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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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 Posted: Mon Dec 17, 2007 7:33 pm Post subject: Tricky at the end |
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I found this one interesting:
| Code: | Puzzle: M6538195sh(11)
+-------+-------+-------+
| . . . | 3 . . | . 7 . |
| . 4 . | . . . | . . 1 |
| 3 . . | 2 6 7 | . . . |
+-------+-------+-------+
| . . 9 | 8 . 2 | 7 . 3 |
| . . 5 | . . . | 6 . . |
| 2 . 4 | 6 . 3 | 9 . . |
+-------+-------+-------+
| . . . | 5 9 6 | . . . |
| 5 . . | . . . | . 3 . |
| . 2 . | . . 4 | 1 . . |
+-------+-------+-------+ |
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Earl
Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
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| Posted: Mon Dec 17, 2007 9:58 pm Post subject: From Keith |
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Kieth,
I did it with two xy-chains, eliminatiing first the 8 in R5C8, which made possible a second chain eliminating the 1 in R5C5. xy-chains are my last resort. Is there a neater solution?
Earl |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Mon Dec 17, 2007 10:43 pm Post subject: |
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Some coloring eliminations (first 6, then 9, then 8) to get to this point:
| Code: |
+--------------------------+--------------------------+--------------------------+
| 689 589 268 | 3 4 1 | 258 7 268 |
| 67 4 27 | 9 8 5 | 3 26 1 |
| 3 58 1 | 2 6 7 | 58 9 4 |
+--------------------------+--------------------------+--------------------------+
| 1 6 9 | 8 5 2 | 7 4 3 |
| 78 3 5 | 4 17 9 | 6 12 28 |
| 2 78 4 | 6 17 3 | 9 158 58 |
+--------------------------+--------------------------+--------------------------+
| 4 1 3 | 5 9 6 | 28 28 7 |
| 5 79 67 | 1 2 8 | 4 3 69 |
| 689 2 68 | 7 3 4 | 1 56 569 |
+--------------------------+--------------------------+--------------------------+
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Good thing I learned about UR type 6 today!
r13c27 (58). Since 5 forms an x-wing, r1c27 cannot be 8.
After that, coloring again (8:-r1c9=r3c7-r3c2=r6c2-) |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Mon Dec 17, 2007 11:11 pm Post subject: |
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Basic moves get you to here:
| Code: | +----------------+----------------+----------------+
| 689 589 268 | 3 4 1 | 258 7 2689 |
| 67 4 267 | 9 8 5 | 3 26 1 |
| 3 589 1 | 2 6 7 | 58 89 4 |
+----------------+----------------+----------------+
| 1 6 9 | 8 5 2 | 7 4 3 |
| 78 3 5 | 4 17 9 | 6 128 28 |
| 2 78 4 | 6 17 3 | 9 158 58 |
+----------------+----------------+----------------+
| 4 1 3 | 5 9 6 | 28 28 7 |
| 5 79 67 | 1 2 8 | 4 3 69 |
| 689 2 68 | 7 3 4 | 1 569 569 |
+----------------+----------------+----------------+ |
Let me see if I can remember what I did! It involved NOT using the Type 6 UR. It becomes more useful later on!
A kite in R8 and C8 (turbot fish, skyscraper) takes out <6> in R2C3.
The UR on <58> is in R13C27. Let it be!
A skyscraper in R38 takes out <9> in R1C9. Solving <9> in B3.
The UR has become a Type 4, and takes out <8> in R1C27.
Coloring on <8> from R5C1 to R7C8 takes out <8> in R5C8.
A swordfish in R159 or C278 (your choice) takes out <8> in R6C9, and you are done!
Kind of like Boston: Good seafood among the skyscrapers.
Best wishes,
Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Mon Dec 17, 2007 11:19 pm Post subject: |
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My solution:
Kite/strong link/turbot fish or whatever on 9 with the common candidates in box 1
Type 4 UR on 58.
ER on 6.
ER on 8 finished it off.
Keith, what's the source of these puzzles? |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Tue Dec 18, 2007 12:07 am Post subject: |
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| Marty R. wrote: | | Keith, what's the source of these puzzles? |
Marty:
http://www.menneske.no/sudoku/eng/
On the left, click on Random ... Super Hard.
(You may get a Very Hard. Go back, click on Super Hard again.)
You will get a puzzle, with an ID at the top, and Super Hard (nn) at the bottom.
The nn is important! If it is less than 10, you are likely looking at XY-wings or remote pairs. (Thankfully, these puzzles are low on X-wings.) If nn is 10 to 15, you are looking at one or two short chains: A W-wing, an extended XY-wing, coloring, etc.
Above about 20, all bets are off. These are ravel type puzzles. (And, the difficulty extends into the hundreds!)
What I particularly like is that I have no idea what techniques will solve the puzzle.
By the way, I just repeatedly look at random puzzles and print those that meet my criteria. You can always get back to a particular puzzle by using the link Sudoku ... Show Puzzle Number and entering the puzzle ID.
Happy Holidays!
Keith |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Tue Dec 18, 2007 1:02 am Post subject: |
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Thanks Keith.
| Quote: | | By the way, I just repeatedly look at random puzzles and print those that meet my criteria. |
I do the same thing with Vanhegan's Fiendish, what with his convoluted rating system.[/quote] |
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