EC Scoring:
=========
Basic Methods:                 1pt
 Includes X-Wings, (X)Y-Wings, XYZ-wings, W-Wings, Swordfish, Jellyfish,
 Simple Colouring, Skyscraper/2-String Kites & other Turbofish,
 Empty Rectangle/Hinge, Unique Rectangle 1-6, Bug +X (eg. Bug +1,+2 etc.),
 ALS-xz rule
 ---------------------------------------------------
Simple Chains:                 1pt
 XY-Chains or equivalent eg. AICs or ALS Chains with all bivalues
---------------------------------------------------
AICs                           2pts
Multi-Colouring
Bug-Lite
AUR-based stand-alone chains/nets
Mutant Fish Patterns >X-Wing
ALS Chains >2 sets with >bivalues
---------------------------------------------------
AALS stand-alone chains/nets   3pts
---------------------------------------------------
Multi-Inference Chains/Nets:   4pts
AAICs, Kraken Cell/Row/Column, AAHSs, Proving Loops
---------------------------------------------------
Special Conditions:
a)There is a surcharge of 0.5pt on Chains (AICs, AAICs/Krakens/Proving Loops)
for each Almost-pattern' (except ALS & AHP) used within the chain.
(eg. Almost X-Wing or Swordfish, Almost UR)
b)If at least 3 consecutive strong links of a previous AIC are used in a
subsequent chain, 1 pt can be substracted from that chain, but in no event,
can an AIC be scored at less than 1 pt.
---------------------------------------------------
Miscellaneous:
a)Solutions purposely containing chains that others have posted aren't
eligible for scoring. There is no penalty for unintended duplication
or near-duplication of chains posted by others.
b)Sorry: Bifurcation and/or Forcing Chain techniques not acceptable
       for the Eureka Challenge.

Eureka Challenge rules:

The Eureka Challenge is designed to appeal to those of us who use a similar standardized approach to advanced solving, including the use of the Eureka AIC Notation. This and the application of a scoring system necessitates more rigourous requirements in the both the manner of solving and declaring of solutions and does not infer that there is only one good way to solve or notate puzzles. By entering a solution here, it is assumed that you understand that the scoring system is part of the competition and that the rules are necessary for solution comparisons.

1) Puzzle acceptable difficulty range SE=8.1 to 8.6 and solving will start at the post-SSTS (Simple Sudoku Technique Set) point. Posting of the original puzzle string is encouraged.

2) Eureka notation must be used for all chains.

3) Each person should post their solution and score with each individual technique that requires a score given an accepted descriptive name or mnemonic (eg. AIC: (2)r3c4=2-4(r3c8) etc.). The presentation should be clear enough that others might understand one's solution and score. As in golf, the lowest score is the best score.

4) Please try to avoid using terminology or shorthand that is not intuitive or likely to be understood by most other solvers. If a terminology being used is starting to gain acceptance or has certain benefits, but isn't likely to be widely known, please define it when it is first used.

5) A Solver's final competitive score will be that which is in the solver's first posted solution which, however, can be updated within that post (and the score updated if necessary) as long as it can be edited. A solver can show an updated solution in a future post for interest sake, but it is the score in the solver's initial post that will be that poster's final entry score with one exception: If a solver's first solution is found to be in any way defective but cannot now be edited, it can be resubmitted and scored.

6) The sole purpose of the Eureka Challenge is for people to enjoy an advanced solving challenge and to benefit from the clever solving approaches others may use. Some discussion and analysis of puzzles and techniques is encouraged at any time, but in-depth discussion will be particularly welcome after people have had a chance to become familiar with the puzzle.

7) This is categorically not be the place for people to promote recurring agendas that do not have a direct application to solving advanced puzzles. The person who posts a Eureka Challenge puzzle will be the host of that thread and will have a wide latitude to police the thread: If anyone appears to be in any way trying to hijack the thread to further an off-topic agenda, the host can ask the person to desist, disallow the person's solution and ask others to not respond to that person's posts.

EC-10 SE=8.8

000189000070000030005000600801000259207050103500000704000000800050608320000273000

SSTS Position:

This is a puzzle that was presented by a newer solver, Jasper32, in the Player's forum. I don't know where the puzzle originally came from, not much in the way of solving was performed on the puzzle when it was presented and there was no indication as to the difficulty rating. In any event, it turned out to be a very interesting puzzle with several possible solution paths and many different patterns which, as always, makes it a good candidate for the EC. The snarf/string above is for the puzzle as was originally presented and I don't know whether the puzzle was presented in its original form. However, the number of 'givens' suggests that this might be the original puzzle. FWIW: it took only one locked candidate move to bring it to the SSTS position above.

