The New Sudoku Players' Forum

[claudiarabia]

Where can I find 18er Sudokus with 180° rotational Symmetry. I browsed the forum but the results were quite ample with many pages I can't overview at the moment. Has anybody such?

thanks for your help
Claudia

[ab]

here's one I generated:

Code: Select all

...|4..|...
..6|51.|...
.2.|...|7..
-----------
28.|...|...
.9.|...|.3.
...|...|.54
-----------
..3|...|.4.
...|.72|8..
...|..9|...


I got the pattern off the web somewhere, can't remember where, but some guy posted several sudokus with this pattern. This one is different from the ones he posted though

Also there's one at this link on page 20:
http://www.geometer.org/mathcircles/sudoku.pdf

[Ocean]

Where can I find 18er Sudokus with 180° rotational Symmetry. I browsed the forum but the results were quite ample with many pages I can't overview at the moment. Has anybody such?

thanks for your help
Claudia

This one also has both rotational and reflectional symmetry:

Code: Select all

[sym18]
 . . . | . . . | . 1 .
 . . . | . . 1 | . 2 3
 . . 4 | . 5 . | . . .
-------+-------+-------
 . . . | 6 . . | . 4 .
 . . 7 | . . . | 5 . .
 . 3 . | . . 2 | . . .
-------+-------+-------
 . . . | . 4 . | 6 . .
 8 2 . | 3 . . | . . .
 . 1 . | . . . | . . .

... but it's not minimal. This is the related 'almost symmetrical' 17 (isomorphic to one from Gordon's list of 17s):

Code: Select all

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

Code: Select all

Some minimal 18s with the same pattern (rotational and reflectional symmetry):

000000010000001023004050000000400050006000700030002000000070400820900000010000000 M18
000000010000001023004050000000600050007000400030002000000080700920400000010000000 M18
000000010000001023004050000000600070005000400030002000000070800820900000010000000 M18
000000010000001023004050000000600070005000800030002000000040600920800000010000000 M18
000000010000001023004050000000600070006000400030002000000070600820400000010000000 M18
000000010000001023004050000000600070008000400030002000000080700720400000010000000 M18
000000010000001023004050000000600070008000900030002000000040600920500000010000000 M18

[claudiarabia]

[quote="ab"]

Code: Select all


...|4..|...
..6|51.|...
.2.|...|7..
-----------
28.|...|...
.9.|.6.|.3.
...|...|.54
-----------
..3|...|.4.
...|.72|8..
...|..9|...


thank you for this nice pattern. It has two solutions as I found out. Thus I changed it a bit. I added a 6 in the center and now it is one-way-defined.

With best regards
Claudia

[ab]

Code: Select all


...|4..|...
..6|51.|...
.2.|...|7..
-----------
28.|...|...
.9.|.6.|.3.
...|...|.54
-----------
..3|...|.4.
...|.72|8..
...|..9|...


thank you for this nice pattern. It has two solutions as I found out. Thus I changed it a bit. I added a 6 in the center and now it is one-way-defined.

With best regards
Claudia

It only has one solution, you don't need the extra clue in the middle.

If you think otherwise post your solutions here

more links for you:
http://www.csse.uwa.edu.au/~gordon/sudokupat.php?cn=8
http://forum.enjoysudoku.com/viewtopic.php?t=1150&highlight=symmetric+18s

[claudiarabia]

Thank you Ocean,

yes, Gordon's list is realy treasurous. I'll check it out and I'm very happy about your nice figures. It looks like a fly. I'm fascinated by outspoken figures in Sudokus.

With best regards
Claudia