The New Sudoku Players' Forum

[kraus]

Hi! My name is Mario and I'm a Sudoku and languages addicted... I'm trying to solve this puzzle, but after finding an X-wing (R6C35 - R8C35) I'm stuck:

Code: Select all

+-----+-----+-----+
|7 . 1|9 5 .|6 . .|
|2 . 5|. . 4|7 . 9|
|8 . .|7 . .|5 . 3|
+-----+-----+-----+
|9 1 4|6 2 7|3 5 8|
|3 . 7|. 9 5|1 6 .|
|6 5 .|. . .|9 . 7|
+-----+-----+-----+
|5 . 3|2 7 .|4 9 .|
|4 7 .|5 . 9|2 3 .|
|1 . .|3 4 6|8 7 5|
+-----+-----+-----+

Could someone please help me? Thanks in advance

[kraus]

Code: Select all

+---------+-------------+---------------+
|7 34. 1..|9... 5... 238|6.. 248.. 24...|
|2 36. 5..|18.. 36.. 4..|7.. 18... 9....|
|8 469 69.|7... 16.. 12.|5.. 124.. 3....|
+---------+-------------+---------------+
|9 1.. 4..|6... 2... 7..|3.. 5.... 8....|
|3 28. 7..|48.. 9... 5..|1.. 6.... 24...|
|6 5.. 28.|14.. 138. 13.|9.. 24... 7....|
+---------+-------------+---------------+
|5 68. 3..|2... 7... 18.|4.. 9.... 16...|
|4 7.. 68.|5... 18.. 9..|2.. 3.... 16...|
|1 29. 29.|3... 4... 6..|8.. 7.... 5....|
+---------+-------------+---------------+

[daj95376]

Code: Select all

 +-----------------------------------------------------+
 |  7    34   1    |  9    5    238  |  6    248  24   |
 |  2    36   5    |  18   36   4    |  7    18   9    |
 |  8    469  69   |  7    16   12   |  5    124  3    |
 |-----------------+-----------------+-----------------|
 |  9    1    4    |  6    2    7    |  3    5    8    |
 |  3    28   7    |  48   9    5    |  1    6    24   |
 |  6    5    28   |  14   138  13   |  9    24   7    |
 |-----------------+-----------------+-----------------|
 |  5    68   3    |  2    7    18   |  4    9    16   |
 |  4    7    68   |  5    18   9    |  2    3    16   |
 |  1    29   29   |  3    4    6    |  8    7    5    |
 +-----------------------------------------------------+
 # 34 eliminations remain

 <18+6>  XY-Wing  r8c5/r3c5+r8c3         <> 6    r3c3


[kraus]

Thank you very much!

[aran]

Mario
As per daj's post an XY wing exists on the board here.
Note however that if they don't exist, they can sometimes be created to useful effect.
Two examples from this grid :

1. Consider r6c56+r8c5 :
if r6c5 is not 1, then an XY wing (138) exists which would eliminate 1r7c6, leaving 8 in that cell. Hence the strong link 1r6c5=8r7c6 is established giving : 1r6c5=8r7c6-(8=1)r8c5 => <1>r3c5 hence r3c5=6

2. Consider r1c6+r2c4+r6c6 :
if r1c6 is not 2, then the XY wing (138) exists which would eliminate 1r6c4, leaving r2c4 as the only vacancy for 1 in the column. Hence the strong link 2r1c6=1r2c4. Giving :
2r1c6=1r2c4-(1=6)r3c5-(6=3)r2c5 : hence r1c6 cannot be 3, so r2c5=3

[kraus]

These 2 points are a bit more complicated, but after a few minutes I've understood them too.
Many thanks Aran!