The New Sudoku Players' Forum

[NoClue]

Hi, all,

Here is a 28-clue Sudoku, # 648959 - which I couldn´t solve at all: (difficulty: very hard)

Code: Select all

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

With this Sudoku I could hardly find ANY hidden singles (only 31), so I had to pencilmark 22 cells!

Code: Select all

+---------+----------+-------+
|6. 9. 1..|24. 47. 3.|27 8. 5|
|58 4. 28.|1.. 57. 6.|27 9. 3|
|7. 35 238|258 9.. 28|6. 1. 4|
+---------+----------+-------+
|3. 1. 9..|6.. 2.. 4.|5. 7. 8|
|4. 8. 5..|3.. 1.. 7.|9. 2. 6|
|2. 6. 7..|9.. 8.. 5.|4. 3. 1|
+---------+----------+-------+
|1. 7. 4..|28. 6.. 28|3. 5. 9|
|58 2. 368|45. 345 9.|1. 46 7|
|9. 35 36.|7.. 345 1.|8. 46 2|
+---------+----------+-------+

I need a lot of tips and hints, how I can go on further...thanks in advance!

[Pat]

Here is a 28-clue Sudoku,
# 648959 (difficulty: very hard)

Code: Select all


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



after 31 "singles" --

Code: Select all


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



finned X-wing
to exclude 5 at r8c1

the 5 for columns 2,4
is in rows 3,8
except ("fin") r9c2