The New Sudoku Players' Forum

[200e200w]

Code: Select all

. 8 .|. . 9|. 3 .
9 2 .|. . .|6 . 4
. . .|6 2 .|. 8 .
-----+-----+-----
. . 8|. 9 .|. . 2
. . 9|8 . 1|4 . .
5 . .|. 6 .|8 . .
-----+-----+-----
. 9 .|. 5 2|. . .
6 . 3|. . .|. 2 5
. 5 .|1 . .|. 4 .


Enjoy solving!

200e200w

[Cenoman]

Complex one-step solutions exist. I'd rather this 3-step solution:

Code: Select all

 +-----------------------+-------------------+----------------------+
 |  47     8       6     |  5     14   9     |  2     3     17      |
 |  9      2       5     | b37    18  b378   |  6     17    4       |
 |  1347   1347    147   |  6     2   c47    |  5     8     9       |
 +-----------------------+-------------------+----------------------+
 |  1347   13467   8     |  347   9    5     |  137   167   2       |
 |  2      367     9     |  8     37   1     |  4     5     367     |
 |  5      1347    147   |  2     6    347   |  8     9     137     |
 +-----------------------+-------------------+----------------------+
 |  1478   9       147   |  347   5    2     |  137   167   13678   |
 |  6      147     3     |  9     48  a48-7  |  17    2     5       |
 |  78     5       2     |  1     37   6     |  9     4     378     |
 +-----------------------+-------------------+----------------------+

(8)r8c6 = (83-7)r2c46 = (7)r3c6 => -7 r8c6; r4c4=4
and two simple steps for finish:

Code: Select all

 +----------------------+------------------+----------------------+
 |  47     8      6     |  5    14   9     |  2     3     17      |
 |  9      2      5     |  37   18   378   |  6     17    4       |
 |  1347  C1347   147   |  6    2   B47    |  5     8     9       |
 +----------------------+------------------+----------------------+
 |  137    1367   8     |  4    9    5     |  137   167   2       |
 |  2      367    9     |  8   c37   1     |  4     5     367     |
 |  5     D147-3  147   |  2    6  Ad37    |  8     9     17-3    |
 +----------------------+------------------+----------------------+
 |  1478   9      147   |  37   5    2     |  137   167   13678   |
 |  6      17     3     |  9    48   48    |  17    2     5       |
 |  78     5      2     |  1   b37   6     |  9     4    a378     |
 +----------------------+------------------+----------------------+

(3)r9c9 = r9c5 - r5c5 = r6c6 => -3 r6c9
(3=7)r6c6 - (7=4)r3c6 - r3c2 = (4)r6c2 => -3 r6c2; stte

[eleven]

Can be solved with basic advanced moves (kite, skyscraper, xy-wing, w-wing). So no need for this one:

Code: Select all

 *------------------------------------------------------------------*
 | f47     8       6     |  5    g14   9     |  2     3    c17      |
 |  9      2       5     |  37   g18   37-8  |  6     17    4       |
 |  1347   1347    147   |  6     2   a47    |  5     8     9       |
 |-----------------------+-------------------+----------------------|
 |  1347   13467   8     |  347   9    5     |  137   167   2       |
 |  2      367     9     |  8    b37   1     |  4     5     367     |
 |  5      1347    147   |  2     6   a347   |  8     9    c137     |
 |-----------------------+-------------------+----------------------|
 |  1478   9       147   |  347   5    2     |  137   167   13678   |
 |  6      147     3     |  9     4-8 a478   |  17    2     5       |
 | e78     5       2     |  1    d37   6     |  9     4    d378     |
 *------------------------------------------------------------------*

(8=347)r368c6 - (3=71)r5c5&r16c9 - r9c59 = r9c1 - (7=4)r1c1 - (4=81)r12c5 => -8r2c6,r8c5, solves with skyscraper

[200e200w]

Hi, eleven!

Can be solved with basic advanced moves (kite, skyscraper, xy-wing, w-wing).

This is a Nightmare, because it has a SE rating of 7.1, and the potential one-step solution is very complex.

200e200w

[eleven]

SE does not know w-wings, that's the reason for the higher rating.
So it's a long, but nice puzzle for pattern players.

[200e200w]

So, eleven,
This is what Sudoku Explainer says (apart from basic moves):

This Sudoku can be solved using the following logical methods:
...
3 x Turbot Fish
1 x Forcing X-Chain
3 x Forcing Chain

And this is what Hodoku says (apart from basic moves):
1 x Skyscraper
2 x Turbot Fish
2 x Empty Rectangle
1 x Multi Colors
1 x W-Wing
1 x XY-Wing
What do you think?

200e200w

[eleven]

I counted

3 w-wings
3 (grouped) kites (maybe empty rectangles)
1 Skyscraper
1 XY-Wing

[Added:] tried hodoku now, did not see a "multi colors" move.

[200e200w]

eleven,

Even if it is not as hard as I was thinking, I think it still can be classificated as a Nightmare.
However, if SE would count Empty Rectangles as Grouped Forcing X-Chains, and if it would have W-Wings, then the rating of this puzzle could fall to approx. 6.7 to 6.8, I think.

200e200w

[eleven]

Yes, and often puzzles with a lot of naked singles/pairs/triples take much longer than one with a unique rectangle or w-wing ...
E.g. in a puzzle i saw a hidden quad before a naked single.

[200e200w]

eleven,

I have developed my own system of rating that is rating puzzles by its hardest step according to Hodoku.
It will be used to rate all the future Nightmares and One-Trick Ponies, so some puzzles will go out and be replaced by harder ones.
I will post it later with an example.

200e200w

[eleven]

Thanks for your puzzles. I do know, that it is a lot of work to generate interesting ones.
It seems, that Dan also enjoys to be able to lean back.

[200e200w]

Hi, eleven!

I rated all of my 33 unposted Nightmares and 6 unposted One-Trick Ponies using my new rating system, and 2 Nightmares went away because of their too low rating in my system. Its name will be revealed when I'll publish it.

200e200w