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Oct 8 VH

 
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Clement



Joined: 24 Apr 2006
Posts: 686
Location: Dar es Salaam Tanzania

PostPosted: Mon Oct 08, 2012 12:46 am    Post subject: Oct 8 VH Reply with quote

Code after Basics
Code:

+--------------+-------------+--------------+
| 189  7  1689 | 49  3    68 | 468  5   2   |
| 58   68 4    | 7   568  2  | 3    1   9   |
| 3    2  569  | 459 5689 1  | 468  46  7   |
+--------------+-------------+--------------+
| 2    4  57   | 6   1    9  | 57   3   8   |
| 15   16 3    | 8   7    4  | 9    2   156 |
| *178  9  16-78 | 3   2    5  | 16-7  *67  4   |
+--------------+-------------+--------------+
| 4    18 178  | 2   568  68 | -1567 9   3   |
| *1789 5  2    | 19  689  3  | 146-7 *467 16  |
| 6    3  19   | 159 4    7  | 2    8   15  |
+--------------+-------------+--------------+
X-Wing on 7 in col 18; r6c37<>7, r8c7<>7 leads to m-wing 16
(1=6)r6c7-r6c3=(1=6)r5c2=1r7c2; r7c7<>1 solves it.
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Mindwarp



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

PostPosted: Mon Oct 08, 2012 5:05 am    Post subject: Reply with quote

Pretty sure I had cleared it further than that. Key square for me was c4r9.
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JC Van Hay



Joined: 13 Jun 2010
Posts: 373
Location: Charleroi, Belgium

PostPosted: Mon Oct 08, 2012 7:26 am    Post subject: Reply with quote

A shorter path : XWing(1C29) :=> 1r7c2=1r7c3 :=> +9r9c3; stte
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Marty R.



Joined: 12 Feb 2006
Posts: 5179
Location: Rochester, NY, USA

PostPosted: Mon Oct 08, 2012 9:36 am    Post subject: Reply with quote

Code:

+--------------+-------------+--------------+
| 189  7  1689 | 49  3    68 | 468  5   2   |
| 58   68 4    | 7   568  2  | 3    1   9   |
| 3    2  569  | 459 5689 1  | 468  46  7   |
+--------------+-------------+--------------+
| 2    4  57   | 6   1    9  | 57   3   8   |
| 15   16 3    | 8   7    4  | 9    2   156 |
| 178  9  1678 | 3   2    5  | 167  67  4   |
+--------------+-------------+--------------+
| 4    18 178  | 2   568  68 | 1567 9   3   |
| 1789 5  2    | 19  689  3  | 1467 467 16  |
| 6    3  19   | 159 4    7  | 2    8   15  |
+--------------+-------------+--------------+

Play this puzzle online at the Daily Sudoku site

Mindwarp indicated that he took the basics further, but I'm stuck here.

JC played an X-Wing, but it's not an X-Wing as generally understood here. Based on the grids shown thus far, it's a Sashimi X-Wing.

For the first time in ages, I am stuck as far as solving this puzzle using the standard VH techniques, i.e., X-, XY- and XYZ-Wing.
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hughwill



Joined: 05 Apr 2010
Posts: 228
Location: Birmingham UK

PostPosted: Mon Oct 08, 2012 9:53 am    Post subject: Oct 8 VH Reply with quote

Clements X wing on 7 leads to a hidden pair (57) in
column 7 which then leads to a box-line reduction on 1s in
box 7. Then it falls. For me the X wing was the easy part-
I needed some help for the hard-to-see basics which followed!
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Clement



Joined: 24 Apr 2006
Posts: 686
Location: Dar es Salaam Tanzania

PostPosted: Mon Oct 08, 2012 1:35 pm    Post subject: Oct 8 VH Reply with quote

hughwill
Thanks, the m-wing was not needed to eliminate the 1 in r7c7, so, the x-wing on 7 was enough.
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Marty R.



