The hardest sudokus

Everything about Sudoku that doesn't fit in one of the other sections

Postby champagne » Sun Jan 04, 2009 8:38 pm

Hi coloin,

I checked your last lot.

Only the 2 first are in the scope.
The first one can be solved without entering the last level, but seems to be a tough one.
The second one is limit down in the family of hardest.
Others are far below.

This has been checked with a version of the solver dated 07/2008.
I am not 100% sure of the reliability of the current version due to changes in progress.
I made a very fast overview on the solution and I did not see the SK loop in this lot.

Here my statistics for the two first

Code: Select all
.......1......4.32.2..3.5.......7....4..2...5..89..4....78..6...3..1..5.9........ # coly004 #  203 21.2  146K
..6.....1.7.4...2.....5.3...8...7........4.8.9.28.......1...5...2.9...7.3.......6 # coly005 #  188 24.4  215K



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Postby ttt » Tue Jan 06, 2009 1:49 am

champagne wrote:I checked your last lot.

Only the 2 first are in the scope.
The first one can be solved without entering the last level, but seems to be a tough one.
The second one is limit down in the family of hardest.
Others are far below.

This has been checked with a version of the solver dated 07/2008.
I am not 100% sure of the reliability of the current version due to changes in progress.
I made a very fast overview on the solution and I did not see the SK loop in this lot.

Here my statistics for the two first

Code: Select all
.......1......4.32.2..3.5.......7....4..2...5..89..4....78..6...3..1..5.9........ # coly004 #  203 21.2  146K
..6.....1.7.4...2.....5.3...8...7........4.8.9.28.......1...5...2.9...7.3.......6 # coly005 #  188 24.4  215K



For coly004, it seems as FM with floor (789)r12c7…
I don’t know why… I have to drink so much…:D

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Postby champagne » Tue Jan 06, 2009 2:22 am

ttt wrote:For coly004, it seems as FM with floor (789)r12c7…
I don’t know why… I have to drink so much…:D

ttt


hi ttt,

sharp eye despite vodka.:D

cells r5c8 r8c9 linked.


That family should be downgraded when the solver will integrate that pattern. For the time being, it is just able to identify it.

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Postby coloin » Tue Jan 06, 2009 3:16 am

Thanks for analysing those.

For coly004 - It explains the false positive -q2 with a low sxt [similar to FM]

For coly005 the high sxt confirms the difficulty.

But for coly013 - i had hoped for better, it is the best of a new batch. For a 21 clue [pearl ?] puzzle the sxt is leagues above other puzzles.

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Postby champagne » Tue Jan 06, 2009 3:43 am

coloin wrote:Thanks for analysing those.


But for coly013 - i had hoped for better, it is the best of a new batch. For a 21 clue [pearl ?] puzzle the sxt is leagues above other puzzles.

C


I had a quick look on the solution proposed by my solver.

The first step is made of 5 "medium size" AIC's nets, the rest is routine.

I can publish it if you are interested.

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Postby ronk » Tue Jan 06, 2009 4:07 am

Maximum similarity between Fata Morgana and coly004 is 14 clues, but the same logic set applies, as ttt found. See Allan Barker's First Loop in FM.
Code: Select all
........3..1..56...9..4..7......9.5.7...5...8.5.4.2....8..2..9...35..1..6........ # Fata Morgana
........3..1...6...2..4..7....7.9.5...2.5.8...5.4......4..7..9...3...1..6..2..... # coly004 morphed



 . . . | . . . | . . 3                . . . | . . . | . . 3
 . . 1 | . . 5 | 6 . .                . . 1 | . . . | 6 . .
 . 9 . | . 4 . | . 7 .                . 2 . | . 4 . | . 7 .
-------+-------+-------              -------+-------+-------
 . . . | . . 9 | . 5 .                . . . | 7 . 9 | . 5 .
 7 . . | . 5 . | . . 8                . . 2 | . 5 . | 8 . .
 . 5 . | 4 . 2 | . . .                . 5 . | 4 . . | . . .
-------+-------+-------              -------+-------+-------
 . 8 . | . 2 . | . 9 .                . 4 . | . 7 . | . 9 .
 . . 3 | 5 . . | 1 . .                . . 3 | . . . | 1 . .
 6 . . | . . . | . . .                6 . . | 2 . . | . . .
# Fata Morgana                        # coly004 morphed


