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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Fri Dec 25, 2009 4:48 pm Post subject: Free Press Dec 25, 2009 |
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On the impossible side:
| Code: | Puzzle: FP122509
+-------+-------+-------+
| . . 7 | 1 . . | 4 . . |
| . . 8 | 9 . 3 | . . . |
| . 9 . | . . . | . 7 . |
+-------+-------+-------+
| 7 . . | 2 . . | . 6 . |
| 6 . 2 | . . . | 5 . 4 |
| . 1 . | . . 6 | . . . |
+-------+-------+-------+
| . 2 . | . . . | . 9 . |
| . . . | 3 . 9 | 1 . . |
| . . 1 | . . 8 | 7 5 . |
+-------+-------+-------+
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Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Dec 25, 2009 10:06 pm Post subject: |
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| Quote: | | On the impossible side: |
Choose your words carefully; someone may have a one-stepper. 
However, the word works for me, unfortunately. 
Here's my position after a Finned X-Wing (6), Skyscraper (3), Medusa Wrap and an ER ( 8 ):
| Code: |
+----------------+---------------+---------------+
| 235 356 7 | 1 568 25 | 4 238 9 |
| 245 456 8 | 9 7 3 | 26 1 56 |
| 1 9 356 | 4568 4568 245 | 2368 7 3568 |
+----------------+---------------+---------------+
| 7 3458 3459 | 2 3458 45 | 389 6 1 |
| 6 38 2 | 7 9 1 | 5 38 4 |
| 345 1 3459 | 458 3458 6 | 2389 23 7 |
+----------------+---------------+---------------+
| 3458 2 3456 | 456 1 7 | 368 9 368 |
| 58 7 56 | 3 25 9 | 1 4 268 |
| 9 346 1 | 46 246 8 | 7 5 236 |
+----------------+---------------+---------------+
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Play this puzzle online at the Daily Sudoku site |
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wapati
Joined: 10 Jun 2008
Posts: 472
Location: Brampton, Ontario, Canada.
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| Posted: Sat Dec 26, 2009 2:28 am Post subject: Re: Free Press Dec 25, 2009 |
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| keith wrote: | On the impossible side: ...
Keith |
A handful, at the least. Nasty puzzle. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Dec 26, 2009 4:14 am Post subject: |
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| Quote: | | Choose your words carefully; someone may have a one-stepper. Laughing |
Marty, I would be delighted if someone proved my assessment wrong! In the meantime, I am with wapati on this one.
Keith |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Dec 26, 2009 4:27 am Post subject: |
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| Marty R. wrote: |
| Code: |
+----------------+---------------+---------------+
| 235 356 7 | 1 568 25 | 4 238 9 |
| 245 456 8 | 9 7 3 | 26 1 56 |
| 1 9 356 | 4568 4568 245 | 2368 7 3568 |
+----------------+---------------+---------------+
| 7 3458 3459 | 2 3458 45 | 389 6 1 |
| 6 38 2 | 7 9 1 | 5 38 4 |
| 345 1 3459 | 458 3458 6 | 2389 23 7 |
+----------------+---------------+---------------+
| 3458 2 3456 | 456 1 7 | 368 9 368 |
| 58 7 56 | 3 25 9 | 1 4 268 |
| 9 346 1 | 46 246 8 | 7 5 236 |
+----------------+---------------+---------------+
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Marty,
There is a short chain: 6 in R9C2 forces 6 in R8C3, via the links on 2 in C9 and on 6 in R8. R9C2 is not 6. Then, there is an XYZ-wing 23-5 in R1C2, leaving us here:
| Code: | +----------------+----------------+----------------+
| 235 36 7 | 1 568 25 | 4 238 9 |
| 245 456 8 | 9 7 3 | 26 1 56 |
| 1 9 35 | 4568 4568 245 | 2368 7 3568 |
+----------------+----------------+----------------+
| 7 3458 3459 | 2 3458 45 | 389 6 1 |
| 6 38 2 | 7 9 1 | 5 38 4 |
| 345 1 3459 | 458 3458 6 | 2389 23 7 |
+----------------+----------------+----------------+
| 3458 2 3456 | 456 1 7 | 368 9 368 |
| 58 7 56 | 3 25 9 | 1 4 268 |
| 9 34 1 | 46 246 8 | 7 5 236 |
+----------------+----------------+----------------+ |
Your move.
