# ANN Sukodu puzzles--again

Jim Hurley jhurley at infostations.com
Wed Nov 2 08:55:51 CST 2005

```Our local paper has begun to carry a daily Sukodu puzzle. A friend
challenged me to solve one that he had trouble with. I couldn't find
a solution; I kept running into situations where I could find no
possible entry without guessing.

To work on it I loaded up Alex Tweedly wonderful Sukodu Assistant.
But I  needed something that would determine in there was a unique
one-stage solution, i.e. a solution in which there was always at
least one cell  with a determined digit, given the present
configuration.

Well, one thing lead to another and Sukodu--see below--resulted. It
uses Alex's very nice interface. The drop down menu is an excellent
way to enter this limited assortment of discrete data into a field.

The stack also does an analysis of the puzzle after each step and
will display in each cell the possible entries. It also looks at the
constraints on rows, columns, and blocks, to determine what's
possible in these components--applying the restriction that each row,
column and block are to contain all nine digits. This analysis is
displayed in separate fields.

If you choose the mode in which this info is displayed, the solution
to any puzzle will be trivial. But I found it a very useful tutorial
to run through a few of the harder puzzles this way. There were
strategies available which I had never guessed at. (You can toggle
the display of this analysis on and off with a right-click or
control-click. You can turn any  entry green with a shift-click. This
is useful if you have to make a guess. Then, if  you run into a
contradiction at some point down the road, you can undo back to the
green entry.)

When the puzzle is first loaded, the stack uses this analysis of
rows, columns and blocks to run through the puzzle (with the screen
locked) step by step to obtain a solution--if there is a one-stage
solution. With this solution available, it is then possible to choose
a mode of play which will not allow an incorrect entry into a
cell--comforting.

I have tested this in Mac OS X, but not thoroughly in Windows. I had
one stinker of a problem with the Window version. It read a menuPick
handler in a button which I had commented out, and did not pass the
menuPick message to the card. Took a while to find this bug.

Turned out that the puzzle my friend had given me was missing a
number. With friends like this----

The stack (and file folder) are at:

http://home.infostations.net/jhurley/SudokuFolder.zip

Keep the file folder with the stack. The folder contains a few