The New Sudoku Players' Forum

[JPF]

Are there any other symmetric 18-clues puzzles, or are these two the first to be published?

You should have a look here.

JPF

[gsf]

Do you mean sudokus with 17 clues and rotationally symmetric?
I scanned Gordon's list searching for sudokus that are equivalent to a pattern with 17 clues and rotationally symmetric, and none appeared.

Yes, that's what I meant. Thanks for doing the search. Are there any other symmetric 18-clues puzzles, or are these two the first to be published?

I have a background process (slowly) symmetrizing gfroyle's 22M 18s
symmetrization searches each puzzle for the highest order symmetry
in the first 1177855 there are 291 with diagonal symmetry and 409 with 180 rotational symmetry (both order 2)

[m_b_metcalf]

Are there any other symmetric 18-clues puzzles, or are these two the first to be published?

You should have a look here.

Thanks. That thread started the day I joined; I was clearly not paying attention .

Regards,

Mike Metcalf

[Pat]

Yes, but I was wondering about rotational (crossword) symmetry. And is something like the following conceivable?

Do you mean sudokus with 17 clues and rotationally symmetric?

I scanned gordon's list searching for sudokus that are equivalent to a pattern with 17 clues and rotationally symmetric,
and none appeared.

thanks for the update!

this had been known for the old list,
but as the list grows we do indeed need to re-check such stuff

[claudiarabia]

Code: Select all

. . 4 . . 5 2 9 .
. 8 . . 1 . . . .
. 3 . . 7 . . . .
. 1 . . 5 . . . .
. . 3 . . 2 . . .
. . . 4 . . 7 . .
. . . . 9 . . 8 .
. . . . 2 . . 1 .
. 7 1 8 . . 6 . .


SE 2,6 r8c5 can be omitted.

[m_b_metcalf]

r8c5 can be omitted.

But if r1,c3 -> 6 and r1,c7 -> 3, it becomes minimal. And then there's the venomous:

Code: Select all

 . . 7 . . 9 8 3 .
 . 3 . . 1 . . . .
 . 5 . . 8 . . . .
 . 1 . . 6 . . . .
 . . 9 . . 4 . . .
 . . . 2 . . 4 . .
 . . . . 3 . . 1 .
 . . . . 2 . . 6 .
 . 8 2 7 . . 9 . .  SE 7.1


Regards,

Mike Metcalf

[Mauricio]

Two snakes

The majority of the credit is to the creator of the pattern:

Code: Select all

. . 1|. . 2|3 4 .
. 5 .|. 6 .|. . .
. 7 .|. 8 .|. . .
-----+-----+-----
. 6 .|. 2 .|. . .
. . 9|. . 7|. . .
. . .|4 . .|8 . .
-----+-----+-----
. . .|. 3 .|. 5 .
. . .|. 4 .|. 6 .
. 1 3|5 . .|9 . .   ER 9.1

[claudiarabia]

r8c5 can be omitted.

But if r1,c3 -> 6 and r1,c7 -> 3, it becomes minimal. And then there's the venomous:

Code: Select all

 . . 7 . . 9 8 3 .
 . 3 . . 1 . . . .
 . 5 . . 8 . . . .
 . 1 . . 6 . . . .
 . . 9 . . 4 . . .
 . . . 2 . . 4 . .
 . . . . 3 . . 1 .
 . . . . 2 . . 6 .
 . 8 2 7 . . 9 . .  SE 7.1


Regards,

Mike Metcalf

Thank you very much. I was not patient enough to grade it up and make it minimal like this. Thanks also to mauricio. Never thought it will get a high rating like this.

Here is an upgrade of one of my first puzzles - the Loving hearts.
They aren't together anymore and r7c3 can be omitted too.

Code: Select all

. . . 1 . 8 . . .
. . 7 . 3 . 8 . .
. . 2 . . . 6 . .
6 . . 8 . 1 . . 5
. . . . . . . . .
1 . . 6 . 7 . . 9
. . 1 . . . 2 . .
. . 3 . 9 . 4 . .
. . . 4 . 5 . . .


SE 1,5

[claudiarabia]

Code: Select all

. . . 1 . 9 . . .
. . 7 . 3 . 8 . .
. . 2 . . . 6 . .
6 . . 8 . 1 . . 5
. . . . 9 . . . .
1 . . 6 . 7 . . 9
. . 8 . . . 7 . .
. . 3 . 7 . 4 . .
. . . 4 . 5 . . .