Keith |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sat Dec 26, 2009 7:03 am Post subject: |
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sorry for the intrusion as I wasn't part of the volleying...
| Code: | +-------------------+-------------------+--------------------+
| 235 356 7 | 1 568 25 | 4 238 9 |
| 1245 456 8 | 9 7 3 | 26 12 156 |
| 1235 9 356 | 4568 4568 245 | 2368 7 13568 |
+-------------------+-------------------+--------------------+
| 7 3458 3459 | 2 13458 145 | 389 6 18-3 |
| 6 8(3) 2 | 78 9 17 | 5 18(3) 4 |
| 345 1 3459 | 458 3458 6 | 2389 238 7 |
+-------------------+-------------------+--------------------+
| 3458 2 3456 | 4567 1456 1457 | 368 9 368 |
| 58 7 56 | 3 256 9 | 1 4 268 |
| 9 46(3) 1 | 46 246 8 | 7 5 26(3) |
+-------------------+-------------------+--------------------+ |
1...skyscraper 3, r4c9 <> 3
| Code: | +------------------+---------------------+----------------------+
| 235 356 7 | 1 568 25 | 4 238 9 |
| 1245 456 8 | 9 7 3 | 26 12 156 |
| 1235 9 356 | 4568 4568 245 | 2368 7 13568 |
+------------------+---------------------+----------------------+
| 7 3458 3459 | 2 13458 145 | 389 6 (18) |
| 6 (38) 2 | 7-8 9 17 | 5 (138) 4 |
| 345 1 3459 | 45(8) 345(8) 6 | 239(8) 23(8) 7 |
+------------------+---------------------+----------------------+
| 3458 2 3456 | 4567 1456 1457 | 368 9 368 |
| 58 7 56 | 3 256 9 | 1 4 268 |
| 9 346 1 | 46 246 8 | 7 5 236 |
+------------------+---------------------+----------------------+ |
2...ALS[(8)r5c28 = (1)r5c8]r5c28 - (1=8)r4c9 - (8)r6c78 = (8)r6c45; r5c4 <> 8
| Code: | +------------------+--------------------+-------------------+
| 235 356 7 | 1 56(8) 25 | 4 23(8) 9 |
| 245 456 8 | 9 7 3 | 26 1 56 |
| 1 9 356 | 456(8) 4568 245 | 2368 7 3568 |
+------------------+--------------------+-------------------+
| 7 3458 3459 | 2 3458 45 | 389 6 1 |
| 6 38 2 | 7 9 1 | 5 38 4 |
| 345 1 3459 | 45(8) 3458 6 | 2389 23-8 7 |
+------------------+--------------------+-------------------+
| 3458 2 3456 | 456 1 7 | 368 9 368 |
| 58 7 56 | 3 256 9 | 1 4 268 |
| 9 346 1 | 46 246 8 | 7 5 236 |
+------------------+--------------------+-------------------+ |
3...kite 8, r6c8 <> 8
| Code: | +--------------------+--------------------+-----------------+
| 235 35(6) 7 | 1 568 25 | 4 238 9 |
| 245 45(6) 8 | 9 7 3 | 26 1 56 |
| 1 9 35(6) | 458(6) 4568 245 | 2368 7 3568 |
+--------------------+--------------------+-----------------+
| 7 3458 3459 | 2 3458 45 | 389 6 1 |
| 6 38 2 | 7 9 1 | 5 38 4 |
| 345 1 3459 | 458 3458 6 | 2389 23 7 |
+--------------------+--------------------+-----------------+
| 3458 2 3456 | 4(56) 1 7 | 368 9 368 |
| 58 7 (56) | 3 26(5) 9 | 1 4 268 |
| 9 34-6 1 | 4(6) 246 8 | 7 5 236 |
+--------------------+--------------------+-----------------+ |
almost m-wing
m-wing is in brackets...
4...[(6=5)r8c3 - (5)r8c5 = (5-6)r7c4 = (6)r9c4] = (6)r3c4 - (6)r3c3 = (6)r12c2;
r9c2 <> 6
A.K.A. - regardless of whether the M-wing is true or false, the 6 in r9c2 can't exist.
