The hardest sudokus (new thread)

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

Re: The hardest sudokus (new thread)

Postby champagne » Mon Aug 05, 2019 12:54 pm

Obi-Wahn wrote:Yes, I did understand that. But you said that the error only affected 02_index.txt. But now there are some puzzles missing from 01_file1.txt that would still belong there, because they aren't redundant.

For example:...
I copied these from the ph_1812 01_file1.txt.

Hi Obi_Whan,
Late answer, but you are right, these ones are not redundant and have been erased (and disappeared in all files).
As I used the 'add' process to reintroduce them, the internal number has been modified.
I surely made a wrong action in the cleaning process.

Thanks
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Re: The hardest sudokus (new thread)

Postby 999_Springs » Thu Aug 08, 2019 10:55 pm

this might be of interest to tarek and the other pencilmark-only sudoku enthusiasts

i was messing around with sudoku explainer's GUI and tried to make champagne's 11.9/11.9/11.8 hardest ever puzzle even harder by adding pencilmarks to known clues. in this puzzle the only clue that lets you add a candidate to it without invalidating the puzzle is 5r7c4, which can be replaced with (56).

modifying the grid in the GUI by changing 5r7c4 to 56, and stepping through the puzzle, you find that the first two hints are -5r7c2 (11.8) and -4r6c8 (11.9)

and then this happens

new SE rating record? :P :mrgreen:

i don't know what the overall rating of the puzzle will be but probably 12.0, there are already 12 hints with that rating in this spot if you click on get next hint

unfortunately you can't rate tarek's ultra hard pencilmark sudokus in se using this method since the interface doesn't process beyond dynamic chains if a puzzle fails the 17 minimum clues check, and also if you remove too many candidates by hand, it throws up some illegal argument exception error that i found a while ago when messing with the gui, so this won't work. but it's nice though

p.s. yeah i know what you're thinking from the pic. this is an old laptop, so don't judge me for having mIRC pinned to the taskbar! i haven't used it in years i promise
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Re: The hardest sudokus (new thread)

Postby tarek » Thu Aug 08, 2019 11:52 pm

999_Springs wrote:this might be of interest to tarek and the other pencilmark-only sudoku enthusiasts

i was messing around with sudoku explainer's GUI and tried to make champagne's 11.9/11.9/11.8 hardest ever puzzle even harder by adding pencilmarks to known clues. in this puzzle the only clue that lets you add a candidate to it without invalidating the puzzle is 5r7c4, which can be replaced with (56).

modifying the grid in the GUI by changing 5r7c4 to 56, and stepping through the puzzle, you find that the first two hints are -5r7c2 (11.8) and -4r6c8 (11.9)

and then this happens

new SE rating record? :P :mrgreen:

i don't know what the overall rating of the puzzle will be but probably 12.0, there are already 12 hints with that rating in this spot if you click on get next hint

unfortunately you can't rate tarek's ultra hard pencilmark sudokus in se using this method since the interface doesn't process beyond dynamic chains if a puzzle fails the 17 minimum clues check, and also if you remove too many candidates by hand, it throws up some illegal argument exception error that i found a while ago when messing with the gui, so this won't work. but it's nice though

p.s. yeah i know what you're thinking from the pic. this is an old laptop, so don't judge me for having mIRC pinned to the taskbar! i haven't used it in years i promise

It is good that you are thinking in this way. The hardest Sukakus hasn't been tapped into properly and having new ideas of how to find/create them is great. At the moment only a handful are discussing sukakus with ways to rate the difficult puzzles using SE. I'm sure we will have another thread for the hardest Sukakus very soon

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Re: The hardest sudokus (new thread)

Postby dobrichev » Fri Aug 09, 2019 5:40 am

999_Springs wrote:new SE rating record? :P :mrgreen:

Surely it is.
You have the chance this puzzle has "backdoor of size 0 in Dynamic Region Forcing Chains". For even harder puzzles, SE gives up after thinking for 2-3 days.
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Re: The hardest sudokus (new thread)

Postby coloin » Fri Aug 09, 2019 9:40 pm

Now I understand pencil mark sudoku .... and I thought sukaku was a typo !!!
I found the puzzle .... and its been given a 12.0 ..... BOOM ....... well found !

