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daj95376
Joined: 23 Aug 2008
Posts: 3854
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 Posted: Tue Aug 09, 2011 9:31 pm Post subject: Puzzle 11/08/09: ~ Advanced BBDB w/fish |
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My solver even used the ?? sink trying to solve this puzzle at the Advanced rating.
| Code: | +-----------------------+
| 2 3 . | . . . | 6 . 4 |
| 1 9 . | . 4 . | . 5 . |
| . . 6 | . . 1 | . . . |
|-------+-------+-------|
| . . . | 8 . 6 | . . . |
| . 7 . | . 5 9 | . . . |
| . . 3 | 4 1 . | . 6 . |
|-------+-------+-------|
| 4 . . | . . . | 5 . . |
| . 6 . | . . 4 | . 3 9 |
| 3 . . | . . . | . 8 1 |
+-----------------------+
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Play this puzzle online at the Daily Sudoku site |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Wed Aug 10, 2011 8:34 am Post subject: |
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Ouch! Well, this goes in a file marked "extreme" for me (It was also an SE7.8 which seems high for an Advanced  )
I did throw the ?? sink at it - but still got nowhere. Finally the "fish" hint steered me towards x-chains and this was my best path in the end (after more than an hour)...
| Code: | x-chain(5) (5)r3c1=r1c3 - r1c6=r9c6 - r9c2=r46c2 ; r46c1<>5
ur(24)[(7)r4c8=(5)r4c3] - (5=2)r6c2 - (2=7)rc6 ; r4c5<>7, r6c9<>7
x-chain(2) (2)r6c9=r6c2 - r9c2=r9c6 - r2c6=r79c2 ; r3c9<>2 |
Look forward to seeing an Advanced solution.  |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Wed Aug 10, 2011 4:31 pm Post subject: |
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The title was suppose to imply that this could be solved as an Advanced rated puzzle ... if ... it wasn't for a fish/X-chain step.
Here are the steps my solver found. I did not check to see which are necessary.
| Code: | after basics
+-----------------------------------------------------------------------+
| 2 3 578 | 579 789 578 | 6 1 4 |
| 1 9 78 | 6 4 2378 | 2378 5 2378 |
| 578 4 6 | 2357 2378 1 | 23789 279 2378 |
|-----------------------+-----------------------+-----------------------|
| 59 125 1245 | 8 237 6 | 12379 2479 2357 |
| 6 7 1248 | 23 5 9 | 1238 24 238 |
| 589 258 3 | 4 1 27 | 2789 6 2578 |
|-----------------------+-----------------------+-----------------------|
| 4 128 12789 | 12379 23789 2378 | 5 27 6 |
| 578 6 12578 | 1257 278 4 | 27 3 9 |
| 3 25 2579 | 2579 6 257 | 4 8 1 |
+-----------------------------------------------------------------------+
# 113 eliminations remain
c1b9 turbot fish/ER <> 7 r3c8
c8b5 turbot fish/ER <> 7 r7c6
(5)r3c1 = r1c3 - r1c6 = r9c6 - r9c2 = (5)r46c2 => r46c1<>5
-or fish-
finned Franken Swordfish c26b1\r19b4 r46c1<>5
<57+2> XY-Wing r8c1/r8c7+r9c2 <> 2 r8c3
-or turbot fish for same elimination-
r6 b3 Empty Rectangle <> 7 r2c6
<47+2> XYZ-Wing r4c8/r4c5+r5c8 <> 2 r4c79
r45c38 <24> UR Type 4.2233 <> 2 r4c38
c38 X-Wing <> 2 r7c46
r38 X-Wing <> 5 r1c4
<25> RP: r3c4 - r8c4 - r9c6 - r9c2 - r6c2 - r6c9 => r3c9<>2
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Interestingly enough, all of the listed steps are restricted to values {2,5,7}.
Yes, this puzzle could have been declared an Extreme rated puzzle !!! |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Wed Aug 10, 2011 5:17 pm Post subject: |
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Peter, I don't know what an X-Chain is, although it appears to involve just one number. Maybe an advanced form of Simple Coloring?
At any rate, as you know, I'm notation-challenged and can't fully follow your first chain, but I can follow it from the grid. Basically, I think, if r3c1<>5, then r46c2=5, thus allowing the eliminations.
That's a very nice move, but how did you find that little isle in this ocean of poly-value cells? |
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peterj
Joined: 26 Mar 2010
Posts: 974
Location: London, UK
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| Posted: Wed Aug 10, 2011 6:12 pm Post subject: |
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| daj95376 wrote: | | Yes, this puzzle could have been declared an Extreme rated puzzle !!! |
Danny, I even put it into Hoduko after to see if I had been stupid - you should see the mess that makes of the solution path by not playing the chain on 5s!!
| Marty R. wrote: | | That's a very nice move, but how did you find that little isle in this ocean of poly-value cells? |
Marty, I use Simple Sudoku as my helper. I used to do simple and multi-colouring - this x-chain on 5 would need three levels of colouring though. Now I tend to look directly for x-chains/turbots. I filter on the candidate and then pick a strong link, look to see if the end can see another strong link, repeat, check for eliminations etc. Easy if using SS, not so on paper... |
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daj95376
Joined: 23 Aug 2008
Posts: 3854
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| Posted: Wed Aug 10, 2011 11:17 pm Post subject: |
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I've removed "w/fish" from the title of puzzles remaining to be posted. These puzzles have been re-labeled "XY" or "Extreme" -- as appropriate.
Regards, Danny |
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