The loving hearts united. SE 4,5 2xy, UR type 1

Claudia

[Mauricio]

A variation of the two snakes

Code: Select all

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

Minimal loving hearts

Code: Select all

. . .|1 . 2|. . .
. . 3|. 4 .|5 . .
. . 6|. . .|2 . .
-----+-----+-----
7 . .|5 . 1|. . 8
. . .|. 6 .|. . .
3 . .|7 . 4|. . 2
-----+-----+-----
. . 5|. . .|3 . .
. . 9|. 3 .|4 . .
. . .|9 . 8|. . .    ER 8.5


[Mauricio]

More little variations of the two snakes, minimal.

Code: Select all

 . . 1 . . 2 3 . .
 . 3 . . 4 . . . .
 . 5 . . 6 . . . .
 . . 7 . 2 . . . .
 . . . 5 . 6 . . .
 . . . . 8 . 1 . .
 . . . . 9 . . 6 .
 . . . . 5 . . 8 .
 . . 3 8 . . 7 . .  ER 7.2


Code: Select all

 . . . 1 . 2 3 . .
 . . 4 . 5 . . . .
 . 5 . 6 . . . . .
 . . 7 . 4 . . . .
 . . . 5 . 3 . . .
 . . . . 8 . 1 . .
 . . . . . 7 . 4 .
 . . . . 9 . 6 . .
 . 3 1 4 . 6 . . .   ER 7.2


[JPF]

The loving hearts united. SE 4,5

or separated. SE 8,4 :

Code: Select all

 . 1 . 2 . . . . .
 3 . 4 . 5 . . . .
 6 . . . 7 . . . .
 . 2 . 4 . . . . .
 . . 1 . . 8 . 3 .
 . . . . 3 . 5 . 6
 . . . . 6 . . . 5
 . . . . . 7 . 8 .
 . . . . . . 4 . .



JPF

[Mauricio]

Helix I

Code: Select all

 . . . . . 1 2 3 4
 . . . . . . 5 . .
 . . . . . . . 6 .
 . . . . . 4 1 7 5
 . . . . 2 . . . .
 8 9 5 6 . . . . .
 . 3 . . . . 4 . .
 . . 9 . . . . . .
 7 2 6 9 . . . . .   ER 7.4


Can we eliminate r7c7?


Helix II

Code: Select all

 1 2 . . . . . . 3
 . . 4 . . . . . 5
 . . . 6 . . . 7 .
 . . . 3 . 5 2 . .
 . . . . 6 . . . .
 . . 7 4 . 8 . . .
 . 8 . . . 9 . . .
 2 . . . . . 1 . .
 3 . . . . . . 6 4   ER  9.0


[JPF]

Helix I

Code: Select all

 . . . . . 1 2 3 4
 . . . . . . 5 . .
 . . . . . . . 6 .
 . . . . . 4 1 7 5
 . . . . 2 . . . .
 8 9 5 6 . . . . .
 . 3 . . . . 4 . .
 . . 9 . . . . . .
 7 2 6 9 . . . . .   ER 7.4


Can we eliminate r7c7?

I don't know

here are some variations (easy puzzles) :

Code: Select all

 . . . . 1 2 3 4 .
 . . . . . . . 5 .
 . . . . . . 6 . .
 . . . . . 4 1 7 8
 . . . . 2 . . . .
 4 5 9 8 . . . . .
 . . 1 . . . . . .
 . 8 . . . . . . .
 . 7 4 5 9 . . . .



Code: Select all

 . . . . 1 2 3 4 .
 . . . . . . . 5 6
 . . . . . . 7 . 8
 . . . . . 1 . . 7
 4 . . . . . . . 2
 5 . . 7 . . . . .
 8 . 3 . . . . . .
 2 1 . . . . . . .
 . 7 6 3 4 . . . .



Code: Select all

 1 2 . . . . . . 3
 . . 4 . . . . . 5
 . . . 5 . . . 6 .
 . . . 7 . . 8 . .
 . . . . 6 . . . .
 . . 1 . . 2 . . .
 . 9 . . . 4 . . .
 8 . . . . . 2 . .
 7 . . . . . . 8 6



JPF

[Mauricio]

More on helices

Code: Select all

 . 1 . . . . . . .
 . . 2 . . . 3 . 4
 . 5 . 6 . . . 7 .
 . . . 8 . 5 1 . .
 . . . . . . . . .
 . . 4 9 . 2 . . .
 . 8 . . . 7 . 6 .
 1 . 3 . . . 4 . .
 . . . . . . . 9 .    ER 7.1