h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

...at http://www.urbanrim.org.uk/sudoku.htm

The claim that in a professionally set puzzle that there will always be an elimination possible is potentially flawed.

Anyone who has spent enough time tackling the Pappocom puzzles as printed in the Times and other papers will have worked out other methods which are not entirely based on elimination, atleast not in the straightforward way suggested at that site.

One method which, for lack of a proper name, I'll call 'The adding up of unknowns' is particularly useful. If, using horozontal slicing you know that a particular number can be in one of, say three squared in the top left box, and all of those three squares are in the first and second columns, and by similar techniques deduce that the same digit can also be in one of three squares in columns one and two of the bottom left box, then you know that that digit appears in the third column in the middle left box. That is one deductive leap that the elmination grid (which I had already created in OpenOffice .sxw format, if anyone wants it mailed to them, or I can do it in Word .doc format or .pdf) does not directly solve.

The really professionally created puzzle will cause all single solving methods to fail at some point, and only when used together will the puzzle unlock its secrets.

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I also note that the site example isn't symmetrical, as the Pappocom puzzles are.

I'd like a copy of your Open Office document please.

You're not making this easy. I need an email address to send it to.

There is an email address on my user page (click on 'Caveman, Evil Unix Sysadmin, ...' and send mail to the address hinted at there)

If you really can't work it out, perhaps I'll plonk it on a website somewhere.

Jim

Using only excel if statements and some conditional cell formatting, I managed to build my own su doku solving assistant.

I know there are dozens available for download but it passed the time.

A couple of checks which set alarms if you have the same number in a row, column or "small box" twice, and a final check which gives you a green box if you have completed the su doku correctly, means that there are 2540 calculations in all on the sheet.

With spaces to make it easier to keep track as it was built the spreadsheet is about 35 by 160 cells, and since it doesn't have a "reset" function I created a pristene duplicate sheet, but in excel the file its only 892kb, which isn't too bad.