[Kde-games-devel] [kde-doc-english] Killer Sudoku and appearance

[Ian Wadham]

Hi Ronald,

On 25/03/2015, at 5:43 AM, Ronald Ellison wrote:
> Hi Ian. Thanks for your reply. When I used Windows I bought a program called SudokuTiger. This has Sudoko 9x9, 16x16 and Killer Sudoku. It has several appearance options and one is that all numbers look the same. Another option disables any background highlighting. I find that this is the least distracting appearance.
> 
> I still have SudokuTiger and it does run under Wine but I can't save settings and it eventually crashes.
> 
> I appreciate all the work that has gone into making your program look and work as good as it does but couldn't you undo the colour changes just by having an option to turn stuff off rather than do something new? My ideal setting would be your Scribble mode with options to turn the background highlighting off and have the input numbers look the same as the original. No change to the functionality, just the appearance. Really a super simple version with just the numbers and the grid. The wrong numbers ringed red already exists and could work unchanged. 
> 
> I have a small amount of experience with C but not C++. I don't think I'm up to this standard at all.

I have no plans to work on KSudoku in the near future.  So please post your request
for uniform styling of numbers as a Wish List item on the https://bugs.kde.org website.
That way it will be remembered if/when anyone _does_ get around to doing some
maintenance on KSudoku.

> If you have access to the Times Web page they have a daily interactive Killer Sudoku puzzle and there is another similar interactive online version here
> 
> http://killersudokuonline.com/play.html?puzzle=D34b3vy2894&year=2013
> 
> This puzzle brings simple maths into Sudoku and I find it the most addictive of all.

I have done some Googling around re Killer Sudoku and I must say it does pose an
interesting design and programming challenge.  The problems are to find a Killer
Sudoku generator, an accurate difficulty grader and a Killer Sudoku solver.

Naturally, KSudoku always "knows" the solution of the current puzzle, but the last
item would be needed to Check a Killer Sudoku if it is entered in, to find whether
a generated Killer Sudoku has a unique solution and to assess what its level of
difficulty might be.

It is easy enough to generate a square of 9x9 random numbers that satisfy Sudoku
rules and that is what KSudoku already does.  That becomes the known solution.
The same method could be used for the first step of generating a Killer Sudoku.

Currently KSudoku then generates a Sudoku puzzle by starting with an empty square,
inserting or removing numbers taken from the known solution, solving the resulting
puzzle and stopping when the solution is unique and equals or exceeds the user's
chosen level of difficulty.

The problem with Killer Sudoku is how to fill the puzzle with "cages" so that there
are not too many of size 1 or 2 and not so many larger cages as to make the puzzle
too hard to solve or above the user's selected difficulty level.  I believe there is also
a convention that no cage should contain more than one instance of a number.

I do not (yet) know the answers to these questions and have not found much public
information on them.  Nor have I found any Open Source Killer Sudoku algorithms.
That leads me to think that adding Killer Sudoku to KSudoku would be quite a lot
of work.  And I do not have time for it at the moment.

Again, please submit a (separate) Wish List request on bugs.kde.org for Killer Sudoku.

Meanwhile, please try some of the many variants in KSudoku.  I can recommend
Aztec, XSudoku and Samurai.  Each has its own unique flavour.

Cheers, Ian W.