dailysudoku.com Forum Index dailysudoku.com
Discussion of Daily Sudoku puzzles
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Puzzle 11/08/09: ~ Advanced BBDB w/fish

 
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Puzzles by daj
View previous topic :: View next topic  
Author Message
daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Tue Aug 09, 2011 9:31 pm    Post subject: Puzzle 11/08/09: ~ Advanced BBDB w/fish Reply with quote

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 |
 +-----------------------+

Play this puzzle online at the Daily Sudoku site
Back to top
View user's profile Send private message
peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Wed Aug 10, 2011 8:34 am    Post subject: Reply with quote

Ouch! Well, this goes in a file marked "extreme" for me (It was also an SE7.8 which seems high for an Advanced Exclamation )
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. Smile
Back to top
View user's profile Send private message
daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Wed Aug 10, 2011 4:31 pm    Post subject: Reply with quote

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

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 !!!
Back to top
View user's profile Send private message
Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Wed Aug 10, 2011 5:17 pm    Post subject: Reply with quote

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?
Back to top
View user's profile Send private message
peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Wed Aug 10, 2011 6:12 pm    Post subject: Reply with quote

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...
Back to top
View user's profile Send private message
daj95376



Joined: 23 Aug 2008
Posts: 3854

PostPosted: Wed Aug 10, 2011 11:17 pm    Post subject: Reply with quote

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
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    dailysudoku.com Forum Index -> Puzzles by daj All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group