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another one while we wait ...

 
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Mon Nov 19, 2007 7:02 pm    Post subject: another one while we wait ... Reply with quote

another one while we wait ...

yesterday's diabolical (on a new server):

http://sudoku.labhoo.com/DailySudoku.asp?day=18/11/2007

(can't remember exactly how I did it, but as far as I recall there was one xy-chain and the regular vh stuff like xy-wings, x-wings and the like)
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Mon Nov 19, 2007 8:09 pm    Post subject: Reply with quote

ok, I got really far with this one. boiled it down to a UR which eliminated the 6's in r1c7 and r3c7.

then after that a number of things can happen, you can do an xy chain that eliminates the 7 in r7c8

or there is a finned x-wing that eliminates the 3 in r8c6.

please forgive me I am horrible at typing out grids. maybe someone else can show the grid at which the finned x-wing can be found.


after that finned on the 3's there is a finned on the 5's that eliminates the 5 in r9c6 and that is where I am now.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Mon Nov 19, 2007 8:16 pm    Post subject: Reply with quote

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



this is the original puzzle
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Mon Nov 19, 2007 8:45 pm    Post subject: Reply with quote

I believe this is where basics take us:
Code:

+--------------------------+--------------------------+--------------------------+
| 5       26      19       | 378     69      378      | 126     4       37       |
| 7       3       19       | 269     4       269      | 16      5       8        |
| 8       26      4        | 1       5       37       | 267     367     9        |
+--------------------------+--------------------------+--------------------------+
| 9       8       7        | 4       3       15       | 56      16      2        |
| 3       4       6        | 259     19      1259     | 8       17      57       |
| 2       1       5        | 68      7       68       | 3       9       4        |
+--------------------------+--------------------------+--------------------------+
| 1       9       8        | 357     2       4        | 57      37      6        |
| 46      5       2        | 3679    169     13679    | 49      8       137      |
| 46      7       3        | 569     8       1569     | 49      2       15       |
+--------------------------+--------------------------+--------------------------+


from here there is a w-wing (15 r4 and r9, but it only removes 1 from r9c6) and a few xy-chains, most notably this one

71'(58)='16'(48)='65'(47)='57'(77)

which makes r7c8=3

There are some xy-wings (pivot r4c7, r5c9, r3c8) that don't do anything. Maybe someone'll find a way to transport them?

Oh,yes I almost forgot. Coloring helps, too:

r5c4, 5:-r4c6=r4c7-r5c9=r9c9-r7c7=r7c4-
r9c6, 5:-r4c6=r4c7-r5c9=r9c9- (not the same elimination as the w-wing)
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nataraj



Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria

PostPosted: Mon Nov 19, 2007 8:57 pm    Post subject: Re: another one while we wait ... Reply with quote

nataraj wrote:
can't remember exactly how I did it, but as far as I recall there was one xy-chain and the regular vh stuff like xy-wings, x-wings and the like


I must have been slightly intoxicated last night. Now that I try to do the puzzle again, there is definitely more than just ONE xy chain and none of "the regular stuff" Embarassed
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Mon Nov 19, 2007 8:59 pm    Post subject: Reply with quote

Code:
+--------------------------+--------------------------+--------------------------+
| 5       *26     19       | @378     69     378      | *126    4       @37      |
| 7       3       19       | 269     4       269      | 16      5       8        |
| 8       *26     4        | 1       5       37       | *267    367     9        |
+--------------------------+--------------------------+--------------------------+
| 9       8       7        | 4       3       15       | 56      16      2        |
| 3       4       6        | 259     19      1259     | 8       17      57       |
| 2       1       5        | 68      7       68       | 3       9       4        |
+--------------------------+--------------------------+--------------------------+
| 1       9       8        | @357    2       4        | 57      37      6        |
| 46      5       2        | @3679   169     @13679   | 49      8       @137     |
| 46      7       3        | 569     8       1569     | 49      2       15       |
+--------------------------+--------------------------+--------------------------+


the * marks the UR which eliminates the 6's in r1c7 and r3c7

the @ marks the finned x-wing that eliminates the 3 in r8c6
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Mon Nov 19, 2007 9:00 pm    Post subject: Reply with quote

thanx for the applaus, that was my first grid, cigars not welcome however Shocked
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA

