The New Sudoku Players' Forum

[Javier Cia]

This is a very hard sudoku puzzle.
Next move, please?
Thanks
Javier
[code]
15....2.....47...|.17......146...3......|.9.....8.....1567.|
19....8.....6.....|.179....2........5.....|.4.....17...3.......|
159..37...347.|.8.......1469..1769|.2.....56...1567.|
-----------------+----------------------+------------------+
8.....367..357.|.135....1356..4......|.356...2.....9.....|
2.....36....1.....|.359....7........69....|.8.......56.. 4.....|
4.....9.....35....|.2.......3568...68....|.356..17....17...|
------------------+----------------------+------------------+
37....4.....8.....|.1357..135...127...|.56....9.....256..|
6.....1.....2......|.4........589...89.....|.7......3.....58....|
37....5....9......|.6........38....278....|.1..... 4.....28....|
-----------------+-----------------------+------------------+

[/code]

[Animator]

Look at column 6.

It has a naked tripple in the numbers 6, 8, 9.

This allows you to remove 6 and 9 from r3c6.

Then you have a naked pair in box 2 in the numbers 1 and 7.
This allows you to remove 1 and 7 from r2c4 leaving only one candidate.

(Alternative move for box 2: hidden pair 4 6 in r1c5 and r3c5. Remove 9 from r3c5 this leaves only one place for the 9 in box 2. (and in row 3))

[QBasicMac]

column 6 naked tripple 689

Dang! That's hard for me to spot. I could stare all day. I always expect to see 68 689 89 or even 689 69 689.

Of course, after that it's all easy. Nice work!

Mac

[tarek]

another alternative solution:

Code: Select all

*--------------------------------------------------------*
| 15    2     47   | 17    146   3    | 9     8     1567 |
| 19    8     6    | 179   2     5    | 4     17    3    |
| 159   37    347  | 8     1469  1679 | 2     56    1567 |
|------------------+------------------+------------------|
| 8     367   357  | 135   1356  4    | 356   2     9    |
| 2     36    1    | 359   7     69   | 8     56    4    |
| 4     9     35   | 2     3568  68   | 356   17    17   |
|------------------+------------------+------------------|
| 37    4     8    | 1357  135   127  | 56    9     256  |
| 6     1     2    | 4     589   89   | 7     3     58   |
| 37    5     9    | 6     38    278  | 1     4     28   |
*--------------------------------------------------------*
r3c6 Must only have 17 as valid Candidates (127 is a Hidden Triple in Column 6)
r9c6 Must only have 27 as valid Candidates (127 is a Hidden Triple in Column 6)
*--------------------------------------------------------*
| 15    2     47   | 17    146   3    | 9     8     1567 |
| 19    8     6    | 179   2     5    | 4     17    3    |
| 159   37    347  | 8     1469  17   | 2     56    1567 |
|------------------+------------------+------------------|
| 8     367   357  | 135   1356  4    | 356   2     9    |
| 2     36    1    | 359   7     69   | 8     56    4    |
| 4     9     35   | 2     3568  68   | 356   17    17   |
|------------------+------------------+------------------|
| 37    4     8    | 1357  135   127  | 56    9     256  |
| 6     1     2    | 4     589   89   | 7     3     58   |
| 37    5     9    | 6     38    27   | 1     4     28   |
*--------------------------------------------------------*
Eliminating 6 From r4c5 (Column 6 & Box 5 Box-line interaction)
Eliminating 6 From r6c5 (Column 6 & Box 5 Box-line interaction)
*--------------------------------------------------------*
| 15    2     47   | 17    146   3    | 9     8     1567 |
| 19    8     6    | 179   2     5    | 4     17    3    |
| 159   37    347  | 8     1469  17   | 2     56    1567 |
|------------------+------------------+------------------|
| 8     367   357  | 135   135   4    | 356   2     9    |
| 2     36    1    | 359   7     69   | 8     56    4    |
| 4     9     35   | 2     358   68   | 356   17    17   |
|------------------+------------------+------------------|
| 37    4     8    | 1357  135   127  | 56    9     256  |
| 6     1     2    | 4     589   89   | 7     3     58   |
| 37    5     9    | 6     38    27   | 1     4     28   |
*--------------------------------------------------------*
r1c5 Must only have 46 as valid Candidates (46 is a Hidden Double in Column 5)
r3c5 Must only have 46 as valid Candidates (46 is a Hidden Double in Column 5)


[Animator]

my solver comes to it later as it tries easier techniques first.

That's not entirely true...

The pencilmarks you have, right before the triple in column 6, are exactly the same as those that are initially posted.

Yes you found some pairs but those elimineations are already made in the grid that is posted.

[tarek]

Yes you found some pairs but those elimineations are already made in the grid that is posted.

You are right Animator, The deductions made prior to the triple had been concluded already. I'll edit the post to remove the extra unnecessary bits.