The New Sudoku Players' Forum

[Amonra]

I am relatively new to the advanced techniques. I have been doing pretty good though... Until I ran across this puzzle that got me stuck for 2 days. It just doesn't appear to be anything available to eliminate. I would love to learn how to move forward with it though, so any help would be appreciated.

Here is the puzzle:

5 3 6 . 7 . . . 1
8 1 9 . 3 . 6 . .
. . . 1 6 9 8 3 5
. 2 . . 4 6 . . 3
. . . . . . . . .
7 . . 9 2 . . 8 6
. . . 6 8 . . . .
. . 1 . 9 . . 5 8
3 . . . . . . 6 4

Thanks!

[Pat]

Code: Select all


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



look in box 4
where can you put 1,6,9 ?

[Leren]

Code: Select all

*--------------------------------------------------------------------------------*
| 5       3       6        | 248     7       248      | 249     249     1        |
| 8       1       9        | 245     3       245      | 6       247     27       |
| 24      47      247      | 1       6       9        | 8       3       5        |
|--------------------------+--------------------------+--------------------------|
|#19      2      *58       | 578     4       6        | 1579    179     3        |
|#169-4  #69-458 *3458     | 3578    15      13578    | 124579  12479   279      |
| 7      *45     *345      | 9       2       135      | 145     8       6        |
|--------------------------+--------------------------+--------------------------|
| 249     4579    2457     | 6       8       123457   | 12379   1279    279      |
| 246     467     1        | 2347    9       2347     | 237     5       8        |
| 3       5789    2578     | 257     15      1257     | 1279    6       4        |
*--------------------------------------------------------------------------------*

I'll be a bit more merciful than Jason and give you a complete spoiler - so don't read on if you want to follow up on Jason's hint.

There is a locked quad (3458) in the 4 cells I've marked *. Alternatively there is a hidden triple (169) in the 3 cells I've marked #.

Either way you can reduce the # cells to 169 as I've indicated. The puzzle should solve easily via a cascade of singles from there.

Leren

[Amonra]

Thanks! I did miss that - have to develop a better eye to spot these!
Still no cascades of singles, but it does get me closer.
Now on to finding the next hiding pair or triple.

[Amonra]

I got it! Thank you guys!

[eleven]

Thanks! I did miss that - have to develop a better eye to spot these!

It's easier to find the hidden triple without candidates filled in, than the (naked) quad with candidates.
You can see 169 in column 3 (so none possible in r456c3), and the 1 in c2 plus 69 in row 6 (so none in r6c2) only leave 3 cells for the 3 numbers in box 4.

Code: Select all

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