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Impossible Menneske No. 09
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keith



Joined: 19 Sep 2005
Posts: 3150
Location: near Detroit, Michigan, USA

PostPosted: Sun Mar 17, 2013 1:09 am    Post subject: Impossible Menneske No. 09 Reply with quote

Can't believe the last No. 08 could be solved by a skyscraper!

Code:
 M6911894  Impossible (4637)
+-------+-------+-------+
| 2 5 . | 6 . . | . . 9 |
| . . . | . . . | . 5 . |
| . . . | . 3 . | . 6 . |
+-------+-------+-------+
| 6 . . | . 4 3 | . . . |
| . . 7 | . . . | . . 5 |
| . . . | 2 1 . | . 4 . |
+-------+-------+-------+
| . 7 . | 1 . . | 4 . . |
| . . . | . . . | . 1 . |
| 1 9 . | . . 6 | . . 7 |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

Keith
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JC Van Hay



Joined: 13 Jun 2010
Posts: 364
Location: Charleroi, Belgium

PostPosted: Sun Mar 17, 2013 8:08 am    Post subject: Reply with quote

#1. Locked Subsets and Nishio; UP27
r5c5=6
NP(89)r5c46

Skyscraper(4R19):=> -4r23c4.r8c6; HP(34)r89c4
LC(5r789c5)
X-Chain(7R86C8) :=> -7r1c56; LC(7r1c78);r1c5=8=r5c4,r5c6=9
LC(9r78c5)
Code:
+----------------------+----------------------+------------------------+
| 2      5      134    | 6    8        14     | 137        37    9     |
| 34789  13468  134689 | 79   27       124-7  | 1238       5     12348 |
| 4789   148    1489   | 579  3        1245-7 | 128        6     1248  |
+----------------------+----------------------+------------------------+
| 6      128    12589  | 57   4        3      | 12789      2789  128   |
| 34     1234   7      | 8    6        9      | 123        23    5     |
| 3589   38     3589   | 2    1        5(7)   | -389(67)   4     368   |
+----------------------+----------------------+------------------------+
| 358    7      23568  | 1    259      28     | 4          2389  2368  |
| 3458   23468  234568 | 34   -25(79)  28(7)  | -2358(69)  1     2368  |
| 1      9      23458  | 34   25       6      | 2358       238   7     |
+----------------------+----------------------+------------------------+
#2. Loop[4] : 7r6c6=(7-6)r6c7=(6-9)r8c7=(9-7)r8c5=7r8c6 @ :=> -7r23c6,r6c7=67,r8c7=69,r8c5=79; UP59; LC(1r12c3); UP81
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DonM



Joined: 15 Sep 2009
Posts: 51

PostPosted: Mon Mar 18, 2013 1:39 am    Post subject: Reply with quote

JC, I'm wondering where the Nishio came from. I haven't seen it mentioned as part of a solution for a long time.
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keith



Joined: 19 Sep 2005
Posts: 3150
Location: near Detroit, Michigan, USA

PostPosted: Mon Mar 18, 2013 2:46 am    Post subject: Reply with quote

DonM wrote:
JC, I'm wondering where the Nishio came from. I haven't seen it mentioned as part of a solution for a long time.

Sudoku Susser does both Bowman's Bingo and Nishio.

Keith
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JC Van Hay



Joined: 13 Jun 2010
Posts: 364
Location: Charleroi, Belgium

PostPosted: Mon Mar 18, 2013 8:26 am    Post subject: Reply with quote

DonM wrote:
JC, I'm wondering where the Nishio came from. I haven't seen it mentioned as part of a solution for a long time.

I borrowed the term Nishio from Ruud's SudoCue Solver to mean the elimination of all the candidates that do not occur in any of the solutions of a single digit. In some sense, it is the easiest and fastest first thing to do while filling the puzzle with pencilmarkings as it requires no technique in the usual sense, but only a global description of all the solutions of a single digit. For reasons of "esthetical presentation", to find a "simple" interpretation of each elimination is another, but not always as easy and as fast, interesting task to do afterwards!

