The New Sudoku Players' Forum

[tiago85]

I'm stuck in this puzzle for a long time...

Code: Select all

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

this is what i could do until now...

Code: Select all

.---------------------.---------------------.---------------------.
| 45     47     9     | 346    346    8     | 1      2      567   |
| 2458   3      1478  | 246    12469  129   | 468    578    5678  |
| 248    124    6     | 5      124    7     | 348    389    89    |
:---------------------+---------------------+---------------------:
| 1      2459   3     | 47     8      25    | 26     79     2679  |
| 2468   246    48    | 9      47     12    | 5      178    3     |
| 7      259    58    | 23     1235   6     | 28     189    4     |
:---------------------+---------------------+---------------------:
| 39     57     57    | 1      29     4     | 238    6      28    |
| 39     146    14    | 8      569    259   | 7      345    25    |
| 46     8      2     | 67     567    3     | 9      45     1     |
'---------------------'---------------------'---------------------'

what now? any ideas? thanks anyway...

[tarek]

Hi tiago85,

This puzzle is very difficult for an average player ... How far advanced are you in terms of techniques ?

My solver suggests this next move ...

Code: Select all

*-----------------------------------------------------------------*
| 45     47     9     | 346    346    8     | 1      2      567   |
| 2458   3      1478  | 246    12469  129   | 468    578   567-8  |
| 248    124    6     | 5      124    7     | 348   *389   *89    |
|---------------------+---------------------+---------------------|
| 1      2459   3     | 47     8      25    | 26     79     2679  |
| 2468   246    48    | 9      47     12    | 5      178    3     |
| 7      259    58    | 23     1235   6     | 28     189    4     |
|---------------------+---------------------+---------------------|
| 39     57     57    | 1      29     4     | 238    6     ^28    |
| 39     146    14    | 8      569    259   | 7     %345   ^25    |
| 46     8      2     | 67     567    3     | 9     %45     1     |
*-----------------------------------------------------------------*
Eliminating 8 from r2c9(ALS-XY  A(%)=345 in r9c8,r8c8   B(^)=258 in r8c9,r7c9   C(*)=389 in r3c9,r3c8   x=5 y=3 z=8)

You can also see it as an ALS-XZ if you put all the ALSs in box 9 together.

I'm afraid that My solver gets to a dead end on this.

tarek

[tiago85]

man, this is insane, but i understood the move...

the more complex techniques i used on this was XY-wing and XYZ-wing...

it's too hard to find this sets in a way that they combine and eliminate candidates...

let's see what i get from now on...do you know where i find a good explanation for that ALS techniques?

thanks...

[eleven]

No, but i can recommend aran's method to find such eliminations:

Code: Select all

    .---------------------.---------------------.---------------------.
    | 45     47     9     | 346    346    8     | 1      2      567   |
    | 2458   3      1478  | 246    12469  129   | 468    578    5678  |
    | 248    124    6     | 5      124    7     | 348    389    89    |
    :---------------------+---------------------+---------------------:
    | 1      2459   3     | 47     8      25    | 26     79     2679  |
    | 2468   246    48    | 9      47     12    | 5      178    3     |
    | 7      259    58    | 23     1235   6     | 28     189    4     |
    :---------------------+---------------------+---------------------:
    | 39     57     57    | 1      29     4     | 238    6      28    |
    | 39     146    14    | 8      569    259   | 7      345    25    |
    | 46     8      2     | 67     567    3     | 9      45     1     |
    '---------------------'---------------------'---------------------'


You have the almost pair 3/89 in row 3, i.e. either r3c8=3 or r3c89=89.
Now you can look if r3c8=3 can lead to a 8 or 9, which at least sees one of the pair cells.
(or also, if both lead to a common elimination)

This is easy here: r3c8=3 -> r89c8=45 -> r8c9=2 -> r7c9=8

So 8 must be in at least one of the cells r3c89 and r7c9.
(You would get the same, when starting with the almost pair 3/45 in r89c8)


The same method can be used with almost hidden pairs like the 19 in row 2:
Either r2c3=1 or r2c56=19.
r2c3=1 -> r8c3=4 -> r9c1=6 -> r8c5=6 => r2c5<>6
or
(r2c3=1 -> r5c6=1 AND r2c3=1 -> r8c3=4 -> r5c3=8) -> r5c8=7 -> r5c5=4 => r2c5<>4

However, when you have found this, you can see, that r2c3=1 also leads to a 4 in r4c4:
r2c3=1 -> r8c3=4 -> r9c1=6 -> r9c4=7 -> r4c4=4

So you can eliminate it.