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Nice puzzle

 
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Thu Jul 05, 2007 10:54 am    Post subject: Nice puzzle Reply with quote

This is a puzzle, that i found from my search for minimal puzzles with 37 givens:
Code:
 +-------+-------+-------+
 | 1 . . | 4 5 . | . 8 . |
 | 4 . 7 | 1 8 . | . . 3 |
 | 8 . . | 3 2 7 | 1 . 4 |
 +-------+-------+-------+
 | 2 7 . | 6 3 . | 4 . 5 |
 | 3 . . | . 7 . | . 2 6 |
 | . . . | . . . | 3 . . |
 +-------+-------+-------+
 | . 1 . | . . . | . . 2 |
 | . . 2 | 7 1 . | . . . |
 | 7 8 . | 2 6 . | 5 . 1 |
 +-------+-------+-------+
It can be solved with 2 x-wings, 1 xyz-wing, 4 xy-wings and one W Wing (which was called Y Wing on the players forum).
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Marty R.



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

PostPosted: Fri Jul 06, 2007 5:03 am    Post subject: Reply with quote

I'm throwing in the towel. The techniques you used are not exactly rocket science, but I'm obviously missing something. I don't recall a puzzle on which I've done so much and gotten so little in return. I've used eight techniques and solved only eight cells. What I've used are five X-Wings, including two Finned, an XY, a W and an XYZ. All those 34s in the lower band are bugging me too.

Code:

+------------+----------+------------+
| 1  23  36  | 4  5 69  | 279 8   79 |
| 4  25  7   | 1  8 69  | 29  56  3  |
| 8  9   56  | 3  2 7   | 1   56  4  |
+------------+----------+------------+
| 2  7   189 | 6  3 18  | 4   19  5  |
| 3  45  145 | 9  7 15  | 8   2   6  |
| 59 6   18  | 58 4 2   | 3   17  79 |
+------------+----------+------------+
| 56 1   34  | 58 9 348 | 67  347 2  |
| 69 345 2   | 7  1 345 | 69  34  8  |
| 7  8   349 | 2  6 34  | 5   349 1  |
+------------+----------+------------+

Play this puzzle online at the Daily Sudoku site
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Fri Jul 06, 2007 7:24 am    Post subject: Reply with quote

Hi Marty,

you already did it ! One last xy-wing and the puzzle is solved. I cant tell you, where it is Smile
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Fri Jul 06, 2007 2:35 pm    Post subject: Reply with quote

...or if you prefer there is an X-Y chain in boxes 4,5 &6 making an elimination in box 6. Look at the bivalues. Smile
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Marty R.



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

PostPosted: Fri Jul 06, 2007 3:19 pm    Post subject: Reply with quote

ravel wrote:
Hi Marty,

you already did it ! One last xy-wing and the puzzle is solved. I cant tell you, where it is Smile


Ravel, I'm ready for suicide. I don't know how much time I've spent looking for XY-Wings, but if I knew, I'd be too embarrassed to tell you. Embarassed

MM, ditto for XY-Chains. Embarassed
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Fri Jul 06, 2007 3:35 pm    Post subject: Reply with quote

Isn't that the truth ! I often leave a puzzle and then come back to it and sometimes I see a solution immediately - sometimes it is so obvious that I have missed it because I'm looking for a more involved answer.

Take yours - I saw the more involved X-Y chain first and then had to look furiously for ravel's suggested x-y wing, which lets face it, is the shortest x-y chain possible !
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Marty R.



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

PostPosted: Fri Jul 06, 2007 3:56 pm    Post subject: Reply with quote

Update, 35 minutes later. Knowing it was there, I found the XY-Chain and immediately noticed the XY-Wing in the same cells. I miss XY-Chains all the time, but I search systematically for XY-Wings, checking each box for every bivalue cell and seeing if there's a wing. I don't how I missed that. Multiple times, I might add.

A good puzzle for me, one that forces you to work at it, but doesn't require arcane techniques.
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Fri Jul 06, 2007 4:53 pm    Post subject: Reply with quote

There are a couple of W-wings that eliminate the need for any XY-wings or
XY-chains. X-wing, W-wing, XYZ-wing, X-wing, W-wing did it for me (along
with some naked-pairs, hidden pairs, and box-line eliminations).
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Fri Jul 06, 2007 5:18 pm    Post subject: Reply with quote

Which were the pairs you used for the 2 W-Wings Jlo ? I assume you put the 56's to good use ?
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Fri Jul 06, 2007 6:43 pm    Post subject: Reply with quote

Quote:

Which were the pairs you used for the 2 W-Wings Jlo ? I assume you put the 56's to good use ?


The first was <89>s, the second was <18>s.
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Fri Jul 06, 2007 6:49 pm    Post subject: Reply with quote

Sorry for being dense, but I don't see the 89 pairs (I'm looking at Marty's grid).
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jLo



Joined: 30 Apr 2007
Posts: 55

PostPosted: Fri Jul 06, 2007 7:25 pm    Post subject: Reply with quote

Quote:

Sorry for being dense, but I don't see the 89 pairs (I'm looking at Marty's grid).



You'll note that Marty said one of the moves he used to get to that grid was a
W-wing. It was <89>s at R5C7 and R8C9. It opens up the single <8>s in block
6 and block 9 (as reflected in his grid.)
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Mogulmeister



Joined: 03 May 2007
Posts: 1151

PostPosted: Fri Jul 06, 2007 8:03 pm    Post subject: Reply with quote

Thanks jlo- I was looking at the post 89 grid ! Very Happy
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