[Kde-games-devel] ksudoku and kde-games

[Ian Wadham]

From: "Johannes Bergmeier" <Johannes.Bergmeier at gmx.net>
> I had the same problem when i began working on ksudoku.
> so i decided to replace the "push checkpoint" and "pop
> checkpoint" with a simple undo/redo history.
> 
Errrmm ... undo/redo would be useful sometimes, but it is
usually fairly easy to undo a recent mistake.  "Push checkpoint"
and "Pop checkpoint" are a bit different and are very helpful
in the "Diabolical" level of Sudoku.

There are some puzzles where you get to a point when all
you can do is choose at random between two alternatives.  At
this time you "push a checkpoint".  Then you pick an alternative
and play on.  If you get to an impossible position, you "pop a
checkpoint" and try the other alternative.  This kind of thing is
tricky to do in paper Sudokus, so is a valuable part of the
computer version.  Really difficult Sudokus can have several
branch points of this kind.

IIRC the "push checkpoint" does not save your small
"pencilled" numbers, which is rather annoying, especially
in a "Diabolical" puzzle.  Also, the final (maybe the only)
"pop checkpoint" gets you back to the start of the puzzle,
which would be a handy way to implement Restart.

I guess undo/redo with some positions "marked" could
be a way to implement.  Then you could have functions
like "Mark this position", "Go back to mark" and "Go
forward to mark".

All the best, Ian W.