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Feb 26 VH

 
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nataraj



Joined: 03 Aug 2007
Posts: 1047
Location: near Vienna, Austria

PostPosted: Tue Feb 26, 2008 7:14 am    Post subject: Feb 26 VH Reply with quote

Feels like I needed way too many steps for this one.

First, very early, I spotted an xy-wing (almost by accident) 68-18-16 that didn't solve too much.

Coloring on 5 eliminated a few candidates in box 9, which opened an xy-wing 25-12-15, which in turn opend another xy-wing 29-25-59, which finally solved the puzzle.

So many 25, 59 cells, I am sure there must be a w-wing and/or DPs around, too.
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Johan



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

PostPosted: Tue Feb 26, 2008 8:04 am    Post subject: Reply with quote

The possible [25] UR* in R89C16 creates two pincer cells for digit <5>, that takes out both <5>'s in R7C78 and <5> in R9C6 solving the puzzle.
For avoiding the DP

either:
R9C1=9 => R9C5=1 => R9C7=5(B)

or:
R89C6=1=> R9C5=9 => R7C4=5(A)

Code:
+--------------------------+--------------------------+--------------------------+
| 6          7          9  | 2         18      3      | 4         15        158  |
| 1          4          2  | 59        689     568    | 37        37        68   |
| 8          3          5  | 7         4       16     | 2         9         16   |
+--------------------------+--------------------------+--------------------------+
| 3          29         1  | 8         5       7      | 6         4         29   |
| 4          25         6  | 1         3       9      | 8         25        7    |
| 7          59         8  | 6         2       4      | 135       135       159  |
+--------------------------+--------------------------+--------------------------+
| 259        1          3  | 59 A      68      68     |-[5]7      2-[5]7    4    |
|*25         8          4  | 3         7      *125    | 9         6         125  |
|*259        6          7  | 4         19     *12-[5] | 15 B      8         3    |
+--------------------------+--------------------------+--------------------------+
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Tue Feb 26, 2008 9:03 am    Post subject: Reply with quote

I'll post again, but I'm sure this was a two stepper.

and I was reading over on the players forum that Ravel quit posting, is this correct?? hope not.

Norm
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andras



Joined: 31 Oct 2007
Posts: 56
Location: Mid Wales

PostPosted: Tue Feb 26, 2008 9:26 am    Post subject: Reply with quote

Pretty straightforward, I thought; an xy on 1,5,9 broke it right open, making it a one-step job. Smile

John
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Earl



Joined: 30 May 2007
Posts: 590
Location: Victoria, KS

PostPosted: Tue Feb 26, 2008 1:14 pm    Post subject: Feb 26 VH Reply with quote

I got this far and stared at it for some time till I saw a frequent solution to a VH - xy-wings: (125) and (159).

Earl

Code:

+----------+-----------+----------+
| 6   7  9 | 2  18 3   | 4  15 58 |
| 1   4  2 | 59 89 56  | 37 37 68 |
| 8   3  5 | 7  4  16  | 2  9  16 |
+----------+-----------+----------+
| 3   29 1 | 8  5  7   | 6  4  29 |
| 4   25 6 | 1  3  9   | 8  25 7  |
| 7   59 8 | 6  2  4   | 13 13 59 |
+----------+-----------+----------+
| 259 1  3 | 59 6  8   | 57 27 4  |
| 25  8  4 | 3  7  125 | 9  6  12 |
| 259 6  7 | 4  19 25  | 15 8  3  |
+----------+-----------+----------+

Play this puzzle online at the Daily Sudoku site


I did the puzzle again and all I needed was a single xy-wing to make R7C7 = 7. How did I miss that the first time around.?


Last edited by Earl on Tue Feb 26, 2008 5:30 pm; edited 3 times in total
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Mindwarp



Joined: 13 Sep 2007
Posts: 25
Location: St. Ives, England

PostPosted: Tue Feb 26, 2008 2:42 pm    Post subject: Reply with quote

I guess I got lucky with this one I was able to solve it in under 7 minutes. Very Happy It makes a change!
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Marty R.



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

PostPosted: Tue Feb 26, 2008 4:39 pm    Post subject: Reply with quote

Could I have gotten lucky, or more accurately, unlucky? After writing in the candidates, the puzzle did not survive the initial scan, with constant erasing and cell-solving until it was done with nothing more than subsets and locked candidates. One thing I hate more than puzzles I can't solve is puzzles that solve too quickly when I'm looking forward to killing 30-40 minutes.
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storm_norm



Joined: 18 Oct 2007
Posts: 1741

PostPosted: Tue Feb 26, 2008 6:58 pm    Post subject: Reply with quote

I like the xy-wing solution to this one
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