very truly VH!

Earl
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Mon Jul 23, 2007 7:43 pm    Post subject: Re: Truly VH Reply with quote

Earl wrote:
Oops!
That makes it very truly VH!

Earl


After doing Marty's XY-wing and a skyscraper on <7>s to eliminate
<7> from R1C7, you end up here -

Code:

+-------------+-------------+-----------+
|             |     27      |     27    |
|             | 67      26  |     27    |
|             |             |           |
+-------------+-------------+-----------+
|    56       |             |     56    |
|    2356 35  |     12  123 | 59  569   |
|    23       |         23  |           |
+-------------+-------------+-----------+
| 49      357 | 367 47  56  | 579       |
|    135      | 37      15  | 57        |
| 49 15   57  |     147     |     59    |
+-------------+-------------+-----------+


From there, I started coloring <3>s at R8C4 -

Code:

+-------------+-------------+-----------+
|             |     27      |     27    |
|             | 67      26  |     27    |
|             |             |           |
+-------------+-------------+-----------+
|    56       |             |     56    |
|    2356 35  |     12  123 | 59  569   |
|    23       |         23  |           |
+-------------+-------------+-----------+
| 49     +357 |-367 47  56  | 579       |
|    1-35     |+3-7     15  | 57        |
| 49 15   57# |     147     |     59    |
+-------------+-------------+-----------+


I noticed that if <+> is true, then R8C2/R9C2 becomes a nake pair <15> and R9C3=7
if <-> is true, then R8C4=7 and R9C3=7 (only 7 left for the row).

Therefore, R9C3=7

From there, an X-wing on <5>s and an XY-Wing from Box 7 take you home.
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Asellus



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

PostPosted: Mon Jul 23, 2007 7:45 pm    Post subject: Reply with quote

Earl,

There is still a bit of basic cleanup to do. Look at <4>s in C4 and <3>s in C46. That won't really get you anywhere obvious that I can see, though.

I don't see Marty's XY-Wing.

However, there is a Finned X-Wing on 5.

And, there is a Skyscraper on 7.

After that, there are various XY-Chains available, if those are okay with you. I tried one that targets R7C1. Alternately, I tried another that targets R5C8. Either one led to an X-Wing on 5 and a W-Wing on 37 that solved the rest.
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Marty R.



Joined: 12 Feb 2006
Posts: 5165
Location: Rochester, NY, USA

PostPosted: Mon Jul 23, 2007 9:24 pm    Post subject: Reply with quote

Quote:
I don't see Marty's XY-Wing.


Apparently Jlo's comment made Earl realize that his original grid was incorrect, and when he edited his post the XY-Wing disappeared.
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Earl



Joined: 30 May 2007
Posts: 546
Location: St Louis MO

PostPosted: Mon Jul 23, 2007 9:38 pm    Post subject: Truly VH Reply with quote

Asellus,

Thanks for the tips.
An xy-chain based in R9C2 eliminated the 5 in R9C8 and opened the puzzle for me. But I have trouble spotting xy-chains.

Thanks

Earl
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Mon Jul 23, 2007 11:40 pm    Post subject: Reply with quote

I'm not seeing any of these X-Y chains before 5 is eliminated from R5C8.

Someone give me a clue.
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Asellus



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

PostPosted: Tue Jul 24, 2007 1:24 am    Post subject: Reply with quote

jLo,

After the basic simplifications, Finned X-Wing and Skyscraper, the puzzle looks like this:
Code:
+-------------+-------------+-----------+
| 3  9    1   | 8   27  4   | 6   27  5 |
| 5  4    8   | 67  3   26  | 1   27  9 |
| 2  7    6   | 1   5   9   | 4   3   8 |
+-------------+-------------+-----------+
| 1  56   4   | 9   8   7   | 2   56  3 |
| 8  2356 35  | 4   12  123 | 59  569 7 |
| 7  23   9   | 5   6   23  | 8   4   1 |
+-------------+-------------+-----------+
| 49 8    357 | 367 47  56  | 579 1   2 |
| 6  13   2   | 37  9   15  | 57  8   4 |
| 49 15   57  | 2   147 8   | 3   59  6 |
+-------------+-------------+-----------+


Earl's XY-Chain has pincers R9C2 and R8C7 and is only 4 cells long.

One of mine has pincers R9C1 and R7C5 and is more than 4 cells long. The other has pincers R5C7 and R9C8, does not eliminate your pesky 5, and is also more than 4 cells long.

Let me know if you need more clues.
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Tue Jul 24, 2007 4:13 am    Post subject: Reply with quote

Asellus wrote:
jLo,

Let me know if you need more clues.


Thanks, I see it now.

I had not seen the finned X-wing, so I still had a <5> at R8C2 that was
killing all three of those chains.
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