Su Doku Assistant V1.3

V1.3 is now available for download at:

http://www.stokepoges.plus.com

New features and enhancements are listed below.

Best wishes,

Alex Balfour

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Thanks to input from Tony Cooper, Joe Marshall and Giuseppe Matarazzo,
improved the code underlying the Su Doku Assistant's inbuilt strategy
for solving puzzles. Solution techniques added include X-Wings,
XY-Wings, Swordfish and Colouring. As a result, even fewer difficult
puzzles require the use of "Brute Force" for their solution.

In addition, following discussions with Giuseppe Matarazzo, "Brute
Force" has been considerably improved in terms of detecting when
partially completed puzzles will not lead to valid solutions. Brute
Force's ability to find unique solutions has also been strengthened.

Simplified the user interface by hiding many screen components until
required.

Added a "Show all possible values" option button to the main screen.
When solving a puzzle manually, choosing this option will simultaneously
display the possible values for all unfilled cells. This provides a very
powerful tool for supporting the manual solution of puzzles.

To use one of the values listed for a cell, simply left-click anywhere
within the cell and type the desired value. You may also edit a list of
values to remove entries by using the Backspace key.

The display of unfilled cell possible values is automatically updated as
you type in values for cells. Also, to make the lists of possible values
disappear at any point, click the "Off" button.

When solving puzzles manually, you may now choose between "basic
pruning" and "severe pruning" of the lists of possible values for
unfilled cells. By way of explanation, "basic pruning" simply ensures
that the values listed for any unfilled cell are legal, i.e. they do not
break the fundamental rule of Su Doku. "Severe pruning", on the other
hand, uses the full power of the Su Doku Assistant to drastically reduce
the number of possibilities for each unfilled cell.

If you are an inexperienced user, you will learn much more about solving
Su Doku puzzles manually by using the "basic pruning" option. On the
other hand, if you are an experienced user trying to solve extremely
difficult puzzles manually, "severe pruning" will get you more quickly
to the difficult solution stages.

Choosing "basic pruning" or "severe pruning is a "sticky" option, i.e.
your choice is remembered and subsequently re-used until changed.

Whenever a grid is loaded, the Su Doku Assistant now makes an implicit
backup copy.

When the "Store solution steps in a file" checkbox is selected, grid
cell pruning steps are now stored in the file History.dat in addition to
cell value insertion steps.

Added grid cell row and column numbers to support the easy
identification and description of individual grid cells. Suggested by
Giuseppe Matarazzo. For consistency, row and column numbers stored in
the solution history file History.dat are now in the range 1 to 9,
rather than 0 to 8 as in previous releases. Similarly, cell numbers
stored in the file KeyMoves.dat are now in the range 1 to 81, rather
than 0 to 80.

When solving a puzzle manually, the time taken so far is now displayed
on the main screen in the format hh:mm:ss and continuously updated
during manual solution.