The New Sudoku Players' Forum

[MirjamC]

Hello to all sudoku guru experts and swamis out there ,

Thanks for already helping me out.

I have kept myself from posting here through several puzzles and have guessed some solutions or simply skipped or solving a few others…

But in this time i felt like i deserve again some assistance.

Ive thoroughly explored this sudoku,
Im pretty sure there are no naked singles hidden, and no pointing pairs either.
Also i dont think it could be further simplified with naked / hidden triplets / quads…

I scoured it for x-wings and have found one on 8 which eliminated a few canditates but still cant solve it.
Cant find any other x/y wing or swordfish etc…

The only thing i can see is a unique rectangle with digits 12 12 123 123 but no other threes in this column (c7)
So that doesnt give me much…

Is there anything im missing?
A hidden unique rectangle?
Or something else?

I would be very happy to see how an expert approaches the puzzle at this stage.

Much obliged to all helpers in advance ,
Mirjam

https://postimg.cc/B8QxXwnk

[Leren]

9486...7.623...458571.8.6.9.392.6...465978....82.....6..6..1...3..56...........63

Code: Select all

*------------------------------------------------*
| 9   4    8  | 6    235  235  | 123    7    12  |
| 6   2    3  | 17   19   79   | 4      5    8   |
| 5   7    1  | 34   8    234  | 6      23   9   |
|-------------+----------------+-----------------|
| 17  3    9  | 2    145  6    | 578    48   457 |
| 4   6    5  | 9    7    8    | 123    123  12  |
| 17  8    2  | 134  1345 345  | 579    49   6   |
|-------------+----------------+-----------------|
| 28  59   6  | 3478 2349 1    | 2579   249  457 |
| 3   19   47 | 5    6    29   | 1289   1289 47  |
| 28 *15-9 47 | 478  249  2479 |*15-279 6    3   |
*------------------------------------------------*

There is a Hidden pair (15) in r9c27 (cells marked *).

Leren

[MirjamC]

Thanks Leren!

Ive been able to use that in a subsequent puzzle to solve ahead when i was stuck…

First it was the pointing pairs that you taught me,
Now the hidden pairs,
And whats next?

This next one, if you will, is even more simplified and close to its final resolution than the previous

And im really at a loss.

Like, besides using some sort of chain, im really not aure what could be done,
Each analysis of any specific number seems like theres nowhere else to go.

The only thing drawing my attention is the unique rectangle on 37 in the upper center cube and the center cube.

But even that im not sure what to do with….

Would be great to find a solution which does not involve chains…

Here it is:

https://postimg.cc/BtSHPRH5

[marek stefanik]

Hi MirjamC,

There is a skyscraper on 5s giving stte:

Code: Select all

.-------------.----------------.-----------.
| 4   3  #59  |#15   29   8    | 7   6  12 |
| 58  67  589 | 156  29   7–5  | 4   3  12 |
| 1   67  2   | 46   37   347  | 9   8  5  |
:-------------+----------------+-----------:
| 6   8   1   | 3    5    9    | 2   4  7  |
| 3   9   4   | 7    6    2    | 1   5  8  |
| 2   5   7   | 8    4    1    | 3   9  6  |
:-------------+----------------+-----------:
| 9   1   6   | 4–5  378  3457 | 58  2  34 |
| 58  4   3   | 2    1    6    | 58  7  9  |
| 7   2  #58  | 9    38  #345  | 6   1  34 |
'-------------'----------------'-----------'

The UR you mentioned can also help a bit, but not without a chain:

Code: Select all

.-------------.----------------.-----------.
| 4   3   59  | 15   29   8    | 7   6  12 |
| 58  67  589 | 156  29   57   | 4   3  12 |
| 1   67  2   | 46  #37 A#37+4 | 9   8  5  |
:-------------+----------------+-----------:
| 6   8   1   | 3    5    9    | 2   4  7  |
| 3   9   4   | 7    6    2    | 1   5  8  |
| 2   5   7   | 8    4    1    | 3   9  6  |
:-------------+----------------+-----------:
| 9   1   6   | 45  #378 #3457 | 58  2  34 |
| 58  4   3   | 2    1    6    | 58  7  9  |
| 7   2   58  | 9   a38  a35–4 | 6   1 b34 |
'-------------'----------------'-----------'

To prevent the UR either 4r3c6 must be true (the only internal in b2) or 3r9c56 (the externals in b8), forcing 4r9c9. So –4r9c6.
Then you can solve the puzzle with a y-wing.

Marek

[SteveG48]

Hi, MC. Note that because you have Leren's hidden pair, you necessarily have a complimentary naked quintuple as well. Oddly enough, I find it easier to spot a naked quint than to spot a hidden pair. You may as well.

[MirjamC]

Wow , thanks everybody, especially you Marek, this has been more than helpful!
I was not aware of this pattern (Skyscraper) though now I feel kind of lame for having asked for help rather than sticking with it and deciphering the issue....

Actually, I knew that the 5's were the key, and the last step I took before posting the image, ( which took me quite a while to find) had involved a UR in the upper region and have busted many of the 5's ,
especially a UR that was formed with them, even though the UR I used was with the 29's that you can see.

Anyhow, I see what I've missed and I'm sure I would be able to recognize this pattern many times in the future, so thanks a lot : )

And Steve; I definitely find it easier to find a naked quad than a hidden pair!

Thanks guys.

[Leren]

43...876.......43.1.2...985681359247394762158257841396916....2..43216.7972.9..61.

Code: Select all

*--------------------------------------*
| 4  3   59  | 15  29   8    | 7  6 12 |
|a58 67  589 | 156 29   7-5  | 4  3 12 |
| 1  67  2   | 46  37   347  | 9  8 5  |
|------------+---------------+---------|
| 6  8   1   | 3   5    9    | 2  4 7  |
| 3  9   4   | 7   6    2    | 1  5 8  |
| 2  5   7   | 8   4    1    | 3  9 6  |
|------------+---------------+---------|
| 9  1   6   | 45  378  3457 | 58 2 34 |
|b58 4   3   | 2   1    6    | 58 7 9  |
| 7  2  c58  | 9   38  d345  | 6  1 34 |
*--------------------------------------*

Just to be different I used a Two Stringed Kite to solve that last puzzle. You can read about Skyscrapers and Kites here. Leren