Start Pause Reset
40 Comments Previous / NextHelp

Tough Sudoku for 6/January/2011


Choose a number, and place it in the grid above.

  1 2 3 4 5 6 7 8 9
Check out the latest post in the Sudoku Forum

Sudoku Solving Techniques

Submitted by: sudoku lover

Indicate which comments you would like to be able to see

"Pretty bird!"
06/Jan/11 12:07 AM

06/Jan/11 12:22 AM
It must be a lot of fun to watch these birds in your back yard! They are so big and colorful!

Have a great day everyone!
06/Jan/11 12:32 AM
With the amazing native birds, I can't figure out why everyone in Australia is not a "birder"! In the U.S., we spend hours trying to distinguish one drab warbler or sparrow from another!
06/Jan/11 1:52 AM

1)Start at 23,SSTS to UP=29
3)(2=5)c5-c2=a2-(5=2)a9-e9=(2-7) e7=e6-(7=2)h6,=>h5<>2.UP=33
4)kraken cell:(689)h2,=>h7<>8.UP=35
(9)h2-(9=5) More...
06/Jan/11 2:57 AM
going at it from a different angle:
1.SSTS to UP=29
2.kraken cell(167)i1 => i8<>6, UP=37
3.(8=7)f5-e6=e7 -(79=8)bf7-SF:bgh245=f5 => f5=8, UP=45
4.AUR(39)cg46=> (4)c6=(8-3)g4=c4 => c6<>3
5.AUR(89)gh24=> h2=6, UP=81.
06/Jan/11 3:59 AM

Step 1) is not necessary:
1)Start at 23,SSTS to UP=29
2)kraken cell:(689)h2,=>h7<>8.UP=31
(9)h2-(9=5) More...

4)(9 More...
06/Jan/11 4:35 AM
-must be some way to chain sis over interlocking AUR -eg.(389)g4, might speed some paths; will investigate.
06/Jan/11 4:38 AM

farpointer:Instead of steps 4-5 if use my step 4) above,=>UP=81
06/Jan/11 5:53 AM
sotir: the AUR were so simple, I stopped looking at that point - will recheck to see if your step 4 reachable at UP=45.
06/Jan/11 7:07 AM
#0. SSTS -> UP29
#1. (2)i8=(2)i7-(2)e7=(2)e9-[(1)e9=(1)e1 AND (2=5)a9-(5)a2=(5)c2-(7)c2=(7)i2]-(17=6)i1 => i8<>6; UP37
#2. (1)i1=(1)e1-(1=2)e9-(2=5)a9-(5)a2=(5)c2-(7)c2=(7)i2 => i1<>7; UP41
#3. (1)e9=(1)e1-(1)i9=(1)i4-(1=8)b4-(8)b7=(8)i7-(2)i7=(2)e7 => e9<>2; UP81
06/Jan/11 7:14 AM
BTW: is it permitted to include a step like my step 5 under the umbrella of STTE?
06/Jan/11 7:25 AM
JC: is that a typo in your #1 kraken --[...]-- => 0
06/Jan/11 7:30 AM
JC: the content of your [...] also is somewhat unclear, AND means what in relation to what here?
06/Jan/11 7:36 AM
- eureka now uses kraken diagrams (ttt) whenever possible to avoid confusion.
06/Jan/11 7:38 AM
06/Jan/11 7:43 AM
OK: I see what you're doing JC, a variation on what I loosely call 'dynamic' or forwarded weak links, which I never use anymore but probably crop up in your matrices.
06/Jan/11 7:52 AM
-reasons I avoid forwarded weak links:
a) gets confusiong and starts to resemble SST as you go style reasoning ala UP-chainers
b) the AIC chains lose symmetry and become restricted in loops and internal deduction points.
c) the chains are almost always quite deep ala UP-chainers.
06/Jan/11 8:00 AM
- of course krakens as a unit are not symmetric, are restricted as to deduction points and looping, but IMO easier to see where these points are located.
06/Jan/11 8:11 AM
-check out:


makes the occasional wrangle between me and Alfred sound like a polite Sunday school chat.
06/Jan/11 8:44 AM
The krakens will getcha if you don't watch out!
06/Jan/11 9:15 AM
interesting quote from above mentioned page (DonM):

"While the assumptions made in a typical AAIC are greater than a regular chain, they are not nearly as great as with a forcing chain- speaking from the point of view of someone who used forcing chains at one time. With the typical More...
06/Jan/11 9:34 AM
another interesting quote (re our discussion a few days past) DonM:

