The New Sudoku Players' Forum

[Maria]

Code: Select all

9     38    7      / 345    48     458     / 6        2       1
 2     5      38    / 6        7      1         / 938    48      943
 6     4      1      / 38      92     92      / 538     7       53
----------------------------------------------------------------
3      697   48   /  48      5      246     / 1        69     72
1      69     45   /  7       246   3246   /  25      639   8
57    68     2     /  9       1       3268   / 4        63     75
----------------------------------------------------------------
47    217   9     /  148    3       7468   / 728     5       624
8      37     35   /  2       469    74569 / 79       1       649
457   217   6     / 1458  489    74589 / 37289  48     3249

What is the next step? What technique to use? How to use it?
This sudoku taken from Sudoku Megastar published in Barcelona.
Thank you.

[JeJ]

There is some mistake with your puzzle it is invalid because it has multiple solutions. Check again if you made a mistake when you typed the numbers or maybe it is a puzzle with multiple solutions indeed and then I wouldn't know what to advice.

[JasonLion]

The puzzle looks fine to me. The pencil marks aren't in numerical order in various places, but that is the only issue I see.

The next step I see right off is a naked pair of 48 in row 4. There is still quite a bit to do from there. My solver ends up using WXYZ-Wings, a finned swordfish, XY-Chains, and simple coloring, along with a number of simpler moves.

[daj95376]

Code: Select all

 after additional basics: Naked Pair and Naked Quad
 +-----------------------------------------------------------------------+
 |  9      38     7      |  345    48     458    |  6      2      1      |
 |  2      5     a38     |  6      7      1      |  89-3   48     49-3   |
 |  6      4      1      |  38     29     29     |  358    7     f35     |
 |-----------------------+-----------------------+-----------------------|
 |  3      679   b48     |  48     5      26     |  1      69     27     |
 |  1      69    c45     |  7      246    2346   |  25     369    8      |
 | d57     68     2      |  9      1      368    |  4      36    e57     |
 |-----------------------+-----------------------+-----------------------|
 |  47     12     9      |  148    3      4678   |  278    5      246    |
 |  8      37     35     |  2      469    45679  |  79     1      469    |
 |  457    12     6      |  1458   489    45789  |  23789  48     2349   |
 +-----------------------------------------------------------------------+
 # 83 eliminations remain


The last step from my solver also works at this point:

Code: Select all

6-cell XY-Chain: (3=8)r2c3 =4r4c3 =5r5c3 =7r6c1 =5r6c9 =3r3c9  =>  r2c79<>3


Yes, I abbreviate the AIC notation for an XY-Chain.

[JeJ]

When I copy daj95376's notation i get different candidates that when I copy Maria's, for instance r2c8 has 3 and 9 as additional candidates, r3c5 has 8 as an additional candidate and r3c79 have 9 as additional. This way Hodoku says it is a valid "Unfair" puzzle, but i don't see those extra candidates on daj95376's notation. Could someone please explain this?

[ronk]

Maria's pencilmarks won't paste properly into Hodoku, but I don't know why. However, it looks nothing like you describe. For some unknown reason, r6c3 has candidate <2> as a naked single, rather than a clue.

[daj95376]

Maria's pencilmarks won't paste properly into Hodoku, but I don't know why. However, it looks nothing like you describe. For some unknown reason, r6c3 has candidate <2> as a naked single, rather than a clue.

Here is Maria's original grid:

Code: Select all

9     38    7      / 345    48     458     / 6        2       1
 2     5      38    / 6        7      1         / 938    48      943
 6     4      1      / 38      92     92      / 538     7       53
----------------------------------------------------------------
3      697   48   /  48      5      246     / 1        69     72
1      69     45   /  7       246   3246   /  25      639   8
57    68     2     /  9       1       3268   / 4        63     75
----------------------------------------------------------------
47    217   9     /  148    3       7468   / 728     5       624
8      37     35   /  2       469    74569 / 79       1       649
457   217   6     / 1458  489    74589 / 37289  48     3249


Here it is after I edited (/) to be (|):

Code: Select all

9     38    7      | 345    48     458     | 6        2       1
 2     5      38    | 6        7      1         | 938    48      943
 6     4      1      | 38      92     92      | 538     7       53
----------------------------------------------------------------
3      697   48   |  48      5      246     | 1        69     72
1      69     45   |  7       246   3246   |  25      639   8
57    68     2     |  9       1       3268   | 4        63     75
----------------------------------------------------------------
47    217   9     |  148    3       7468   | 728     5       624
8      37     35   |  2       469    74569 | 79       1       649
457   217   6     | 1458  489    74589 | 37289  48     3249


Here's what my solver (and HoDoKu) consider an invalid grid:

Code: Select all

 +-----------------------------------------------------------------------+
 |  9      38     7      |  345    48     458    |  6      2      1      |
 |  2      5      38     |  6      7      1      |  389    48     349    |
 |  6      4      1      |  38     29     29     |  358    7      35     |
 |-----------------------+-----------------------+-----------------------|
 |  3      679    48     |  48     5      246    |  1      69     27     |
 |  1      69     45     |  7      246    2346   |  25     369    8      |
 |  57     68     2      |  9      1      2368   |  4      36     57     |
 |-----------------------+-----------------------+-----------------------|
 |  47     127    9      |  148    3      4678   |  278    5      246    |
 |  8      37     35     |  2      469    45679  |  79     1      469    |
 |  457    127    6      |  1458   489    45789  |  23789  48     2349   |
 +-----------------------------------------------------------------------+
 # 87 eliminations remain


Here's what Simple Sudoku returns after loading the above grid:

Code: Select all

 +-----------------------------------------------------------------------+
 |  9      38     7      |  345    48     458    |  6      2      1      |
 |  2      5      38     |  6      7      1      |  389    48     349    |
 |  6      4      1      |  38     29     29     |  358    7      35     |
 |-----------------------+-----------------------+-----------------------|
 |  3      679    48     |  48     5      246    |  1      69     27     |
 |  1      69     45     |  7      246    2346   |  25     369    8      |
 |  57     68     2      |  9      1      368    |  4      36     57     |
 |-----------------------+-----------------------+-----------------------|
 |  47     127    9      |  148    3      4678   |  278    5      246    |
 |  8      37     35     |  2      469    45679  |  79     1      469    |
 |  457    127    6      |  1458   489    45789  |  23789  48     2349   |
 +-----------------------------------------------------------------------+
 # 86 eliminations remain


Yet another example of all the peers of clues/givens not being eliminated by a manual player!!!

From here, the Naked Pair and Naked Quad eliminations can be performed -- leaving my grid above.

[ronk]

Yet another example of all the peers of clues/givens not being eliminated by a manual player!!!

But filled cells, meaning clues and placements, should take precedence IMO. I'd like to know why anyone thinks it should be otherwise!!!

[daj95376]

Yet another example of all the peers of clues/givens not being eliminated by a manual player!!!

But filled cells, meaning clues and placements, should take precedence IMO. I'd like to know why anyone thinks it should be otherwise!!!

In another thread, sometime back, I was convinced that the best perspective of a PM grid was that of an incomplete solution. As such, it's possible that a solved cell didn't have all of its peers eliminated.

The alternative perspective is that some of the peers of clues/givens in the original puzzle were never eliminated prior to posting the PM grid.

Without the original puzzle, either perspective is valid. However, I've had more problems with PM grids since I implemented the first perspective.

Regards, Danny

BTW: Hobiwan was among those who convinced me to use the first perspective. You now know why HoDoKu wouldn't load the original PM grid, either.

[Maria]

There is some mistake with your puzzle it is invalid because it has multiple solutions. Check again if you made a mistake when you typed the numbers or maybe it is a puzzle with multiple solutions indeed and then I wouldn't know what to advice.

it is fine, reconfirmed.

[Maria]

Here is Maria's original grid:
...
Here it is after I edited (/) to be (|):

sorry I am too new on this, how do you write this symbol (|) - cannot find it in my computer

[ronk-moderator edit: Maria, I truncated your quote to give you a better idea of what I meant by quoting "selectively and appropriately." Also, people don't generally put their current response inside quote tags, so I changed that too.]

[Maria]

Yet another example of all the peers of clues/givens not being eliminated by a manual player!!!

But filled cells, meaning clues and placements, should take precedence IMO. I'd like to know why anyone thinks it should be otherwise!!!

In another thread, sometime back, I was convinced that the best perspective of a PM grid was that of an incomplete solution. As such, it's possible that a solved cell didn't have all of its peers eliminated.

The alternative perspective is that some of the peers of clues/givens in the original puzzle were never eliminated prior to posting the PM grid.

Without the original puzzle, either perspective is valid. However, I've had more problems with PM grids since I implemented the first perspective.

Regards, Danny


BTW: Hobiwan was among those who convinced me to use the first perspective. You now know why HoDoKu wouldn't load the original PM grid, either.

Original puzzle (did I complete it trying to solve it?)

Code: Select all

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


Much better now?

[JeJ]

Original puzzle (did I complete it trying to solve it?)

Code: Select all

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


Much better now?

It still nedds to be improved:
Replace the astherisks with dots
Eliminate whatever in r9c9 that is not a 9
There is no blank space before or after the vertical lines that signal de boxes

[Pat]

Original puzzle

Code: Select all

///
 |  *      *    6      |  *    *    *   |   *     *     *9    |


Much better now?

close but no cigar -- that extra 9 in r9c9---

and i too would prefer dots for empty cells, thus --

Code: Select all

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


[JeJ]

It is not just a matter of personal preferences, the most important reason is that many people use computer programs to analize whatever you ask about and these program require a specific format to accept the data, which was defined long ago as to require dots to replace empty cells (you can write the candidate on that too, just write them one after the other whithout any soace in between them).