My path to solve this one :

1) (hp28)r2c3/r3c2=(2)r1c23-(2=ht457)r1c789-(hp49=1)r2c7/r3c8 => r3c2<>1

2) (hp23)r7c23=(3-7)r7c1=(7)r8c1-(7=1)r8c9-(1)r9c89=(1)r9c2 => r7c2<>1, some singles

3) (4)r1c13=(4)r1c78-(4=9)r2c7-(9)r2c3=(9)r3c1 => r3c1<>4, some singles

4) 4's : r1c13=r2c3-r2c4=r7c4 – r7c8=r9c7 => r1c7<>4, some singles

5) (7)r7c1=(7)r7c8-(7=4)r1c8-(4=3)r1c1 => r7c1<>3, some singles

6) (4)r1c3=(4-7)r1c8=(7)r7c8-(7=4)r7c1-(4)r7c4=(4)r2c4 => r2c3<>4, singles to the end

Score : 2x6(AIC) =12 and don't think that is good score for this one – there are some ways to solve…

DonM, not likely to be useful, but here is one of several possible minimal puzzles that can be made from the non-minimal Jasper32 posted. The SE rating remains 8.8.

 . . . | 1 8 9 | . . .
 . 7 . | . . . | . 3 .
 . . 5 | . . . | 6 . .
-------+-------+-------
 8 . 1 | . . . | . . 9
 2 . . | . 5 . | 1 . .
 . . . | . . . | 7 . 4
-------+-------+-------
 . . . | . . . | 8 . .
 . 5 . | 6 . . | . 2 .
 . . . | 2 7 3 | . . .

DonM: I'm not going to try to find out, but I wonder whether SSTS would take that potential earlier version of the puzzle to the same endpoint above?

Which reminds me, how did you get SSTS to make the elimination r7c6<>4?

Ronk: Which reminds me, how did you get SSTS to make the elimination r7c6<>4?

Never had to deal with it. I originally copied the puzzle over just as Jasper presented it (where r7c6=1,5) and ran it through SSTS from there.

Here's mine- obviously there's room for more pruning, but even so, I was able to get rid of 5 moves. As this & ttt's solutions indicate, this is one of the few SE >= 8.5 puzzles that I've come across that acted more like a basic-AIC-only puzzle in the 8.3 or less range.

1.  AIC: als(1=49)r2c7/r3c8 - grp(4)r1c78 = grp(4)r1c13 - als(4=19)  => r3c2<>1

            -> linebox(1)r23c1->r789c1<>1

2.  AIC: (1)r2c1 = r3c1 - als(1=49) - grp(4)r1c78 = grp(4)r1c13  => r2c1<>4

3.  AIC: (9=4)r2c7 - grp(4)r1c78 = grp(4)r1c13) - als(4=19)  => r2c3<>9

4.  AIC: als(49=7)r8c13 - (7=1)r8c9 - als(1=4569)r9c1789  => r9c23<>9

5.  AIC: grp(1)r79c8 = r3c8 - r3c1 = (1-9)r2c1 = r2c7 - r9c7 = grp(9)r79c8  => r3c8<>9

            ->r2c7=9, r2c1=1

6.  AIC: (9)r9c8 = r9c1 - r3c1 = (9-8)r3c2 = (8-1)r3c9 = grp(1)r789c9  => r9c8<>1

7.  AIC: (9)r3c1 = (9-8)r3c2 = r2c3 - r9c3 = (8-1)r9c2 = r9c9 - r8c9 = (1-9)r8c5 = grp(9)r8c13  => r79c1<>9

            -> r9c8=9

8.  AIC: (1)r9c2 = r7c2 - (1=5)r7c6 - (5=4)r7c4 - r7c8 = (4-5)r9c7 = (5)r9c9  => r9c9<>1

            -> r9c2=1, r9c3=8, r3c2=8, r2c9=8, r3c1=9

9.  AIC: (5)r9c1 = r1c9 - (5=4)r1c7 - (4)r3c8 = grp(4)r3c56 - (4)r2c4 = r7c4 - r8c5 = grp(4)r8c13 => r9c9<>6=5

            -> numerous singles solved.

