Sudoku guessing
CaptainObvious_
Posts: 3,881 Forum Member
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Now I love Sudoku and like to think I'm quite good at them but I end up guessing placement of a number or two for the most difficult puzzles.
Is this something you are meant to do? (most likely not )or is there a way of doing as puzzle as normal?
Have you a tried and tested technique for when it seems impossible without guessing?
Is this something you are meant to do? (most likely not )or is there a way of doing as puzzle as normal?
Have you a tried and tested technique for when it seems impossible without guessing?
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Comments
You're right - you're not supposed to guess.
I find it helpful to write all the possible numbers (in small print) at the top of the box and then cross them out - 60% of the time, it works all the time.
Really depends on the setter. Some of the more complex newspaper ones (I think in the telegraph) could simply not be solved without guessing. I was quite annoyed when I found out you were expected to guess, sorry I mean bifurcate
But in essence the idea is to pick one of the squares with only two options. Choose one of them, solve the puzzle from that using pencil till you either complete or hit an error (at which point you know you should have chosen the other)
I meant bifurcate (see below
ah yes, this is what I have been doing, although I never seem to have a pen handy and I stopped doing the tiny numbers up in the corner of the box for some unknown reason
Good to know that it's actually a recognised technique and not just me being rubbish at Sudoku.
I have to be certain before I write it in. If I've got a square down to a possible two numbers I pencil them in little in the corner.
Edit: I see I'm so slow replying that the little numbers in corners has been covered already :cool:
I know someone who doesn't pencil in little numbers and I honestly don't know how she manages to complete them. I couldn't.
If you steadily go through each vertical number by number, then each horizontal and then each 9X9 box over and over again there is always at least one certainty.
I do the samurai sudoku in the times (5 overlapping sudoku in one puzzle) each Saturday and even in the most difficult ones (termed by them as fiendish) I've never had to guess.
Sorry.
I also do this over and over again but sometimes to no avail >:(
My ex husband used to do the little numbers in the top of the box thing and it drove me mad. One night he tried all night to tell me that there was no other way until I showed him painstakingly by doing it without guessing that it could be completed....
Sorry again.
I do it because, for example, if I know for sure two boxes in a line, or square of nine, are definitely, say, 2 or 7 and then I find a third square could be either 2, 7 or 9 I'll know that it must be 9 because my doodles will have told me so. Is this bifurcation?
Not even sure why I care so much.
This is a good strategy site.
Bifurcation is taking educated guesses I think and yes it includes doing the two numbers in a box thing until you decide which one it is.
The example you give is exactly how sudoku is solved (I remember the numbers that might go there rather than writing them in). Logic and patience. If you do it line by line and number by number there is never a 'chance' placing and there will always be somewhere else that a definite number goes that may then lead to your '2 numbers in box' by eliminating one of the numbers.
Hope that makes sense.
I'd agree with that - I've never had a problem with the times ones. That's why I was trying to remember which paper it was that cheats and I'm fairly sure it was the telegraph. It's been years mind so could have been the observer say
It does. That's how I do it. I'm in awe that you can remember the possible numbers.
Agree with your other post - sometimes you need to set it down and go back to it when you can't get any further. Every time I've done that I've immediately found a really obvious one that I had missed in my frustration.
I found this from Michael Mepham (Telegraph setter)
http://www.sudoku.org.uk/pdf/solving_sudoku.pdf
I think I've met you.
Can't get on with killer sudoku at all. I must be missing something. I think, "hmmm, let's write down all the ways you can get 19 with four numbers and eliminate the digits that can't be right" and discover almost every time that I haven't eliminated any digits at all.