“A Sudoku puzzle is therefore, in formal terms, a critical set for a gerechte design for the 9x9 grid partitioned into 3x3 subsquares.”
So says David Spiegelhalter in his very informative article Pure Randomness in Art which is based on a talk he gave at the recent John Cage exhibition in Kettles Yard gallery in Cambridge. It’s good to know.
It took me a while to get going on Sudoku – my initial reaction to The Times revival of the pastime in England was Boring – not a patch on the cryptic crossword, & definitely no jokes, but I started to get interested when I had to give up my habit of doing the crossword on the bus home – not enough light to read the very small print size of the clues.
I now need my daily Sudoku fix.
The craze has demonstrated once more the importance of practice & training & learning to know what is required of you – be that as a puzzle solver, a candidate for GCSE or A level, sportsman, musician, or anything else in which you want to succeed.
Gradually the Easy Sudokus have largely disappeared from the daily paper – we have moved on through medium, difficult, fiendish & now super fiendish.
I have tried to understand how the puzzles are given grades – the one thing I can say is that there is a lot of variation between different setters & publications. Some of the Super Fiendish I find laughably easy – easier than Easy in fact; once you find the pattern it all tends just to fall into place – there is even a definite rhythm as you fill in the squares, so that I can immediately feel it if I have made a mistake - another small indicator perhaps of the link between mathematical logic & music. Easy is boring, you just have to go round & round filling in the blanks, with no pattern for a guide.
I have read explanations of all this, but because they tend to be based on 'consider all the options & eliminate the ones that do not work', all that does is put my head in a spin – I really cannot cope with writing in all the possibilities & then rubbing them out. The secret is to look for the pattern & fill in each square only when you are sure.
Another tip is to try to find the key starting point(s) - diagonally opposite corners are good, sometimes the edges, sometimes the centre square; if you do get stuck, rub it all out & find a different starting point.
I also wonder if the Latin square approach offers a mathematical way of determining whether a given puzzle has a unique solution – I have come across several which do not.
