17-clue and 18-clue Sudoku update

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

Re: 17-clue and 18-clue Sudoku update

Postby StrmCkr » Tue Sep 27, 2022 1:59 pm

This one was posted on redit this morning apprently it might not be in the list of 17s any one care to check

000035080209000000000000000700200000080000030000006000600900200050080000000000407
Some do, some teach, the rest look it up.
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Re: 17-clue and 18-clue Sudoku update

Postby JPF » Tue Sep 27, 2022 3:27 pm

Not new

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Re: 17-clue and 18-clue Sudoku update

Postby StrmCkr » Tue Sep 27, 2022 4:23 pm

Thanks for checking
Some do, some teach, the rest look it up.
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Re: 17-clue and 18-clue Sudoku update

Postby WosRet » Sat Feb 04, 2023 9:51 pm

Hello.
Can someone please confirm this 17 clue sudokus as new ones?
Thanks in advance.
Code: Select all
...4...89.56......7..2............7..3.1...........56.....78.......6.....1......3 # 49159
...4...89.56.....27...............7..3.1...........56.....78.......6.....1......3 # 49160
..3.5.7............8.1..........4..1...8.2..49.5............5...1...8.........93. # 49161
...4....9..6.8...27......5........7..3.1...........86.....75....1......3....6.... # 49162
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Re: 17-clue and 18-clue Sudoku update

Postby eleven » Sat Feb 04, 2023 10:04 pm

There are no new 17 clue sudokus at all, see here. Don't waste your time.
[Added] in the 17 clue list i have they are equivalent to
Code: Select all
23847:..............1..2..3.4..5.......64..1.7......7.8.2......2....1..4......5.6......
34844:........1.......2...3..4........35...6.......12......7....7.......21..6...4...8.9
35709:........1.......2...3..4..5.....36...5.......21....7......7.......12......4...89.
35716:........1.......2...3..4..5.....36...7.......12...........5.......21.7....4...8.9
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Re: 17-clue and 18-clue Sudoku update

Postby WosRet » Sat Feb 04, 2023 11:19 pm

Ok. Thank you for the check.
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Re: 17-clue and 18-clue Sudoku update

Postby denis_berthier » Mon Mar 04, 2024 6:55 am

.
What's the latest update to the collection of 18-clue puzzles (preferably in minlex and still better in solution-minlex form)?
.
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Re: 17-clue and 18-clue Sudoku update

Postby coloin » Tue Mar 05, 2024 3:43 pm

Unfortunately the main collator of the project was Mathemagics who sadly is no longer with us. here

One of his last posts on the LCT-18 project was here ....
The end of the low/Hi clue thresholds thread was his last comment on the subject
Mathemagics wrote: The current 18C grid count is 635,256,482.

The estimated number of grids with an 18 is ~ 960 million. Collating those puzzles and grid solutions was a pretty good achievement.

Over the years contributors have searched for 18 clue puzzles of varous distributions.
In an 18C puzzle there has to be at least 6 clues in one of the 6 bands and in one of the 6 diagonal boxes !
There is a range of 18C puzzles with 6 clues in all bands. Of these there can be 2 clues in every box which was investigated very nicely here
There is a range of 18C puzzles with maximum number of clues in one ot the 6 diagonals [ 6-13] here

And these 18C puzzles from their respective template were not easy to find by our homework team !
Code: Select all
+---+---+---+        +---+---+---+             
|...|...|...|        |...|...|...|             
|.xx|xxx|xx.|        |...|1..|2..|             
|.xx|xxx|xx.|        |.3.|..4|.5.|             
+---+---+---+        +---+---+---+             
|.xx|...|xx.|        |..2|...|6..|             
|.xx|...|xx.|        |.4.|...|.7.|             
|.xx|...|xx.|        |..8|...|1..|             
+---+---+---+        +---+---+---+             
|.xx|xxx|xx.|        |..1|2..|8..|             
|.xx|xxx|xx.|        |.5.|.37|.4.|             
|...|...|...|        |...|...|...|             
+---+---+---+        +---+---+---+    18C   JPF                                                 
                                               
+---+---+---+        +---+---+---+             
|...|...|...|        |...|...|...|             
|...|...|..x|        |...|...|..9|             
|.xx|xxx|xx.|        |..6|.34|7..|             
+---+---+---+        +---+---+---+             
|.xx|xxx|xx.|        |..7|.9.|...|             
|.xx|xxx|xx.|        |.65|..7|1..|             
|.xx|xxx|xx.|        |...|.2.|.3.|             
+---+---+---+        +---+---+---+             
|.xx|xxx|xx.|        |...|5.1|68.|             
|x..|...|...|        |2..|...|...|             
|...|...|...|        |...|...|...|             
+---+---+---+        +---+---+---+   18C   blue                                           
                                               
+---+---+---+        +---+---+---+             
|...|...|.xx|        |...|...|..1|             
|...|...|.xx|        |...|...|.23|             
|...|..x|...|        |...|..4|...|             
+---+---+---+        +---+---+---+             
|xxx|xxx|x..|        |5..|..6|4..|             
|xxx|xxx|...|        |2..|...|...|             
|xxx|xxx|...|        |37.|.89|...|             
+---+---+---+        +---+---+---+             
|xxx|xxx|...|        |...|.2.|...|             
|xxx|xxx|...|        |..1|37.|...|             
|xxx|xxx|...|        |.48|...|...|             
+---+---+---+        +---+---+---+   18C   JPF
Last edited by coloin on Wed Mar 06, 2024 9:52 pm, edited 1 time in total.
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Re: 17-clue and 18-clue Sudoku update

Postby denis_berthier » Tue Mar 05, 2024 4:45 pm

Hi Coloin

Thanks for your answer,
960 M would be about 75 GB (non compressed), much too large for any place on the web. I wonder if anyone is still keeping them now.
I found a 2M collection by gsf or JPF (I lost the link).

