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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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 Posted: Mon Nov 19, 2007 7:02 pm Post subject: another one while we wait ... |
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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
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| Posted: Mon Nov 19, 2007 8:09 pm Post subject: |
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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
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| Posted: Mon Nov 19, 2007 8:16 pm Post subject: |
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| 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
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| Posted: Mon Nov 19, 2007 8:45 pm Post subject: |
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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 |
+--------------------------+--------------------------+--------------------------+
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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
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| Posted: Mon Nov 19, 2007 8:57 pm Post subject: Re: another one while we wait ... |
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| 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"  |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Mon Nov 19, 2007 8:59 pm Post subject: |
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| 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
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| Posted: Mon Nov 19, 2007 9:00 pm Post subject: |
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thanx for the applaus, that was my first grid, cigars not welcome however  |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Mon Nov 19, 2007 9:53 pm Post subject: |
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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 |
+-------------------+-------------------+-------------------+
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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
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| Posted: Tue Nov 20, 2007 12:46 am Post subject: |
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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
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| Posted: Tue Nov 20, 2007 1:50 am Post subject: |
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| 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 |
+----------+----------------+-------------+ |
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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
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| Posted: Tue Nov 20, 2007 10:07 am Post subject: |
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| 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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