The New Sudoku Players' Forum

[mseno]

I'm still trying to learn different techniques. Which one can I use to solve this one?

[Leren]

6.45.293.2.9...5.61.5.69247568291374713485629942637.5.497.5..628517264933269..7.5

Here are three solutions. The first one uses a Skyscraper, that we saw in the previous puzzle.

Code: Select all

*--------------------------------------*
| 6 78  4 | 5   b17  2   | 9   3   a18 |
| 2 378 9 | 138  147 348 | 5   8-1  6  |
| 1 38  5 | 38   6   9   | 2   4    7  |
|---------+--------------+-------------|
| 5 6   8 | 2    9   1   | 3   7    4  |
| 7 1   3 | 4    8   5   | 6   2    9  |
| 9 4   2 | 6    3   7   | 18  5    18 |
|---------+--------------+-------------|
| 4 9   7 | 138  5   38  | 18  6    2  |
| 8 5   1 | 7    2   6   | 4   9    3  |
| 3 2   6 | 9   c14  48  | 7  d18   5  |
*--------------------------------------*

Next is a Two Stringed Kite, which you can read about here.

Code: Select all

*-------------------------------------*
| 6 78  4 | 5   a17  2   | 9   3  b18 |
| 2 378 9 | 138  147 348 | 5  c18  6  |
| 1 38  5 | 38   6   9   | 2   4   7  |
|---------+--------------+------------|
| 5 6   8 | 2    9   1   | 3   7   4  |
| 7 1   3 | 4    8   5   | 6   2   9  |
| 9 4   2 | 6    3   7   | 18  5   18 |
|---------+--------------+------------|
| 4 9   7 | 138  5   38  | 18  6   2  |
| 8 5   1 | 7    2   6   | 4   9   3  |
| 3 2   6 | 9    4-1 48  | 7  d18  5  |
*-------------------------------------*

Thirdly, there is an Empty Rectangle, which you can read about here.

Code: Select all

*-------------------------------------*
| 6 78  4 | 5   c17  2   | 9   3   18 |
| 2 378 9 |d138 c147 348 | 5   8-1 6  |
| 1 38  5 | 38   6   9   | 2   4   7  |
|---------+--------------+------------|
| 5 6   8 | 2    9   1   | 3   7   4  |
| 7 1   3 | 4    8   5   | 6   2   9  |
| 9 4   2 | 6    3   7   | 18  5   18 |
|---------+--------------+------------|
| 4 9   7 | 138  5   38  | 18  6   2  |
| 8 5   1 | 7    2   6   | 4   9   3  |
| 3 2   6 | 9   b14  48  | 7  a18  5  |
*-------------------------------------*

Leren

[mseno]

Thank you Leren!!!

[SpAce]

Here are three solutions. The first one uses a Skyscraper, that we saw in the previous puzzle.
Next is a Two Stringed Kite, which you can read about here.
Thirdly, there is an Empty Rectangle, which you can read about here.

For pedagogic purposes (from my point of view) I'd just like to add that those three techniques are just different manifestations of the same pattern: single-digit chains of length 4 (i.e. having two strong links) called Turbot Fishes. The ER in this case (and by default) just has a "group" node which makes it a bit more complicated -- but both Skyscrapers and Kites can be grouped as well, though they get more difficult to spot if they are.

Instead of learning three patterns independently, at least I would find it much easier to understand how they're related to each other (but I can only speak for myself). It gets even easier if you learn that they're just special cases of X-Chains which are special cases of AICs. Those relationships are depicted and discussed here. (As also discussed there, chains aren't the only way to see those patterns. They can be seen as complex fishes too, but I think that's a more difficult POV.)

Once you understand those relationships and how they work, there's no need to learn specific patterns at all unless you want to, and you can solve much more complicated cases with the same simple principles. I'd been using Skyscrapers, Kites and ERs as generic chains much before I even learned those patterns had names. (However, learning the names eventually became necessary for communication purposes and for somewhat easier spotting of those common patterns.)