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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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 Posted: Thu Jul 24, 2008 6:20 pm Post subject: Simply Colorful |
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| Code: | *-----------*
|76.|..3|.1.|
|3.4|.6.|..2|
|...|9..|...|
|---+---+---|
|..7|..2|...|
|62.|.4.|.31|
|...|6..|7..|
|---+---+---|
|...|..4|...|
|1..|.3.|4.5|
|.7.|2..|.63|
*-----------* |
This puzzle is from Sudoku Online for July 24th
Ted |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Thu Jul 24, 2008 8:02 pm Post subject: |
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Very colorful!
I found coloring eliminations in "5", "8" and "9" (this one was the best harvest)
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Thu Jul 24, 2008 9:40 pm Post subject: |
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Would someone verify if I've correctly understood the so-called "Finned XY-Wing." Here's where I am after basics:
| Code: | +-------------+---------------+--------------+
| 7 6 589 | 4 2 3 | 589 1 89 |
| 3 589 4 | 158 6 158 | 589C 7 2 |
| 2 58 1 | 9 7 58 | 3 4 6 |
+-------------+---------------+--------------+
| 89 14 7 | 3 189 2 | 6 5 489 |
| 6 2 589 | 58A 4 7 | 89B 3 1 |
| 589 14 3 | 6 1589 1589 | 7 2 489 |
+-------------+---------------+--------------+
| 589 3 6 | 158 1589 4 | 2 89 7 |
| 1 89 2 | 7 3 6 | 4 89 5 |
| 4 7 589 | 2 589 589 | 1 6 3 |
+-------------+---------------+--------------+ |
ABC would be an XY-Wing if the 8 weren't present in C. So C is either an 8 or the 59 pincer. Either way, r1c7 would be 5. Is that the correct application of the Fin?
If that's correct, then following that move, one Remote Pairs of 89 finishes it off. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Thu Jul 24, 2008 10:25 pm Post subject: |
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| Code: | +-------------+---------------+--------------+
| 7 6 589 | 4 2 3 | 589D 1 89 |
| 3 589 4 | 158E 6 158 | 589C 7 2 |
| 2 58 1 | 9 7 58 | 3 4 6 |
+-------------+---------------+--------------+
| 89 14 7 | 3 189 2 | 6 5 489 |
| 6 2 589 | 58A 4 7 | 89B 3 1 |
| 589 14 3 | 6 1589 1589 | 7 2 489 |
+-------------+---------------+--------------+
| 589 3 6 | 158 1589 4 | 2 89 7 |
| 1 89 2 | 7 3 6 | 4 89 5 |
| 4 7 589 | 2 589 589 | 1 6 3 |
+-------------+---------------+--------------+ |
ABC would be an XY-Wing if the 8 weren't present in C. Yes.
So C is either an 8 or the 59 pincer. Yes.
Either way, r1c7 would be 5.
If C is <8>, B is <9>, and D is <5>.
If C is <59>, the XY-wing elimination takes out <5> in E. Which does not lead anywhere obvious, at first glance.
Is that the correct application of the Fin? I think not, unless you have a different logic than I have assumed. You seem to have missed that the <5> in B1 must be in C2, which solves D as <5> immediately.
Whch is not really a logical problem, if you can show that r1c7 is solved by the XY-wing elimination.
Edit: And, I think you can argue your case. The XY-wing elimination solves <5> in C2, and thus <5> in D.
(By the way, I drove past your town today. Crummy weather. I left behind a gorgeous few days in Detroit. I am in Ithaca, where it is cool and drizzling.)
Best wishes,
Keith |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Thu Jul 24, 2008 10:30 pm Post subject: |
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Marty, I don't get the connection between the pincers and the r1c7 cell.
I think you got the finned xy-wing right in that it is either
- r2c7=8 or
- xy.wing which takes out 5 in r2c4
why r2c4<>5 leads to r1c7=5 still eludes me.
But it is late. I'll re-consider tomorrow |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Thu Jul 24, 2008 10:31 pm Post subject: |
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| again, seems like we posted at the same time ... |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Jul 25, 2008 12:09 am Post subject: |
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| Quote: | | Is that the correct application of the Fin? I think not, unless you have a different logic than I have assumed. You seem to have missed that the <5> in B1 must be in C2, which solves D as <5> immediately. |
I'm still missing it after staring at it.
| Quote: | | If C is <59>, the XY-wing elimination takes out <5> in E. Which does not lead anywhere obvious, at first glance. |
That elimination locks the B2 5s in c6 which sets off a chain of eliminations.
| Quote: | | (By the way, I drove past your town today. Crummy weather. I left behind a gorgeous few days in Detroit. I am in Ithaca, where it is cool and drizzling.) |
Yes, crummy, but we've been in somewhat of a drought condition and desperately needed the rain.
Next time, don't just drive past, stop by!!
| Quote: | | why r2c4<>5 leads to r1c7=5 still eludes me. |
It wasn't real direct, rather it involved a chain of eliminations to reach that point. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Jul 25, 2008 3:55 am Post subject: |
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Well, I am very happy that this puzzle stimulate much interest, even if it is regarding a finned xy-wing.
I solved the puzzle using coloring on <5>, <8> and <9> (in that order) just as Nataraj did. For me, coloring is a very easy and efficient solving technique, but I was especially interested to determine if "others" readily solved the puzzle using different approaches.
Did anyone else solve this puzzle and not use coloring? If so, please respond.