Code: Select all
+----------------------+----------------------+----------------------+
| 9      8      12345  | 7      346    1246   | 1234   145    235    |
| 7      1235   12345  | 12348  3489   12489  | 6      14589  23589  |
| 1234   123    6      | 12348  5      12489  | 123478 14789  23789  |
+----------------------+----------------------+----------------------+
| 1268   4      129    | 168    678    5      | 278    3      26789  |
| 12368  1236   7      | 9      3468   1468   | 5      468    268    |
| 3568   3569   359    | 3468   2      4678   | 478    46789  1      |
+----------------------+----------------------+----------------------+
| 12346  12367  8      | 5      467    2467   | 9      167    367    |
| 2356   235679 2359   | 268    1      26789  | 378    5678   4      |
| 1456   15679  1459   | 468    46789  3      | 178    2      5678   |
+----------------------+----------------------+----------------------+    Champagne Dry ED=11.9/11.9/11.8


+----------------------+----------------------+----------------------+
| 9      8      12345  | 7      346    1246   | 1234   145    235    |
| 7      1235   12345  | 12348  3489   12489  | 6      14589  23589  |
| 1234   123    6      | 12348  5      12489  | 123478 14789  23789  |
+----------------------+----------------------+----------------------+
| 1268   4      129    | 168    678    5      | 278    3      26789  |
| 12368  1236   7      | 9      3468   1468   | 5      468    268    |
| 3568   3569   359    | 3468   2      4678   | 478    46789  1      |
+----------------------+----------------------+----------------------+
| 123456 123567 8      | 2456   467    2467   | 9      1567   3567   |
| 2356   235679 2359   | 2568   1      26789  | 378    5678   4      |
| 1456   15679  1459   | 4568   46789  3      | 178    2      5678   |
+----------------------+----------------------+----------------------+    5@r7c4 removed


the 2 and 4 give multiple solutions - so we remove them and we are left with the sukaku puzzle
so....
the 6 gives no solutions ... quite difficult to show that this is so ...
the 5 defines the puzzle


+----------------------+----------------------+----------------------+
| 9      8      12345  | 7      346    1246   | 1234   145    235    |
| 7      1235   12345  | 12348  3489   12489  | 6      14589  23589  |
| 1234   123    6      | 12348  5      12489  | 123478 14789  23789  |
+----------------------+----------------------+----------------------+
| 1268   4      129    | 168    678    5      | 278    3      26789  |
| 12368  1236   7      | 9      3468   1468   | 5      468    268    |
| 3568   3569   359    | 3468   2      4678   | 478    46789  1      |
+----------------------+----------------------+----------------------+
| 123456 123567 8      | 56     467    2467   | 9      1567   3567   |
| 2356   235679 2359   | 2568   1      26789  | 378    5678   4      |
| 1456   15679  1459   | 4568   46789  3      | 178    2      5678   |
+----------------------+----------------------+----------------------+           


no such pm clues in 11.4:m_b_metcalf .... ? but bound to be in others ....
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Re: The hardest sudokus (new thread)

Postby tarek » Sat Aug 10, 2019 9:40 am

As I told Mladen on a different thread: With Sukaku, the concept of Minimal puzzle can get a bit confusing as we are adding candidates to the puzzle to achieve that. A minimal Sukaku is a valid single solution puzzle where adding any candidate to the pencilmark grid would result in multiple solutions!

Translating what happens in a vanilla sudoku to sukaku; Removing a clue from a vanilla sudoku cell means that your actually adding 8 candidates to the pencilmark grid in that cell.

No need to test a Sukaku for difficulty unless it is minimal and therefore the potential of using already known difficult vanilla sudokus is huge.

All of the hardest vanilla sudokus will be good seeds for SE defeating Sukakus. The Singles backdoor size 3 puzzles (e.g. Easter monster) could be a good starting point.

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Re: The hardest sudokus (new thread)

Postby 999_Springs » Sat Aug 10, 2019 4:27 pm

tarek wrote:Translating what happens in a vanilla sudoku to sukaku; Removing a clue from a vanilla sudoku cell means that your actually adding 8 candidates to the pencilmark grid in that cell.

No need to test a Sukaku for difficulty unless it is minimal and therefore the potential of using already known difficult vanilla sudokus is huge.


um no actually you're adding way more than 8 candidates because you're also adding the value of the clue that you removed to all the cells that can see the clue.

for instance when i got rid of 5r7c4 i'm adding extra 5's to all cells in r7, b8 and c4 that don't already see a 5

so you can extend this idea as follows, if a puzzle has multi solutions when you add a candidate to a known cell, you can remove some of those extra pencilmarks created and see if it's valid. this still gives you a proper superset of what you started with. for instance if you take the champagne puzzle with r7c4 replaced with 56 as above, you can then also replace 5r5c7 with 58 but the puzzle will have multi solutions, you can make it unique again by removing candidate 5r8c7 and this still covers all candidates of the puzzle you started with.

