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hint to how to solve 11/2/2012 classic sudoku

 
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moshero3



Joined: 11 Feb 2012
Posts: 12

PostPosted: Sat Feb 11, 2012 3:02 pm    Post subject: hint to how to solve 11/2/2012 classic sudoku Reply with quote

+---------------+-------------+------------+
| 345 2 459 | 6 1 49 | 34 8 7 |
| 7 3469 4689 | 48 24 5 | 234 1 269 |
| 468 1 4689 | 3 7 2489 | 5 49 269 |
+---------------+-------------+------------+
| 9 46 1 | 2 5 46 | 8 7 3 |
| 468 467 2 | 478 3 468 | 9 5 1 |
| 358 37 58 | 78 9 1 | 6 2 4 |
+---------------+-------------+------------+
| 2 49 7 | 5 6 3 | 1 49 8 |
| 1 8 3 | 9 24 24 | 7 6 5 |
| 46 5 469 | 1 8 7 | 24 3 29 |
+---------------+-------------+------------+

does anyone has an idea ?

Thanks!
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Sat Feb 11, 2012 4:15 pm    Post subject: Reply with quote

You missed a basic move in column 1, and then you'll still need a couple of advanced moves.

Code:
 +--------------------------------------------------------------+
 |  345   2     459   |  6     1     49    |  34    8     7     |
 |  7     3469  4689  |  48    24    5     |  234   1     269   |
 |  468   1     4689  |  3     7     2489  |  5     49    269   |
 |--------------------+--------------------+--------------------|
 |  9     46    1     |  2     5     46    |  8     7     3     |
 |  468   467   2     |  478   3     468   |  9     5     1     |
 |  358   37    58    |  78    9     1     |  6     2     4     |
 |--------------------+--------------------+--------------------|
 |  2     49    7     |  5     6     3     |  1     49    8     |
 |  1     8     3     |  9     24    24    |  7     6     5     |
 |  46    5     469   |  1     8     7     |  24    3     29    |
 +--------------------------------------------------------------+
 # 53 eliminations remain
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moshero3



Joined: 11 Feb 2012
Posts: 12

PostPosted: Sat Feb 11, 2012 4:26 pm    Post subject: Reply with quote

daj95376 wrote:
You missed a basic move in column 1, and then you'll still need a couple of advanced moves.

Code:
 +--------------------------------------------------------------+
 |  345   2     459   |  6     1     49    |  34    8     7     |
 |  7     3469  4689  |  48    24    5     |  234   1     269   |
 |  468   1     4689  |  3     7     2489  |  5     49    269   |
 |--------------------+--------------------+--------------------|
 |  9     46    1     |  2     5     46    |  8     7     3     |
 |  468   467   2     |  478   3     468   |  9     5     1     |
 |  358   37    58    |  78    9     1     |  6     2     4     |
 |--------------------+--------------------+--------------------|
 |  2     49    7     |  5     6     3     |  1     49    8     |
 |  1     8     3     |  9     24    24    |  7     6     5     |
 |  46    5     469   |  1     8     7     |  24    3     29    |
 +--------------------------------------------------------------+
 # 53 eliminations remain



i am new to this i saw waht you said in C1, what more can i do ?
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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Sat Feb 11, 2012 4:36 pm    Post subject: Reply with quote

This is the grid with c1 taken further.

Code:

+---------------+-------------+------------+
| 35  2    459  | 6   1  49   | 34  8  7   |
| 7   3469 4689 | 48  24 5    | 234 1  269 |
| 468 1    4689 | 3   7  2489 | 5   49 269 |
+---------------+-------------+------------+
| 9   46   1    | 2   5  46   | 8   7  3   |
| 468 467  2    | 478 3  468  | 9   5  1   |
| 35  37   58   | 78  9  1    | 6   2  4   |
+---------------+-------------+------------+
| 2   49   7    | 5   6  3    | 1   49 8   |
| 1   8    3    | 9   24 24   | 7   6  5   |
| 46  5    469  | 1   8  7    | 24  3  29  |
+---------------+-------------+------------+

Play this puzzle online at the Daily Sudoku site

Welcome to the forum. Obviously, we don't know what techniques you're familiar with. But look for an X-Wing to start things off.
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George Woods



Joined: 28 Mar 2006
Posts: 231
Location: Dorset UK

PostPosted: Sat Feb 11, 2012 4:47 pm    Post subject: A solution that I am not proud of! Reply with quote

If r5c4 is 7 then a deadly rectangle in 46 is set up immediately since r6c4 is 8 and these two leave the 46s in block 4 and 5 clean so r6c4 must be 7. This is a single stepper but as I say I don't like it

Last edited by George Woods on Sat Feb 11, 2012 4:49 pm; edited 1 time in total
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moshero3



Joined: 11 Feb 2012
Posts: 12

PostPosted: Sat Feb 11, 2012 4:48 pm    Post subject: Reply with quote

Marty R. wrote:
This is the grid with c1 taken further.

