SO stuck

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SO stuck

Postby Niklas73 » Tue Sep 27, 2005 7:48 pm

Is there ANYWAY tyo solve this without takin a guess somewhere? If you see the logic please dont just give me the soulution but how you did it Please!

2OOO48OOO
4OOO75OO8
O83261OOO
8OOOOOO4O
O25O3O98O
O64O8OOO7
OOO6O387O
OOO89OOO1
OO8O1OOO3
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Postby emm » Tue Sep 27, 2005 8:01 pm

There's only one place for a 6 in column 9. There's a naked pair 3,9 in column 4. Ask again if you don't see it.
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Postby Doyle » Tue Sep 27, 2005 9:35 pm

em is correct in some ways, but his hint is phrased in a misleading way, and could be misdirecting, IMO. At this stage in the solution, there's more than one cell in column 9 that could take a 6, but there's a cell in that column where 6 is the only possibility. For those who want jargon (no, not you Mac) em implies that there's a hidden single, whereas actually there's a naked single.
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Postby emm » Tue Sep 27, 2005 10:04 pm

I've noticed that you've said some very sensible things in the past, Doyle, and one of these is another - I stand corrected on the misleading hint. It should have read 'there's only one 6 for a place in column 9' ... but you're not right about everything - I'm not a his! I'm going to go on the record here as I'm getting concerned that a number of people are making this mistake. I'd like to know - do I come across in a particularly macho-butch manner or do guys just assume everyone is male until proven otherwise!

Sorry about the tone, Nicklas73, I hope you're an oldish-sort-of-Nick and won't be put off. (There is a junior forum if you need to retire.) If you decide to stay I do have one unmisleading hint for you -

There are clearer ways to present your puzzle - if you ever want to - in the future.

Code: Select all
 2 . . | . 4 8 | . . .
 4 . . | . 7 5 | . . 8
 . 8 3 | 2 6 1 | . . . 
-------+-------+------
 8 . . | . . . | . 4 .
 . 2 5 | . 3 . | 9 8 .
 . 6 4 | . 8 . | . . 7
-------+-------+------
 . . . | 6 . 3 | 8 7 .
 . . . | 8 9 . | . . 1
 . . 8 | . 1 . | . . 3


2** *4* ***
4** *75 **8
*83 261 ***

8** *** *4*
*25 *3* 98*
*64 *8* **7

*** 6*3 87*
*** 89* **1
**8 *1* **3
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Postby r.e.s. » Tue Sep 27, 2005 10:13 pm

em wrote:I'm not a his! I'm going to go on the record here as I'm getting concerned that a number of people are making this mistake. I'd like to know - do I come across in a particularly macho-butch manner or do guys just assume everyone is male until proven otherwise!

Not since Dorothy returned from Oz to her "auntie em" would I think of "em" as likely to be a man's moniker.
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Postby Doyle » Wed Sep 28, 2005 12:28 am

em wrote:but you're not right about everything - I'm not a his! I'm going to go on the record here as I'm getting concerned that a number of people are making this mistake. I'd like to know - do I come across in a particularly macho-butch manner or do guys just assume everyone is male until proven otherwise!


My apologies for the mistake and for the implied sexism. I plead quilty for making the assumption, and no, it wasn't from the tone of anything you've posted. I'll watch myself!
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Postby Niklas73 » Wed Sep 28, 2005 8:02 am

I have taken so mych heat in forums so I am not that easy to put off. Please give me that hint U talked about.
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Postby emm » Wed Sep 28, 2005 8:28 am

No hay problema, Doyle - I should apologise for my huffy tone. Cripes, I sound snappy out loud! It’s difficult determining the implied intent in the text here and also striking the right note … I have noticed, for example, how things that seemed profoundly hilarious the night before can look pretty trashy in the morning – like other things in life I guess! From now on I’ll annotate with script-like-emotion-indicators as in (tongue-in-cheek, big-toothy-grin, jus’jestin’!) or use the cheesy-smiley faces a la stuartn!
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Postby emm » Wed Sep 28, 2005 8:32 am

Nik, you came back! In column 9 there is one cell in which there is only one possible candidate ie numero 6.

Then you should find a pair of 3s & 9s in column 4. This allows you to eliminate all the other 9s from column 4.

Then you should find a pair of 2s and 5s in row 4. This allows you to eliminate all the other 2s & 5s from row 4 - and by then you should be flying solo.:)
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Re: SO stuck

Postby Pat » Wed Sep 28, 2005 9:10 am

.

