Help please

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Help please

Postby seturner » Sat Apr 30, 2016 5:33 pm

Hello,
The following is the source puzzle and how far I can get it with pencil marks. This is an intermediate level puzzle from Sudoku MKS 1.0 for iPhone.
I solve most puzzles on this level from this source, but every 8 or so puzzles I will get one like this where I have to punt.
Code: Select all
. . . | 5 . . | . . 6 |
. . . | 8 7 . | 3 . 2 |
2 7 . | 3 . . | . 8 1 |
——————————————————————-
. . . | . 3 4 | 9 . . |
7 9 3 | . 5 . | 6 1 4 |
. . 8 | 7 9 . | . . . |
——————————————————————-
9 2 . | . . 3 | . 5 7 |
5 . 6 | . 8 7 | . . . |
3 . . | . . 5 | . . . }


Code: Select all
8   3   149 | 5   14   2 | 7   49   6
146 146  5  | 8   7   19 | 3   49   2
2   7    49 | 3   46  69 | 5    8   1
—————————————————————————————————————
16   5    2 | 16   3   4 | 9    7   8
7    9    3 | 2    5   8 | 6    1   4
146  146  8 | 7    9  16 | 2    3   5
—————————————————————————————————————
9    2   14 | 146  16  3 | 8    5   7
5   14    6 | 9    8   7 | 14   2   3
3    8    7 | 14   2   5 | 14   6   9
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Re: Help please

Postby JasonLion » Sun May 01, 2016 1:23 am

I see a W-Wing on 49, which is fairly complex for something that calls it's self "intermediate". Once you have done that, it is singles to the end.
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Re: Help please

Postby seturner » Sun May 01, 2016 1:38 am

Thank you for the response. Can you tell me where the "strong link" is for this? I am new to advanced techniques.
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Re: Help please

Postby Leren » Sun May 01, 2016 1:52 am

Code: Select all
*--------------------------------------------------------------*
| 8     3     49-1   | 5    a14    2      | 7     49    6      |
| 146   146   5      | 8     7     19     | 3     49    2      |
| 2     7    c49     | 3    b46    69     | 5     8     1      |
|--------------------+--------------------+--------------------|
| 16    5     2      | 16    3     4      | 9     7     8      |
| 7     9     3      | 2     5     8      | 6     1     4      |
| 146   146   8      | 7     9     16     | 2     3     5      |
|--------------------+--------------------+--------------------|
| 9     2    d14     | 146   6-1   3      | 8     5     7      |
| 5     14    6      | 9     8     7      | 14    2     3      |
| 3     8     7      | 14    2     5      | 14    6     9      |
*--------------------------------------------------------------*

I'll be a bit more merciful than Jason and show you where the W Wing is. It's in the cells I've marked abcd and shows that at least one of r1c5 and r7c3 must be 1, so you can remove the 1 from r1c3 and r7c5.

I can explain further if you want, or you can learn about W Wings by following this link http://hodoku.sourceforge.net/en/tech_wings.php#w

There was also an X Wing in 1's in Columns 35 Rows 17, which removes the 1 from r7c4, and a finned XWing in 1's in Columns 16 Rows 26 with a fin at r4c1, which removes the 1 from r7c4.

However, if you play the W Wing first, the X Wings are not necessary.

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Re: Help please

Postby seturner » Sun May 01, 2016 1:58 am

Thank you very much! I see exactly what you are saying.
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