Code:

+---------------+-------------+------------+
| 35  2    459  | 6   1  49   | 34  8  7   |
| 7   3469 4689 | 48  24 5    | 234 1  269 |
| 468 1    4689 | 3   7  2489 | 5   49 269 |
+---------------+-------------+------------+
| 9   46   1    | 2   5  46   | 8   7  3   |
| 468 467  2    | 478 3  468  | 9   5  1   |
| 35  37   58   | 78  9  1    | 6   2  4   |
+---------------+-------------+------------+
| 2   49   7    | 5   6  3    | 1   49 8   |
| 1   8    3    | 9   24 24   | 7   6  5   |
| 46  5    469  | 1   8  7    | 24  3  29  |
+---------------+-------------+------------+

Play this puzzle online at the Daily Sudoku site

Welcome to the forum. Obviously, we don't know what techniques you're familiar with. But look for an X-Wing to start things off.


did the X-wing, removed the 8 from c3r3, and c4r5,

still don't see the light
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hughwill



Joined: 05 Apr 2010
Posts: 142
Location: Birmingham UK

PostPosted: Sat Feb 11, 2012 4:51 pm    Post subject: Feb 11 VH Reply with quote

I'm also having major trouble on this one. After the X wing (and a possibly useless XYZ wing removing the 4 from r5c1)
I'm guessing we're into colouring territory and some very long chains. Is this the case or are there some of Marty's
'traditional VH' methods that I'm missing?
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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Sat Feb 11, 2012 4:55 pm    Post subject: Reply with quote

Quote:
After the X wing (and a possibly useless XYZ wing removing the 4 from r5c1)

Hugh, it's far from useless.
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moshero3



Joined: 11 Feb 2012
Posts: 12

PostPosted: Sat Feb 11, 2012 4:57 pm    Post subject: Reply with quote

Marty R. wrote:
Quote:
After the X wing (and a possibly useless XYZ wing removing the 4 from r5c1)

Hugh, it's far from useless.


on what cells do you do this XYZ wing
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hughwill



Joined: 05 Apr 2010
Posts: 142
Location: Birmingham UK

PostPosted: Sat Feb 11, 2012 5:02 pm    Post subject: Reply with quote

Code:

+---------------+------------+------------+
| 35  2    459  | 6  1  49   | 34  8  7   |
| 7   3469 4689 | 48 24 5    | 234 1  269 |
| 468 1    469  | 3  7  2489 | 5   49 269 |
+---------------+------------+------------+
| 9   46   1    | 2  5  46   | 8   7  3   |
| 68  467  2    | 47 3  468  | 9   5  1   |
| 35  37   58   | 78 9  1    | 6   2  4   |
+---------------+------------+------------+
| 2   49   7    | 5  6  3    | 1   49 8   |
| 1   8    3    | 9  24 24   | 7   6  5   |
| 46  5    469  | 1  8  7    | 24  3  29  |
+---------------+------------+------------+


Grid after the X wing and XYZ wing

George replied while I was replying to a previous. With the eliminations above do we have a standard 46 UR?
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moshero3



Joined: 11 Feb 2012
Posts: 12

PostPosted: Sat Feb 11, 2012 5:08 pm    Post subject: Reply with quote

thanks all!

really learned a lot !
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Marty R.



Joined: 12 Feb 2006
Posts: 5063
Location: Rochester, NY, USA

PostPosted: Sat Feb 11, 2012 5:20 pm    Post subject: Reply with quote

hughwill wrote:
Code:

+---------------+------------+------------+
| 35  2    459  | 6  1  49   | 34  8  7   |
| 7   3469 4689 | 48 24 5    | 234 1  269 |
| 468 1    469  | 3  7  2489 | 5   49 269 |
+---------------+------------+------------+
| 9   46   1    | 2  5  46   | 8   7  3   |
| 68  467  2    | 47 3  468  | 9   5  1   |
| 35  37   58   | 78 9  1    | 6   2  4   |
+---------------+------------+------------+
| 2   49   7    | 5  6  3    | 1   49 8   |
| 1   8    3    | 9  24 24   | 7   6  5   |
| 46  5    469  | 1  8  7    | 24  3  29  |
+---------------+------------+------------+


Grid after the X wing and XYZ wing

George replied while I was replying to a previous. With the eliminations above do we have a standard 46 UR?