Ted  |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Fri Jul 25, 2008 5:22 am Post subject: |
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Other possibilities?
Since Ted is asking for it  :
After basics (and with 5 removed by box/line (column 2 / box 1) from r1c3 which gives 5 in r1c7):
| Code: |
+--------------------------+--------------------------+--------------------------+
| 7 6 89*# | 4 2 3 | 5 1 8-9* |
| 3 5-89 4 | 158 6 158 | 89*# 7 2 |
| 2 58 1 | 9 7 58 | 3 4 6 |
+--------------------------+--------------------------+--------------------------+
| 89 14 7 | 3 189 2 | 6 5 489 |
| 6 2 5-8-9# | 58 4 7 | 89*# 3 1 |
| 589 14 3 | 6 1589 1589 | 7 2 489 |
+--------------------------+--------------------------+--------------------------+
| 589 3 6 | 158 1589 4 | 2 89 7 |
| 1 89 2 | 7 3 6 | 4 89 5 |
| 4 7 589 | 2 589 589 | 1 6 3 |
+--------------------------+--------------------------+--------------------------+
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There are two w-wings that help a lot:
a) w-wing (89 r1c3 to r5c7) marked * removes 8 AND 9 from r5c3
b) w-wing (89 r1c3 to rc27) marked # removes 8 from r1c9 and r2c2 |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Fri Jul 25, 2008 5:25 am Post subject: |
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| Quote: | | I'm still missing it after staring at it. |
| Code: | +-------------+---------------+--------------+
| 7 6 589 | 4 2 3 | 589 1 89 |
| 3 589 4 | 158 6 158 | 589C 7 2 |
| 2 58 1 | 9 7 58 | 3 4 6 |
+-------------+---------------+--------------+
| 89 14 7 | 3 189 2 | 6 5 489 |
| 6 2 589 | 58A 4 7 | 89B 3 1 |
| 589 14 3 | 6 1589 1589 | 7 2 489 |
+-------------+---------------+--------------+
| 589 3 6 | 158 1589 4 | 2 89 7 |
| 1 89 2 | 7 3 6 | 4 89 5 |
| 4 7 589 | 2 589 589 | 1 6 3 |
+-------------+---------------+--------------+ |
Marty,
The <5> in C2 must be in B1. R1C3 is not <5>, so R1C7 must be <5> by a box-line interaction.
Leaving that aside, if the XY-wing is true, it takes out <5> in R2C4. | Quote: | Edit: And, I think you can argue your case. The XY-wing elimination solves <5> in C2, and thus <5> in D.
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This statement of mine is, I believe, incorrect.
Marty, I think your idea is correct, but the same elimination can be made by basic methods.
(By the way, I had a lunch meeting in Honeoye Falls, or I would have called you.)
Best wishes,
Keith |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Fri Jul 25, 2008 5:47 am Post subject: |
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After basics: | Code: | +----------------+----------------+----------------+
| 7 6 89a | 4 2 3 | 5 1 89b |
| 3 589 4 | 158 6 158 | 89c 7 2 |
| 2 58 1 | 9 7 58 | 3 4 6 |
+----------------+----------------+----------------+
| 89 14 7 | 3 189 2 | 6 5 489 |
| 6 2 5-8-9| 58 4 7 | 89d 3 1 |
| 589 14 3 | 6 1589 1589 | 7 2 489 |
+----------------+----------------+----------------+
| 589 3 6 | 158 1589 4 | 2 89 7 |
| 1 89 2 | 7 3 6 | 4 89 5 |
| 4 7 589 | 2 589 589 | 1 6 3 |
+----------------+----------------+----------------+ |
and a remote naked pair <89> solves it.
Keith |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Fri Jul 25, 2008 1:31 pm Post subject: |
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| I found an ER and an x-wing - but all this did was leave more 59s instead of 589s. I ended up finding a "colour wrap"(?) on 9. (I think this is what it's called - two 9s facing each other in violation of the prime directive). Not a satisfying conclusion though. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Fri Jul 25, 2008 3:40 pm Post subject: |
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| Quote: | | The <5> in C2 must be in B1. R1C3 is not <5>, so R1C7 must be <5> by a box-line interaction. |
Easy to see now.  Very basic. Not that I have a very large arsenal, but it does come in handy to have alternative methods to bail one out when one misses something that should've been seen. |
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tlanglet
Joined: 17 Oct 2007
Posts: 2468
Location: Northern California Foothills
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| Posted: Fri Jul 25, 2008 6:16 pm Post subject: |
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Thank you one and all for your input on how you solved this puzzle; we seem to have had a typical variation, with individuals generally using the approach that they typically employ.
I assume that we all start off after basics using what we believe is the most easy and efficient techniques and revert to other schemes only when they do not kill the beast. To me the fact that all the different techniques and the sequence they are used still normally results in completing the puzzle indicates that no specific approach has an advantage. I think this is one of the pleasures of Sudoku.
Ted  |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Fri Jul 25, 2008 8:53 pm Post subject: |
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| I believe that there is a 1489 MUG in r46c1259: one of r6c1 or r6c5 must be <5>, thus r6c6<>5. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Fri Jul 25, 2008 9:09 pm Post subject: |
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I've never heard of a MUG before - but I found this site for reference.
http://www.sudoku.com/boards/viewtopic.php?p=21050#21050
I thought I understood the first bit - which said that MUGs are used for several BUG lites. But then I realised I had read it as BUD lites.
I'll persevere though. |
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