With the Disjoint Subsets, it produces a "clean" initial Possibility Matrix.
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DonM



Joined: 15 Sep 2009
Posts: 51

PostPosted: Wed Mar 20, 2013 12:54 am    Post subject: Reply with quote

JC Van Hay wrote:
DonM wrote:
JC, I'm wondering where the Nishio came from. I haven't seen it mentioned as part of a solution for a long time.

I borrowed the term Nishio from Ruud's SudoCue Solver to mean the elimination of all the candidates that do not occur in any of the solutions of a single digit. In some sense, it is the easiest and fastest first thing to do while filling the puzzle with pencilmarkings as it requires no technique in the usual sense, but only a global description of all the solutions of a single digit. For reasons of "esthetical presentation", to find a "simple" interpretation of each elimination is another, but not always as easy and as fast, interesting task to do afterwards!

With the Disjoint Subsets, it produces a "clean" initial Possibility Matrix.


I'm still totally confused. Nishio was always used to refer to a method that involved plugging in a number in a cell and seeing where it went and fell out of use around 2006 after more elegant methods were 'discovered'. It has never been used (afaik) as a method to prepare a puzzle for more advanced solving.

You are such a clever solver and I'd like to be able to follow your solutions, but I find it hard to do so (except for the part(s) following a grid) because of a lack of a common standard starting point.
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DonM



Joined: 15 Sep 2009
Posts: 51

PostPosted: Wed Mar 20, 2013 1:17 am    Post subject: Reply with quote

Menneske Impossible 9 (ER=7.2) at SSTS (post Simple Sudoku Technique Set ie. 'No hint possible'):
Code:
 
 *--------------------------------------------------------------------------------------*
 | 2        5        1348     | 6        78       148      | 1378     378      9        |
 | 34789    13468    134689   | 789      2789     124789   | 12378    5        12348    |
 | 4789     148      1489     | 5789     3        1245789  | 1278     6        1248     |
 |----------------------------+----------------------------+----------------------------|
 | 6        128      12589    | 57       4        3        | 12789    2789     128      |
 | 34       1234     7        | 89       6        89       | 123      23       5        |
 | 3589     38       3589     | 2        1        57       | 36789    4        368      |
 |----------------------------+----------------------------+----------------------------|
 | 358      7        23568    | 1        2589     289      | 4        2389     2368     |
 | 3458     23468    234568   | 34       25789    2789     | 235689   1        2368     |
 | 1        9        23458    | 34       258      6        | 2358     238      7        |
 *--------------------------------------------------------------------------------------*

1. grp(7)r23c4=r4c4-r4c8=(7)r1c8 => 3 singles -> LC(9):-9r2c5, LC(7):-7r23c6
2. (7)r4c4=grp(7)r23c4-r2c5=(7-9)r8c5=r7c5-r7c8=(9)r4c8 => -7r4c8 -> r1c8=7 -> nq(1238)r1235c7 => r9c7=5
stte
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JC Van Hay



Joined: 13 Jun 2010
Posts: 364
Location: Charleroi, Belgium

PostPosted: Wed Mar 20, 2013 7:16 pm    Post subject: Reply with quote

DonM wrote:
JC Van Hay wrote:
DonM wrote:
JC, I'm wondering where the Nishio came from. I haven't seen it mentioned as part of a solution for a long time.

I borrowed the term Nishio from Ruud's SudoCue Solver to mean the elimination of all the candidates that do not occur in any of the solutions of a single digit. In some sense, it is the easiest and fastest first thing to do while filling the puzzle with pencilmarkings as it requires no technique in the usual sense, but only a global description of all the solutions of a single digit. For reasons of "esthetical presentation", to find a "simple" interpretation of each elimination is another, but not always as easy and as fast, interesting task to do afterwards!

With the Disjoint Subsets, it produces a "clean" initial Possibility Matrix.


I'm still totally confused. Nishio was always used to refer to a method that involved plugging in a number in a cell and seeing where it went and fell out of use around 2006 after more elegant methods were 'discovered'. It has never been used (afaik) as a method to prepare a puzzle for more advanced solving.