Niklas73 wrote:Is there ANYWAY to solve this without takin a guess somewhere?

please dont just give me the soulution but how you did it

Code: Select all
 2 . . | . 4 8 | . . .
 4 . . | . 7 5 | . . 8
 . 8 3 | 2 6 1 | . . .
-------+-------+------
 8 . . | . . . | . 4 .
 . 2 5 | . 3 . | 9 8 .
 . 6 4 | . 8 . | . . 7
-------+-------+------
 . . . | 6 . 3 | 8 7 .
 . . . | 8 9 . | . . 1
 . . 8 | . 1 . | . . 3





try doing it in this order:

r5c9 must be 6

in column 6,
place the 6, then the 9

in the central box,
place the 2;
and finish column 5

in column 9,
place the 2,4,9,5;
and finish the 2nd box

in row 3,
place the 9,7,5

in box 1,
place the 5,7,6,1

in row 7,
place the 4,9,1

in column 3,
place the 2,1

did you really want this type of advice?

( so far, it's all Basic Elimination and no duo needed )

Pat

.
User avatar
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Postby emm » Wed Sep 28, 2005 11:18 am

Well, there’s more than one way to skin a cat. For mine own part, I have a blind spot when it comes to hidden singles (truly) and for some reason can pick a naked pair at twice the speed. Very Freudian, I suspect.
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Postby Niklas73 » Wed Sep 28, 2005 1:35 pm

Here is the thing I dont get. Abut the 6 in column 9 row 4. Explain to a rookie why the 6 cant go in the left top box of this box. And is it so that if there must be a number, either 2 or 5 in this case in column 5 row 4 the 2 and 5 is eliminated for the mid rightbox and vice cersa in the leftbox (and if so why?)? - I mean if one of this numbers have to go in the top mid box - none of them can exist in the right left box top row....?

em wrote:Nik, you came back! In column 9 there is one cell in which there is only one possible candidate ie numero 6.

Then you should find a pair of 3s & 9s in column 4. This allows you to eliminate all the other 9s from column 4.

Then you should find a pair of 2s and 5s in row 4. This allows you to eliminate all the other 2s & 5s from row 4 - and by then you should be flying solo.:)


em wrote:Nik, you came back! In column 9 there is one cell in which there is only one possible candidate ie numero 6.

Then you should find a pair of 3s & 9s in column 4. This allows you to eliminate all the other 9s from column 4.

Then you should find a pair of 2s and 5s in row 4. This allows you to eliminate all the other 2s & 5s from row 4 - and by then you should be flying solo.:)
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Postby Doyle » Wed Sep 28, 2005 2:40 pm

Nik: Good questions, here's (I hope) a clear answer: It's not that the 6 can't go in some of the other cells in that box, it's that 6 is the ONLY number that can go in r5c9, so it MUST go there and nowhere else.

Focus for a moment on just that cell. Look at all the numbers in the entire row 5, column 9 and box 6 that intersect that cell. All the other numbers, except 6, are already accounted for, and can't be repeated. So it's 6 by default, and that is certain, not a guess. (This is what we call a "naked single.")

Having placed that 6, you can (and should) now eliminate 6 from all the others cells (in that row, column and box) where it was previously a candidate. They were, in effect, red herrings.

In solving Sudoku, sometimes you focus on "what cell(s) can this number go in", and that's what you were apparently doing. Sometimes you focus on "what number(s) can go in this cell", which is what works in this instance. Both approaches are valid, both are necessary, and you need to consciously use first one then the other as you work through a puzzle.
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Postby emm » Wed Sep 28, 2005 6:31 pm

Niklas73 wrote:Here is the thing I don't get. Abut the 6 in column 9 row 4.

Hi again Nik, you mean the 6 in column 9 row 5, eh?:)

It helps to call the little boxes 'cells' and the groups of 3x3 cells 'boxes'. The candidates are all the possible numbers for the empty cells.

Look at the whole puzzle. Have you got just one candidate for r5c9? This is called a naked single 6 and must go in this cell because no other number is eligible. Now you can eliminate all other 6s from this row, column and box.

Look at the whole puzzle again. There are no more naked singles so now you need to look for other things - hidden singles, pairs etc. Have you read the How to Solve on the homepage of this program or http://www.angusj.com/sudoku/

This puzzle is rated Hard by Pappacom. It might be easier to start off with a few easy ones to get the hang of it. Good luck!
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Postby Niklas73 » Wed Sep 28, 2005 10:07 pm

Doyle: Thanx. That was a tip i surely needed.

I have a paper where I solveed every puzzle up to this one so I gave it a shot. Will try that HP though. Thanx for explaining terms and solving teqniques. I will surely come back in this thread ;)
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