The New Sudoku Players' Forum

[danlm]

In the "Tazuku SUDOKU Ultra" n°7 page 9
I find one complicate way to solve the puzzle...
I would like to know if there is a simple way to solve it.

Therefore, what is the next step now?:

Code: Select all

*---------------------------------------*
| 9  48  7   | 2   5    3  | 6   1   48 |
| 1  6   2   | 489 489  7  | 345 348 59 |
| 45 348 35  | 6   489  1  | 47  2   79 |
|------------+-------------+------------|
| 8  7   359 | 1   2349 49 | 25  34  6  |
| 25 1   39  | 489 3489 6  | 34  7   25 |
| 6  23  4   | 7   23   5  | 8   9   1  |
|------------+-------------+------------|
| 7  5   1   | 3   6    2  | 9   48  48 |
| 3  49  6   | 49  1    8  | 27  5   27 |
| 24 249 8   | 5   7    49 | 1   6   3  |
*---------------------------------------*

I will explain my complicate way after...

[Glyn]

A longish chain avoiding more complex structures
(4)r8c2=(4)r8c4-(4)r9c6=(4)r4c6-(4)r4c8=(4)r5c7-(4=7)r3c7-(7=9)r3c9-(9=5)r2c9-(5=2)r5c9-(2=5)r5c1-(5=4)r3c1
In simpler form
Either r8c2=4 or r8c4=4.
r8c2=9 => r8c4=4, r9c6=9,r4c6=4,r4c8=3,r5c7=4,r3c7=7,r3c9=9,r2c9=5,r5c9=2,r5c1=5,r3c1=4.
Conclusion either r8c2 or r3c1=4 => r9c1<>4. Singles from here.

[Jean-Christophe]

Glyn, you went the loooooooongish way!
Here is a shorter way:

Code: Select all

X-Chain (4): r5c7=r4c8-r4c6=r9c6-r9c1=r3c1 -> r3c7 <> 4 = 7

Or
Finned Jellyfish on 4 in r1258 and c2457 with fin in r1c9, r2c8 -> r3c7 <> 4 = 7

You could also use Weak coloring or Nishio to get the very same result

PS: Sorry for using AIC, but I can't read nor write NL

[Glyn]

Thanks JC much better than mine.
The NL for that is
[r3c7]-4-[r5c7]=4=[r4c8]-4-[r4c6]=4=[r9c6]-4-[r9c1]=4=[r3c1]-4-[r3c7]

[daj95376]

JC's X-Chain as a fish

Code: Select all

 finned Franken Swordfish c16b6\r349 w/fin [r5c7]  =>  [r3c7]<>4
 +--------------------------------------------------------------+
 |  9     48    7     |  2     5     3     |  6     1     48    |
 |  1     6     2     |  489   489   7     |  345   348   59    |
 | *45    348   35    |  6     489   1     |  7-4   2     79    |
 |--------------------+--------------------+--------------------|
 |  8     7     359   |  1     2349 *49    |  25   *34    6     |
 |  25    1     39    |  489   3489  6     | #34    7     25    |
 |  6     23    4     |  7     23    5     |  8     9     1     |
 |--------------------+--------------------+--------------------|
 |  7     5     1     |  3     6     2     |  9     48    48    |
 |  3     49    6     |  49    1     8     |  27    5     27    |
 | *24    249   8     |  5     7    *49    |  1     6     3     |
 +--------------------------------------------------------------+


There's also four long XY-Chains: (No, I'm not going to convert them to NL notation.)

Code: Select all

 -2r5c9  5r5c9  9r2c9  7r3c9  4r3c7  3r5c7  4r4c8  9r4c6  4r9c6  2r9c1 [XY-Chain] <> 2 [r5c1]
 -2r8c7  7r8c7  4r3c7  3r5c7  4r4c8  9r4c6  4r9c6  2r9c1  5r5c1  2r5c9 [XY-Chain] <> 2 [r4c7],[r8c9]
 -5r4c7  2r4c7  7r8c7  4r3c7  3r5c7  4r4c8  9r4c6  4r9c6  2r9c1  5r5c1 [XY-Chain] <> 5 [r4c3],[r5c9]
 -7r3c7  4r3c7  3r5c7  4r4c8  9r4c6  4r9c6  2r9c1  5r5c1  2r5c9  7r8c9 [XY-Chain] <> 7 [r3c9],[r8c7]
____________________________________________________________________________________________________


[daj95376]

Thanks JC much better than mine.
The NL for that is
[r3c7]-4-[r5c7]=4=[r4c8]-4-[r4c6]=4=[r9c6]-4-[r9c1]=4=[r3c1]-4-[r3c7]

Personally, I like JC's AIC/forcing chain best. However, I believe NL notation allows for an X-Chain to be expressed as:

Code: Select all

(4) [r3c7]-[r5c7]=[r4c8]-[r4c6]=[r9c6]-[r9c1]=[r3c1]-[r3c7]


But don't bet any $$$ on my being right.

[danlm]

Thank you Glyn and Jean-Christophe !

I'am not very fluent with your notation...

Could you tell me if it is correct? :
(N)rxcx=(N)rycy means there is a strong link with the candidate N, between the two cells rxcx and rycy, right?
(N)rxcx-(N)rycy means this two cells rxcx and rycy are buddies, right?

Using this notation here is my way to solve the puzzle:

(4)r4c6=(4)r9c6-(4)r9c1=(4)r3c1-(4)r1c2=(4)r1c9-(4)r7c9=(4)r7c8.

The candidate 4 is present in cell r4c6 or in cell r7c8
Therefore cell r4c8 <> 4, cell r4c8 = 3 !!

Is it correct for you ?

Jean-Christophe your chain is a little bit shorter than mine!
Wahoo.. Now, I am not so bad for solving sudoku!!

Jean-Christophe I do not know the Finned Jellyfish, could you give me please some links that explain this method?

Thank you to all.

Daniel

[Glyn]

Spot on danim your chain is correct in the Eureka notation. You've twigged the strong/weak link connection as well.

There are two major notations used Nice Loop and Eureka you'll see both posted. See Nice loop Notation and Eureka Notation

For a quick look at finned fish
Finned Fish at Sudopedia

To expand from there Mike Barker's collection of links in Advanced Solving Techniques is the launch point.