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No Rating: Puzzle CB_84

 
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Tue Sep 23, 2008 1:45 am    Post subject: No Rating: Puzzle CB_84 Reply with quote

Code:
 +-----------------------+
 | . . . | . 4 . | 1 . . |
 | . 4 . | . 6 . | . . 8 |
 | . . 8 | 5 . 7 | . . . |
 |-------+-------+-------|
 | . . 6 | 9 . 1 | . . 4 |
 | 9 5 . | . 3 8 | . . 1 |
 | . . 4 | 6 7 . | . . 9 |
 |-------+-------+-------|
 | 6 . . | . . . | . . . |
 | . . . | . . . | . 8 5 |
 | . 9 . | 1 5 6 | . 4 2 |
 +-----------------------+
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Earl



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

PostPosted: Tue Sep 23, 2008 2:06 pm    Post subject: unrated Reply with quote

Many advanced moves in this knotty puzzle. A key move for me was a UR (36) in boxes 1&3 which eliminated some 7's in Row 1. A few more advanaced moves after that, but rather evident.

Earl
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Marty R.



Joined: 12 Feb 2006
Posts: 5179
Location: Rochester, NY, USA

PostPosted: Tue Sep 23, 2008 3:44 pm    Post subject: Reply with quote

I was stymied after a half-dozen moves and needed extended Medusa to bail me out.
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arkietech



Joined: 31 Jul 2008
Posts: 1733
Location: Northwest Arkansas USA

PostPosted: Tue Sep 23, 2008 5:05 pm    Post subject: Reply with quote

There are two xy-wings. One moves you to a ur that solves the puzzle.
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Tue Sep 23, 2008 9:28 pm    Post subject: Reply with quote

I really enjoyed this puzzle Exclamation
I actually made eight moves to complete the puzzle including in no order
two x-wings,
3 xy-wings
type 2 UR<36> (which also had an x-wing on <6> that deleted <3> from r1c29 in addition to the <7>s noted by Earl)
Remote Pair <23> and
BUG+2 which forced r1c1=5

I now intent to do the puzzle again to determine which moves were needed. It was a good day after all.

Ted
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Tue Sep 23, 2008 10:11 pm    Post subject: Reply with quote

Ted, et. al.:

The (36) UR Type 2 is also a Type 4. It makes the next step a little easier. Also, An XYZ-Wing takes some of the complexity out of the final steps.

I'm glad that my puzzle was interesting!
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Wed Sep 24, 2008 2:30 am    Post subject: Reply with quote

daj95376 wrote:


The (36) UR Type 2 is also a Type 4. It makes the next step a little easier.


We have recently had so much confusion on "naming" different forms of URs, that I am only naming Type 1 and Type 2 because I believe they are explicitly defined. All other URs I simply call a "UR" and provide the unique conditions such as a strong link in either candidate, a X-wing overlay or a diagonal condition. One day the community may agree on a naming convention, which I will then adopt.

In this situation, I saw the UR<36> as a Type 2 with a x-wing overlay on <6>. This provided eliminations for the Type 2 on <7> and on <3> for the x-wing.

Ted

ps: I should add that I liked Nataraj's suggest to call "funny" URs a "weasel".
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Marty R.



Joined: 12 Feb 2006
Posts: 5179
Location: Rochester, NY, USA

PostPosted: Wed Sep 24, 2008 3:55 am    Post subject: Reply with quote

Ted, have you read Keith's article on URs? There are definitions for more than Type 1&2.

http://www.sudoku.com/boards/viewtopic.php?p=29105#29105
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Wed Sep 24, 2008 1:45 pm    Post subject: Reply with quote

Thanks for the comment Marty.

Yes, I have read Keith's article, several times in fact, and found it to be a excellent explanation; it was my class book to learn about URs. It names some basic arrangements and how to deal with them but, as noted in many different forum comments recently, combinations of these basic arrangements are unnamed and some new conditions have evolved. Is the UR<36> in this thread, a Type 2 or a Type 4 or both? I called it a Type 2 with an x-wing overlay, which is a Type 4 condition, and I also noted the specific eliminations due to each type. Given all that info, I do not think that having a name for this combination is critical. What is critical is that the "basic" terms used to describe the exact conditions of any UR are named, described and accepted by the user community.

However, I have now decided that my previous approach is not appropriate after further thinking motivated by your comment.In the future, I will identify a UR by stating all the conditions as defined by Keith's note. Thus, I would identify the UR <36> in this thread as a UR with Type 2 and Type 4 conditions, and provide the resultant actions for each.

I enjoy working on puzzles much more than terminology Exclamation

Ted
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