My idea was as follows.
I've shown long ago that the mean complexity of minimal puzzles increases slowly with the clue count (however, with large variations for each fixed clue count).
For the 49,158 17-clue puzzles, the situation is very simple: they are all in T&E(0 or 1) and the hardest has relatively low W rating = 8.

I wondered if there could be 18-clue ones in T&E(2) - and indeed the answer is yes. I found 4 (in the 2M) , with their BpB classifications:

Code: Select all
..3....8..5.1....6.....2....6.7..9.......3.....4..8................34.2.91.6.....; B1B
..345............6..9.2.....7...13.8.6.............5..5......2......84...1...7...; B1B
1..........7..9..36.....45......8.........61..9...3....3....897.............6.1..; B1B
............1.92...6......4.7..4.............8.1..59...4..6...7..9........2..1..6; B2B


I now have no doubt larger values of p could be obtained with the 960M collection.
.
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Re: 17-clue and 18-clue Sudoku update

Postby m_b_metcalf » Tue Mar 05, 2024 5:42 pm

Does this one also qualify?

Code: Select all
..............1..2..3.4.56............753.....2......8......3...1..5.7...8...2..1


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Re: 17-clue and 18-clue Sudoku update

Postby JPF » Tue Mar 05, 2024 6:19 pm

Mike wrote:Does this one also qualify?
Code: Select all
..............1..2..3.4.56............753.....2......8......3...1..5.7...8...2..1

Ah, yes, an excellent puzzle featured in this list! :)

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Re: 17-clue and 18-clue Sudoku update

Postby denis_berthier » Tue Mar 05, 2024 7:18 pm

m_b_metcalf wrote:Does this one also qualify?
Code: Select all
..............1..2..3.4.56............753.....2......8......3...1..5.7...8...2..1

Yes, it's in B2B.
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Re: 17-clue and 18-clue Sudoku update

Postby blue » Fri Mar 08, 2024 6:11 am

Hi Denis,

I posted an extension to JPF's list, here.
Would you post the BpB ratiings for the ER=10.x cases, please ?

Cheers.
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Re: 17-clue and 18-clue Sudoku update

Postby denis_berthier » Fri Mar 08, 2024 7:13 am

blue wrote:Hi Denis,
I posted an extension to JPF's list, here.
Would you post the BpB ratiings for the ER=10.x cases, please ?.

Hi Blue
Nice to see you here; it's been a long time.
Here are the results for the two lists, in the same order. BpB = 0 means that the puzzle is in T&E(1).

You can see that:
- the max value of p in both lists is 2,
- it is reached in your list much more often than in JPF's,
- it is not restricted to the highest SER values (which was to be expected, as there's only a very vague correlation between SER and BpB).

Code: Select all
;;; JPF
2
1
1
1
1
1
1
0
1
2
2
1
0
1
0
1
1
1
2
1
1
0
0
1
1
1
0
0
1
0
1
0
0
0
1
1
1
1
0
0
0
0
1
0
0
0
0
1
1
;;; blue
2
2
2
2
2
2
2
2
2
2
2
2
2
1
2
2
2
2
1
2
2
1
1
1
2
2
2
1
2
2
2
2
2
2
2
2
1
1
1
2
1
1
1
2
2
1
2
1
2
2
1
1
2
1
2
1
1
1
1
1
1
1
1
1
2
1
2
1
2
2


BTW, do you have any reference to a list of 2,000,000 18c. I copied it from somewhere, but I can't find it again.
.
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Re: 17-clue and 18-clue Sudoku update

Postby blue » Fri Mar 08, 2024 8:29 am

denis_berthier wrote:Here are the results for the two lists, in the same order. BpB = 0 means that the puzzle is in T&E(1).

You can see that:
- the max value of p in both lists is 2,
- it is reached in your list much more often than in JPF's,
- it is not restricted to the highest SER values (which was to be expected, as there's only a very vague correlation between SER and BpB).

Thank you.
I thought the 10.3 might rate a little higher, after looking at the "after singles" PMs, but nope !

denis_berthier wrote:BTW, do you have any reference to a list of 2,000,000 18c. I copied it from somewhere, but I can't find it again.

I don't, sorry.

I have a big list, locally, with ~1.5G puzzles in it.
I extracted all of the T&E(2) puzzles from it, but there were only 780 of them.
Close to half of them were solvable with basics ... due to the bit with naked triples, I think.
I could put that list in a post, if you like ... FWIW :(
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