Sudoku

Great fun but very frustrating at times. I get them from here.

I enjoy sudoku and after a bit of practice can now solve even the fiendish level ones in the Times. This can come in handy if you get stuck.
John

quote:

Originally posted by TomK:
Great fun but very frustrating at times. I get them from here.

Your not kidding!!!
I picked up a book of them at the airport and was doing fine at the easy ones, but now pride is taking over and im trying to crack some of the 'evil' ones...

I might just use your link John!

Cheers

Hawk

How many pre-filled boxes are required for the solution to be unique? I'm doing a couple at the moment and I've been through all the usual processes i.e. checked columns, rows, inner squares etc against each other and I'm at the stage where I think I'm going to have to start guessing which I don't like.

quote:

How many pre-filled boxes are required for the solution to be unique? I'm doing a couple at the moment and I've been through all the usual processes i.e. checked columns, rows, inner squares etc against each other and I'm at the stage where I think I'm going to have to start guessing which I don't like.

Tom,
That is a difficult mathematical problem that I don't believe anyone has solved. The computer simulations however, have never found a solution with fewer than 18 starting numbers. Have a look at the link in my earlier post. If you enter the numbers you have been given you can analyse whether the puzzle has a unique solution or indeed any solution at all.
John

quote:

Originally posted by Hawk:
I picked up a book of them at the airport and was doing fine at the easy ones, but now pride is taking over and im trying to crack some of the 'evil' ones...

I started, about two months ago, doing whichever type was in that day's Times, which meant that some of the first few I did were "difficult" and "fiendish" ones. However, I find the harder ones too much effort - I often take half an hour or more, or go wrong somewhere - so I collect them, and only do them when I've run out of easy and mild ones.

I can't decide which strategy is best for improving one's speed most efficiently, but focusing on the easier ones is a novel approach for me, and I'm hoping it will prove more effective than my usual approach to things...

Someone said that Carol Vorderman can solve a "difficult" one in ten minutes - I don't think I've ever solved a "difficult" one that quickly...

I'm seriously into crosswords, like, I suspect, many folk who are getting into Sudoku, and tend to do both late at night accompanied by a beer or two and a dram or two, headphones on. I'm finding a fundamental difference between the two though as a slight alcoholic relaxation helps to ease the inhibitions and the crossword solutions sometimes come a bit easier but the slightest lapse in concentration is fatal for Sudoku. How annoying is it to be approaching the completion and find that you can't avoid putting two fives in the same row? For me there's no way back at that point.

quote:

Originally posted by TomK:
I'm finding a fundamental difference between the two though as a slight alcoholic relaxation helps to ease the inhibitions and the crossword solutions sometimes come a bit easier but the slightest lapse in concentration is fatal for Sudoku.

Usually, I find it difficult to concentrate on any type of activity that is new to me, so I've learnt to work in a way that accommodates my poor concentration. My biggest problem is that I run out of mental energy very easily - again, particularly with a new type of activity - so I only do difficult ones when I'm feeling particularly energised.

quote:

How annoying is it to be approaching the completion and find that you can't avoid putting two fives in the same row? For me there's no way back at that point.

If I make a mistake I just stop. It teaches me not to make mistakes!

BTW, I started by writing useful information in the squares, as suggested, but found I was making most of my mistakes in doing this. Now I write nothing but the answers. This may be an inferior strategy, in the short term, but it exercises one's brain more and seems to suit these carefully designed sudoku, which never seem to reach the level of logical complexity to need it (as opposed to benefit from it). Anyway, if I'm still as slow as I am now in a year's time then I'll know I was wrong to think it was the best long term strategy...

Myself and a colleague had a competition to write a spreadsheet to solve these puzzles.

I won

It's amazing that everyone is playing these, everytime I get a train to london I see at 2 epople with the books.