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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Thu Nov 01, 2007 9:10 am Post subject: A VH? |
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From the London Times:
| Code: | +-------+-------+-------+
| . . 8 | . . . | 9 3 . |
| 4 2 . | . . 1 | . 7 . |
| 7 . . | 5 . . | . . 4 |
+-------+-------+-------+
| . 7 . | 2 . 9 | 3 . . |
| . . . | . 6 . | . . . |
| . . 2 | 1 . 4 | . 6 . |
+-------+-------+-------+
| 5 . . | . . 8 | . . 7 |
| . 9 . | 3 . . | . 1 8 |
| . 4 1 | . . . | 6 . . |
+-------+-------+-------+ |
Keith
edit: from http://entertainment.timesonline.co.uk/tol/arts_and_entertainment/games_and_puzzles/sudoku/
Last edited by keith on Thu Nov 01, 2007 10:48 pm; edited 1 time in total |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Thu Nov 01, 2007 10:24 am Post subject: |
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There are a lot of different options in this puzzle, making it interesting.
I found two different ways to solve it in a single step. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Thu Nov 01, 2007 11:56 am Post subject: |
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this is amazing. Usually The Times don't go further than x-wing, but this puzzle certainly needs more than that.
After basics and the expected x-wing in 8 (I think it was in rows 3 and 4 but not sure), this is where something else is needed:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 1 5 8 | 467 247 27 | 9 3 26 |
| 4 2 39 | 68 39 1 | 58 7 56 |
| 7 36 369 | 5 2389 23 | 1 28 4 |
+--------------------------+--------------------------+--------------------------+
| 6 7 45 | 2 58 9 | 3 458 1 |
| 39 1 45 | 78 6 357 | 24578 245 259 |
| 39 8 2 | 1 357 4 | 57 6 59 |
+--------------------------+--------------------------+--------------------------+
| 5 36 36 | 49 1 8 | 24 249 7 |
| 2 9 7 | 3 45 6 | 45 1 8 |
| 8 4 1 | 79 257 257 | 6 59 3 |
+--------------------------+--------------------------+--------------------------+
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Of course, there is
(1) an UR (36) in box 1 and box7 (making r3c3=9)
AND another UR (45) in box 4 and 6 (together with 28 in r3c7 removes 2 from r7c8)
OR
(2) going the coloring way, 5 can be removed from r5c7, which sees both ends of
-56=96-85=87-
and extending the chain one "element" ( -27=29- ) also from r5c9.
BUT
none of this solves the puzzle.
What about the short chain "58" (r4c5) - "78" (r5c4) - "79" (r9c4) ?
This little chain can be extended at both ends and yields a lot of eliminations, e.g.
| Code: |
... - "59" (r9c8) => r9c5<>5
... - "49" (r7c4) - "45" (r8c5) => r6c5<>5
"45" (r4c3) - ... - "59" (r9c8) => r4c8<>5
"45" (r5c3) - "45" (r4c3) - ... - "59" (r9c8) => r5c8 <> 5
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with all those "5"s gone, there is nothing but singles left ...
Don't know if that counts as "one move". Just the same, it is amazing how much one can do with one simple chain.
But I am more concerned about "The Times" publishing a difficult puzzle like this one ...
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re'born
Joined: 28 Oct 2007
Posts: 80
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| Posted: Thu Nov 01, 2007 12:16 pm Post subject: |
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| nataraj wrote: |
What about the short chain "58" (r4c5) - "78" (r5c4) - "79" (r9c4) ?
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What about extending this short chain into an xy-loop earlier in the puzzle?
| Code: | .---------------------.---------------------.---------------------.
| 1 5 8 | 46-7 247 27 | 9 3 26 |
| 4 2 39 | 68-9 389 1 | 58 7 56 |
| 7 36 369 | 5 2389 23 | 1 28 4 |
:---------------------+---------------------+---------------------:
| 6 7 45 | 2 58* 9 | 3 458 1 |
| 39 1 45 | 78* 6 357 | 24578 2458 259 |
| 39 8 2 | 1 37-5 4 | 57 6 59 |
:---------------------+---------------------+---------------------:
| 5 36 36 | 49* 1 8 | 24 249 7 |
| 2 9 7 | 3 45* 6 | 45 1 8 |
| 8 4 1 | 79* 27-59 257 | 6 59 3 |
'---------------------'---------------------'---------------------' |
r4c5 -8- r5c4 -7- r9c4 -9- r7c4 -4- r8c5 -5- r4c5, => r1c4 <> 7, r69c5 <> 5, r2c4,r9c5 <> 9, solving the puzzle.
Last edited by re'born on Fri Nov 02, 2007 12:21 am; edited 1 time in total |
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Steve R
Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England
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| Posted: Thu Nov 01, 2007 12:45 pm Post subject: Changing Times |
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Nowadays (post Pappacom) the Times publishes a “super fiendish” puzzle every week or so. They usually include a swordfish, as here, though I seem to remember one or two in which a triple was sufficient.