[edit: 1) with only 2 elims, the smaller First Loop in FM is the "better fit"; 2) top coly004 was the original]
Last edited by ronk on Tue Jan 06, 2009 1:11 am, edited 2 times in total.
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Postby champagne » Tue Jan 06, 2009 4:37 am

ronk wrote:Maximum similarity between Fata Morgana and coly004 is 14 clues, but the same logic set applies, as ttt found.[code]


On my side, Fata Morgana remains "special". Without help of Allan Barker first loop or equivalence, the solvers fails.

That one is solved without these specific tools.
Using the direct search for the specifc pattern of FM Allan first loop, I hope to get a shorter and nicer path.

May be a preliminary idea next week.

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Postby tarek » Fri Jan 09, 2009 3:59 am

I'm glad that there is still some activity on the hardest puzzles generation front.

There hasn't been an update on g.r.emlin's hardest puzzles compilation.

I will be starting a new thread -- The hardest sudokus (new thread) -- with the 1st post having the list of puzzles in a similar fashion to the one currently on wikipedia.

This is mainly due to the the fact that ravel is no longer an active member of this forum, with so much going on since his departure.

Hopefully this OLD thread would then be renamed in a manner that reflects that & closed with a post linking to the new one.

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Re:

Postby gurth » Tue Sep 07, 2010 12:51 pm

ronk wrote:Ocean, that's an amazing set of puzzles. Six of them won't fall to elimination-by-contradiction (EBC) that is based on singles only. Not surprisingly, they are the puzzles with the highest Explainer ratings:

.....1..2.1..2..3.4..5.......4.....6.7..3..1.8.....9..5....8.......1..7...64..5.. # ER=10.0
.....1..2.1..3..4.5..6.......4.....1.7..8..3.2.....6..9....2.......4..7...35..8.. # ER=9.9
.....1..2.1..3..4.5..6.......4.....1.7..8..3.2.....9..9....2.......4..7...35..8.. # ER=9.9
.....1..2.3..4..5.6..2.......5.....3.7..8..4.2.....9..9....4.......5..7...41..6.. # ER=9.8
.....1..2.3..4..5.6..7.......5.....4.8..2..9.7.....3..1....4.......5..8...96..7.. # ER=9.8
.....1..2.3..2..4.5..6.......6.....5.7..4..8.1..8..9..7....2.......3..1...89..6.. # ER=9.7

Thanks for your contributions, Ron

P.S. As you listed above, that is #1, #2, #3, #10, #14, and #17.


- These 6 sudokus are indeed Sapphires, as defined by udosuk : they "won't fall to elimination-by-contradiction (EBC) that is based on singles only."

But the same also goes for #6 (ER=9.4) and #11 (ER=9.5). They too are Sapphires. (under singles).
P.S. The quote from ronk was dated Aug 16, 2006.
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Re: The hardest sudokus

Postby ttt » Thu Sep 09, 2010 4:40 pm

Hi gurth,
Just to say: “HI” to see you comeback... :D

PS. I think that Mods should keep your old nickname: “gurth” – the famous name here and on Eureka!

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Re: The hardest sudokus

Postby gurth » Thu Sep 09, 2010 6:00 pm

ttt wrote:Hi gurth,
Just to say: “HI” to see you comeback... :D

PS. I think that Mods should keep your old nickname: “gurth” – the famous name here and on Eureka!

ttt


Hi ttt! Yes, I agree, I should keep my old identity. I've emailed the administrator to fix it, hopefully he will.

Edited 7.30 a.m. (South African time), Sep 10, 2010: ... and as you can see, he speedily has! Thanks Jason.
And congratulations on the job of reconstruction you did after the "great crash".
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