"IMO, what ... is that the term, forcing chain, has been used without any kind of apparent standardization of the meaning. Apparently, it has gone from being a term almost interchangeable with nice loops ie. b/b plot More...
06/Jan/11 10:19 AM
finally from DonM (a true Eurekan):

"...I will resist to my last solving breath that an AAIC net or its relatives are comparable to forcing chains, as often defined in tutorials these days, whereby a bivalue cell is randomly used as the source for 2 chains that prove another cell digit More...
06/Jan/11 10:51 AM
1. Note pairs 27 at h56;17 at i12.Unique possibilities to 29.
2. If e9=5,a9=2=i8,e4=6;column i is devoid of 6.So e9=12.
3. Whether a2=5,a9=2,e9=1;OR a2=9=d3,d1=7,i1=1;e1=6.UP81.
06/Jan/11 11:51 AM
There have been discussions in Sudokuland lately, about constructing an Alternate Incarceration Centre (AIC) in the province of Upland. The purpose: to constrain the minority of Eukereans who can't constrain themselves. The worst perpetrators will be locked into chain gangs.
06/Jan/11 12:13 PM
Alfred: in step 3, why does 1 plug into i1 in the second half of your bi-value FC guess?
- the presented solution is nonsense as documented.
06/Jan/11 12:25 PM
BTW, your first chain fully documented is:

(5=2)a9-ac8=(2-6)i8=g8-g6=ef6-(6=5)e4 => e9<>5

a chain I judged to be fair, but not weakening the position enough to justify it's depth.
06/Jan/11 12:32 PM
You're right farpointer. I wrongly had 17 at i12. Have to go back to the drawing board.
06/Jan/11 12:46 PM
curious that that point of contention here is the kraken cell of my first step.
06/Jan/11 12:57 PM
A band-aid job, re-working the second part of step 3:
3. Whether a2=5,a9=2,e9=1;OR a2=9,c2=5;and now, both h8=8,h2=6;and h8=5=e4=b5,b4=1,i2=7,i1=1; make e1=6.UP81.
06/Jan/11 1:41 PM
Lovely pic Bev, and what a lovely garden your aunt has!
06/Jan/11 1:56 PM
-still insufficiently documented, you can't follow the logic (if any) w/o filling in the grid. Some day, if I have absolutely nothing better to do, I'll look for the errors and omissions that probably exist.
06/Jan/11 2:03 PM
Alfred's comment is a wonderful antidote to the super-serious conversation, which has indeed gotten to a point of self-ridicule.
06/Jan/11 2:22 PM
Hi Alfred,

In your note above, you should have mentioned that the chain gangs were to prepare quadrilateral blocks of stone from impervious puzzles; these blocks are often called Unique Rectangles.
06/Jan/11 7:47 PM
Thanks Neil. I also forgot, those needing maximum security, are to be confined to the feared kraken cell.
06/Jan/11 9:05 PM

Those not in the feared kraken cell, may be subject to lots of BUGs in the various other cells.

And grids on the backdoors.
06/Jan/11 9:57 PM
My goodness, I didn't expect so much comments after the proof I proposed for today!
I think I should stop speaking Eurekanese and go back to the dark Strongly Interacting Stones (SIS) linked by red Weakly Invisible Strips (WIS).

Note : To whom it may be of interest : to locate the "AIC", cryptically ask Steve on this site : "How does one spot forbidding chains?".
06/Jan/11 10:38 PM
Hi JC,

Your style of posting before you started using Eureka, was a 'breath of fresh air'. I really think that you should continue using that style.

After all, your WIS SIS (wissies/wizzies/whizzies) through the puzzles.

Best regards, Neil
06/Jan/11 11:20 PM
Hopefully, a better attempt:
1. UP29
2. Whether i7=2=e9;OR i8=2,g7=6,locked 6s at hi4,e4=5;e9=12.
3. Whether c2=5,b45=15,locked 8s at ab6;OR a2=5,a9=2,e9=1,f9=4,f78=79;f5=8.UP33.
4. Whether i8=2,i7=8;OR i7=2=e9,a9=5,a2=9=d3,d1=7=i2,e1=1=g2,i2=8;h7=5.UP42.
5. Whether a2=5,a9=2,e9=1;OR a2=9=d3,d1=7,i1=1;e1=6.UP81.
06/Jan/11 11:47 PM
Please Log in to post a comment.

Not a member? Joining is quick and free. As a member you get heaps of benefits.

Join Now Login