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ravel
Joined: 21 Apr 2006
Posts: 536
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 Posted: Tue Jan 08, 2008 4:46 pm Post subject: A 17 clue |
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Most puzzles with 17 givens are very easy. The hardest (according to the rating of Sudoku Explainer) is about that hard as the one Asellus has solved here recently.
This one is just nice to solve:
| Code: | +-------+-------+-------+
| . . . | 8 . . | . . 1 |
| . 3 . | . . . | . . . |
| 6 . . | . . . | . . . |
+-------+-------+-------+
| 1 . 8 | . . . | 3 . . |
| . . . | . 7 2 | . 4 . |
| 5 . . | . . . | . . . |
+-------+-------+-------+
| . 2 . | . . . | . 7 . |
| . . . | . 3 . | 4 . . |
| . . . | 1 . 6 | . . . |
+-------+-------+-------+
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Tue Jan 08, 2008 8:21 pm Post subject: |
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felt like bingo for the first stage of the puzzle. I guess 17 clues feel that way because you have so many cells to fill.
| Code: | 2 9 47 | 8 56 345 | 57 36 1
8 3 47 | 467 1259 159 | 259 29 467
6 1 5 | 47 29 39 | 289 2389 47
------------------------+-------------------------+------------------
1 7 8 | 46 69 49 | 3 5 2
3 6 9 | 5 7 2 | 1 4 8
5 4 2 | 3 18 18 | 79 69 67
------------------------+-------------------------+------------------
4 2 1 | 9 58 58 | 6 7 3
9 8 6 | 2 3 7 | 4 1 5
7 5 3 | 1 4 6 | 28 28 9
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Tue Jan 08, 2008 8:28 pm Post subject: |
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Ravel,
you pointed out the three pair DP in the other puzzle, and I thank you. is there one in this puzzle??
in r267c56
the {58} {18} {15} pairs???
there is a 47 UR in r23c49 |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Tue Jan 08, 2008 8:53 pm Post subject: |
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| storm_norm wrote: | ... three pair DP .. .in r267c56
the {58} {18} {15} pairs??? |
Yes, to use it efficiently, you first should resolve a UR type 4. There is also an xyz-wing in your grid, which does not help so much. | Quote: | | there is a 47 UR in r23c49 |
Thanks, i missed this one. With it's 2 strong links it solves it directly. |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Tue Jan 08, 2008 10:36 pm Post subject: |
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| You can use that 3-pair DP immediately in the grid above without an intervening step. r2c56 must contain <2> and/or <9>, forming a locked pair with r2c8 and making r2c7=5. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Jan 08, 2008 11:44 pm Post subject: |
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I get it to here, with an XY-wing:
| Code: | +-------------+-------------+-------------+
| 2 9 47 | 8 56 345 | 57 36 1 |
| 8 3 47 | 467 159 159 | 59 2 467 |
| 6 1 5 | 47 2 39 | 8 39 47 |
+-------------+-------------+-------------+
| 1 7 8 | 46 69 49 | 3 5 2 |
| 3 6 9 | 5 7 2 | 1 4 8 |
| 5 4 2 | 3 18 18 | 79 69 67 |
+-------------+-------------+-------------+
| 4 2 1 | 9 58 58 | 6 7 3 |
| 9 8 6 | 2 3 7 | 4 1 5 |
| 7 5 3 | 1 4 6 | 2 8 9 |
+-------------+-------------+-------------+
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In the <18> <58> <15> deadly pattern, one of R2C56 must be <9>, R2C7 is <5>, and the puzzle is solved.
You do not need the <47> UR to say that one of R2C49 is <6>, information which, I believe, is not useful at all.
Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Jan 09, 2008 1:54 am Post subject: |
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I never saw the DP. I used a couple of URs, a W-Wing and finished it off with Medusa.
| Quote: | | Most puzzles with 17 givens are very easy. |
Learn something new everyday, I would've thought just the opposite. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Wed Jan 09, 2008 8:18 am Post subject: |
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| keith wrote: | | You do not need the <47> UR to say that one of R2C49 is <6>, information which, I believe, is not useful at all. |
With the strong link for 7 in c4 you have r3c4=4 => r2c4=7 and with the strong link for 4 in c9 r3c9=7 => r2c9=4.
So you can eliminate the 4 in r3c4=4 and the 7 in r3c9, because they lead to a deadly pattern 4-7-4-7. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Wed Jan 09, 2008 11:35 pm Post subject: |
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| ravel wrote: | | keith wrote: | | You do not need the <47> UR to say that one of R2C49 is <6>, information which, I believe, is not useful at all. |
With the strong link for 7 in c4 you have r3c4=4 => r2c4=7 and with the strong link for 4 in c9 r3c9=7 => r2c9=4.
So you can eliminate the 4 in r3c4=4 and the 7 in r3c9, because they lead to a deadly pattern 4-7-4-7. |
ravel,
Thank you. I learn something new every day, often from you!
Keith |
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