The New Sudoku Players' Forum

[Pat]

Quick! Get back on topic!!

thanks for pointing out the 1,8,9 trio

but the 2,7 duo already existed all along,
there are only 2 cells available for them in r8

- Pat

[Karyobin]

Yeah, I know. But I tend to look for Naked stuff before Hidden stuff. Probably a personality thing.

[PaulIQ164]

I'm sure Freud would have something to say on the matter.

[emm]

You two are such copycats! (I'm going to start copyrighting some of my more famous sayings!)

Now I've done my 15 min on the naughty chair I can put in my tuppence worth.

Now as most everybody knows if the guessing factor is used then LOGIC IS NOT.

Confusion often arises in the definition of the terms. Logic and guess are not absolutes - they are part of a spectrum from outright wild conjecture at one end to dead cert at the other.

All decisions we make are based on hypotheses - the ones that are based on tested techniques or known facts we tend to call logic, the ones that we really have no idea why we made them we tend to call guess. But there isn't always a fine line between the two and different people have different ideas about what goes on either side of the line eg some people call forcing chains guessing.

PS : Most people here call naked triples logic

[Pat]

I tend to look for Naked stuff before Hidden stuff.

one type is more obvious (evident, nude)
the other type is more obscure (hidden, clothed)

the only trouble is, what most of you consider evident, to me is hidden - and vice versa!

[emm]

Precisely. The Emperor Has No Clothes!

[CathyW]

I think a lot depends on whether you are a candidate eliminator having put in all possibilities or a candidate inputter. I definitely prefer not to have all possible candidates in a puzzle to begin with - gets too cluttered and I find it more difficult to see the hidden pairs and triples - these often become naked if you only put in the candidates you need as was the case in row 8 of the puzzle in question in this topic.

[emm]

Relating this to the original question - are you saying that the number of visible candidates can determine the difference between logic and guess?

[Pat]

Relating this to the original question - are you saying that the number of visible candidates can determine the difference between logic and guess?

personally, i'm trying not to relate it to the original question, as it appears that Smart3 has different ideas than mine about Logic.

the 2,7 duo in r8 is entirely evident right from the start,
and only becomes obscure if you write in the possibilities.

how the duo is Logically employed - what inferences are we allowed to derive - that seems to be where Smart3 differs from me and (i hope) from most of us.

- Pat

[CathyW]

Relating this to the original question - are you saying that the number of visible candidates can determine the difference between logic and guess?

Not quite - I'm saying that if you only enter definite candidates (e.g. the obvious doublets) then fairly often, at least in not too fiendish puzzles, a pair or triplet will present itself and is easy to see.

Evidently the rest of us have a different view on what is logical to Smart3 - I wonder why he hasn't replied?

[lunababy_moonchild]

Evidently the rest of us have a different view on what is logical to Smart3 - I wonder why he hasn't replied?

Dunno, could it be that he/they got trashed? (Nicely done though, very classy)

I really was looking forward to that explanation.

Luna

*favourite bumper sticker? My Karma just ran over your Dogma*

[Karyobin]

I think a lot depends on whether you are a candidate eliminator having put in all possibilities or a candidate inputter.

Thassit!! Zigackly! (Ooops, Stella-pixie in the building) I'm by nature an inputter, not an eliminator. I just dubbed the original into Simple Sudoku, then played with what angusj gave me. Must admit I didn't see the {2,7} pair until I'd spotted the triple, but I like to think I'd have seen it if I'd done all the leg work myself.

I take it you were referring to me there Luna, I hoped I wasn't being too bad. Just another one of those straws, I guess.

Someone is going to have to write a newbie gateway thingy.

Maybe we should have a competition for the best one?

[tso]

We don't have enough information to solve the mystery of Smart3 by deductive logic -- but I can make a guess. Based on the early point of the puzzle where Smart3 got stuck and the odd point of view in the posts, I think Smart3 and friends solve without using pencil marks and very well may not know what they are. Hasn't read much, if any, of the forum. There is a language issue as well.

Though this puzzle is rated only HARD by Pappocom -- a level that it seems Wayne has implied to be solvable without pencilmarks -- this one seems beyond most solver's pen-only capabilities -- certainly mine.

One seems to have to enter a LOT of marks in cells very early in the solving -- lots of eliminations by locked candidates, naked triples, etc. For comparison, I just created two Pappocom HARD at random -- both required only naked and hidden singles to solve -- both could be solved easily in pen without pencil marks. Here's one:

Code: Select all

 . 4 8 | . . 1 | 5 . .
 5 . . | 7 . . | 2 . .
 . 7 . | . 9 . | 6 . .
-------+-------+------
 . . . | . 7 . | . . 9
 . . . | 8 . 3 | . . .
 8 . . | . 1 . | . . .
-------+-------+------
 . . 1 | . 5 . | . 2 .
 . . 2 | . . 8 | . . 6
 . . 9 | 6 . . | 1 7 .


Reread Smart3's posts with this in mind see if you agree. If I hadn't heard of pencil marks and considered any entering of information into the grid as equivalent to guessing, this puzzle might very well be impossible.

