The New Sudoku Players' Forum

[Danu Pr]

I have tried to find fish, xy wing, skysracper still no answer,, help please..

[Leren]

38..71.95.1....673..739.1.8....17834731.....9.489237.1462835917195742386873169..2

Not an easy finish but here goes.

Code: Select all

*--------------------------------------*
| 3     8  b46 | 246 7  1   |a24 9   5 |
| 29    1   49 | 245 58 48  | 6  7   3 |
|b256  b25  7  | 3   9  46  | 1  4-2 8 |
|--------------+------------+----------|
| 2569  25  69 | 56  1  7   | 8  3   4 |
| 7     3   1  | 456 58 468 | 25 256 9 |
| 56    4   8  | 9   2  3   | 7  56  1 |
|--------------+------------+----------|
| 4     6   2  | 8   3  5   | 9  1   7 |
| 1     9   5  | 7   4  2   | 3  8   6 |
| 8     7   3  | 1   6  9   | 45 45  2 |
*--------------------------------------*

This technique is called ALS XZ Rule: X = 4, Z = 2: (2=4) r1c7 - (4=2) r1c3, r3c12; => - 2 r3c8, which solves the puzzle.

Let me explain this in words. Suppose r1c7 was not 2. Then it would be 4. Then r1c7 would be 6. So r3c12 would both be 25. In other words at least one of r1c7 and r3c12 would be 2, then r3c8 can't be 2, since it can see all three cells.

Sorry about the complicated solution, but is a well known one. You can read more about this technique here.

Leren

[SpAce]

Probably the easiest solution:

Code: Select all

.-----------------.-----------------.--------------.
| 3     8   a4(6) | 24-6  7    1    | b24   9    5 |
| 29    1    49   | 245   58   48   |  6    7    3 |
| 25-6  25   7    | 3     9   d4(6) |  1   c24   8 |
:-----------------+-----------------+--------------:
| 2569  25   69   | 56    1    7    |  8    3    4 |
| 7     3    1    | 456   58   468  |  25   256  9 |
| 56    4    8    | 9     2    3    |  7    56   1 |
:-----------------+-----------------+--------------:
| 4     6    2    | 8     3    5    |  9    1    7 |
| 1     9    5    | 7     4    2    |  3    8    6 |
| 8     7    3    | 1     6    9    |  45   45   2 |
'-----------------'-----------------'--------------'

W-Wing:

(6=4)r1c3 - r1c7 = r3c8 - (4=6)r3c6 => -6 r1c4,r3c1; stte

[Leren]

SpAce's W Wing is also an XY chain :

Code: Select all

*----------------------------------------*
| 3    8  a46 | 24-6 7   1   |b24  9   5 |
| 29   1   49 | 245  58  48  | 6   7   3 |
| 25-6 25  7  | 3    9  d46  | 1  c24  8 |
|-------------+--------------+-----------|
| 2569 25  69 | 56   1   7   | 8   3   4 |
| 7    3   1  | 456  58  468 | 25  256 9 |
| 56   4   8  | 9    2   3   | 7   56  1 |
|-------------+--------------+-----------|
| 4    6   2  | 8    3   5   | 9   1   7 |
| 1    9   5  | 7    4   2   | 3   8   6 |
| 8    7   3  | 1    6   9   | 45  45  2 |
*----------------------------------------*

XY Chain Length 4: (6=4) r1c3 - (4=2) r1c7 - (2=4) r3c8 - (4=6) r3c6 => - 6 r1c4; r3c1, which sloves the puzzle. You can read about XY chains here.

Leren