Steve |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Thu Nov 01, 2007 1:25 pm Post subject: |
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That's right, Steve, they introduced the "super fiendish" category a while ago.
I've been doing both the fiendish and super fiendish for quite some time now, and I never - positively never! - encountered one that could not be solved by x-wing or swordfish (plus basic moves, of course).
In fact, if I remember correctly, there even used to be a short "help" section explaining the x-wing and swordfish techniques, plus they said that those two would be sufficient every time.
I cannot find that information on the current Times pages but I'm sure it was there this summer....
Speaking of summer, there was a "summer special" with some (compared to the weekly fare) extra hard puzzles. But those could be solved with xwing and swordfish, too.
@keith: which edition of the Times did you take the puzzle from?
@Steve | Quote: | | They usually include a swordfish, as here |
I am notoriously bad in spotting swordfish patterns. Didn't see one here. Does it solve the puzzle?
@re'born. Spot on. I can't believe I played around with those 58 45 78 ... and failed to close the loop ... 
too preoccupied with the harvest those fives yielded, I guess ...
edit: that leaves the question: what is the SECOND move?
| Asellus wrote: | There are a lot of different options in this puzzle, making it interesting.
I found two different ways to solve it in a single step. |
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Steve R
Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England
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| Posted: Thu Nov 01, 2007 5:57 pm Post subject: |
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I don’t tackle the super fiendish largely because I find looking for swordfish inexpressibly tedious. However, I’m happy to have a go if someone else fills in the pencil marks!
In your grid it is on 5, based on rows 2, 6 and 8. The elimination of 5 from r4c5 does indeed solve the puzzle.
Steve |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Thu Nov 01, 2007 6:35 pm Post subject: |
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Thx, Steve!
| nataraj wrote: | | I never - positively never! - encountered one that could not be solved by x-wing or swordfish |
so ... I should have looked. Kinda stupid to know the solution and not look for it. Hm. Very embarrassing |
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Asellus
Joined: 05 Jun 2007
Posts: 865
Location: Sonoma County, CA, USA
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| Posted: Thu Nov 01, 2007 8:31 pm Post subject: |
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Yep! It is the Swordfish and the XY Loop.
That {45} UR is also interesting.
nataraj - That little <5> coloring you did could be called a "Kite" or "Turbot Fish," I believe. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Thu Nov 01, 2007 8:59 pm Post subject: |
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| Asellus wrote: | | nataraj - That little <5> coloring you did could be called a "Kite" or "Turbot Fish," I believe. |
I believe so, too. But I am never sure ...
So many colorful names for basically the same thing -
strong link - weak link.
Turbot fish, jellyfish. Kraken? Sushi? Sashimi? Fillet?
Oh-fish! Yes.
Don't get me wrong. I like dancing. And I call the dances by their proper names. Tango. Waltz. Rumba. And not: left foot, right foot.
So - I'll probably join the legitimate fishermen's crowd eventually.
And know a trout from a salmon.
Until then: "it's still rock and roll to me..."  |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Thu Nov 01, 2007 10:39 pm Post subject: |
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| Quote: | | @keith: which edition of the Times did you take the puzzle from? |
I found it here:
http://entertainment.timesonline.co.uk/tol/arts_and_entertainment/games_and_puzzles/sudoku/
They don't seem to have an archive. It was SuDoku No. 1588, "Super Fiendish".
I was going to post it "for Nataraj" to challenge his new skills, until I realized the UR's are there but don't help to solve it.
Disregarding the UR's, at this point:
| Code: | +-------------------+-------------------+-------------------+
| 1 5 8 | 467 247 27 | 9 3 26 |
| 4 2 39 | 689 389 1 | 58 7 56 |
| 7 36 369 | 5 2389 23 | 1 28 4 |
+-------------------+-------------------+-------------------+
| 6 7 45 | 2 58 9 | 3 458 1 |
| 39 1 45 | 78 6 357 | 24578 2458 259 |
| 39 8 2 | 1 357 4 | 57 6 59 |
+-------------------+-------------------+-------------------+
| 5 36 36 | 49 1 8 | 24 249 7 |
| 2 9 7 | 3 45 6 | 45 1 8 |
| 8 4 1 | 79 2579 257 | 6 59 3 |
+-------------------+-------------------+-------------------+ |
There is an X-wing on <8>, it doesn't help.
There are a pair of complementary (making the same eliminations) swordfish on <5>, to be found either in the rows or the columns.
I found it interesting that the swordfish is kind of essential, in that for me the puzzle would not succumb to coloring, W-wings, etc.
Keith |
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re'born
Joined: 28 Oct 2007
Posts: 80
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| Posted: Fri Nov 02, 2007 12:22 am Post subject: |
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| keith wrote: |
I found it interesting that the swordfish is kind of essential, in that for me the puzzle would not succumb to coloring, W-wings, etc.
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The xy-loop above solves the puzzle without the swordfish. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Fri Nov 02, 2007 12:33 am Post subject: |
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re'born,
Yes. But time is tight for me during the week, I can only examine the details over the weekend. My problem  ,not yours!
Keith |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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