Difficult Puzzles. Chains can be avoided.

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Postby re'born » Sun Jun 10, 2007 5:13 pm

wapati wrote:There is a robust Jellyfish in this puzzle, as well as many smaller patterns.

Code: Select all
. . 3 | . . . | . . 1
. 9 4 | . . . | . . .
. 7 . | 2 . 4 | 9 3 .
---------------------
. . . | . 3 . | 8 . 7
. 2 . | 4 . 8 | . 9 .
3 . 6 | . 9 . | . . .
---------------------
. 4 2 | 3 . 7 | . 8 .
. . . | . . . | 5 7 .
7 . . | . . . | 4 . .


After the basics, we get:
Code: Select all
 *--------------------------------------------------------------------*
 | 28     56     3      | 569    78     569    | 27     4      1      |
 | 12568  9      4      | 156    15678  3      | 267    256    568    |
 | 1568   7      15     | 2      1568   4      | 9      3      568    |
 |----------------------+----------------------+----------------------|
 | 4      15A    9      | 156    3      1256   | 8      1256   7      |
 | 15a    2      7      | 4      156A   8      | 3      9      56     |
 | 3      8      6      | 7      9      125    | 12     125    4      |
 |----------------------+----------------------+----------------------|
 | 156    4      2      | 3      15-    7      | 16c    8      9      |
 | 9      3      18     | 168    4      16     | 5      7      2      |
 | 7      156a   158    | 1589   2      159    | 4      16C    3      |
 *--------------------------------------------------------------------*

where a little multicoloring implies r7c5<>1.
[r7c5]-1-[r7c7]=1=[r9c8]-1-[r9c2]=1=[r4c2]-1-[r5c1]=1=[r5c5]-1-[r7c5]

But r7c5=5 implies r7c1<>5 and now we get an xy-chain:
6-[r9c2]-1-[r7c7]-6-[r7c1]-1-[r5c1]-5-[r9c5]-6, => r4c8<>6, which solves the puzzle.
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Postby ravel » Sun Jun 10, 2007 6:10 pm

See also my solution at the end of the short chains thread.
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Postby wapati » Mon Jun 11, 2007 9:26 pm

A large bag of methods. Quite a few, but not big fish category. (OK, maybe a finned swordfish.}

Code: Select all
. 6 .|. 9 .|. 7 .
. . .|. 5 .|3 . 1
2 . .|. . 3|. . .
-----+-----+-----
7 . .|9 . .|. 1 3
. . .|. 6 .|. . .
1 9 .|. . 5|. . 2
-----+-----+-----
. . .|2 . .|. . 9
3 . 4|. 1 .|. . .
. 1 .|. 7 .|. 2 .
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Postby re'born » Mon Jun 11, 2007 11:11 pm

wapati wrote:A large bag of methods. Quite a few, but not big fish category. (OK, maybe a finned swordfish.}

Code: Select all
 *-----------------------------------------------------------*
 | 458   6     3     | 4A8a  9     1     | 2     7     5-48  |
 | 489   478   789   | 6     5     2     | 3     4a8A  1     |
 | 2     458   1     | 7     48    3     | 4589  59    6     |
 |-------------------+-------------------+-------------------|
 | 7     458   568   | 9     2     48    | 4568  1     3     |
 | 458   3     2     | 1     6     7     | 4589  59    458   |
 | 1     9     68    | 4a8A  3     5     | 7     4A68  2     |
 |-------------------+-------------------+-------------------|
 | 568   578   578   | 2     48    468   | 1     3     9     |
 | 3     2     4     | 5     1     9     | 68    68    7     |
 | 689   1     89    | 3     7     68    | 45    2     45    |
 *-----------------------------------------------------------*

A little 3D coloring implies r1c9<>4,8. This solves the puzzle. Note that the elimination of 8 can be seen as a Y-wing style, while the elimination of the 4 is just a skyscraper.
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Postby wapati » Tue Jun 12, 2007 12:41 am

Whew, I didn't expect such a fast solution.

This is also pretty good.



Code: Select all
. . .|. 4 .|. . .
. 4 .|2 . 7|. 6 .
. 3 .|1 . 9|. 5 .
-----+-----+-----
. . 2|. . .|7 . .
3 . .|5 . 8|. . 1
. 8 .|. 7 .|. 3 .
-----+-----+-----
. 5 3|6 . 2|8 7 .
. 7 9|. . .|3 2 .
. . .|. 3 .|. . .
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Postby re'born » Tue Jun 12, 2007 10:48 am

wapati wrote:Whew, I didn't expect such a fast solution.

This is also pretty good.



Code: Select all
. . .|. 4 .|. . .
. 4 .|2 . 7|. 6 .
. 3 .|1 . 9|. 5 .
-----+-----+-----
. . 2|. . .|7 . .
3 . .|5 . 8|. . 1
. 8 .|. 7 .|. 3 .
-----+-----+-----
. 5 3|6 . 2|8 7 .
. 7 9|. . .|3 2 .
. . .|. 3 .|. . .



