[help] Can you find some pattern?

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[help] Can you find some pattern?

Postby Danu Pr » Mon Mar 04, 2019 8:43 am

Image
I cant identify any pattern here please help?
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Re: [help] Can you find some pattern?

Postby SpAce » Mon Mar 04, 2019 10:18 am

Look at the candidates of digit 6 on rows 2 and 6, connected by column 6. Can you see any pattern in that?

Details: Show
That's a Skyscraper:

Code: Select all
.------------------.--------------.---------------.
| 1    2     5     | 4   3   9    | 8   7     6   |
| 479  8    *4(6)7 | 2   57  5(6) | 3   49    1   |
| 479  4-6   3     | 68  78  1    | 5   2     49  |
:------------------+--------------+---------------:
| 8    5     4-6   | 1   9   2    | 7   46    3   |
| 27   146   27    | 68  58  3    | 14  4569  459 |
| 3   *1(6)  9     | 7   4   5(6) | 12  8     25  |
:------------------+--------------+---------------:
| 24   7     1     | 3   6   8    | 9   45    245 |
| 6    9     24    | 5   1   7    | 24  3     8   |
| 5    3     8     | 9   2   4    | 6   1     7   |
'------------------'--------------'---------------'

The pattern proves that at least one or the other of r2c3 or r6c2 must be 6, so other cells that see both of them can't have a 6. That gives us two eliminations and as a result two placements (4r3c2, 4r4c3), which solves the puzzle.
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Re: [help] Can you find some pattern?

Postby Leren » Mon Mar 04, 2019 10:18 am

Code: Select all
*-------------------------------------------*
| 1     2    5     | 4  3  9  | 8  7    6   |
| 479   8    467   | 2  57 56 | 3  49   1   |
| 479   46   3     | 68 78 1  | 5  2    49  |
|------------------+----------+-------------|
| 8     5   a46    | 1  9  2  | 7  46   3   |
| 27-4 b146  27-46 | 68 58 3  | 14 4569 459 |
| 3    c16   9     | 7  4  56 | 12 8    25  |
|------------------+----------+-------------|
| 24    7    1     | 3  6  8  | 9  45   245 |
| 6     9    24    | 5  1  7  | 24 3    8   |
| 5     3    8     | 9  2  4  | 6  1    7   |
*-------------------------------------------*

You probably overlooked the naked triple (146) in Box 4 cells abc which removes some candidates in that box.

Code: Select all
*-----------------------------------------*
| 1   2    5   | 4  3  9  | 8    7    6   |
| 479 8    467 | 2  57 56 | 3    49   1   |
| 479 46   3   | 68 78 1  | 5    2    49  |
|--------------+----------+---------------|
| 8   5   b46  | 1  9  2  | 7   a46   3   |
| 27  146  27  | 68 58 3  | 1-4  4569 459 |
| 3   16   9   | 7  4  56 | 12   8    25  |
|--------------+----------+---------------|
| 24  7    1   | 3  6  8  | 9    5-4  245 |
| 6   9   c24  | 5  1  7  |d24   3    8   |
| 5   3    8   | 9  2  4  | 6    1    7   |
*-----------------------------------------*

The next move is a Skyscraper in cells abcd, which shows that at least one of cells a or d must be 4. This solves 2 cells and the puzzle.

If you are unfamiliar with Skyscrapers you can read about them here.

Leren
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Re: [help] Can you find some pattern?

Postby SpAce » Mon Mar 04, 2019 12:29 pm

Leren wrote:You probably overlooked the naked triple (146) in Box 4 cells abc which removes some candidates in that box.

Good point. I missed to notice/mention that one.

The next move is a Skyscraper in cells abcd, which shows that at least one of cells a or d must be 4. This solves 2 cells and the puzzle.

Just to avoid any confusion, this is obviously a different Skyscraper from what I presented. This puzzle state has a total of four Skyscrapers available, and they all solve the puzzle. Most of the same eliminations can also be seen as 2-String Kites or Empty Rectangles, which are in the same single-digit pattern family called Turbot Fishes. They can also be seen as various kinds of X-Chains or Finned Fishes, or through Simple Coloring. So, lots of options here, and not just these single-digit techniques (though they're probably easiest).
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Re: [help] Can you find some pattern?

Postby Danu Pr » Mon Mar 04, 2019 4:31 pm

yes,, it is very obvious then.. just more practice of course, did you guys use some software to identify patterns or just with naked eyes,,

thanks,,
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Re: [help] Can you find some pattern?

Postby SpAce » Mon Mar 04, 2019 6:57 pm

Danu Pr wrote:yes,, it is very obvious then.. just more practice of course, did you guys use some software to identify patterns or just with naked eyes

Both (speaking for myself). I plugged your puzzle into Hodoku (probably the best free sudoku software publicly available) and let it clear basics. Then I used its digit filters to look for single digit patterns which seemed to be bountiful (and were). They're not hard to see from plain pencil marks or even without them in this case, though. I picked the first Skyscraper I found and, after checking that it solved the puzzle, presented that.

I let Hodoku find the other possibilities I mentioned, but they could have been easily found manually too. It just requires some practice, as you said. Coloring helps a lot if you can't see those patterns directly, and with more complicated chains and patterns it's an invaluable tool. Probably the single best way to improve your solving is to learn to use coloring (and have a software helper that supports it). It works on paper too, but then it's easier to use symbols instead of actual colors, unless you don't mind switching markers all the time.
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