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Dec 13 DB

 
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Earl



Joined: 30 May 2007
Posts: 677
Location: Victoria, KS
PostPosted: Sat Dec 13, 2008 3:38 pm    Post subject: Dec 13 DB Reply with quote
The Dec 13 DB has many paths, but falls to a single skyscraper (6), which eliminates the 6 in R8C3.


Earl

Code:

+-------+-------+-------+
| . . . | 6 . . | . . 5 |
| 4 6 . | . 8 . | . 2 . |
| 3 8 . | . 7 2 | . . . |
+-------+-------+-------+
| . . . | 8 . . | 4 . 7 |
| . . . | . . . | . . . |
| 7 . 4 | . . 1 | . . . |
+-------+-------+-------+
| . . . | 4 2 . | . 5 3 |
| . 4 . | . 3 . | . 8 1 |
| 2 . . | . . 5 | . . . |
+-------+-------+-------+

Play this puzzle online at the Daily Sudoku site

Last edited by Earl on Sun Dec 14, 2008 5:05 pm; edited 1 time in total
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sun Dec 14, 2008 3:14 am    Post subject: Reply with quote
Basics get to this endgame:
Code:
+-------------+-------------+-------------+
| 19  7   2   | 6   19  4   | 8   3   5   |
| 4   6   15  | 15  8   3   | 7   2   9   |
| 3   8   59  | 59  7   2   | 1   4   6   |
+-------------+-------------+-------------+
| 169 2   3   | 8   5   69  | 4   169 7   |
| 8   19  169 | 3   4   7   | 5   169 2   |
| 7   5   4   | 2   69  1   | 3   69  8   |
+-------------+-------------+-------------+
| 169 19  7   | 4   2   8   | 69  5   3   |
| 5   4   69  | 7   3   69  | 2   8   1   |
| 2   3   8   | 19  169 5   | 69  7   4   |
+-------------+-------------+-------------+
A skyscraper on <9> in R38 solves R9C4 as <1>. Then. a remote pair finishes it off.

A quicker route is coloring on <6>, which leads to contradictions in R4 or C8, solving R4C8 as <6>. I did not see Earl's skyscraper.

Keith
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
PostPosted: Sun Dec 14, 2008 4:46 am    Post subject: Reply with quote
There's a skyscraper in c36. There was that, simple coloring on 6, or multi-coloring or, of course, Medusa.
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cgordon



Joined: 04 May 2007
Posts: 769
Location: ontario, canada
PostPosted: Sun Dec 14, 2008 5:02 pm    Post subject: Reply with quote
Maybe it was the same thing as the skyscraper - but for me it was an ER using R8 and Box 4 which removes <6> in R4C6
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sudocraz



Joined: 28 Apr 2008
Posts: 53
PostPosted: Sun Dec 14, 2008 8:55 pm    Post subject: Reply with quote
Since I haven't the faintest idea what skyscrapers, coloring, ERs are, this puzzle had me completely stumped. My husband solved it by that great old standby-Guessing. Very Happy
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keith



Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
PostPosted: Sun Dec 14, 2008 9:35 pm    Post subject: Reply with quote
sudocraz wrote:
Since I haven't the faintest idea what skyscrapers, coloring, ERs are, this puzzle had me completely stumped. My husband solved it by that great old standby-Guessing. Very Happy
Code:
+-------------+-------------+-------------+
| 19  7   2   | 6   19  4   | 8   3   5   |
| 4   6   15  | 15  8   3   | 7   2   9   |
| 3   8   59a | 59A 7   2   | 1   4   6   |
+-------------+-------------+-------------+
| 169 2   3   | 8   5   69  | 4   169 7   |
| 8   19  169 | 3   4   7   | 5   169 2   |
| 7   5   4   | 2   69  1   | 3   69  8   |
+-------------+-------------+-------------+
| 169 19  7   | 4   2   8   | 69  5   3   |
| 5   4   69a | 7   3   69A | 2   8   1   |
| 2   3   8   |1-9  169 5   | 69  7   4   |
+-------------+-------------+-------------+

Sudocraz,

This is not very difficult! Take a look at R3 and R8. Each has only two candidates <9>. They are a and A. Look at C3. One or both of the a cells are false (not <9>). So, one or both of the A cells is true (is <9>). The A cells are pincers attacking R9C4, which cannot be <9>.

Notice that you are loooking at only one candidate value. None of that XY stuff! (This is a classic skyscraper.)

Keith
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sudocraz



Joined: 28 Apr 2008
Posts: 53
PostPosted: Tue Dec 16, 2008 12:41 am    Post subject: Reply with quote
Hi Keith,

Thank you. I will make a copy of this puzzle and your explanation and study it.
Cool
It would be nice to add to my Sudoko Solving Repertoire Smile It hasn't been that long ago since I learned how to do XYwings.

Regards
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