Help with only one move.

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Help with only one move.

Postby asdfgh » Sat Jan 23, 2016 8:16 pm

Hello guys.

I'm new to the forum and I'm fascinated at solving Sudokus, but I'm stuck now and I appreciate if you can help me just showing me one movement and telling me why!

Here we go:

5.9463.7.
6...8.453
.34752...
7453.6.2.
961248735
....756.4
.965.7.4.
4..6....7
...824...

Thank you.
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Joined: 21 January 2016

Re: Help with only one move.

Postby JasonLion » Sat Jan 23, 2016 10:10 pm

Welcome to the forum!

Code: Select all
5.9463.7.6...8.453.34752...7453.6.2.961248735....756.4.965.7.4.4..6....7...824...

5      128    9      | 4      6      3      | 128    7      128   
6      127    27     | 19     8      19     | 4      5      3     
18     3      4      | 7      5      2      | 189    1689   1689 
---------------------+----------------------+---------------------
7      4      5      | 3      19     6      | 189    2      189   
9      6      1      | 2      4      8      | 7      3      5     
238    28     238    | 19     7      5      | 6      189    4     
---------------------+----------------------+---------------------
1238   9      6      | 5      13     7      | 1238   4      128   
4      1258   238    | 6      139    19     | 123589 189    7     
13     157    37     | 8      2      4      | 1359   169    169   

There is a finned swordfish in rows 3, 4, and 7 on the digit 8. It should be singles from there to the end.

You can read more about Finned Swordfish at Sudopedia, or any of several other websites.
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Re: Help with only one move.

Postby Leren » Sun Jan 24, 2016 12:26 am

Code: Select all
*-----------------------------------------------------------------------*
| 5      18     9       | 4      6      3       | 128    7      128     |
| 6      27     27      | 19     8      19      | 4      5      3       |
| 1-8    3      4       | 7      5      2       | 189   a1689   1689    |
|-----------------------+-----------------------+-----------------------|
| 7      4      5       | 3      19     6       | 189    2      189     |
| 9      6      1       | 2      4      8       | 7      3      5       |
| 238    28     238     | 19     7      5       | 6      19     4       |
|-----------------------+-----------------------+-----------------------|
|d1238   9      6       | 5      13     7       |c1238   4     c128     |
| 4      1258   238     | 6      139    19      | 12358 b18     7       |
| 13     157    37      | 8      2      4       | 1359   169    169     |
*-----------------------------------------------------------------------*

There is a two stringed kite in the cells I've marked abcd.

If r3c8 (Cell a) is not 8 then r8c8 (Cell b) must be 8 (only 2 8's in Column 8). So both r7c79 (Cells c) can't be 8, so r7c1 (Cell d) must be 8 (Only 3 8's in Row 7).

You can reverse the argument and assume that Cell d is not 8 and conclude that Cell a must be 8. So at least one of Cells a and d must be 8. They might both be 8 but they can't both be not 8.

Since r3c1 sees both of Cells a and d it can't be 8, so it is 1. The puzzle solves easily after that.

Here is a link to a site that discusses two stringed kites (and a lot else as well) http://hodoku.sourceforge.net/en/tech_sdp.php#t2sk

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