I was first attracted to these puzzles when I was co-writing the helpdesk
pages for PC Plus magazine with the late Wilf Hey - he was also writing
Wilf's Programmer's Workshop. Wilf looked at the problem with a view to getting
some copy for the magazine about alogorithms - I looked at is as an interesting
puzzle so the first thing I did was look at the methods that I used to solve them
and then write a solver. With a solver, you can then write a program that fills
the grid and then adds random pairs of symmetrically positioned clue cells (or
the centre cell on its own) until you get a puzzle that can be solved by the solver
that I wrote.
This is how it is done here. Every day, I put a brand new, unique, symmetrical Sudoku
puzzle on this web site for you to print out and solve - the page with the last four
on it is more economical with paper.
Of course, the problem is entirely one of logic - there is no maths involved so it would
come as no surprised to find out that you don't need numbers at all. You can use any
category of squiggle that has at least nine shapes and with that in mind, letters of the
alphabet can be used - any nine letter word with all of the letters different.
It really doesn't matter to the COMPUTERS that are
the puzzles because the production
are independent of even the
sets. However, it seems that it is the number set that
perhaps because people are
the Latin numbers which pretty much everyone recognises.
of other systems has happened
but seems to have been treated as an
because it lacks
with the common man/woman.
Instead of Latin numbers, you can make the puzzles more difficult by
using an alternative number set so I have produced Sudoku puzzles
using the Gurmukhi numbers. Now, it is not imediately obvious which
charaters are missing from any row, column or 3x3 square - unless
you are from Punjab, of course.
The limit with 9 characters is clearly that we use base ten
and excluding zero (people generally don't start counting with
'zero', they use 'one') you have nine recognisable characters.
With words, you have 26 to choose from in the latin alphabet and
if you are going to insist that it is made from a word, there
aren't many to choose from - one at fifteen letters in the
Dictionary I use - and you might find that the idea was
Another problem with using letters is that you need to avoid accidentally
creating puzzles with built-in profanity so that needs checking as well.
With numbers, you are probably not going to get somebody complaining that
you have put their phone number in there.