The New Sudoku Players' Forum

[Guest]

I've started Sudoku just this week and found it extremely addictive - so much that after completing the easy ones in the Times archive (26/4 onwards) I was desperate to play more and so I started on the fiendish ones. Had a stroke of luck and completed one. So desperate was I to play some more I went on to no. 130.

Now I'm truly stuck .... Need help!

987|536|412
643|172|895
251|849|763

51a|324|6a9
496|751|32a
a32|96a|541

a25|613|9a4
364|297|15a
179|485|236

a denotes 7 or 8.

Actually I completed most of the puzzle until I hit upon two 7s and two8s in column 8 and 9.

Where have I gone wrong?

Can't sleep now ....

[Guest]

r4c1 should be 7

r8c7 and r8c8 should be 5 and 8

Visit:

http://www.easysurf.cc/su-doku.htm

[Animator]

take a close look at row 8... you said a stands for 7 or 8, but row8 already has a 7....

[Guest]

Thanks!!

But how do I avoid this?

I mean, if one gets to the point where it seems only the last two digits in the whole puzzle don't fit, how does one go about finding out how far back to go to change ... am I making any sense?

Like, before your replies, I changed:

r8c9 to 8

but then r5c9 cannot be 7 either

So, eventually I decided that all 7s and 8s had to be changed in both directions. And that's what I posted in my query.

I did not see that r4c1 needed to be changed ...

Or, would it be best when one gets into this knot to erase everything and start again and hope not to make the same mistakes?

[Animator]

Well, you made some other mistakes...

http://www.timesonline.co.uk/article/0,,18209-1589284,00.html that's the solution of the puzzle... it isn't quite the same as yours...

If you make a mistake (as in, if you come at a point where no other move is invalid) then you basiccly need to restart... unless when you write down all your moves (so you can undo them)

[Guest]

No, I know I've got it wrong ...

But short of having to be told that r4c1 is 7 instead of 5 and/or checking it against the solution how do I investigate on my own without the aid of kind and helpful friends. I still can't fathom how far back to change my digits - without the benefit of the solution or clever friends, I might change digits in wrong cells and still not be any wiser!?

[Animator]

You can't...

If you fail to complet the puzzle (as in, if you end up with a cell that has no valid candidates) then you made a mistake at some point in solving the puzzle...

It is impossible to tell what mistake you made, or correct it... Why not? because if you make one mistake then you will use that number to eliminate candidates from other cells, which you shouldn't have eliminated.

This basically means that if you make one mistake you make a lot mistakes...

For exampe, r4c1 is not your only mistake, r6c7, r6c8 and r6c9 are also incorrect...

If you made a mistake then you need to re-start... (unless you spot it immediatly)

[Guest]

No, I know I've got it wrong ...

But short of having to be told that r4c1 is 7 instead of 5 and/or checking it against the solution how do I investigate on my own without the aid of kind and helpful friends. I still can't fathom how far back to change my digits - without the benefit of the solution or clever friends, I might change digits in wrong cells and still not be any wiser!?

Urh, that was wrongly posted as 'Guest' when it should have read midsummernight i.e. me!


I've been looking at my puzzle and looking at it and wondering how do 5 determine which other digits to rub out in order to finish it - I know I got it wrong but I only found out when I reached the last two two digits in columns 8 and 9. So, if I do not have access to the solution or this forum, can anyone help me to learn how to 'discover' the wrong digits input earlier that led me to the wrong last two digits? Or, am I not making sense anymore?

[Guest]

Urh, that was wrongly posted as 'Guest' when it should have read midsummernight i.e. me!


I've been looking at my puzzle and looking at it and wondering how do 5 determine which other digits to rub out in order to finish it - I know I got it wrong but I only found out when I reached the last two two digits in columns 8 and 9. So, if I do not have access to the solution or this forum, can anyone help me to learn how to 'discover' the wrong digits input earlier that led me to the wrong last two digits? Or, am I not making sense anymore?[/quote]


Thanks for your feedback Animator!
I posted the above before I saw yours - guess was still writing it when you posted ... but thanks a bunch anyway!

[Guest]

I am on the sixth effort with 130 and keep getting either two sixes or two eights in the same row or column. (never the same each time) Have done every one so far since first publication so must have a blank spot where this one is concerned. keep trying!!

[Animator]

Are you sure you are using the correct starting-grid?

(Or didn't you copy the puzzle?)

[Guest]

I am on the sixth effort with 130 and keep getting either two sixes or two eights in the same row or column. (never the same each time) Have done every one so far since first publication so must have a blank spot where this one is concerned. keep trying!!

Agree! I've not done that many puzzles yet (although quickly trying to catch up with everyone else) but #130 had given me some obstacles certainly. Very easy to slip up. It's solved now so it's off my mind.
I now try to solve some of the older puzzles again - just to make sure it wasn't a fluke that I got them right ;-)

Have got into the annoying habit of pencilmarking - and now can't manage without them! Tips anyone (other than discipline and an iron-will)?

[simes]

Tips anyone

Keep an eraser handy.