10.AIC: (5=1)r7c6 - r7c8 = (1-4)r3c8 = grp(4)r3c56 - r2c4 = (4)r7c4  => r7c4<>5=4

            -> r2c4=5 -> r7c6=5 -> linebox(1)r78c5->r6c5<>1=2 -> r6c6=1 -> linebox(3)r4c45->r4c2<>3

11.AIC: (4)r1c8 = (4-1)r3c8 = r7c8 - (1=9)r7c5 - grp(9)r7c23 = (9-4)r8c3 = grp(4)r12c3  => r1c1<>4=3

STTE

Score: 11 AICs x 2 = 22

Fwiw: I came across a couple of AURs that were interesting though of no use in solving the puzzle:

1. AIC: (6)r2c5=(6-5)r2c6=(5-1)r7c6=r6c6-(1=2)r6c5 => r2c5<>2
2. ALS-xz: r7c4568(14579),r8c9(17),x=7,z=1 => r7c9<>1
3. ALS-xz: r2c14567(124569),r3c14568(123479),x=2,z=1 => r3c2<>1
4. ALS-xz: r8c139(1479),r9c1789(14569),x=1,z=9 => r9c23<>9
5. ALS-xz: r8c9(17),r8c13+r9c123(146789),x=7,z=1 => r9c89<>1
6. Coloring in 9's: r3c18,r29c7 => r9c1<>9
7. AIC: (9)r7c5=(9-1)r8c5=r8c9-(1=2)r3c9-(2=346)r234c5 => r7c5<>4
8. AIC: (1)r8c5=r8c9-(1=2)r3c9-(2=346)r234c5 => r8c5<>4
9. AIC: (7)r7c1=r8c1-(7=1)r8c9-r7c8=(1-9)r3c8=r3c1 => r7c1<>9
10. XY-wing (347): r1c18,r7c1 => r7c8<>7

Greenlantern- that's a clever use of the ALS xz-rule patterns particularly since you get some nice exclusions for only 1 pt per move.

However, I don't think all is well with:

5. ALS-xz: r8c9(17),r8c13+r9c123(146789),x=7,z=1 => r9c89<>1

Unless I'm missing something there still is a 1 in r8c1 which means that not all the 1s of the r8c13+r9c123(146789) set are 'seeing' the 1s in r9c89.

Greenlantern: After step #3 (r3c2<>1), a box-line interaction results in r789c1<>1, so I think my 4th ALS-xz is valid.

Great! Which just goes to show you that the 'Unless I'm missing something...' was operative... :)

Don, this swine of yours has so many lines of attack! I started by going heavy on AUR deductions but although elegant, they weren't very productive. I then looked for ways to kill single digits in group nodes rather than picking them off piecemeal, but with limited success. With so many openings available at any time, I found it really difficult to decide which ones would do the most damage. Here's my last effort based on a straight run-though using the knowledge gained from earlier efforts, I haven't checked it for any redundant steps though. Sadly a quick scan of the other entries shows it's not the shortest, so I guess I'll have to admit defeat. I'll probably kick myself when I run through them.     

01: (1)r7c56 = (1)r8c5 - (1=7)r8c9 - (7)r8c1 = (237)AHT:r7c123 => r7c12 <> 1

     (18)HiddenPair:r39c2 = r39c2 <> 269

02: (8)r2c9 = (8)r3c9 - (8=1)r3c2 - (1)r3c8 = (18)AHT:r23c9 => r2c9 <> 2

03: (2)r2c3 = (2)r2c45 - (2)r3c45 = (2-8)r3c9 = (8)r2c9 => r2c3 <> 8

     Singles r2c9,r3c2,r9c3 = 8, r2c1,r9c2 =1

04: (2=1)r6c5 - (1)r6c6 = (1)r7c6 - (1)r7c8 = (1)r3c8 - (1=2)r3c9 => r3c5 <> 2

05: (2=1)r6c5 - (1)r6c6 = (1-5)r7c6 = (5-6)r2c6 = (6)r2c5 => r2c5 <> 2

     Singles r6c5=2, r6c6 =1

     (45)NakedPair:r7c46 => r7c1358,r8c5 <> 4

     (4)LineBox:r9b9 => r9c1 <> 4

     (45)UER:r27c46 => r2c6 <> 45

     Singles r2c4,r7c6 = 5, r7c4 =4

06: (9=4)r2c7 - (4)r2c5 = (4)r3c45 - (4=9)r3c1 => r2c3 <> 9

     Singles r3c1,r2c7,r9c8 = 9, r9c7= 4, r1c7,r9c9 = 5, r9c1,r7c9 = 6 

07: (5)r1c7 = (5)r1c9 - (5=6)r9c9 - (6=9)r9c1 - (9)r3c1 = (9)r3c8 - (9=4)r2c7 => r1c7 <> 4

      Singles r1c7,r9c9 = 5, r7c9,r9c1 = 6

     (9)LineBox:r9b9 => r7c8 <> 9

08: (4)r1c13 = (4-7)r1c8 = (7-2)r1c9 = (2-1)r3c9 = (1-9)r3c8 = (9)r3c1 => r3c1 <> 4

     Singles r3c1,r2c7,r9c8 = 9, r9c7 =4

09: (4=7)r1c8 - (7)r1c9 = (7)r8c1 - (7=4)r8c1 => r1c1 <> 4

     Singles to the end