## Unsolvable without Trial & Error?

All about puzzles in newspapers, magazines, and books

### Unsolvable without Trial & Error?

I note below a recent Times puzzle - I cannot proceed without trial & error OR am I missing something?

9|?|1|?|?|2|?|?|3
2|8|7|9|4|3|6|1|5
?|4|3|7|?|1|9|2|8
?|?|?|3|9|7|1|5|4
7|?|?|4|?|6|?|8|9
?|9|4|?|?|8|?|?|?
?|7|?|6|?|?|5|?|?
?|?|9|?|7|?|?|3|?
4|?|?|2|?|?|8|?|7

The ORIGINAL numbers are

9|?|1|?|?|2|?|?|3
?|8|?|?|4|3|6|?|?
?|?|3|?|?|1|?|?|?
?|?|?|3|?|?|1|5|?
7|?|5|?|?|?|?|?|9
?|9|4|?|?|8|?|?|?
?|?|?|6|?|?|5|?|?
?|?|9|?|7|?|?|3|?
4|?|?|2|?|5|8|?|7

I have completed the puzzle by guessing one of the items and the answer is as follows

9|6|1|5|8|2|4|7|3
2|8|7|9|4|3|6|1|5
5|4|3|7|6|1|9|2|8
6|2|8|3|9|7|1|5|4
7|1|5|4|2|6|3|8|9
3|9|4|1|5|8|7|6|2
8|7|2|6|3|9|5|4|1
1|5|9|8|7|4|2|3|6
4|3|6|2|1|5|8|9|7

This was in The Times a few days ago. Can anybody tell me what the next LOGICAL move is.

Thanks

ALHAMI
Guest

### sudoku

hello Alhami,
it can be done without trial and error. It was the first fiendish level sudoku I've completed, so it can't be that hard!!!
I've given up on the one from 4 march. I've wasted too much time on it already.
Keep trying!
Mike
Guest

### A hint

Hello Alhami.

A hint: think about 1 and 3 in box 4.

A request: could you mention the number or the date of The Times puzzle in the Subject line, next time you post? That way, others will know immediately whether it's the puzzle they are wanting information about.

Also, I moved your post into this forum because it's a question about a particular Times puzzle.

I won't always be here, offering tips! But I maybe sometimes. I won't be offering tips until quite a few days have gone by since the puzzle was published - that's just to make sure that puzzlers get desperate first!

If you don't know which box is box 4, could you take a look at the "Basic terms" post in the "General/program" forum. Thanks.

- Wayne.
Pappocom

Posts: 599
Joined: 05 March 2005

### Still confused

Thanks Papocom

I did try that but the 1 and the 3 can be interchanged in box 4 and you can almost finish the puzzle until the last 4 numbers without thinking you have made a mistake. I would have thought that having to go that far would be classed as trial and error. There does not seem to be a LOGICAL reason for putting the 1 and the 3 in their respective correct boxes.

I am a fairly logical person but even slicing/dicing and applying reason - I must be missing the logic somewhere along boxes 1 4 5 6 and 9.

Can you supply me with where the logic kicks in in the other boxes.

Regards

ALHAMI
Guest

Hi Alhami.

OK, so you know where the 1 and 3 go in box 4. Now, forget about placing 1 and 3 for the time being - as you say, they are interchangeable (at this stage). But think about what it means for the other numbers in box 4.

- Wayne
Pappocom

Posts: 599
Joined: 05 March 2005

### Not Confused - Just Feeling Silly

Wayne

The words "wood" and "trees" spring to mind.

Too busy looking for something complicated.

The 5 in box 4 is now easily placed.

Thanks and regards

Alhami
Guest

### times 4 march

Hello Alhami,
I went back to fiendish Times 4 march today and cracked it. It feels good to solve these difficult SUDOKUS ..... BUT think of the hours you have to put in, not to mention the bad dreams!
MIKE
Guest

I thought, until yesterday, that there were odd puzzles that couldn't be solved without a single guess and allowed for such in my software. I have spent literally hours trying to deduce the logic of these and have now found it and can now solve every puzzle published so far, including the book. When you get really stuck try looking within the boxes. Invariably one will contain the situation where one or two values must sit within either a column or row. If they are in that column or row then they can be eliminated as possible values in the other bands or stacks as applicaple.
malcolmr

Posts: 4
Joined: 05 March 2005

Malcolmr

At the risk of teaching grandma how to suck eggs and of course only reading between the lines what your actual technique is, one piece of advice is to be very abstemious with pencilling in candidates.

I personally only enter candidates if they are a pair or triplet IN A LINE in a block. I won't even enter a double if they aren't in the same row or column of the block. As well as removing clutter, I find that it is hardly ever necessary to apply the locked column or row rules as they are easily trapped before writing the numbers in.

Obviously there comes the point (unless it's a really trivial puzzle) where you have to do a full analysis but this is also more easily done when you add the candidates incrementally alongside the more basic pattern.
Max Beran

Posts: 57
Joined: 17 August 2005

Max Beran wrote:Malcolmr

At the risk of teaching grandma how to suck eggs and of course only reading between the lines what your actual technique is, one piece of advice is to be very abstemious with pencilling in candidates...

Isn't it interesting how different people use totally different strategies, systems and techniques?

If required (by the difficulty of the puzzle) I enter ALL candidate numbers and then eliminate. I find that this prevents me from overlooking a candidate.

I have not yet found a puzzle I cannot complete, although some of them take me a while...!

The Druid
The Druid

Posts: 33
Joined: 22 April 2005