Standard UR? I think it qualifies as a Type 3 and has an easy solution. But the puzzle is now able to be finished with basics. Carefully examine box 4.
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Clement



Joined: 24 Apr 2006
Posts: 639
Location: Dar es Salaam Tanzania

PostPosted: Sat Feb 11, 2012 9:13 pm    Post subject: Reply with quote

After the basics the skyscraper on 9 r7c28 setting r3c3<>9 and r2c9<>9 results in the following Grid:-
Code:

+---------------+------------+------------+
| 345 2    45   | 6   1  9   | 34  8  7   |
| 7   3469 4689 | 48  24 5   | 234 1  26  |
| 468 1    468  | 3   7  248 | 5   49 269 |
+---------------+------------+------------+
| 9   46   1    | 2   5  46  | 8   7  3   |
| 468 467  2    | 478 3  468 | 9   5  1   |
| 358 37   58   | 78  9  1   | 6   2  4   |
+---------------+------------+------------+
| 2   49   7    | 5   6  3   | 1   49 8   |
| 1   8    3    | 9   24 24  | 7   6  5   |
| 46  5    469  | 1   8  7   | 24  3  29  |
+---------------+------------+------------+
We can eliminate 8 in r6c4 because of the candidates left in r6c3 by Dual Cell Forcing Chains as follows:-
If r6c3=8; r6c4<>8.
If r6c3=5 so,r1c3=4 so,r1c7=3 which leaves a locked pair 24 in row 2; r2c4<>4, hence r6c4<>8 solves the puzzle.
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daj95376



Joined: 23 Aug 2008
Posts: 3855

PostPosted: Sat Feb 11, 2012 10:02 pm    Post subject: Reply with quote

Using my post of the initial grid:

Code:
   c1    Naked  Triple                   <> 468  r16c1

   c16   X-Wing                          <> 8    r3c3,r5c4 -or-
 r26     X-Wing                          <> 8    r3c3,r5c4

 <67+4>  XYZ-Wing r5c2/r4c2+r5c4         <> 4    r5c1

   c2b4  Locked Candidate 1              <> 4    r27c2
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Ema Nymton



Joined: 17 Apr 2009
Posts: 83

PostPosted: Mon Feb 13, 2012 11:20 am    Post subject: Reply with quote

.

Bring your "A" game.

One is sorely challenged to find the subtle interlocking play of this puzzle. Well done.

I was totally stopped until I turned here for help. Thank you all.

Ema Nymton
~@:o?
.
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eddieg



Joined: 12 Jan 2006
Posts: 47
Location: San Diego, CA USA

PostPosted: Tue Feb 14, 2012 12:14 am    Post subject: Reply with quote

Thanks for the help. Needed the hints. I have never had to substitute values into a square and "force" a UR to materialize like this. Nice technique that I will hopefully get to use again soon.
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RobertRattley



Joined: 24 Jun 2007
Posts: 53
Location: Australia

PostPosted: Wed Feb 15, 2012 2:36 pm    Post subject: Reply with quote

Without exception since the beginning (I've solved them all) every "very hard" can be solved with "hard" techniques (pairs, triples, quadruples and other more basic things) plus

x wing or (very rarely nowadays) swordfish

xy wing

xyz wing

Good luck to all skyscraper builders and this-that-and-the-other rectangle finders etcetera, but in some kind of obsessive purism I refuse to use anything but the above.

So for this puzzle too, though I found it particularly challenging: a pair (35 in column 1), an x wing (8), an xyz wing (467 pinching row 5 column 1 on (4))

and finally a basic: column 2's (4) must be in row 4 or 5 and can't be in row 7.

Again, not to denigrate the other techniques, I encourage fellow solvers to be confident that the wings are always enough. I've been waiting for the creator to introduce "extremely hard" where that confidence would finally fail, but the years have gone by ...

As a mathematician I wonder (vaguely) if some theorem might exist that if a puzzle can be solved with a skyscraper or a (whatever) rectangle or one of the other techniques discussed in this forum, then it can also be solved with wings.

I continue to be thoroughly impressed virtually daily at the ingenuity in the creation of these puzzles. On top of all the other wonders, there is the reliable cross-word-puzzle style symmetry!
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