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prakash
Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA
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 Posted: Sun Mar 16, 2008 12:51 am Post subject: March 16 - VH |
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| Very straight forward. An XY wing 58-89-59 cracked open the puzzle. |
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Stanley P
Joined: 27 Feb 2008
Posts: 20
Location: Tennessee, USA
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| Posted: Sun Mar 16, 2008 6:09 am Post subject: |
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| Same xy-wing did it for me. |
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andras
Joined: 31 Oct 2007
Posts: 56
Location: Mid Wales
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| Posted: Sun Mar 16, 2008 9:17 am Post subject: |
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And me!
(Pivot on R6C1 for anyone who doesn't see it). 
John |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Sun Mar 16, 2008 11:50 am Post subject: March 16 |
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Just one more step.
Earl
| Code: |
+-------------+----------+------------+
| 578 3 248 | 6 458 1 | 28 57 9 |
| 1 47 248 | 3 458 9 | 268 57 26 |
| 58 6 9 | 25 258 7 | 1 3 4 |
+-------------+----------+------------+
| 2 5 3 | 1 6 4 | 7 9 8 |
| 79 47 46 | 8 59 2 | 56 1 3 |
| 89 18 168 | 59 7 3 | 4 2 56 |
+-------------+----------+------------+
| 6 9 7 | 4 12 5 | 3 8 12 |
| 3 128 158 | 29 129 6 | 25 4 7 |
| 4 12 15 | 7 3 8 | 9 6 125 |
+-------------+----------+------------+
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Play this puzzle online at the Daily Sudoku site |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sun Mar 16, 2008 1:28 pm Post subject: |
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| Looked for ERs and URs but couldn't find any. I have tremendous difficulty with xy wings. Solved this one by a method that often works for me - screwed up and got lucky!!! |
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prakash
Joined: 02 Jan 2008
Posts: 67
Location: New Jersey, USA
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| Posted: Sun Mar 16, 2008 1:33 pm Post subject: |
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I was always assume that the XY wing would not be in a regular shape (square or rectangle). Having one so straight forward was a challenge to find.
Prakash |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Mar 16, 2008 4:20 pm Post subject: |
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| This puzzle required no steps for me. Just started the initial scan of rows and my eraser never stopped until it was done. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sun Mar 16, 2008 8:32 pm Post subject: |
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| Quote: | | This puzzle required no steps for me. Just started the initial scan of rows and my eraser never stopped until it was done. |
Nay! Methinks you erred like what I did. I did it again and one definitely has to resort to clever VH stuff. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Mar 16, 2008 9:39 pm Post subject: |
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| cgordon wrote: | | Quote: | | This puzzle required no steps for me. Just started the initial scan of rows and my eraser never stopped until it was done. |
Nay! Methinks you erred like what I did. I did it again and one definitely has to resort to clever VH stuff. |
Craig, since your credentials are unimpeachable, I tried it again, this time online rather than P&P and you may be right. Basics only got me this far:
| Code: |
+-------------+----------+------------+
| 578 3 248 | 6 458 1 | 28 57 9 |
| 1 47 248 | 3 458 9 | 268 57 26 |
| 58 6 9 | 25 258 7 | 1 3 4 |
+-------------+----------+------------+
| 2 5 3 | 1 6 4 | 7 9 8 |
| 79 47 46 | 8 59 2 | 56 1 3 |
| 89 18 168 | 59 7 3 | 4 2 56 |
+-------------+----------+------------+
| 6 9 7 | 4 12 5 | 3 8 12 |
| 3 128 158 | 29 129 6 | 25 4 7 |
| 4 12 15 | 7 3 8 | 9 6 125 |
+-------------+----------+------------+
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Play this puzzle online at the Daily Sudoku site
The deadly pattern on 28 in boxes 1 and 3 can be broken up by a 6 in r2c7 or a 4 in r1c3 or r2c3. All three result in a 6 in r5c3 and that solves it. I'll probably take a look at other methods as well. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Mon Mar 17, 2008 11:28 am Post subject: |
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| Quote: | | The deadly pattern on 28 in boxes 1 and 3 can be broken up by a 6 in r2c7 or a 4 in r1c3 or r2c3. All three result in a 6 in r5c3 |
Marty: I kept staring at these 4 cells because they look like a UR but they don't fit in to the Types given in the Sudoku technique references. There are two options - is it a pair of 4s or a 6. So really you have to do a bit of trial and error - don't you think?? Nonetheless I do see these patterns now and again and I think they should be acknowledged - i.e., given a label.
Just a thought.
Craig |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Mon Mar 17, 2008 3:42 pm Post subject: |
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| Quote: | | There are two options - is it a pair of 4s or a 6. So really you have to do a bit of trial and error - don't you think?? |
Yes, I do think there's some trial-and-error there, but there are degrees of trial-and-error and this ranks above something like picking a bivalue cell and testing it for a forcing chain.
The deadly pattern was the first thing I noticed; when I looked at it later, the 89-58-59 XY-Wing solves the puzzle. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Mon Mar 17, 2008 10:08 pm Post subject: |
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| Quote: | | Yes, I do think there's some trial-and-error there, but there are degrees of trial-and-error and this ranks above something like picking a bivalue cell and testing it for a forcing chain. |
Sadly I think this Post will get lost by the wayside - because often I see many UR looking patterns that have too many numbers for a UR solution. For example - a 458, 458, 458, 4589. If I were in a Sudoku competion where speed was involved - I would look for these patterns - and find a quick chain. As did you. |
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