Notice

I am no longer posting new puzzles to this blog. For all of my Sudoku puzzles, old and new, please visit Sudoku in another section of this website. I will still create and offer new puzzles, in batches of a couple of hundred, once a week or so.

Sudoku #40

Category: Sudoku
Wed, 03 Aug 2005, 09:19

First, for those who landed yesterday on Air France flight 358, welcome to Toronto!

During the past weekend, I added some improvements to my Sudoku program to generate puzzles with four-fold symmetry. There are several ways to have puzzles with four-fold symmetry. The first is four-fold rotational symmetry. That is, a puzzle that has the same pattern when rotated 90, 180, or 270 degrees.

There are also a couple of varieties of four-fold mirror symmetry. One type is reflection about both the horizontal and the vertical. Another is reflection about the two diagonals.

Of these types of symmetry, generating puzzles with four-fold rotational symmetry seems the fastest, with puzzles generated only a bit slower than with two-fold rotation symmetry. Mirror symmetry about the two diagonals is slower, and about the vertical and horizontal much slower still.

Todays puzzle features four-fold rotational symmetry. I rather like the appearance of this type of symmetry, so I may be doing more of this style of puzzle.

Hans

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

path: /Sudoku | permanent link to this entry

triangle