EDIT:

For further comparision, below is a randomly generated Pappocom Very Hard:

Code: Select all

 . 4 . | . . . | . . .
 3 . 9 | . . 5 | . . .
 . 8 . | . . 9 | . 1 6
-------+-------+------
 . . 4 | . . 7 | . 9 .
 2 . . | . . . | . . 7
 . 9 . | 6 . . | 8 . .
-------+-------+------
 7 3 . | 9 . . | . 5 .
 . . . | 8 . . | 2 . 3
 . . . | . . . | . 8 .


Though an x-wing is eventually required, the first 30 or so placements are just naked and hidden singles, not requiring any pencil marks to be entered. At this point, with only about 25 or so cells left, the puzzle can be solved without ever putting more than 3 pencil marks in a cell -- maybe only two if you were to tough it out. I would find this puzzle *much* easier to solve than the one posted.

I'm not trying to point out a glitch in the ratings system used, only that it is possible that Smart3 never came across a puzzle that required pencil marks, though the Smart3-group had been solving puzzles equivalent to Pappocom HARD before.

[Karyobin]

...and considered any entering of information into the grid as equivalent to guessing...

To be fair then, that's quite a language barrier! I appreciate your point of course, but use of specific vocabulary would suggest to me that Smart3 (3 of 7?) knows exactly what they're saying.

They do claim that their little cabal solve hard ones from newspapers though, don't they? As we know, these very rarely require pencil marks, though anyone could be lazy and choose to use them. It also seems as though the mysterious 'syndicate producer' (?!) doesn't recognise them as logical either. Maybe we have inadvertantly discovered an entirely new country? Or a new definition of Zen-logic - 'Thinking-without-thinking'?

Certainly makes you think. Or not.

(P.S. I will reread the posts, I promise. Just as soon as I can hold the mouse with only one hand.)

[PaulIQ164]

Though this puzzle is rated only HARD by Pappocom -- a level that it seems Wayne has implied to be solvable without pencilmarks -- this one seems beyond most solver's pen-only capabilities -- certainly mine.

Indeed. I had a crack at it w/o pencilmarks. Couldn't do very much. Here's what Susser does in between the last 'simple' move and the succeeding one:

* A set of 2 squares can be constrained. R8C1 and R8C2 share possibilities <27>. No other squares in row 8 have those possibilities. Thus, any additional possibilities they have can be eliminated.

R8C1 - removing <89> from <2789> leaving <27>.
R8C2 - removing <18> from <1278> leaving <27>.

Deduction pass 2; 34 squares solved; 47 remaining.

* 2 squares in block 7 form a simple locked pair. R8C1 and R8C2 share possibilities <27>. Thus, these possibilities can be removed from the rest of the block.

R7C1 - removing <7> from <36789> leaving <3689>.
R7C2 - removing <7> from <1578> leaving <158>.

Deduction pass 3; 34 squares solved; 47 remaining.

Deduction completed...

Deduction pass 1; 34 squares solved; 47 remaining.

* Intersection of row 2 with block 2. The value <4> only appears in one or more of squares R2C4, R2C5 and R2C6 of row 2. These squares are the ones that intersect with block 2. Thus, the other (non-intersecting) squares of block 2 cannot contain this value.

R3C4 - removing <4> from <478> leaving <78>.

Deduction pass 2; 34 squares solved; 47 remaining.

* Intersection of row 2 with block 3. The values <19> only appears in one or more of squares R2C7, R2C8 and R2C9 of row 2. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain these values.

R3C7 - removing <1> from <1237> leaving <237>.
R3C8 - removing <1> from <13678> leaving <3678>.

Deduction pass 3; 34 squares solved; 47 remaining.

* A set of 2 squares can be constrained. R2C7 and R7C7 share possibilities <19>. No other squares in column 7 have those possibilities. Thus, any additional possibilities they have can be eliminated.

R2C7 - removing <7> from <179> leaving <19>.
R7C7 - removing <7> from <179> leaving <19>.

Deduction pass 4; 34 squares solved; 47 remaining.

* Intersection of row 8 with block 8. The value <8> only appears in one or more of squares R8C4, R8C5 and R8C6 of row 8. These squares are the ones that intersect with block 8. Thus, the other (non-intersecting) squares of block 8 cannot contain this value.

R7C5 - removing <8> from <3489> leaving <349>.
R7C6 - removing <8> from <1348> leaving <134>.

Deduction pass 5; 34 squares solved; 47 remaining.

* Intersection of column 4 with block 5. The value <4> only appears in one or more of squares R4C4, R5C4 and R6C4 of column 4. These squares are the ones that intersect with block 5. Thus, the other (non-intersecting) squares of block 5 cannot contain this value.

R4C5 - removing <4> from <2348> leaving <238>.
R4C6 - removing <4> from <34578> leaving <3578>.
R5C5 - removing <4> from <248> leaving <28>.
R5C6 - removing <4> from <1478> leaving <178>.

Deduction pass 6; 34 squares solved; 47 remaining.

* Intersection of column 7 with block 3. The value <7> only appears in one or more of squares R1C7, R2C7 and R3C7 of column 7. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain this value.

R2C8 - removing <7> from <178> leaving <18>.
R2C9 - removing <7> from <789> leaving <89>.
R3C8 - removing <7> from <3678> leaving <368>.
R3C9 - removing <7> from <2678> leaving <268>.

Deduction pass 7; 34 squares solved; 47 remaining.

* R2C6 is the only square in row 2 that can be a <7>. It is thus pinned to that value.

I'm not sure how much of that was relevant to the move it made in the end, but still!