| Code: | +-------------------+------------------+-----------------+
| (235) 36-5 7 | 1 568 (25) | 4 238 9 |
| 245 456 8 | 9 7 3 | 26 1 56 |
| 1 9 (35) | 4568 4568 245 | 2368 7 3568 |
+-------------------+------------------+-----------------+
| 7 3458 3459 | 2 3458 45 | 389 6 1 |
| 6 38 2 | 7 9 1 | 5 38 4 |
| 345 1 3459 | 458 3458 6 | 2389 23 7 |
+-------------------+------------------+-----------------+
| 3458 2 3456 | 456 1 7 | 368 9 368 |
| 58 7 56 | 3 256 9 | 1 4 268 |
| 9 34 1 | 46 246 8 | 7 5 236 |
+-------------------+------------------+-----------------+ |
5...xyz-wing {2,3,5}, removes 5 from r1c2
| Code: | +---------------------+-----------------+-----------------------+
| 23-5 36 7 | 1 568 25 | 4 28(3) 9 |
| 24-5 46(5) 8 | 9 7 3 | 26 1 56 |
| 1 9 (35) | 4568 4568 245 | 268(3) 7 568(3) |
+---------------------+-----------------+-----------------------+
| 7 -34(58) 3459 | 2 3458 45 | 389 6 1 |
| 6 3(8) 2 | 7 9 1 | 5 (38) 4 |
| 345 1 3459 | 458 3458 6 | 2389 2-3 7 |
+---------------------+-----------------+-----------------------+
| 3458 2 3456 | 456 1 7 | 368 9 368 |
| 58 7 56 | 3 256 9 | 1 4 268 |
| 9 34 1 | 46 246 8 | 7 5 236 |
+---------------------+-----------------+-----------------------+ |
6...loop... (3=5)r3c3 - (5)r2c2 = (5-8)r4c2 = (8)r5c2 - (8=3)r5c8 - (3)r1c8 = (3)r3c79;
r12c1 <> 5
r4c2 <> 3,4
r6c8 <> 8
| Code: | +--------------------+-----------------+----------------+
| 3(2) 36 7 | 1 568 5(2) | 4 38 9 |
| (24) 6-4(5) 8 | 9 7 3 | 26 1 56 |
| 1 9 35 | 468 468 (24) | 2368 7 3568 |
+--------------------+-----------------+----------------+
| 7 8(5) 3459 | 2 3458 (45) | 389 6 1 |
| 6 38 2 | 7 9 1 | 5 38 4 |
| 345 1 3459 | 458 3458 6 | 389 2 7 |
+--------------------+-----------------+----------------+
| 3458 2 3456 | 456 1 7 | 368 9 368 |
| 58 7 56 | 3 256 9 | 1 4 268 |
| 9 34 1 | 46 246 8 | 7 5 236 |
+--------------------+-----------------+----------------+ |
7...extended w-wing {2,4} pincers in r2c1 and r3c6
(4=2)r2c1 - (2)r1c1 = (2)r1c6 = (2=4)r3c6 - (4=5)r4c6 - (5)r4c2 = (5)r2c2; r2c2 <> 4 |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Dec 26, 2009 4:27 pm Post subject: |
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I know nothing about puzzle construction, but it seems odd that a puzzle of this complexity would be published in a mass medium.  |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Dec 26, 2009 8:12 pm Post subject: |
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| Marty R. wrote: | | I know nothing about puzzle construction, but it seems odd that a puzzle of this complexity would be published in a mass medium. |
Yes,
This happens every few weeks - the Friday puzzle is impossible. The last time it happened, I sent an e-mail to the LA Times, asking them who is the source for their puzzles. They never replied. Maybe I should ask the Freep.
Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat Dec 26, 2009 10:05 pm Post subject: |
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Keith, do you get to see a print copy? Our local fish-wrapper has had two different puzzles since they started publishing Sudoku's and the source has always been right next to the puzzle in fine print.
They ran Poppacom for a couple of years and Janric since then. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat Dec 26, 2009 11:19 pm Post subject: |
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Marty,
I have checked both the electronic (Freep, LA Times) and printed versions (Freep). No source is given.
Keith |
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chas47
Joined: 29 Jan 2008
Posts: 2
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| Posted: Sun Dec 27, 2009 5:20 am Post subject: Freep source |
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Also in Baltimore Sun. Again no source given.
Charlie |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Dec 27, 2009 7:10 am Post subject: |
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I don't subscribe to our local paper, but the newspaper's website gives Uclick LCC. as the source.
but I haven't found any of the puzzles to be hard. in fact I don't think any of them require pencil marks.
http://content.uclick.com/about.html
this raises the question...
Is it more likely that people who live in areas where the newspaper prints harder (requiring VH+ techniques) puzzles generate more interest in researching sudoku online?
