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Puzzle 11/07/21: ~ Advanced

 
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Thu Jul 21, 2011 3:05 pm    Post subject: Puzzle 11/07/21: ~ Advanced Reply with quote

After so many singles, you'd think the puzzle wouldn't need much to crack it. Maybe you're right.

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

Play this puzzle online at the Daily Sudoku site



For those who don't need experience finding Singles:

Code:
 +--------------------------------------------------------------+
 |  8     137   1347  |  9     34    5     |  17    2     6     |
 |  13    2     9     |  17    8     6     |  157   4     135   |
 |  5     6     1347  |  17    34    2     |  9     137   8     |
 |--------------------+--------------------+--------------------|
 |  7     18    6     |  3     5     4     |  18    9     2     |
 |  13    4     138   |  2     6     9     |  1578  17    15    |
 |  2     9     5     |  8     7     1     |  3     6     4     |
 |--------------------+--------------------+--------------------|
 |  9     5     2     |  6     1     3     |  4     8     7     |
 |  6     138   138   |  4     9     7     |  2     5     13    |
 |  4     137   137   |  5     2     8     |  6     13    9     |
 +--------------------------------------------------------------+
 # 40 eliminations remain
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Fri Jul 22, 2011 2:17 pm    Post subject: Reply with quote

I initially found a couple of single digit (1) steps and decided to attempt to complete the puzzle by deleting only (1s). Here is the minimum set I found.

Code:
*-----------------------------------------------------------*
 | 8     137   1347  | 9     34    5     | 17    2     6     |
 | 13    2     9     | 17    8     6     | 157   4     135   |
 | 5     6     1347  | 17    34    2     | 9     137   8     |
 |-------------------+-------------------+-------------------|
 | 7     18    6     | 3     5     4     | 18    9     2     |
 | 13    4     138   | 2     6     9     | 1578  17    15    |
 | 2     9     5     | 8     7     1     | 3     6     4     |
 |-------------------+-------------------+-------------------|
 | 9     5     2     | 6     1     3     | 4     8     7     |
 | 6     138   138   | 4     9     7     | 2     5     13    |
 | 4     137   137   | 5     2     8     | 6     13    9     |
 *-----------------------------------------------------------*


#1: Kraken x-wing(1)r25c19=(1-3)r8c9=r2c9=(3=1)r2c1; r2c47<>1
#2: skyscraper(1)r2c19 plus transport: (1=3)r5c1-(3=1)r2c1-r2c9=r8c9-r9c8=r5c8; r5c37<>1

Code:
*-----------------------------------------------------------*
 | 8     137   1347  | 9     34    5     | 17    2     6     |
 | 13    2     9     | 7     8     6     | 5     4     13    |
 | 5     6     347   | 1     34    2     | 9     37    8     |
 |-------------------+-------------------+-------------------|
 | 7     18    6     | 3     5     4     | 18    9     2     |
 | 13    4     38    | 2     6     9     | 78    17    5     |
 | 2     9     5     | 8     7     1     | 3     6     4     |
 |-------------------+-------------------+-------------------|
 | 9     5     2     | 6     1     3     | 4     8     7     |
 | 6     138   138   | 4     9     7     | 2     5     13    |
 | 4     137   137   | 5     2     8     | 6     13    9     |
 *-----------------------------------------------------------*


#3:
Code:
axy-wing(37-1)b1q24+r1c7=(1)r1c2-r1c3*=(1)r8c3-(8)r8c3=(8-3)r5c3=(3-1)r5c1=r2c1; r1c3*,r2c9<>1
                                      |                                                                                                                      =(1)r9c3-r9c8=r8c9;r1c3*,r2c9<>1


Ted
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susume



Joined: 13 May 2011
Posts: 36
Location: Southeastern US

PostPosted: Sat Jul 23, 2011 2:53 am    Post subject: Reply with quote

Found several deletions of 1s, but in the end only needed two of them:

XYZ wing 137 pivot r1c2 => r1c3<>1
anp (18=3)r48c2-r8c9=r2c9-(3=1)r2c1 => r1c2<>1

Ted, I learned the ANP from your posts, and now they jump out at me when I'm looking for XY wings.
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Sat Jul 23, 2011 8:37 am    Post subject: Reply with quote

