Simple Problem?

Post the puzzle or solving technique that's causing you trouble and someone will help

Simple Problem?

Postby 5krunner » Mon Dec 19, 2005 10:53 pm

I am an intermediate at Sudoku and can usually complete the harder puzzles with the basic techniques and tenacity. In any case, I am stumped on the following puzzle and was hoping someone can point me to the next step. I guess even if you can get me one more #, that should put me on the right path. I have pretty much exhausted my usually set of techniques. I know it's probably straightforward for you experts. Thanks very much in advance.

x 1 x ! x x x ! x x 9
x 5 x ! x x 7 ! 1 x 4
2 x x ! x 1 x ! x 3 x
----------------------
1 6 2 ! x 7 x ! 4 9 x
4 7 9 ! 1 x 2 ! 6 x 3
8 3 5 ! x 4 x ! x 1 x
----------------------
x 4 x ! x 3 1 ! x x 6
6 x 1 ! 8 x 4 ! 3 7 x
5 x 3 ! 7 x x ! x 4 1

Thanks again. J.:?:
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Postby Carcul » Mon Dec 19, 2005 11:18 pm

Hi 5krunner.

First, welcome to this forum. Second, the next step in your puzzle could be the naked pair in column 6.

Regards, Carcul
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Postby Lardarse » Mon Dec 19, 2005 11:33 pm

There's a naked pair to be found, and then a naked triple. After that, it's easy.
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Postby Ruud » Tue Dec 20, 2005 12:24 am

Hi,

to anticipate your next question, (and before Mac gets angry again:) )

To detect a naked pair, you need to write pencilmarks for each candidate that can go into each cell.

A naked pair is made up of 2 cells that belong to the same row, column or box. When you can find 2 cells that only allow the same 2 digits, you have located the naked pair.

As there are 2 digits for 2 cells, those digits cannot go into any other cell in that column, row, or box. So you can eliminate those pencilmarks. Then go back to other techniques to see if it helped you advance.

More information can be found here. (the most popular link in the Solving Sudoku forum)

Ruud.
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Postby 5krunner » Tue Dec 20, 2005 2:00 pm

Thank you very much for the replies. I understand the concept of naked pairs and triples, but my problem seems to be more in the execution. I see the naked pair in column 6 (don't see any of the naked triples) but it isn't helping me. I see: 6,9 - 6,9 - 5,8 - 3,5,8 - 3,5,8 in column 6. That information doesn't seem to help me uncover anything else. What am I missing (sorry for being dense). Appreciate any insights. Thx. J.

Carcul wrote:Hi 5krunner.

First, welcome to this forum. Second, the next step in your puzzle could be the naked pair in column 6.

Regards, Carcul
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Postby Carcul » Tue Dec 20, 2005 2:12 pm

Hi 5krunner.

Now, try to see a naked triple in row 3, which will solve the rest of the puzzle.

Regards, Carcul
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Postby 5krunner » Tue Dec 20, 2005 2:47 pm

Thank you Carcul!! However (being dense again) I still do not see the triple. In row 3, I have the following (maybe I have something wrong):

! 2 - 8,9 - 4,6,7 ! 4,5,6,7 - 1 - 5,8 ! 5,7,8 - 3 - 5,7,8 !

I appreciate any insights. Thx ... J.

Carcul wrote:Hi 5krunner.

Now, try to see a naked triple in row 3, which will solve the rest of the puzzle.

Regards, Carcul
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duo leading to another duo

Postby Pat » Tue Dec 20, 2005 2:50 pm

5krunner wrote:I can usually complete the harder puzzles. I am stumped on the following puzzle:
Code: Select all
 . 1 . | . . . | . . 9
 . 5 . | . . 7 | 1 . 4
 2 . . | . 1 . | . 3 .
-------+-------+------
 1 6 2 | . 7 . | 4 9 .
 4 7 9 | 1 . 2 | 6 . 3
 8 3 5 | . 4 . | . 1 .
-------+-------+------
 . 4 . | . 3 1 | . . 6
 6 . 1 | 8 . 4 | 3 7 .
 5 . 3 | 7 . . | . 4 1


the advice to look at c6 and then at r3 is entirely correct;
but a trio (a set of 3 digits or a set of 3 cells) can be hard to find -
i'd rather solve with a duo (a set of 2 digits or a set of 2 cells) where possible.

in the present case -
the {6,9} duo in c6 eliminates these digits as possibilities at r3c6,
which creates a new duo:
the 4,6 for r3 have only 2 cells available!
so, {r3c3,r3c4} = {4,6}, and now you know the 9 for r3.
[ sorry i originally gave the wrong column-numbers ]

- Pat
Last edited by Pat on Thu Dec 22, 2005 4:50 am, edited 1 time in total.
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Re: duo leading to another duo

Postby 5krunner » Tue Dec 20, 2005 3:45 pm

Yipee!!! Pat, that did it! Thank you for the clue.

I missed the {4,6} pairs on row 3. Once you pointed that out it started to all fall into place.

Thanks again ... Jay.

Pat wrote:
5krunner wrote:I can usually complete the harder puzzles. I am stumped on the following puzzle:
Code: Select all
 . 1 . | . . . | . . 9
 . 5 . | . . 7 | 1 . 4
 2 . . | . 1 . | . 3 .
-------+-------+------
 1 6 2 | . 7 . | 4 9 .
 4 7 9 | 1 . 2 | 6 . 3
 8 3 5 | . 4 . | . 1 .
-------+-------+------
 . 4 . | . 3 1 | . . 6
 6 . 1 | 8 . 4 | 3 7 .
 5 . 3 | 7 . . | . 4 1


the advice to look at c6 and then at r3 is entirely correct;
but a trio (a set of 3 digits or a set of 3 cells) can be hard to find -
i'd rather solve with a duo (a set of 2 digits or a set of 2 cells) where possible.

in the present case -
the {6,9} duo in c6 eliminates these digits as possibilities at r3c6,
which creates a new duo:
the 4,6 for r3 have only 2 cells available!
so, {r3c4,r3c5} = {4,6}, and now you know the 9 for r3.

- Pat
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Re: duo leading to another duo

Postby QBasicMac » Tue Dec 20, 2005 7:51 pm

5krunner wrote:Yipee!!! Pat, that did it! Thank you for the clue.


Glad you figured it out!

I guess you saw the two 69's in column 6 and thus erased 6 from r1 and r3 and erased 9 from r3.

The naked triple in row 3 was c6(58) c7(578) and c9(578) in case you are still interested. Three cells which contain only the same three candidates, 578. As you indicated, if you saw that, you would know to erase all other 578s in row 3.

But the other naked pair, 46 in r3c34 were easier to spot and lead to an easy solution, so spotting the naked triple was not important.:)

Mac
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Re: duo leading to another duo

Postby 5krunner » Tue Dec 20, 2005 8:41 pm

Mac,

Thanks for the advice. That was important for me since I really didn't think about 58, 578, 578 as being a triple but I guess once you think about it it is indeed. So that would have worked just as well.

Thx ... Jay.

QBasicMac wrote:
5krunner wrote:Yipee!!! Pat, that did it! Thank you for the clue.


Glad you figured it out!

I guess you saw the two 69's in column 6 and thus erased 6 from r1 and r3 and erased 9 from r3.

The naked triple in row 3 was c6(58) c7(578) and c9(578) in case you are still interested. Three cells which contain only the same three candidates, 578. As you indicated, if you saw that, you would know to erase all other 578s in row 3.

But the other naked pair, 46 in r3c34 were easier to spot and lead to an easy solution, so spotting the naked triple was not important.:)

Mac
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