Novice Sudoku player, looking for the next step

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Novice Sudoku player, looking for the next step

Postby Milk » Tue May 02, 2006 6:36 pm

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


That was the original puzzle.
After umm... cross-eliminating? I can't find a glossary of terms used on this site. I was able to add:

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


Is this correct so far?

I believe I don't know enough advanced techniques to solve this puzzle any further. (And no, I don't think trial and error counts as an advanced technique :p) I don't understand the techniques mentioned on this forum are, like swordfish, or XY wing, etc.

I don't want the SOLUTION to the puzzle, just a step in the right direction.
Milk
 
Posts: 3
Joined: 02 May 2006

Postby Ruud » Tue May 02, 2006 6:51 pm

Hi Milk,

It is useful to work with pencilmarks at this stage. Or if you have a very good short term memory, you can use that instead.

I will not give too much away...

Column 1 is the key. Check the places where digits 5 and 9 can go, and try to figure out for yourself where they cannot go.

cheers, Ruud.
Ruud
 
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Joined: 28 October 2005

Postby tarek » Tue May 02, 2006 6:52 pm

If you passed a few box-line eliminations (I'm not sure if you have)...

The puzzle can be solved using a naked double (look at column1)

You may find that the Hidden triple counterpart in the same column is easier to spot.

The hidden double in Row 3 is fruitless.

tarek
User avatar
tarek
 
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Postby re'born » Tue May 02, 2006 6:55 pm

Milk,

Here is a picture rrepresenting what can go into each cell (called the candidate grid).

Code: Select all
 
 *-----------------------------------------------------------*
 |-2589  2589  2569  | 1257  3     4     | 1569  157   159   |
 |*59    1     459   | 57    6     8     | 3459  3457  2     |
 | 3     7     2456  | 125   125   9     | 1456  8     15    |
 |-------------------+-------------------+-------------------|
 | 4     2359  8     | 125   7     6     | 1359  135   1359  |
 | 6     235   1     | 9     245   235   | 7     345   8     |
 |*59    359   7     | 8     145   135   | 2     1345  6     |
 |-------------------+-------------------+-------------------|
 |-1258  6     25    | 3     1258  7     | 158   9     4     |
 | 7     2358  235   | 4     9     125   | 1358  6     135   |
 |-1589  4     359   | 6     158   15    | 1358  2     7     |
 *-----------------------------------------------------------*


The starred cells both can only take on the values 5 and 9. Note that they both are in the same column. This is called a locked pair or naked pair. It allows you to deduce that there cannot be any more 5's or 9's in that column (see if you can figure out why). After that step, you should be on your way.

Ah, I see tarek is giving you the same advice.
re'born
 
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Postby Milk » Tue May 02, 2006 7:49 pm

Wow, thank you for the very speedy replies, I did not expect an answer within 10 minutes!

Eliminating 5 and 9 from R1, 7, and 9 in C1 ends up giving me this:

Code: Select all
 *-----------------------------------------------------------*
 | 28    2589  2569  | 1257  3     4     | 1569  157   159   |
 | 59    1     459   | 57    6     8     | 3459  3457  2     |
 | 3     7     2456  | 125   125   9     | 1456  8     15    |
 |-------------------+-------------------+-------------------|
 | 4     2359  8     | 125   7     6     | 1359  135   1359  |
 | 6     235   1     | 9     245   235   | 7     345   8     |
 | 59    359   7     | 8     145   135   | 2     1345  6     |
 |-------------------+-------------------+-------------------|
 | 128   6     25    | 3     1258  7     | 158   9     4     |
 | 7     2358  235   | 4     9     125   | 1358  6     135   |
 | 18    4     359   | 6     158   15    | 1358  2     7     |
 *-----------------------------------------------------------*

Correct?
Maybe I'm just having a momentary brain lapse, but now what can I do? How do I eliminate anything with that 28, 128, or 18 in column 1 now?
Milk
 
Posts: 3
Joined: 02 May 2006

Postby FEARDIZ » Tue May 02, 2006 7:56 pm

Milk,
try this program
http://angusj.com/sudoku/
or any other
they have some good help topics and puzzles to teach you some of these 'tricks'
FEARDIZ
 
Posts: 21
Joined: 28 March 2006

Postby Ruud » Tue May 02, 2006 7:58 pm

Milk wrote:but now what can I do?

It's not the candidates left, but the candidates removed that matter here.

Look at box 7, digit 9.

Ruud.
Ruud
 
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Postby Milk » Tue May 02, 2006 8:28 pm

Ahh thank you! I knew I was missing something totally obvious.
Milk
 
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