Having played an RP in my first pass on this (confession), I wondered if... an oddagon one-stepper!
Code:
 *-----------------------------------------------------------*
 | 8    13(7)  1347  | 9     34    5     |(17)   2     6     |
 |*13   2      9     | 17    8     6     | 157   4    *13+5  |
 | 5    6      1347  | 17    34    2     | 9     137   8     |
 |-------------------+-------------------+-------------------|
 | 7   (18)    6     | 3     5     4     |-18    9     2     |
 |*13   4     *13+8  | 2     6     9     | 1578  17   (15)   |
 | 2    9      5     | 8     7     1     | 3     6     4     |
 |-------------------+-------------------+-------------------|
 | 9    5      2     | 6     1     3     | 4     8     7     |
 | 6    138    138   | 4     9     7     | 2     5    *13    |
 | 4    13(7) *13+7  | 5     2     8     | 6    *13    9     |
 *-----------------------------------------------------------*

oddagon(13) r2c1,r5c1,r5c3,r9c3,r9c8,r8c9,r2c9 ==> r4c7<>1
(8)r5c3 - (8=1)r4c2
||
(5)r2c9 - (5=1)r5c9
||
(7)r9c3 - r9c2=r1c2 - (7=1)r1c7

And an elimination on 1 to boot!
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Luke451



Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California

PostPosted: Sat Jul 23, 2011 1:36 pm    Post subject: Reply with quote

peterj wrote:
Having played an RP in my first pass on this (confession), I wondered if... an oddagon one-stepper!

Oddagonagain! Very nice and concise.
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tlanglet



Joined: 17 Oct 2007
Posts: 2461
Location: Northern California Foothills

PostPosted: Sat Jul 23, 2011 2:26 pm    Post subject: Reply with quote

Hey, you folks are as crazy as I am solving puzzles in weird ways; hope you enjoyed yourselves. Cool

So, I had a "hidden" reason for making this post: Oddogans. This technique has come up a couple of times recently, primarily posted by Luke and Peter, and I tried unsuccessfully to use it on this puzzle.

I found very little info on the topic but have a grasp of how it works; what I don't have is an understanding of how to "spot" the critical pattern. I would greatly appreciate any info on this technique.

Ted
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Luke451



Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California

PostPosted: Sat Jul 23, 2011 4:17 pm    Post subject: Reply with quote

tlanglet wrote:
I found very little info on the topic but have a grasp of how it works; what I don't have is an understanding of how to "spot" the critical pattern. I would greatly appreciate any info on this technique.
Ted


One place to start is the Sudopedia Broken Wing article. As far as spotting them, candidate filtering will make them pop out.

To my knowledge, the "oddagon" term has come into use only in the last couple of years. The first I saw of it was in the work of Steve Kurzhals, who goes deep with the idea. I'm not sure if he originated the term, though.

Here is a "Type 1" oddagon from last year, not deep at all.

Just another "DP/impossible pattern" technique for the quiver.
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peterj



Joined: 26 Mar 2010
Posts: 974
Location: London, UK

PostPosted: Sat Jul 23, 2011 4:50 pm    Post subject: Reply with quote

Ted, Luke,
These are fun patterns - but I have to say I have not yet found a BrokenWing i.e. odd number of strong bi-location links in a loop, that did anything more than perhaps compress two turbot moves (kite or sky) into one. I have read they exist but not so far for me. Now Oddagons i.e. odd number of identical bivalues in a loop (my working definition anyway), seem to do more damage.

Couple of things on spotting them...
- you always seem to need a strong link or pair of bivalues in a diagonal orientation in a block (b9 in this case). Otherwise it's hard to form a loop with an odd number of cells.
- if you get that "remote pair feeling" start looking! An "almost remote pair" is going to be an oddagon. A remote pair which makes both eliminations is a type-1 oddagon I guess.
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Luke451



Joined: 20 Apr 2008
Posts: 310
Location: Southern Northern California

PostPosted: Sat Jul 23, 2011 5:34 pm    Post subject: Reply with quote

This makes me wonder: is the "oddagon" term reserved only for bivalue patterns?

It's the same concept as guardians/broken wings, but I can't recall a single digit pattern labeled as an oddagon.
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ronk



Joined: 07 May 2006
Posts: 397

PostPosted: Sat Jul 23, 2011 6:18 pm    Post subject: Reply with quote

Luke451 wrote:
This makes me wonder: is the "oddagon" term reserved only for bivalue patterns?

It's the same concept as guardians/broken wings, but I can't recall a single digit pattern labeled as an oddagon.

Steve Kurzhals coined the oddagon term AFAIK, so this question should be to him. Steve generally likes broadly-defined terms, so my guess is the answer would be "no".
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Sat Jul 23, 2011 10:09 pm    Post subject: Reply with quote

* I'm not surprised that an oddagon pattern existed.

* I'm not even surprised that three of the cells contained only one extra candidate.

* But Peter knocked my socks off when he managed to get those extra candidates to lead to a common elimination that cracked the puzzle!!!
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