The New Sudoku Players' Forum

[saul]

I can provide a snapshot of the position I reached before this if someone can advise how to copy paste the snapshot into the discussion forum.

The way I've done it in the past is to post the picture on dropbox, as I explained in an earlier post. However,while answering your
question, I found a better way.

Below the text entry area, there is a tab labeled "Upload attachment." Click this and choose the file you want to upload. Then click on "Add the file." A button titled "Place inline" will appear. Click this also. You can repeat the process if you want to add more than one picture. You will see the file names in your post, surrounded by HTML starting and ending "attachment" tags. It seems like this will be inserted at the point of the insertion cursor in the text entry, but you can cut and paste this text to have the attachment appear elsewhere in the text.

[denis_berthier]

To Saul's trial-and-error theme, I like to add puzzle H62352 of ATK.
[...]
Perhaps it is possible to arrive at this solution without trial-error but the extent of visualisation of resulting cell values goes so deep as to challenge reasonable human competence.

A tough one indeed, but still solvable without T&E (it is in W9).

I'm not sure to understand your last remark. As this puzzle requires whips[9], any T&E solution will have at least one elimination with a larger step, i.e. with a sequence of at least 2x9 inferences (9 negative + 9 positive).
If you mean that, for such puzzles, no one cares for finding the "simplest" solution (i.e. using the smallest chains), I agree.

[saul]

I'm not sure to understand your last remark.

I think what Mani is saying is that it might be possible to do this mentally by building up the inference chain in your head, but it probably contains too much information for most of us to remember.

[denis_berthier]

I'm not sure to understand your last remark.

I think what Mani is saying is that it might be possible to do this mentally by building up the inference chain in your head, but it probably contains too much information for most of us to remember.

Sure, as the chain length increases, it becomes more and more difficult to keep it only in mind. One needs to write links on the board.
The main difference I see between a whip (or braid) with target some candidate C and T&E based on C is, in T&E one doesn't have to remember how other candidates are asserted or eliminated when propagating the consequences of C; but I doubt that T&E for C can be done mentally (correct me if I'm wrong - I've never tried).

[Mani]

Oh yeah, I did mean that it is too much to remember and visualise a chain of cell values that may result from one assumption, it would be easier to save a position and try out a T&E sequence to save time and avoidable brain-crunching, limiting such T&E where one is clear that 2 or 3 alternative assumptions is all that will take to reach the right solution.

No one has replied to my request, how to paste kakuro grids as Saul has done before in this trail.

[Mani]

I would add H31452, which I just solved, where again such T&E or simulation was called for.

[denis_berthier]

No one has replied to my request, how to paste kakuro grids as Saul has done before in this trail.

Did you miss Saul's answer? http://forum.enjoysudoku.com/can-you-solve-this-without-trial-and-error-t30960-234.html

I would add H31452, which I just solved, where again such T&E or simulation was called for.

This is very much easier than the previous ones. You must have missed some easy eliminations. All those I need are in-sector contradictions (whips[2]), except:

- an x-wing (the only whips[2] that lie on more than a single sector):
x-wing-in-horiz-sectors: n4{r2 r5}{c5 c7} ==> r4c7 ≠ 4, r4c5 ≠ 4, r3c7 ≠ 4, r3c5 ≠ 4

- a single bivalue-chain[5]:
biv-chain[5]: r3c5{n2 n3} - r3c4{n3 n2} - r4c4{n2 n1} - hr4c3{n25 n16} - r4c5{n5 n6} ==> vr0c5 ≠ 13459

[Mani]

H62352 before TnE.docx

(86.09 KiB) Downloaded 457 times

[Mani]

Denis,
Thanks for clarifying, sorry I missed Saul's post. Hope you are able to see my upload, to me it shows a file still embedded, which is fine but I wanted to see it inline, which I chose.

[saul]

Denis,
Hope you are able to see my upload, to me it shows a file still embedded, which is fine but I wanted to see it inline, which I chose.

That's because you uploaded a docx file, which the application is unable to display. If you want to insert an image, I suggest using a png file. When you use the snipping tool to capture a rectangle from the screen you have the option of saving the snip to a file, rather than pasting it to the clipboard. Choose this option, and save it as a png. Once you've posted your reply with the image attached, you can trash the file, if you like.

I'm not using Windows at present, so I can't give step-by-step instructions. I know there's a snipping tool in Windows 7 and 8, but I can't remember if it's present in earlier versions.

http://windows.microsoft.com/en-us/windows/snipping-tool-faq#1TC=windows-7

[Mani]

H62352 Position.png (136.87 KiB) Viewed 1470 times

Thanks Saul, hope this works!

[Mani]

The pic I inserted is H62352 status before I started on a limited trial and error to reach the solution

[Mani]

Another nice puzzle, again ATK, was H24562 which forced a TnE to get to the answer

[saul]

Another nice puzzle, again ATK, was H24562 which forced a TnE to get to the answer

I thought I was on the point of solving it without trial and error, but when I got down to the end I realized I had made a mistake somewhere.

H24562.png (88.03 KiB) Viewed 1455 times

I had a lot of difficulty with this puzzle. I started working at it when I read Mani's post, and have been attacking it from time to time, saving my work as I went along. I hadn't even gotten to the point where I could see how to attempt trial and error, when this morning I saw a hidden single that I'd overlooked. I then made lots of progress, but all for naught.

I'm not sure I'll have the heart to try again.

[Mani]

Saul,
Do you want me to share the answer?