Sudoku (Part 1)

A few weeks ago, I made some observations about things that people do on the train. If you would normally do something like a Sudoku puzzle, then I can suggest another intellectual pursuit that you can do if you only have a pencil and the back of an envelope (or that paperwork that you don't feel like doing any more).

You can try to build your own Sudoku.

For the next few posts I am going show you an approach to doing just this. These will not be definitive 'how to' tutorials - just a few things that you can play with in order to get going. Perhaps if you have some insights, or ideas, you could share them by posting a comment.

In this first entry, we will look at the matrix, a 9x9 grid.

In this post and in all the later ones, the letters a-g will be used instead of numbers. The reason for this is that this makes notation easier for me, and will have the bonus that when you set the problems for other people, you could set a, for example, to be any of the numbers from 1-9. The starting grid will always be the left-top one, and the letters will always be arranged as shown:

(This is just my preference - playing around with different starting positions, could probably be a whole hour of fun on its own!)

The most facile matrix is made simply by moving entire mini-rows...

... and mini-columns.