So du you sue do ku?

Over the last week or two I've been introduced to, learnt how to play, created a spreadsheet to solve and now got somewhat bored with that infuriating Japanese numbers puzzle, Sudoku.

What is it? According to Su|do|ku.com:

"It's fun. It's challenging. It's addictive!"

Well, its actually fairly simple. Its a 9x9 grid filled so that every row, every column, and every 3x3 box contains the digits 1 through 9.

It's also, highly mathematical and logical (for full details you should take a look at the Wikipedia entry), that's why I thought a spreadsheet would be a great idea.

I started off with the obvious. Create the grid. Hmm. The next bit was basically the equivalent of using a pencil to solve it - put space above each grid cell for the numbers 1-9. That way you can just delete them when they're not available. But, hang-on, I thought. Couldn't I just write a formula to do that. Was a bit tricky.

You have to check every row column and cell to see which numbers can be placed in each cell. I then mapped them back into small cells above each square. To highlight options I showed cells with 2 numbers possible in amber and 1 number in green. The final bit was to store the initial numbers and highlight them in yellow. As an after thought, I'm now also highlighting the numbers for each column and row that only have one entry.

Sad thing is, with all this automation, most of the puzzles available online seem to easy. The owners of sudoku.com, Pappadom, erm, Pappacom, produce the puzzles for the Times in the UK, and they are FAR too easy. Even the Diabolical rated ones only have one logic puzzle in each. Solve that and everything else just rolls out.

The Telegraph has much more difficult puzzles, but the Fiendish ones tend to dead-end on logic and required trying a path to see if it causes problems. At least with the rules I've been able to work out so far. I'll try and post a few if I get chance...

Here's a screen shot of my excel solver...

I'll let anyone have a copy if you visit here and leave a comment with your contact info...