you can also replace cells with bilocations rather than bivalues, like you can then replace 9r1c1 with 9r1c13 in block 1 (i.e. get rid of all other 9s in block 1) and you still get a unique solution, and then replace 6r3c3 with 6r13c3 similarly

finally i can then replace 5r3c5 with 345r3c5+5r3c89. am on phone right now otherwise i'd show the full modified pm grid

the resulting puzzle after these 5 modifications is rated se 12 to get the first number but i spent a few hours stepping through the puzzle and there are a lot of se 12 steps but no 12.1 is reasonably in sight. i can't remove another clue because then se would yell at me that it's only got 16 clues and won't do any processing beyond dynamic chains

i'll take a closer read of your sukaku related stuff in the interactive games forum but it looks interesting for sure, i'll comment on it in a while

also if se is this pathetically slow at rating puzzles at this level then what we really need is a pencilmark version of skfr instead. anyone up for it?
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Re: The hardest sudokus (new thread)

Postby 1to9only » Sat Aug 10, 2019 4:56 pm

coloin wrote:
Code: Select all
+----------------------+----------------------+----------------------+
| 9      8      12345  | 7      346    1246   | 1234   145    235    |
| 7      1235   12345  | 12348  3489   12489  | 6      14589  23589  |
| 1234   123    6      | 12348  5      12489  | 123478 14789  23789  |
+----------------------+----------------------+----------------------+
| 1268   4      129    | 168    678    5      | 278    3      26789  |
| 12368  1236   7      | 9      3468   1468   | 5      468    268    |
| 3568   3569   359    | 3468   2      4678   | 478    46789  1      |
+----------------------+----------------------+----------------------+
| 123456 123567 8      | 56     467    2467   | 9      1567   3567   |
| 2356   235679 2359   | 2568   1      26789  | 378    5678   4      |
| 1456   15679  1459   | 4568   46789  3      | 178    2      5678   |
+----------------------+----------------------+----------------------+


coloin's version of 999_Springs's sukaku of champagne's 11.9/11.9/11.8 is rated by SukakuExplainer as ED=12.0/12.0/11.8.

I think tarek's nasty#1 sukaku here is at least a 12.6, as after a few hours I Ctrl-C'ed out of SE.
.
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Re: The hardest sudokus (new thread)

Postby tarek » Sat Aug 10, 2019 4:58 pm

999_Springs wrote:
tarek wrote:Translating what happens in a vanilla sudoku to sukaku; Removing a clue from a vanilla sudoku cell means that your actually adding 8 candidates to the pencilmark grid in that cell.

No need to test a Sukaku for difficulty unless it is minimal and therefore the potential of using already known difficult vanilla sudokus is huge.


um no actually you're adding way more than 8 candidates because you're also adding the value of the clue that you removed to all the cells that can see the clue.

for instance when i got rid of 5r7c4 i'm adding extra 5's to all cells in r7, b8 and c4 that don't already see a 5
This happens because many electronic solvers perform an automatic cleanup of the pencilmark grid when paste in a vanilla sudoku. This cleanup is a form of solving and what you did is correct in that environment. Disable this cleanup or Minimise (or should I say Maximise) the grid before making any alterations as an alternative.

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Re: The hardest sudokus (new thread)

Postby coloin » Sat Aug 10, 2019 6:00 pm

1to9only wrote:.....SukakuExplainer as ED=12.0/12.0/11.8..


Sukaku Explaner :!:

We better be careful to only abbreviate this to SKD=12.0/12.0/11.8 :oops:
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Re: The hardest sudokus (new thread)

Postby tarek » Sat Aug 10, 2019 6:09 pm

coloin wrote:
1to9only wrote:.....SukakuExplainer as ED=12.0/12.0/11.8..


Sukaku Explaner :!:

We better be careful to only abbreviate this to SKD=12.0/12.0/11.8 :oops:


:lol: :lol:

Reminds me of "South Exchange Street" :lol:
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Hello

Postby Ellenhip » Sun Aug 11, 2019 1:42 pm

Hello, thanks!
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Re: The hardest sudokus (new thread)

Postby denis_berthier » Sun Aug 18, 2019 8:44 am

999_Springs wrote:i was messing around with sudoku explainer's GUI and tried to make champagne's 11.9/11.9/11.8 hardest ever puzzle even harder by adding pencilmarks to known clues. in this puzzle the only clue that lets you add a candidate to it without invalidating the puzzle is 5r7c4, which can be replaced with (56).

