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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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 Posted: Sun Oct 28, 2007 4:09 pm Post subject: URs - an acquired taste |
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Maybe it's just that I am getting the hang of it or that there were a few puzzles recently that didn't yield to "normal" means without resorting to uniqueness arguments, anyway - I am starting to like those UR, BUG+1 etc. techniques.
Here is one from last Wednesday at sudocue.net:
http://www.sudocue.net/olddaily.php?id=681&sol=0
After basics (and maybe an x-wing or two) I seemed stuck in this position:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 7 1458 145 | 56 2 13 | 1346 9 138 |
| 28 6 14 | 39 7 139 | 134 28 5 |
| 125 9 3 | 56 4 8 | 167 127 127 |
+--------------------------+--------------------------+--------------------------+
| 346 47 9 | 2 1 5 | 8 34 67 |
| 16 17 8 | 34 9 34 | 5 27 267 |
| 345 45 2 | 7 8 6 | 19 34 19 |
+--------------------------+--------------------------+--------------------------+
| 458 458 6 | 1 3 479 | 2 57 789 |
| 9 2 147 | 48 5 47 | 137 6 1378 |
| 158 3 157 | 89 6 2 | 179 1578 4 |
+--------------------------+--------------------------+--------------------------+
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But this being the Wednesday puzzle I went looking for a possible deadly pattern and - lo and behold - found a possible DP in r46c18 ("34").
To avoid the deadly pattern, r4c1=6 or r6c1=5.
But either assumption gives r4c1<>4 and r6c1<>4:
r4c1=6 => r6c1=3 (strong link on 3 in c1)
r6c1=5 => r4c1=3 (by the same strong link)
and thus r7c1=4 and the puzzle is solved. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Oct 28, 2007 5:12 pm Post subject: |
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Nataraj,
Just as a point of information, that's a conventional "Type 4" rectangle. With a strong link of 3 on the corners, 4 must be removed from both cells. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Sun Oct 28, 2007 6:03 pm Post subject: |
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Thanks, Marty!
I am just beginning to get into URs so I am not yet familiar with the different subtypes. As I understand it now, knowing the types obviously helps a lot in getting the result much faster - like all the other patterns I guess. So: time to do some reading ... |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Tue Oct 30, 2007 12:35 pm Post subject: |
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Hail all nice people in this forum who have so patiently been pointing me in the right direction!
With your help (and especially Marty and keith providing information on URs other than type 1) I was able to solve last Friday's nightmare. It was a type 3 that did the trick, and (after the suggested reading) not too hard to find.
Gratefully yours |
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