IOW, if the newspaper puzzles in your area are easy enough to solve withouth pencil marks, would those people not be curious about researching it elsewhere?
it would seem to me that if I saw a puzzle in a paper which I could not arrive at a solution, I would be curious enough about it to look it up.
maybe not everyone is as curious as that tho?
the reason I looked up sudoku online in the first place is because I saw a book with a puzzle I could not solve without pencil marks only to find out that it required no more than a ONE naked pair after I did research on the subject.  |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Sun Dec 27, 2009 4:55 pm Post subject: |
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| Code: | After basics
+-----------------------------------------------------------------------+
| 235 356 7 | 1 568 25 | 4 238 9 |
| 1245 456 8 | 9 7 3 | 26 12 156 |
| 1235 9 356 | 4568 4568 245 | 2368 7 13568 |
|-----------------------+-----------------------+-----------------------|
| 7 3458 3459 | 2 13458 145 | 389 6 138 |
| 6 38 2 | 78 9 17 | 5 138 4 |
| 345 1 3459 | 458 3458 6 | 2389 238 7 |
|-----------------------+-----------------------+-----------------------|
| 3458 2 3456 | 4567 1456 1457 | 368 9 368 |
| 58 7 56 | 3 256 9 | 1 4 268 |
| 9 346 1 | 46 246 8 | 7 5 236 |
+-----------------------------------------------------------------------+
# 106 eliminations remain
|
It's the same grid as the one posted by Norm. My solver didn't find Marty's finned X-Wing on <6> nor a short chain for Keith's r9c2<>6. This is important for what follows.
ncantral posted this puzzle on the Players' Forums, and ttt replied with a single step. The step doesn't solve the puzzle, but it does advance the solution so that my solver doesn't need a network step. I'm going to rephrase his step below.
There is a potential <26> UR in r89c59. ttt calls it an AUR. A way to prevent the UR is through one of the <6>s in r7c4579,r9c4. Now, here's where it gets interesting. Cell r7c3 contains a <6> and sees four of the five <6>s to prevent the UR.
| Code: | r7c3= 6 => r9c4=6 to prevent UR => r8c5<>6
r7c3<>6 => ER r1b7 => r8c5<>6
*--------------------------------------------------------------------*
| 235 356 7 | 1 568 25 | 4 238 9 |
| 1245 456 8 | 9 7 3 | 26 12 156 |
| 1235 9 356 | 4568 4568 245 | 2368 7 13568 |
|----------------------+----------------------+----------------------|
| 7 3458 3459 | 2 13458 145 | 389 6 138 |
| 6 38 2 | 78 9 17 | 5 138 4 |
| 345 1 3459 | 458 3458 6 | 2389 238 7 |
|----------------------+----------------------+----------------------|
| 3458 2 3456 | 4567 1456 1457 | 368 9 368 |
| 58 7 56 | 3 *256 9 | 1 4 *268 |
| 9 346 1 | 46 *246 8 | 7 5 *236 |
*--------------------------------------------------------------------*
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Don't ask me how ttt managed to find his step  |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sun Dec 27, 2009 9:59 pm Post subject: |
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maybe just a tad easier to understand.
in the UR 26 in r89c59
you should notice that the 2's are locked into a perfect x-wing.
this means that in rows 8 and 9 the only other 6's are in
A... r9c2 and r9c4
B... r8c3
------
A...either the 6's in r9c2 and r9c4 have to be true...
these 6's combined with the 6's in r1c2 and r1c5 form a skyscraper which eliminates the 6 in r8c5
| Code: | +-------+-------+-------+
| . 6 . | . 6 . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+-------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+-------+-------+-------+
| . . . | . . . | . . . |
| . . . | . X . | . . . |
| . 6 . | 6 . . | . . . |
+-------+-------+-------+ |
or
B... the 6 in r8c3 is true, which still eliminates the 6 in r8c5...
| Code: | +-------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+-------+-------+-------+
| . . . | . . . | . . . |
| . . . | . . . | . . . |
| . . . | . . . | . . . |
+-------+-------+-------+
| . . . | . . . | . . . |
| . . 6 | . X . | . . . |
| . . . | . . . | . . . |
+-------+-------+-------+ |
either way the 6 in r8c5 can't exist.
------
these moves are sneaky when dealing with more difficult puzzles, and ttt is notoriously able to spot these.
the chain is rediculous to write out.
UR26[(6)r8c3 = skyscraper {(6)r9c4 = (6)r9c2 - (6)r1c2 = (6)r1c5}]
either the skyscraper is true on 6's
or the 6 is true in r8c3. |
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