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ravel
Joined: 21 Apr 2006
Posts: 536
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 Posted: Thu Jul 05, 2007 10:54 am Post subject: Nice puzzle |
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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 |
+-------+-------+-------+
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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
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| Posted: Fri Jul 06, 2007 5:03 am Post subject: |
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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 |
+------------+----------+------------+
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Play this puzzle online at the Daily Sudoku site |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Fri Jul 06, 2007 7:24 am Post subject: |
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Hi Marty,
you already did it ! One last xy-wing and the puzzle is solved. I cant tell you, where it is  |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Fri Jul 06, 2007 2:35 pm Post subject: |
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| ...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. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Jul 06, 2007 3:19 pm Post subject: |
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| ravel wrote: | Hi Marty,
you already did it ! One last xy-wing and the puzzle is solved. I cant tell you, where it is |
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. 
MM, ditto for XY-Chains. |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Fri Jul 06, 2007 3:35 pm Post subject: |
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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
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| Posted: Fri Jul 06, 2007 3:56 pm Post subject: |
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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
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| Posted: Fri Jul 06, 2007 4:53 pm Post subject: |
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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
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| Posted: Fri Jul 06, 2007 5:18 pm Post subject: |
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| 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
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| Posted: Fri Jul 06, 2007 6:43 pm Post subject: |
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| 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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The first was <89>s, the second was <18>s. |
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Mogulmeister
Joined: 03 May 2007
Posts: 1151
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| Posted: Fri Jul 06, 2007 6:49 pm Post subject: |
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| 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
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| Posted: Fri Jul 06, 2007 7:25 pm Post subject: |
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| Quote: |
Sorry for being dense, but I don't see the 89 pairs (I'm looking at Marty's grid).
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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
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| Posted: Fri Jul 06, 2007 8:03 pm Post subject: |
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Thanks jlo- I was looking at the post 89 grid !  |
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