Code: Select all
 *--------------------------------------------------------------------*
 | 25679  1269   156    | 3      4      56     | 129    189    2789   |
 | 589    4      158    | 2      58     7      | 19     6      3      |
 | 27     3      68     | 1      68     9      | 4      5      27     |
 |----------------------+----------------------+----------------------|
 | 4569   169    2      | 49     16     3      | 7      89     5689   |
 | 3      69     7      | 5      2      8      | 69     4      1      |
 | 4569   8      1456   | 49     7      16     | 2569   3      2569   |
 |----------------------+----------------------+----------------------|
 | 1      5      3      | 6      9      2      | 8      7      4      |
 | 46     7      9      | 8      15     145    | 3      2      56     |
 | 2468   26     468    | 7      3      45     | 1569   19     569    |
 *--------------------------------------------------------------------*


After the basics, one can simultaneously find two empty rectangles, one on 6 (box 1), which implies r6c3<>6, and one on 9 (box 3) that implies r1c2<>9. After cleaning up the resulting mess, a short xy-chain
4-[r6c3]-1-[r6c6]-6-[r1c6]-5-[r9c6]-4, =>r9c3<>4
solves the puzzle.
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Postby wapati » Tue Jun 12, 2007 7:46 pm

There should be a swordfish here, finned or not, depending on your method order.

Code: Select all
. 4 8|1 . 9|5 7 .
9 . .|. 7 .|. . 1
. . .|4 5 3|. . .
-----+-----+-----
. . 3|. . .|2 . .
1 . .|. . .|. . 7
5 2 .|. . .|. 6 3
-----+-----+-----
. 8 .|2 . 4|. 5 .
. . 9|. . .|6 . .
. . .|. 1 .|. . .
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Postby wapati » Tue Jun 12, 2007 9:46 pm

Because of the new owners, I won't post here.

If you care, my thread is moved to:

http://www.setbb.com/sudoku/viewtopic.php?t=1432&mforum=sudoku

I will not be reading, or posting here.


It is the new owners format I protest. And it sucks.

I do not care who owns this place, I very much dislike the visual change.
To the point I will not read or post here.


Edited to deliniate my position.
Last edited by wapati on Tue Jun 12, 2007 9:14 pm, edited 1 time in total.
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Location: Brampton, Ontario, Canada

Postby Mauricio » Tue Jun 12, 2007 10:13 pm

You should try http://forum.enjoysudoku.com/index.php , and then the forum is back to normal.

Edit: The comma was interfering with the link.
Last edited by Mauricio on Wed Jun 13, 2007 3:49 am, edited 1 time in total.
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Postby Havard » Tue Jun 12, 2007 11:21 pm

wapati wrote:Becuase of the new owners, I won't post here.

If you care, my thread is moved to:

http://www.setbb.com/sudoku/viewtopic.php?t=1432&mforum=sudoku

I will not be reading, or posting here.


wapati got a point. A lot of people put in a lot of effort into this place, all knowing it is for the greater good of sudoku. I think people might think twice about contributing if they know that their efforts are making someone else money...

Owning the domainname sudoku.com should be enough in itself. Please let us have this forum for ourselves before it becomes destroyed forever...

Havard
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Postby udosuk » Wed Jun 13, 2007 7:12 am

Mauricio, your link is a dead link. The correct url should be like the following:

http://www.sudoku.com/boards

or

http://forum.enjoysudoku.com/index.php


Too bad wapati is gone because of a minor change. I'll stay put for now and see if there are other changes and see if those changes (if any) are drastical enough to drive me from here.

After all I think "sudoku.com" is the main reason this huge community is established (other than the great software from Wayne Gould and his son Scott). If not for the domain name I doubt if it would be so much bigger than the setbb forum (for programmers) or other forums such as djape's forum or Ruuds' SudoCue forum.
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Postby ronk » Wed Jun 13, 2007 12:08 pm

udosuk wrote:Too bad wapati is gone because of a minor change. I'll stay put for now and see if there are other changes and see if those changes (if any) are drastical enough to drive me from here.

For now I'm staying too, and I wouldn't be surprised if wapati returns. The community on the Programmers' Forum (setbb.com) is not very active, and the site seems much slower. Of course, things might change there too.
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An outstanding sudoku!

Postby claudiarabia » Sun Jul 01, 2007 2:47 pm

This sudoku isn't very symmetric, but has a lot of techniques inside - except forcing chains. I rarely saw a sudoku in my whole life, which combine so many strategies below the forcing chain.
Code: Select all
6 . 7 . 8 . 5 . 3
. 9 . . . . . 8 .
4 . . . . . . . 6
. . . 4 . . . . .
5 . . 2 . 1 . . 4
9 . . . . 3 . . 8
3 . . . . . . . 7
. . . . . . . 6 .
7 . 5 . 1 . 8 . 9
SE 6.6 X-Wing, Swordfish, Hidden Triplet, Unique Rectangle Type 1 and 3, Turbot Fish, 4 xy-wings, a JELLYFISH and a UNIQUE LOOP TYPE 3 (Buglite)!

I also feel sorry that the chains-not-required-threads are so often interrupted by those empty failure-pages in the end. Either you ignore these pages and post your sudokus in the last before page. Then the failure-page will remain but in the end it doesn't affect the thread severely. Or some of the Admins mould the various wapati-no-chain-threads together in a thread which is not affected by this error. So we would have a big nice collection of no-chain-puzzles.

Happy solving

Claudia
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