The New Sudoku Players' Forum

[shawntown]

Hi. I’m on the Sudoku.com site, playing in Expert and Evil difficulties. I don’t know any sudoku technique names or advanced theory, I just started doing sudoku a couple hours a day, and after a few months I’m getting better. But now, I’m occasionally running into these situations that seem unsolvable to me; I’m sure there is a sudoku technique I could learn to figure these situations out, but all these fancy names confuse me (X-Wing, Swordfish, etc). Here are a couple links to recent puzzles I got stuck on near the end:

https://imgur.com/a/a8n8f32

https://i.imgur.com/DuRfIL7.jpg

[SteveG48]

Hello, Shawntown. In the first puzzle you list, you've reduced things to where you have a (1/7) remote pair that eliminates both 1 and 7 at r4c6, essentially completing the puzzle.

I suggest that you Google a program called Hodoku. It's a great program that creates puzzles and gives you exact logical steps to solve them- or let's you do it yourself. More importantly, it comes with guides that explain the techniques you can use, such as the remote pair mentioned above.

[shawntown]

Thanks. I don’t understand the concept of a remote pair. Can you provide a link that explains it in simple terms, for laymen? I’m not good with all the Sudoku jargon.

[Leren]

9.568.34242....568683254...8..3..9263.9.26...2.6....73.3..7.68..9816...4.6.5.8...

Code: Select all

*------------------------------------------*
| 9  b17   5  | 6   8   a17   | 3   4   2  |
| 4   2    17 | 9-7 139  1379 | 5   6   8  |
| 6   8    3  | 2   5    4    | 17  19  79 |
|-------------+---------------+------------|
| 8   1457 17 | 3   14   15-7 | 9   2   6  |
| 3  c47   9  |d478 2    6    | 48  15  15 |
| 2   145  6  | 489 149  159  | 48  7   3  |
|-------------+---------------+------------|
| 15  3    24 | 49  7    29   | 6   8   15 |
| 57  9    8  | 1   6    23   | 27  35  4  |
| 17  6    24 | 5   34   8    | 127 139 79 |
*------------------------------------------*

The first puzzle can be solved with a move called a Skyscraper. It's a simple pattern involving 4 cells, which I've marked a-b-c-d here.

You should be able to see that one of cells a or d must be True, so you can mark off the 7's in r2c4 and r4c6, and the puzzle solves with singles.

You can read about Skyscrapers, and lot more besides, on the Hodoku site here.

Leren

[SteveG48]

Thanks. I don’t understand the concept of a remote pair. Can you provide a link that explains it in simple terms, for laymen? I’m not good with all the Sudoku jargon.

As I said, the Hodoku program and explanations are great for what you want. Find them here: http://hodoku.sourceforge.net/en/index.php

Then select Solving Techniques and scroll down until you find remote pairs under Chains and Loops.