PostPosted: Mon Nov 19, 2007 9:53 pm    Post subject: Reply with quote

I have a question. Myth Jellies did something like this once, I thought it was really brilliant.
Code:
+-------------------+-------------------+-------------------+
| 5     26    19    | 378   69#   378   | 12    4     37    |
| 7     3     19    | 269@  4     269@  | 16    5     8     |
| 8     26    4     | 1     5     37    | 27    367   9     |
+-------------------+-------------------+-------------------+
| 9     8     7     | 4     3     15    | 56    16    2     |
| 3     4     6     | 259@  19#   1259@ | 8     17    57    |
| 2     1     5     | 68    7     68    | 3     9     4     |
+-------------------+-------------------+-------------------+
| 1     9     8     | 357   2     4     | 57    37    6     |
| 46    5     2     | 3679  169%  13679 | 49    8     137   |
| 46    7     3     | 569   8     1569  | 49    2     15    |
+-------------------+-------------------+-------------------+

The UR on <29> labeled @ is also an X-wing on <2>. Two diagonal cells must be <2>, one of the others cannot be <9>. This means either of the cells # must be <9>, and we can eliminate <9> from %.

Correct? If so, I think it is it is the first time I have made an elimination for a UR that has extra candidates on all four corners. Too bad, it does little to help solve the puzzle.

Keith
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Johan



Joined: 25 Jun 2007
Posts: 206
Location: Bornem Belgium

PostPosted: Tue Nov 20, 2007 12:46 am    Post subject: Reply with quote

There is a useless [15-57-17] xy-wing with pivot in R5C9, solving the

puzzle in one step.

One of the two pincer-cells R5C8 or R9C9 must be <1> (in this case they can't be both <1>, because when R9C9=1 => R4C8=1, and when R5C8=1 => R8C9=1)

A=1, a is not

Now we have a contradiction in C6 => R5C8=7 solving the puzzle.


Code:


+----------+----------------+-------------+
| 5  26 19 | 378  69  378   | 126 4   37  |
| 7  3  19 | 269  4   269   | 16  5   8   |
| 8  26 4  | 1    5   37    | 267 367 9   |
+----------+----------------+-------------+
| 9  8  7  | 4    3  A15    |56  a16  2   |
| 3  4  6  | 259  19  1259  | 8  A17  57  |
| 2  1  5  | 68   7   68    | 3   9   4   |
+----------+----------------+-------------+
| 1  9  8  | 357  2   4     | 57  37  6   |
| 46 5  2  | 3679 169 13679 | 49  8   137 |
| 46 7  3  | 569  8  A1569  | 49  2  a15  |
+----------+----------------+-------------+
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Tue Nov 20, 2007 1:50 am    Post subject: Reply with quote

Quote:
Now we have a contradiction in C6 => R5C8=7 solving the puzzle.


Code:
+----------+----------------+-------------+
| 5  26 19 | 378  69  378   | 126 4   37  |
| 7  3  19 | 269  4   269   | 16  5   8   |
| 8  26 4  | 1    5   37    | 267 367 9   |
+----------+----------------+-------------+
| 9  8  7  | 4    3  A15    |56  a16  2   |
| 3  4  6  | 259  19  1259  | 8  A17  57  |
| 2  1  5  | 68   7   68    | 3   9   4   |
+----------+----------------+-------------+
| 1  9  8  | 357  2   4     | 57  37  6   |
| 46 5  2  | 3679 169 13679 | 49  8   137 |
| 46 7  3  | 569  8  A1569  | 49  2  a15  |
+----------+----------------+-------------+


I would get to the same result without proving a contradiction, by using what I have learned to call an XY-Wing with coloring. The little chain you started in box 6 now means that the new pincer in r4c6 works with the old pincer in r9c9 to eliminate the 1 from r9c6, solving r9c9.
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ravel



Joined: 21 Apr 2006
Posts: 536

PostPosted: Tue Nov 20, 2007 10:07 am    Post subject: Reply with quote

keith wrote:
The UR on <29> labeled @ is also an X-wing on <2>. Two diagonal cells must be <2>, one of the others cannot be <9>. This means either of the cells # must be <9>, and we can eliminate <9> from %.

Correct?
Yes. As i recently wrote, you can also see it from the fact that the two 9's are the only 29-candidates in the 2 boxes outside the UR.

From Keiths position you can solve it with a w-ing (37), 2 strong links (skyscraper) in 5 and another w-wing then.
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