The original (Sudoku) puzzle was: 98.7.....7.....6....6.5.....4...5.3...79..5......2...1..85..9......1...4.....3.2.;11.90;11.90;11.80;GP;champagne dry;1;22;
It is by no means the "hardest ever" puzzle. (SER is meaningful in computing hardness, but the next two measures are totally irrelevant.) See below for the real 3 hardest.
The modified (Sukaku) puzzle is: 98.7.....7.....6....6.5.....4...5.3...79..5......2...1..8(56)..9......1...4.....3.2., with the obvious () notation for the candidate-givens.
AFAIK, the above is the first example of a Sukaku derived from a Sudoku and harder than it in the SE rating. As there's some correlation between SER and my BpB classification - but no systematic correspondence - the natural question for me was: is it also harder in the BpB classification?

It's obvious that in any rational rating/classification system, this modified Sukaku should be at least as hard as the original Sudoku. But there's no reason why it couldn't be harder. More generally, although all the known Sudokus are in B7B, there's no reason why some Sukakus couldn't be in B8B or even higher in the classification.

As the original Sudoku is in B6B, is the derived Sukaku also in B6B or do we need to go to B7B or even any higher BpB? Such computations are very time consuming and there has been some suspense for me (the more so that, beyond B7B, there may be memory overflow problems if I had to go there).
- My first computations showed that it cannot be solved in B6B. This required 4 phases of T&E(B6) and a total of 970 candidates tried. (Remember that when the resolution state is changed during a T&E phase, a whole new phase must be tried, so that any candidate has to be tried several times. But it's the first time I see the need for 4 phases. Of course, this may not be meaningful, as the number of phases depends on the order the candidates are tried.)
- And the next computations showed that it can indeed be solved in B7B - a small disappointment: still nothing to see in B8B
Conclusion: The derived Sukaku is indeed harder than the original Sudoku puzzle in the BpB classification, but not beyond the hardest known B7B Sudokus.


A more interesting question for me would now be: can one find a Sukaku not in B7B?
First remember that we know only 3 Sudokus in B7B (and 2 of them have SER=11.8, not even 11.9)
..3....8..5....2.17...........5.8..6.9.12....8....3....6.9....5..4....7.....1.6.2 (eleven; 11.9 11.9 02.6)
.2...67..4...8......9.......3.....7.5.8....4..1.3....2....9..5....6.1..3...2..6.7 (eleven; 11.8 01.2 01.2)
5.......9.2.1...7...8...3...4.6.........5.......2.7.1...3...8...6...4.2.9.......5 (m_b_metcalf; 11.80 11.80 03.40)
They might be a good starting point for finding harder Sukakus (not speaking of the more general Sukakus, not derived from a single change in a Sudoku.)

dobrichev wrote:For even harder puzzles, SE gives up after thinking for 2-3 days.

Do you have such examples?
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Re: The hardest sudokus (new thread)

Postby tarek » Sun Aug 18, 2019 9:05 am

denis_berthier wrote:
dobrichev wrote:For even harder puzzles, SE gives up after thinking for 2-3 days.

Do you have such examples?

Hi Denis,
These are at the moment the most challenging Sukakus to rate.
They all share the same solution and they are all "Singles backdoor size 6" originally posted here

