The New Sudoku Players' Forum

[mayres]

Can someone PLEASE tell me the logic for determining the next box after this point? THANK YOU.

1356 135 135 | 9 18 7 | 2 4 13568
1356 4 8 | 16 2 35 | 7 9 1356
7 2 9 | 168 4 35 | 568 58 13568
--------------------+--------------------+-------------------
23 8 237 | 27 5 6 | 4 1 9
1259 159 125 | 3 18 4 | 568 7 2568
4 6 1257 | 1278 9 12 | 58 3 258
------------------+--------------------+-------------------
1258 15 1245 | 124 6 9 | 3 58 7
1258 7 1245 | 124 3 12 | 9 6 58
39 39 6 | 5 7 8 | 1 2 4

[daj95376]

Are you sure you copied the original puzzle correctly. This is a very difficult puzzle to be in a Sudoku for Dummies book. Assuming that your pencilmarks are correct, the following elimination is probably the easiest among those available.

Code: Select all

# 2-String Kite => [r6c9]<>8
 *-----------------------------------------------------------------------*
 |  1356   135    135    |  9     *18     7      |  2      4     *13568  |
 |  1356   4      8      |  16     2      35     |  7      9      1356   |
 |  7      2      9      | *168    4      35     |  568    58     13568  |
 |-----------------------+-----------------------+-----------------------|
 |  23     8      237    |  27     5      6      |  4      1      9      |
 |  1259   159    125    |  3      18     4      |  568    7      2568   |
 |  4      6      1257   | *1278   9      12     |  58     3      25-8   |
 |-----------------------+-----------------------+-----------------------|
 |  1258   15     1245   |  124    6      9      |  3      58     7      |
 |  1258   7      1245   |  124    3      12     |  9      6      58     |
 |  39     39     6      |  5      7      8      |  1      2      4      |
 *-----------------------------------------------------------------------*


[udosuk]

A "mutant" WXYZ-wing cracks it:

Code: Select all

 *--------------------------------------------------------------------*
 | 1356   135    135    | 9      18     7      | 2      4      13568  |
 | 1356   4      8      | 16     2      35     | 7      9      1356   |
 | 7      2      9      | 168    4      35     | 568    58     13568  |
 |----------------------+----------------------+----------------------|
 | 23     8      237    | 27     5      6      | 4      1      9      |
 | 1259   159    125    | 3     *18     4      | 568    7      2568   |
 | 4      6      1257   |-1278   9     *12     |*58     3     *258    |
 |----------------------+----------------------+----------------------|
 | 1258   15     1245   | 124    6      9      | 3      58     7      |
 | 1258   7      1245   | 124    3      12     | 9      6      58     |
 | 39     39     6      | 5      7      8      | 1      2      4      |
 *--------------------------------------------------------------------*

Pilot/pivot cell: r6c6={12} (could have been {1258} and the move still works)
Wing cells: r5c5={18}, r6c7={58}, r6c9={258}
Elimination: r6c4<>8

Singles solve the rest.

This move can also be represented as a simple ALS-xz move.

[Pat]

Are you sure you copied the original puzzle correctly

it would be nice to see the original puzzle

This is a very difficult puzzle to be in a Sudoku for Dummies book

some tough puzzles from Sudoku for Dummies have been mentioned --

• #186
• #222
• #240
• #___
  

[ronk]

it would be nice to see the original puzzle

Sudoku for Dummies #233 is most likely this 180-degree rotationally symmetric minimal.

Code: Select all

 ...|9.7|2..
 .48|.2.|...
 7.9|.4.|...
----+---+----
 .8.|.5.|.19
 ...|3.4|...
 46.|.9.|.3.
----+---+----
 ...|.6.|3.7
 ...|.3.|96.
 ..6|5.8|...

This minimal still needs only two naked pairs and the ALS xz-rule noted by udosuk.

