View Full Version : Sudoku

SilsoeSid

14th May 2005, 08:22

The latest craze to hit the streets.

All you have to do is insert numbers in the boxes to satisfy only one condition: each row, column and 3x3 box must contain the digits 1 - 9 exactly once.

Just a numerical logic puzzle?

http://www.griffiths-jones.co.uk/sudoku/http://www.griffiths-jones.co.uk/sudoku/img/today.png

(Hopefully this pic will update daily).

There are books and all sorts out there.

However, surely there must be a finite number of puzzles.

But how to work out how many puzzles there are. :confused:

:confused::confused:

3x3 grid = 729

9x9 grid = 387420489

:confused::confused:

The point of this post;

Will sales of books last 'til Christmas?

(40 puzzles per book)

oh yes - I love these ! - so simple - beautiful puzzles.

Being a sad geek I even wrote a computer program to solve them - it still can't do the 'fiendish' ones though.

10002level

29th May 2005, 16:25

I am amazed that this has not brought more of a response. An excellent was of passing the time on the flightdeck. You can buy books of sudoku puzzles (The Times is on book 3 I believe) or download your own copy of the software from www.sudoku.com

The are also progs for sale on ebay which are cheaper, but I have no experience of these.

SilsoeSid

29th May 2005, 18:25

Just to remind you that the puzzle on the first post will update daily. :ok:

I ignored them for ages, lead to believe only Cambridge engineers played them ... did one on a train ... now addicted!!

Question is - will it aid my OASC / AIB application?? ;)

joe2812

29th May 2005, 19:43

Fiis i'm with you on that! Give it a few years and it'll probably be a Cranditz test!

Good site is http://www.mousebreaker.com/games/sudoku/play.php as it changes daily and allows you fill in numbers and possibilities. I've only managed one so far :(

I know it's not really "maths" as such but on the Fiendish ones (I can only do Difficult so far, quickest is 30 mins) the whole thinking ahead and working out the possibilities makes them eligible in some ways, I think.

Either way ... probably worth doing a few to get the grey matter working :rolleyes:

My results are patchy to say the least. I managed all but one of the Independents offerings on Friday; the quick one on the back page, the advanced and intermediate ones, and the comp one. The one which beat me was the elementary one. However, the day before, I only completed one.

I hope too that continuing to do these puzzles will help refine the processes in the Loki brainbox.....either that , or it will f**k things up completely.

mbga9pgf

30th May 2005, 00:41

being a lifelong crossword fl'id I am delighted that a similar numerical puzzle exists!

Dimensional

30th May 2005, 10:26

I ignored them for ages, lead to believe only Cambridge engineers played them

Hey! We have to avoid lectures somehow...;)

...busted, Fii... :P

Onan the Clumsy

30th May 2005, 13:11

sir If you really were a sad geek, you'd do it in hex :E

===

not that I'm competative or anything, but...

36 mins :ok:

Yours swottishly etc etc

quote:

--------------------------------------------------------------------------------

I ignored them for ages, lead to believe only Cambridge engineers played them

--------------------------------------------------------------------------------

Hey! We have to avoid lectures somehow...

...busted, Fii... :P

Damn you wee mammoth!

I know you guys do no work unlike us hard working art types!

Stockpicker

30th May 2005, 20:15

So, anybody try the Samurai in the Times this weekend? (shines fingernails on lapel) :E

Jordan D

30th May 2005, 21:38

Stockpicker - I left it for the train journey I undertook yesterday (Sunday - bank holiday weekend, not clever) .... but gave up soon ... sooo bloody difficult.

Jordan

Onan the Clumsy

31st May 2005, 02:11

How many possibilities? (assuming a nine by nine grid)

The first row can be one of several possibilities, actually 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 = 362,880 if you're interested. (I can explain this if necessary, but it's pretty straight forward really)

For every first row there are a selection of possibilities for the second row. Take the firest column, any one of 8 numbers may be placed there (remember it can't match the number above it, so the number of possible second rows is 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 = 40,320

This is for each possible first row of course.

So extrapolating out it's pretty obvious that the number of possible grids is:

(9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1) multiplied by

(8 x 7 x 6 x 5 x 4 x 3 x 2 x 1) multiplied by

(7 x 6 x 5 x 4 x 3 x 2 x 1) multiplied by

(6 x 5 x 4 x 3 x 2 x 1) multiplied by

(5 x 4 x 3 x 2 x 1) multiplied by

(4 x 3 x 2 x 1) multiplied by

(3 x 2 x 1) multiplied by

(2 x 1) multiplied by

(1)

which of course id really

362,880 multiplied by

40,320 multiplied by

5,040 multiplied by

720 multiplied by

120 multiplied by

24 multiplied by

6 multiplied by

2 multiplied by

1

or...

1,834,933,472,251,084,800,000

So if everyone of the 200,000,000 people in the US did one of these puzzles every day, it would take

9,174,667,361,255 days to complete all of them

or to put it another way

25,136,074,962 years

To put iot another way, there are more possible solutions than there are atoms in the universe.

...unless of course, anyone knows better

Blacksheep

31st May 2005, 02:31

Why bother with sudoku when you can do a reweigh, carry out the calculations and produce a revised weight and balance sheet? Just as much fun and the result actually has a practical use... ;)

Firestorm

31st May 2005, 07:04

Sudoko, otherwise known as Sadbloko. And yes, I attempt it, in the Telegraph most days :(

ukc_mike

31st May 2005, 13:06

For every first row there are a selection of possibilities for the second row. Take the firest column, any one of 8 numbers may be placed there (remember it can't match the number above it, so the number of possible second rows is 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1 = 40,320

For the second row the first three columns cannot contain any of the numbers in columns 1, 2 or 3 (similarily columns 4, 5 and 6 must all be different from columns 4,5 and 6 in the first row, and 7,8 and 9 different from 7,8 and 9 in the first row). For the third row the first three numbers cannot match any of the numbers in the first three columns of row 1 or 2).

So the formula for rows 2 and 3 start:

6*5*4 and 3*2*1.

The correct number of possible solutions will be much less than in the original post, but still a very large number

Onan the Clumsy

31st May 2005, 13:57

Good point. I knew there would be someone who could set me right.

10002level

2nd Jun 2005, 20:00

Stockpicker

So, anybody try the Samurai in the Times this weekend?

Yes. Managed in on the way down to Spain.

Jordan D

2nd Jun 2005, 20:09

10002 - was that before or after they published the answers!

*dives for cover*

Jordan

joe2812

2nd Jun 2005, 20:44

I ran 'sudoku' through Wikipedia (free encyclopedia, excellent site.

This (http://en.wikipedia.org/wiki/Sudoku#Mathematics_of_Sudoku) makes very interesting reading for those interested in the mathematics side of it!

Jordan D

2nd Jun 2005, 23:48

The Times - the newspaper that brought you Su Doku first. The rest: Go f*cku.

Jordan