Joined: 12 Feb 2006
Posts: 5179
Location: Rochester, NY, USA

PostPosted: Mon Oct 08, 2012 3:34 pm    Post subject: Reply with quote

Hughwill,

Good observation. I played the X-Wing and missed that pair in c7.
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kuskey



Joined: 10 Dec 2008
Posts: 127
Location: Pembroke, NH

PostPosted: Tue Oct 09, 2012 12:34 am    Post subject: Oct 8 VH Reply with quote

I agree with everything hughwill wrote but I missed the hidden57s and spotted the 1468 quad in c7 instead. Very satisfying puzzle.
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Marty R.



Joined: 12 Feb 2006
Posts: 5179
Location: Rochester, NY, USA

PostPosted: Tue Oct 09, 2012 1:06 am    Post subject: Re: Oct 8 VH Reply with quote

kuskey wrote:
I agree with everything hughwill wrote but I missed the hidden57s and spotted the 1468 quad in c7 instead. Very satisfying puzzle.


You didn't really miss it. Hidden pairs have complementary subsets, in this case, 1468, which you found. After making the eliminations you're left with the 57 naked pair in col. 7.
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RobertRattley



Joined: 24 Jun 2007
Posts: 58
Location: Australia

PostPosted: Tue Oct 09, 2012 2:35 pm    Post subject: Reply with quote

I also found this a fulfilling puzzle.

I found the 7 x-wing. (Actually, you choose either of two 7 x-wings, for the same eliminations.)

That was the only "very hard" step available, and the only one needed. But it was still "hard" for me! I pored over it for a long time.

Then I found that pair/quadruple in column 7 which enabled a 1 to be eliminated, leading to a sole candidate 9 in the bottom row.
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Kdelle



Joined: 20 Mar 2008
Posts: 59
Location: Hudson, NH

PostPosted: Fri Oct 12, 2012 2:36 pm    Post subject: Reply with quote

Marty R. wrote:
Code:

+--------------+-------------+--------------+
| 189  7  1689 | 49  3    68 | 468  5   2   |
| 58   68 4    | 7   568  2  | 3    1   9   |
| 3    2  569  | 459 5689 1  | 468  46  7   |
+--------------+-------------+--------------+
| 2    4  57   | 6   1    9  | 57   3   8   |
| 15   16 3    | 8   7    4  | 9    2   156 |
| 178  9  1678 | 3   2    5  | 167  67  4   |
+--------------+-------------+--------------+
| 4    18 178  | 2   568  68 | 1567 9   3   |
| 1789 5  2    | 19  689  3  | 1467 467 16  |
| 6    3  19   | 159 4    7  | 2    8   15  |
+--------------+-------------+--------------+

Play this puzzle online at the Daily Sudoku site

Mindwarp indicated that he took the basics further, but I'm stuck here.

JC played an X-Wing, but it's not an X-Wing as generally understood here. Based on the grids shown thus far, it's a Sashimi X-Wing.

For the first time in ages, I am stuck as far as solving this puzzle using the standard VH techniques, i.e., X-, XY- and XYZ-Wing.



Marty,

Two things.....I used an X-wing on 7 in R47C37. Is that NOT an x-wing as commonly understood here? I saw that first, and then isn't there a kite 9 in box 7 that solves R1C4 to be 4. Or do I not understand what I kite is?

Thanks,

Kathy
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Marty R.



Joined: 12 Feb 2006
Posts: 5179
Location: Rochester, NY, USA

PostPosted: Fri Oct 12, 2012 3:35 pm    Post subject: Reply with quote

Quote:
Two things.....I used an X-wing on 7 in R47C37. Is that NOT an x-wing as commonly understood here? I saw that first, and then isn't there a kite 9 in box 7 that solves R1C4 to be 4. Or do I not understand what I kite is?


You understand both. That is a conventional X-Wing, with the candidates only in two rows and two columns.

A Skyscraper has parallel strong links, which obviously means rows or columns. A Kite is the same principle, except it emanates from a box so the lines are perpendicular.

A minor technicality: the effect of that Kite would normally be described as r1c4<>9 because the Kite says it can't contain a 9, even though the practical effect is to set it=4.

Marty
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