[mayres]

I am quite sure that I copied the information down correctly, but I will confirm tomorrow (the book is at work and I am at home) - I will then copy the original format of the puzzle and confirm the last post. The book does have four or five series of puzzles from EASY to DIABOLOICAL. This puzzle was from the fourth level called TOUGH. Meanwhile, can you please explain the logic you have already listed in language that would be a little easier for someone who is not a "pro" to understand?
Also - can you please tell me how to put my information into this forum in nice clear plain format like you all are using instead of the jumbled format that I end up with.
Thanks so much for your patience.
Mike

[Pat]

can you please tell me how to put my information into this forum in nice clear plain format like you all are using instead of the jumbled format that I end up with.

use [code] ... [/code] around the puzzle

you write:
[code]
12345

[/code]

you get:

Code: Select all

12345



~ Pat

[mayres]

I remember reading that but it was not too clear - seemed like I must be missing something - didn't know if the "[code]" was supposed to mean some kind of forum actual code or ????
Okay, I will try - please bear with me....THIS IS A TEST

[code]
|------------------+------------------- -+----------------------|
| 1 2 3 | 456 7 8 | 9 123 45
| 67 8 9 | 1 234 567 | 89 1 23

[/code]

It still doesn't seem to line up perfectly when typing - I'm going to assume that something "magical" happens when I submit this because of the "[code]" inserts and it will then????? Thanks for the input.

[mayres]

WEll, it looks exactly like I typed it into the essage body, so I guess I didn't do that right! Slow learner here! Now I'm guessing I needed to press the code button above instead!? LOL

Code: Select all

|------------------+------------------- -+----------------------|
| 1           2     3 | 456     7         8   |   9      123       45
| 67         8     9 | 1       234      567 | 89      1          23


Looks like I am not undertanding the spacing concept either - not just space bar spaces? Is there a "help", "sticky", or something that I should go read to figure this all out? Link? Here goes again with button "[code]" instead of typed........sheeesh.....
Thanks again......... mike

[udosuk]

Mike,

Well, first I suggest you to read through this link:

http://forum.enjoysudoku.com/faq.php?mode=bbcode

(Well, it's kind of long but you've got to learn the basics before you communicate with others...)

As for the [code][/code] thing, I suggest you to type your data using a word processing program such as Notepad (if you're a Windows user). And in there pick a fixed-width font (Fixedsys or Courier New work fine for me). Then copy and paste the content over to the posting window. If you do your spacing within the posting window, chances are you won't get it aligned properly.

Meanwhile, can you please explain the logic you have already listed in language that would be a little easier for someone who is not a "pro" to understand?

Code: Select all

 *--------------------------------------------------------------------*
 | 1356   135    135    | 9      18     7      | 2      4      13568  |
 | 1356   4      8      | 16     2      35     | 7      9      1356   |
 | 7      2      9      | 168    4      35     | 568    58     13568  |
 |----------------------+----------------------+----------------------|
 | 23     8      237    | 27     5      6      | 4      1      9      |
 | 1259   159    125    | 3     *18     4      | 568    7      2568   |
 | 4      6      1257   |-1278   9     *12     |*58     3     *258    |
 |----------------------+----------------------+----------------------|
 | 1258   15     1245   | 124    6      9      | 3      58     7      |
 | 1258   7      1245   | 124    3      12     | 9      6      58     |
 | 39     39     6      | 5      7      8      | 1      2      4      |
 *--------------------------------------------------------------------*

Okay, from the above diagram, visualise what would happen if r6c4 (marked with "-") had been 8. Then r5c5 would be forced to be 1, and r6c7 & r6c9 would be forced to be 5 and 2 respectively. Then you're forced with no valid placement for the cell r6c6 (a "1" would cause two 1s in block 5, a "2" would cause two 2s on row 6). So we reach a contradiction. Therefore r6c4 cannot be 8, and you can eliminate 8 from there.

Alternatively (if you despise contradiction-based reasonings), we can do a "branching analysis". Note that r6c6 can only be "1" or "2":

If r6c6=1, then r5c5=8, and r6c4 cannot be 8.
If r6c6=2, then r6c79 must contain the naked pair {58}, and r6c4 cannot be 8.

Therefore no matter what r6c4 cannot be 8, and we can make that elimination.

Hope you understand it now.

[mayres]

Pat - Here is what the original puzzle looked like.
The stage I gave it to you is where my thought processes took me on it.
Udosuk - Thanks for the posting tips - I think (hope) I'm getting the hang of it!

Code: Select all

 *-----------*
 |...|9.7|2..|
 |.48|.2.|...|
 |7.9|.4.|...|
 |---+---+---|
 |.8.|.5.|.19|
 |...|3.4|...|
 |46.|.9.|.3.|
 |---+---+---|
 |...|.6.|3.7|
 |...|.3.|96.|
 |..6|5.8|...|
 *-----------*


[mayres]

Udosuk - THANKS SO MUCH for the more detailed explanation. I see how both of the "angles" you took work. What I don't yet understand is how you came to choose either of those options?

How many other cells did you try some form of reasoning on that did not get you any headway until you settled on each of these?