To avoid any confusion, I ought to use the acronym USDE for Unit and single Digit Eliminations instead of Locked Subsets and Nishio ! The basic idea being, before using more "advanced solving", to get a "clean initial Possibility Matrix" where each candidate belongs to a solution of each unit in which it is sitting and of the digit it represents as a direct application of the Sudoku puzzle rules. The only player I know that would do so is my intellectual guide, Stephen Kurzhals, as I can infer from his blog on the au site.

Concerning the actual puzzle and as I never used neither Simple Sudoku Solver nor SSTS, I am confused by the fact that your XWing in step 1 is not included in SSTS as it gives -7r1c56, while SSTS would only give -7r1c6 !?
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DonM



Joined: 15 Sep 2009
Posts: 51

PostPosted: Wed Mar 20, 2013 9:02 pm    Post subject: Reply with quote

JC Van Hay wrote:
DonM wrote:
JC Van Hay wrote:
DonM wrote:
JC, I'm wondering where the Nishio came from. I haven't seen it mentioned as part of a solution for a long time.

I borrowed the term Nishio from Ruud's SudoCue Solver to mean the elimination of all the candidates that do not occur in any of the solutions of a single digit. In some sense, it is the easiest and fastest first thing to do while filling the puzzle with pencilmarkings as it requires no technique in the usual sense, but only a global description of all the solutions of a single digit. For reasons of "esthetical presentation", to find a "simple" interpretation of each elimination is another, but not always as easy and as fast, interesting task to do afterwards!

With the Disjoint Subsets, it produces a "clean" initial Possibility Matrix.


I'm still totally confused. Nishio was always used to refer to a method that involved plugging in a number in a cell and seeing where it went and fell out of use around 2006 after more elegant methods were 'discovered'. It has never been used (afaik) as a method to prepare a puzzle for more advanced solving.

To avoid any confusion, I ought to use the acronym USDE for Unit and single Digit Eliminations instead of Locked Subsets and Nishio ! The basic idea being, before using more "advanced solving", to get a "clean initial Possibility Matrix" where each candidate belongs to a solution of each unit in which it is sitting and of the digit it represents as a direct application of the Sudoku puzzle rules. The only player I know that would do so is my intellectual guide, Stephen Kurzhals, as I can infer from his blog on the au site.


Yes, I recognized Steve K's influence. Smile To the best of my knowledge, outside of his blog, Steve did virtually all of his solving of advanced puzzles with us at Eureka starting in 2007 where we solved the UK forum Extremes and puzzles of ER=8.1 and above for 2-3 years. For a period after that he continued to present advanced solutions with the solver known as ttt.

What Steve presented in his blog and solving with us were two different things. In his blog, he knew that his audience varied from beginners to advanced solvers so he presented puzzles of varying difficulty and didn't start the puzzle from an SSTS position so he could show beginners the more basic beginning moves.

However, virtually all the puzzles that he, we or ttt presented on Eureka started at the SSTS position. None of us wanted to bother with intitial basic methods and we wanted to be able to compare each other's manual solutions which was only possible because we were starting at the same SSTS position (which means simply loading the puzzle into Simple Sudoku and pressing the F11 key until you get a 'No hint available' message at the bottom of the puzzle).

I have to say that I don't think I was ever able to come up with a solution that was better than Steve's. To this day, I think he had a better grasp on the application of the logic of sudoku to manual solving than virtually anyone else and I certainly learned more about advanced manual solving from him than almost anyone else (though there were other great influential sudoku minds around at that time).

edit: Actually, doing a quick check, Steve did use the SSTS position in his later, and final, blogs:
http://sudoku.com.au/sudokutips.aspx?Go=T13-1-1991
http://sudoku.com.au/sudokutips.aspx?Go=P13-1-1991
http://sudoku.com.au/sudokutips.aspx?Go=C9-2-1991

Quote:

Concerning the actual puzzle and as I never used neither Simple Sudoku Solver nor SSTS, I am confused by the fact that your XWing in step 1 is not included in SSTS as it gives -7r1c56, while SSTS would only give -7r1c6 !?


