[Kde-games-devel] Killer Sudoku / Mathdoku

[Ian Wadham]

Hi Richard and Ronald,

On 06/04/2015, at 7:59 PM, Richard Llom wrote:
> Ian Wadham wrote:
>> On 25/03/2015, at 5:43 AM, Ronald Ellison wrote:
>>> 
>>> 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.

You will be pleased to hear that I have added Mathdoku and Killer Sudoku
to KSudoku, with a DLX (Dancing Links) solver.  The Mathdoku is working
quite well, with sizes 3x3 up to 9x9, selected in the Settings dialog. It still
needs some user-friendly messages to be added, plus a little "tuning" to
ensure that the puzzle generator always behaves itself.

There is a 4x4 Tiny Killer, but the full 9x9 Killer Sudoku is on hold until I
can get it to generate more realistic and interesting puzzles.  They are far
too hard ATM - too many possibilities and not enough leads, even when
using "rule of 45", "innies", "outies" and other tips.  Also, the KSudoku
graphics and themes are going to need work in order to display square
3x3 blocks and cages simultaneously without looking messy.

The source code has been committed to the KSudoku repository master
branch and I expect it will be released in August in the KDE Applications
15.08 release, see
https://techbase.kde.org/Schedules/Applications/15.08_Release_Schedule

> Actually "Killer" Soduko is just subset/variant of KenKen:
> https://en.wikipedia.org/wiki/KenKen
> Due to trademark issues this is often available as Mathdoku (which is also a 
> more fitting name, IMHO), e.g.
> https://play.google.com/store/apps/details?id=net.cactii.mathdoku
> This app is open source and the source is here:
> https://code.google.com/p/mathdoku/source/browse/

That Java code was a good source of ideas, as well as some other code
I found for DLX solvers.  Thanks, Richard.  Nobody seems to have a good
algorithm for predicting the difficulty of a generated Mathdoku or Killer
Sudoku puzzle - or if they do, they are not publishing it… ;-)

All the best, Ian W.