How would a person know, for example, to pick r6c4 to try an "8" on? Why not a different number or any other cell with the same form of logic?

The same question applies to your second method - why would you be led to try r6c6 with two options and see where this leads you? Seems like you could use that same process with ANY pair - try one and see where it leads. If it doesn't work then it must be the other one? I actually solved this puzzle using what I have read is called Adriene's (sp?) Thread prior to starting the thread and asking the questions - somehow it seems too much like guessing/"cheating" versus solveing with pure logic. Pick one number out of a pair that sees to have many cells that will be affected by your selection and try a number. If that number doesn't work then try the other one. At what point do you call it good logic and what point guessing? Some people can undoubtedly "see" the ramifications of a move many more cells/moves into the process than another?

Thanks again for your comments and expertise - it is REALLY appreciated.

[udosuk]

Mike, the ways I've explained my move in plain logic doesn't necessarily mean they're the ways I found that move itself. I was just trying to help you see how it works. For more advanced players it's just another pattern-based move such as xy-wing or turbot fish. As you do more hard puzzles and get better you'll start spotting these advanced moves more easily. It's hard to explain in words. It's like asking Roger Federer how he can so easily hit a 200km/h serve directed at him to the opposite corner for a clean winner or asking Tiger Woods how he can hit a 200 yard shot out of a driveway bunker to within 3 feet of the hole. You've either got that skill or you haven't.

As for my particular move, the bottom line is it's a (mutant form of) WXYZ-wing. You first need to learn the mechanism of that move. Try the Advanced solving techniques forum, and look up the Collection of solving techniques thread for that move.

After that, you should be able to recognise the pattern in either it's full form:

Code: Select all

 . . . | .  .  .    | .   . .
 . . . | .  .  .    | .   . .
 . . . | .  .  .    | .   . .
-------+------------+-----------
 . . . | .  .  .    | .   . .
 . . . | .  18 .    | .   . .
 . . . |-8 -8  1258 | 258 . 258
-------+------------+-----------
 . . . | .  .  .    | .   . .
 . . . | .  .  .    | .   . .
 . . . | .  .  .    | .   . .

or any of it's reduced forms, such as:

Code: Select all

 . . . | . .  .  | .  . .
 . . . | . .  .  | .  . .
 . . . | . .  .  | .  . .
-------+---------+----------
 . . . | . .  .  | .  . .
 . . . | . 18 .  | .  . .
 . . . |-8 .  12 | 58 . 258
-------+---------+----------
 . . . | . .  .  | .  . .
 . . . | . .  .  | .  . .
 . . . | . .  .  | .  . .

which is what you can find in this particular puzzle.

[mayres]

Udosuk -
I realize what you are saying, "explain my move in plain logic doesn't necessarily mean they're the ways I found that move itself." What I was trying to get to was HOW DO YOU COME ABOUT FINDING MOVES LIKE THIS? In this particular example did you try many concepts that you have found to work and after some trial and error came to this one - a process that you only learn by doing lots and lots of puzzles? I'm assuming that is what you are telling me. I guess what I hear you saying is that I just have to do more and more puzzles and see if eventually it comes or doesn't. Thankfully I do now understand why your options listed solve the puzzle, I'm just trying to assimilate something that will help me put some principle into practice that will help me in the future. Hmmm Nice tennis example! That WAS some Wimbleton final wasn't it?
"You've either got the skill or you haven't" - YOU GOT IT! Thanks for taking the time to share it with me.......
mike

[Carcul]

Code: Select all

 *--------------------------------------------------------------*
 | 1356   135    135  | 9      18     7   | 2      4      13568 |
 | 1356   4      8    | 16     2      135 | 7      9      1356  |
 | 7      2      9    | 168    4      135 | 568    58     13568 |
 |--------------------+-------------------+---------------------|
 | 23     8      237  | 27     5      6   | 4      1      9     |
 | 1259   159    125  | 3      18     4   | 568    7      2568  |
 | 4      6      1257 | 1278   9      12  | 58     3      258   |
 |--------------------+-------------------+---------------------|
 | 1258   15     1245 | 124    6      9   | 3      58     7     |
 | 1258   7      1245 | 124    3      12  | 9      6      58    |
 | 39     39     6    | 5      7      8   | 1      2      4     |
 *--------------------------------------------------------------*


[r6c3]=7=[r6c4]-7-[r4c4]-2-[r6c6]-1-[r6c3],

which implies r6c3<>1 and the puzzle is solved.