The New Sudoku Players' Forum

[bennys]

Can someone find a puzzle plus candidates list that we cant make any progress
using the following way
1)I can use all the elementary technics in any time
2)I can guess and continue using elementary technics if I get contradiction or I solve thats great I got a progress
3)if I get stuck I don't remove the candidate but move foreword to the next candidate or the next cell if I finished the candidates for a cell.

[PaulIQ164]

No, any sudoku with a unique solution can be solved using that method. In fact, if you're going to use trial and error, then technically you don' even have to use elementary techniques. You could just make a huge series of nested guesses until you find a solution that works - this is how a simple computer program would solve them, though obviously it takes too much number-crunching to be practicable for a human to do it.

[bennys]

Maybe I was not clear but I am not allowing nested guesses here
And that the main point.

[Pi]

All sudoku puzzles with only one puzzle can be solved using logical techniques, however you can get to a point where you need to use a technique such as colouring which is sort of like guessing

[bennys]

You are not answering the question

[Wolfgang]

Im still not sure what you mean, maybe the following?
You use elementary techniques until you get stuck.
Then you can try each remaining candidate - using only elementary techniques again - until you either get a contradiction (then you eliminate it) or solve it (then you are done) or get stuck again (then proceed with the next candidate).
If you mean this, there is no known puzzle you could not solve this way, as far as i know (at least this is true for the "hardest" puzzles posted here)

[bennys]

In this post I am not asking about totally solving I am talking just on one step (which is cell placement or removal of candidate)
I am looking for example that the way that I described will NOT work.
I assume there is example but I didn’t see any.

[Pi]

If a move cannot be made based upon logic then the puzzle has more than one solution

You may not be able to use elementery tactics but if you look hard enough there is always a move

[bennys]

I am not talking about logic I am talking about specific way

[Pi]

There are lots of specific ways of removing candidates, the most common being:

Naked Pair
Nidden Pair
Naked tripple
Hidden Tripple
Locked candidate
X-Wing
Swordfish
Chain

You will find puzzles in which you reach a point where you can't use any of these.

[bennys]

It looks to me that you dont understand the question please read it again

[Pi]

Could you rephrase your question

[Animator]

It looks to me that you dont understand the question please read it again

Perhaps you should learn how to ask a question?

Point 1 of your original post: unclear + dubious
Point 2: a bit dubious but making more sense. You are talking about Trial and Error.
Point 3: completly irrelevant/redundant.

You never defuined something as 'elementary technics'. What do you understand on those two words? ...?

If your question is: does a puzzle exists where I need to use trial and error and then I can continue without guessing and solve it completly (without using Trial and Error) then the answer is both yes and no.

(The no-part: because there is always another way to find the move. (Forcing chains to name one.)

[PaulIQ164]

I think the question he means is:

Can any puzzle be solved using only 'elementary tactics' (whichever set of tactics he considers them to be, my guess is either just singles or just up to Pappocom-Hard tactics) and single guesses, that is, never having to make a guess within a 'branch' of a guess?

[bennys]

Basically the way that PaulIQ164 put it is equivalent to my question.
Just to make it simpler In a sense I want to get the puzzle in a specific stage where I will not be able to make any progress using that method.
Yes Pappocom-Hard tactics sound OK.