I don't see an XWing, but my step 1 is essentially a skyscraper using a group. You're right that ordinarily the skyscraper move would result in -7r1c56 (if 7r1c6 was still there), but Simple Sudoku doesn't have things like skyscrapers or kites in its technique set. Just for giggles I went back and ran the puzzle through SS and it turned out that it removed 7r1c6 using Multiple Colors.
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oaxen



Joined: 10 Jul 2006
Posts: 96

PostPosted: Thu Mar 21, 2013 12:45 pm    Post subject: Reply with quote

To me the Menneske puzzles are interesting as there are very few bivalues and my method is to find out which of them are possible ways to solve. In this case Block E with the 5 and 7 is interesting, all the other ones leads to dead ends. 5 in R6C6 goes direct to the target. 5 in R4C4 needs opening af a seconadary chain. I have a feeling that every puzzle can be one steppers - if you find the right bivalue.
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JC Van Hay



Joined: 13 Jun 2010
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Location: Charleroi, Belgium

PostPosted: Thu Mar 21, 2013 1:16 pm    Post subject: Reply with quote

oaxen wrote:
... I have a feeling that every puzzle can be one steppers - if you find the right bivalue.
Hmmm... What about this puzzle?
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oaxen



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PostPosted: Thu Mar 21, 2013 2:45 pm    Post subject: Reply with quote

JC Van Hay wrote:
oaxen wrote:
... I have a feeling that every puzzle can be one steppers - if you find the right bivalue.
Hmmm... What about this puzzle?


As I said, with a 5 in R6C6 all the rest is basic. Just for fun I afterwards tested other bivalues, but none lead to a solution without opening secondary chains, like 5 in R4C4 demands. Question
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oaxen



Joined: 10 Jul 2006
Posts: 96

PostPosted: Thu Mar 21, 2013 2:50 pm    Post subject: Reply with quote

Sorry I misunderstood you. You sent me a link to something. Now already printed, we will se what happens when I have the time to start with it.
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ronk



Joined: 07 May 2006
Posts: 397

PostPosted: Thu Mar 21, 2013 10:38 pm    Post subject: Reply with quote

JC Van Hay wrote:
#1. Locked Subsets and Nishio; UP27
r5c5=6
NP(89)r5c46

To add some precision to this discussion, would you please provide the pencilmarks and tag the candidates involved in the first (or the most interesting) such "Nishio" move of your solution path?
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JC Van Hay



Joined: 13 Jun 2010
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Location: Charleroi, Belgium

PostPosted: Fri Mar 22, 2013 6:50 am    Post subject: Reply with quote

ronk wrote:
JC Van Hay wrote:
#1. Locked Subsets and Nishio; UP27
r5c5=6
NP(89)r5c46

To add some precision to this discussion, would you please provide the pencilmarks and tag the candidates involved in the first (or the most interesting) such "Nishio" move of your solution path?
I posted a less trivial example of what I called "Nishio" on the Players forum here
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keith



Joined: 19 Sep 2005
Posts: 3150
Location: near Detroit, Michigan, USA

PostPosted: Sat Mar 23, 2013 8:56 pm    Post subject: Reply with quote

JC Van Hay wrote:
ronk wrote:
JC Van Hay wrote:
#1. Locked Subsets and Nishio; UP27
r5c5=6
NP(89)r5c46

To add some precision to this discussion, would you please provide the pencilmarks and tag the candidates involved in the first (or the most interesting) such "Nishio" move of your solution path?
I posted a less trivial example of what I called "Nishio" on the Players forum here

What you did in that puzzle reminds me of Medusa Coloring.

I learned something today, and used it to solve a puzzle that otherwise had me stumped. For a pencil and paper pattern guy, that's something!

Keith
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keith



Joined: 19 Sep 2005
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Location: near Detroit, Michigan, USA

PostPosted: Sat Mar 23, 2013 9:50 pm    Post subject: Reply with quote

Here is what Sudopedia says about Nishio:

http://www.dailysudoku.com/sudoku/forums/viewtopic.php?p=36129

Keith
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