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ravel
Joined: 21 Apr 2006
Posts: 536
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 Posted: Mon May 26, 2008 8:05 am Post subject: Another gsf (one step) |
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| Code: | +-------+-------+-------+
| 9 2 . | . . . | . . . |
| . . . | . . . | 3 4 . |
| 3 . . | . 5 1 | . . . |
+-------+-------+-------+
| 7 . . | 6 . . | 2 . . |
| . 5 . | 8 . 7 | . 6 . |
| . . 6 | . . 2 | . . 4 |
+-------+-------+-------+
| . . . | 4 3 . | . . 5 |
| . 9 7 | . . . | . . . |
| . . . | . . . | . 2 8 |
+-------+-------+-------+
|
>>> play online
(one hour the week must be time for sudoku  ) |
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Johan
Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium
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| Posted: Mon May 26, 2008 2:38 pm Post subject: |
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The 48 UR* in R34C23 deletes <1> in R2C9, solving the puzzle, either R3C2=7 or/both R4C3=9 for avoiding the 48DP
R3C2=[7] => R2C2=[1](a)
or/both
R4C3=|9| => R4C9=|1|(b)
| Code: | +-------------------------+-------------------------+-------------------------+
| 9 2 18 | 3 6 4 | 5 18 7 |
| 6 a [1]7 5 | 279 28 89 | 3 4 {-1}29 |
| 3 *4[7]8 *48 | 279 5 1 | 689 89 269 |
+-------------------------+-------------------------+-------------------------+
| 7 *48 *48|9| | 6 14 3 | 2 5 b |1]9 |
| 24 5 249 | 8 14 7 | 19 6 3 |
| 1 3 6 | 5 9 2 | 78 78 4 |
+-------------------------+-------------------------+-------------------------+
| 28 16 12 | 4 3 689 | 1679 179 5 |
| 458 9 7 | 12 28 568 | 146 3 16 |
| 45 146 3 | 19 7 569 | 1469 2 8 |
+-------------------------+-------------------------+-------------------------+ |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Mon May 26, 2008 4:08 pm Post subject: |
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Its also one of those rare type 5 UR's with extra candidates in diagonal cells.
Because of the strong link for 4 in r3 and for 8 in c2 you can eliminate 4 and 8 from r4c3 (the cell with extra candidates which is not part of the strong link).
Because of the strong link for 8 in row 4 you also can eliminate 8 from r3c2, but its not needed to solve the puzzle. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Mon May 26, 2008 5:51 pm Post subject: Re: Another gsf (one step) |
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| ravel wrote: | | Code: | +-------+-------+-------+
| 9 2 . | . . . | . . . |
| . . . | . . . | 3 4 . |
| 3 . . | . 5 1 | . . . |
+-------+-------+-------+
| 7 . . | 6 . . | 2 . . |
| . 5 . | 8 . 7 | . 6 . |
| . . 6 | . . 2 | . . 4 |
+-------+-------+-------+
| . . . | 4 3 . | . . 5 |
| . 9 7 | . . . | . . . |
| . . . | . . . | . 2 8 |
+-------+-------+-------+
|
>>> play online
(one hour the week must be time for sudoku ) |
Ravel,
This was a fun puzzle. I initially missed the UR and found an x-wing and multi-coloring but they were not helpful when I spotted the killer. I have also enjoyed the other "gsf" puzzles that have posted. Are they available on the web?
Ted |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Mon May 26, 2008 10:53 pm Post subject: |
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The "Type 5" Unique Rectangle is like this:
| Code: | +--------------+
| x - - |
| 46 - 246 |
| x - - |
+--------------+
| 246 - 46 |
| - - x |
| - - x |
+--------------+ |
and you can eliminate <2> from the cells marked x. So far as I know, one that makes eliminations has never been observed in an actual puzzle.
If the UR also happens to be an X-wing, that is a "Type 6". So, if the rectangle above is also an X-wing on <4> you can make eliminations to reach the following:
| Code: | +--------------+
| - - - |
| 4 - 26 |
| - - - |
+--------------+
| 26 - 4 |
| - - - |
| - - - |
+--------------+ |
The UR in this thread is somewhere between these two cases. It was in a post by Myth Jellies that I first saw logic similar to what Johan has used. (Note that Johan's logic does not use the strong links on the UR candidates.)
Ravel is the one who taught me to consider every angle to use a possible UR, and not to see the UR as simply a list of numbered types.
Keith |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Tue May 27, 2008 7:37 am Post subject: |
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| tlanglet wrote: | | I have also enjoyed the other "gsf" puzzles that have posted. Are they available on the web? |
The gsf puzzles are from the Patterns game in the players forum. They try to find as much as possible puzzles of different difficulty to a given pattern. Its hard to say in advance, which of them are interesting (but its also nice sometimes, when you dont know it). Up to ratings 6.6 you can solve them with x/y/z-wings, UR, BUG and coloring, up to 7.3 with relatively short chains. This can be very hard or just a w-wing.
| keith wrote: | | The "Type 5" Unique Rectangle is like this: |
As with many techniques there is some confusion about the UR definitions. I suppose that Keiths definition is the more common one (but not very useful without a real life example). I referred to this one by Havard. |
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