Code: Select all
.-----------------------------------------------------------------------------------------------.
| 35678     13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 12356789  137       123457    | 12389     12346789  1248      | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  123456789 12345678  | 1235689   1234569   123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  46789     12456789  | 1356789   13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     123456789 | 123569    12345679  12347     | 12345689  12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 123689    12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 35678     13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 123456789 137       123478    | 123689    12346789  1248      | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  23456789  12345678  | 1235689   1234569   123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  46789     12456789  | 356789    13456789  145789    | 23456789  146789    12456789  |
| 123689    12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     12345678  | 123569    12345679  12347     | 123456789 12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 23456789  12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       12456789  | 23689     12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 35678     13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 12356789  137       1234578   | 12389     12346789  12478     | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  23456789  12345678  | 1235689   1234569   123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  146789    12456789  | 356789    13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     123456789 | 123569    12345679  12347     | 12345689  12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 23689     12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 35678     13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 123456789 137       12347     | 1289      1234689   1248      | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  123456789 123456789 | 1235689   12345689  123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  146789    12456789  | 356789    13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     123456789 | 123569    12345679  123457    | 12345689  12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 23456789  12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 23689     12346789  12478     | 2356789   1379      12345789  |
| 1235689   12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 345678    13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 123456789 137       1347      | 123689    12346789  12478     | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  123456789 12345678  | 1235689   12345689  123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  46789     12456789  | 356789    13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     123456789 | 123569    12345679  123457    | 12345689  12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 23689     12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 356789    13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 12356789  137       123457    | 123689    12346789  12478     | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  12456789  12345678  | 1235689   12345689  123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  46789     12456789  | 1356789   13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     123456789 | 123569    12345679  12347     | 12345689  12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 23689     12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 356789    13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 12356789  137       123457    | 123689    12346789  12478     | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  12456789  12345678  | 1235689   1234569   123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  46789     12456789  | 1356789   13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     12345678  | 123569    12345679  12347     | 123456789 12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 123689    12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 356789    13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 12356789  137       12345678  | 123689    12346789  12478     | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  23456789  12345678  | 1235689   1234569   123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  46789     12456789  | 356789    13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     123456789 | 123569    12345679  123457    | 12345689  12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 23689     12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 35678     13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 12356789  137       123457    | 123689    12346789  12478     | 1235689   1         12345789  |
| 123456789 1234567   12345678  | 12345689  123456789 12345678  | 1235689   12345689  123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  46789     12456789  | 356789    13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     12345678  | 123569    12345679  123457    | 123456789 12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 23689     12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 356789    13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 12356789  137       123457    | 12689     12346789  1248      | 1235689   1         12345789  |
| 123456789 1234567   12345678  | 12345689  123456789 12345678  | 1235689   12345689  123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  46789     12456789  | 356789    13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     12345678  | 123569    12345679  123457    | 123456789 12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 123689    12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
.-----------------------------------------------------------------------------------------------.
| 356789    13456789  123456789 | 23456789  46789     12456789  | 123456789 13456789  145789    |
| 12356789  137       123457    | 123689    12346789  1248      | 123689    1         12345789  |
| 123456789 1234567   12345678  | 12345689  123456789 12345678  | 1235689   1234569   123456789 |
:-----------------------------------------------------------------------------------------------:
| 23456789  146789    12456789  | 1356789   13456789  145789    | 23456789  146789    12456789  |
| 23689     12346789  123456789 | 12356789  1379      12345789  | 12356789  12346789  12478     |
| 12345689  12346     12345678  | 123569    12345679  12347     | 123456789 12346     12345678  |
:-----------------------------------------------------------------------------------------------:
| 123456789 156789    12456789  | 123456789 12345678  1245678   | 2356789   13456789  123456789 |
| 12356789  179       1245789   | 123689    12346789  12478     | 2356789   1379      12345789  |
| 123569    12345679  123456789 | 12345689  12346     12345678  | 123456789 12345679  123457    |
:-----------------------------------------------------------------------------------------------:
User avatar
tarek
 
Posts: 2971
Joined: 05 January 2006

Re: The hardest sudokus (new thread)

Postby denis_berthier » Sun Aug 18, 2019 11:07 am

Hi Tarek
tarek wrote:They all share the same solution and they are all "Singles backdoor size 6" originally posted here

Thanks for the list. That's something I had totally overlooked when it was published.
I still have to write an input function for Sukakus. In the (only) example I solved above, I cheated by solving the Sudoku with no given in r7c4 and having the other candidates eliminated "manually" before starting.
Is there any "standard" line format for a Sukaku, such as e.g.
Code: Select all
35678 13456789 123456789 23456789 46789 12456789 123456789 13456789 145789 12356789 137 123457 12389 12346789 1248 123689 1 12345789 123456789 1234567   12345678 12345689  123456789 12345678 1235689 1234569 123456789

for the first in your list above.
This seems simpler than having to put parenthesis almost everywhere, as I did in the case of an easily modified Sudoku.
It also seems simpler than your 729 line format:
Code: Select all
..3.5678.1.3456789123456789.23456789...4.678912.4567891234567891.34567891..45.789123.567891.3...7..12345.7..123....891234.678912.4...8.123..6.891........12345.7891234567891234567..12345678.123456.8912345678912345678.123.56.89123456..9123456789.23456789...4.678912.4567891.3.567891.34567891..45.789.234567891..4.678912.456789.23..6.891234.6789123456789123.567891.3...7.912345.789123.567891234.678912.4..78.123456.891234.6...123456789123.56..91234567.91234..7..123456.891234.6...12345678.1234567891...5678912.45678912345678912345678.12.45678..23.567891.3456789123456789123.567891.....7.912.45.789123..6.891234.678912.4..78..23.567891.3...7.912345.789123.56..91234567.9123456789123456.891234.6...12345678.1234567891234567.912345.7..

Is there any problem with spaces in a line?

Another question about these puzzles: has anyone finally found a solution to compute their SER?
denis_berthier
2010 Supporter
 
Posts: 1275
Joined: 19 June 2007
Location: Paris

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