The New Sudoku Players' Forum

[mseno]

Forgive me, I'm still learning. What step can I take to solve this puzzle?

[Leren]

Code: Select all

*----------------------------------*
| 89  1   7  | 3 5 89 | 4   2  6   |
| 2  b89  3  | 7 4 6  | 1   5 a89  |
| 5   6   4  | 2 1 89 | 9-8 3  7   |
|------------+--------+------------|
| 4   239 5  | 8 6 7  | 29  1  39  |
| 78  378 1  | 5 9 2  | 6   4  3-8 |
| 6  c289 29 | 4 3 1  |d289 7  5   |
|------------+--------+------------|
| 3   5   6  | 9 2 4  | 7   8  1   |
| 79  279 29 | 1 8 3  | 5   6  4   |
| 1   4   8  | 6 7 5  | 3   9  2   |
*----------------------------------*

There is a Skyscraper on digit 8 in cells a-b-c-d which solves the puzzle. You can read about Skyscrapers here, for example. Leren

<Edit> Corrected one of the eliminations, which was in the wrong place. Thanks to eleven for pointing out the typo. Also here is the puzzle solved cell status in line format.

.1735.4262.374615.56421..374.5867.1...159264.6..431.75356924781...183564148675392

Leren

[mseno]

Code: Select all

*----------------------------------*
| 89  1   7  | 3 5 89 | 4   2  6   |
| 2  b89  3  | 7 4 6  | 1   5 a89  |
| 5   6   4  | 2 1 89 | 9-8 3  7   |
|------------+--------+------------|
| 4   239 5  | 8 6 7  | 29  1  39  |
| 78  378 1  | 5 9 2  | 6   4  3   |
| 6  c289 29 | 4 3 1  |d289 7  5-8 |
|------------+--------+------------|
| 3   5   6  | 9 2 4  | 7   8  1   |
| 79  279 29 | 1 8 3  | 5   6  4   |
| 1   4   8  | 6 7 5  | 3   9  2   |
*----------------------------------*

There is a Skyscraper on digit 8 in cells a-b-c-d which solves the puzzle. You can read about Skyscrapers here, for example. Leren

THANKS!!!

[eleven]

Leren made a mistake, when copying the grid (see r56c9), the skysraper eliminates the 8 in r5c9.

Code: Select all

+----------------+----------------+----------------+
| 89   1    7    | 3    5    89   | 4    2    6    |
| 2   #89   3    | 7    4    6    | 1    5    8-9  |
| 5    6    4    | 2    1    89   |#89   3    7    |
+----------------+----------------+----------------+
| 4    239  5    | 8    6    7    | 29   1    39   |
| 78   378  1    | 5    9    2    | 6    4    38   |
| 6   @289  29   | 4    3    1    |@289  7    5    |
+----------------+----------------+----------------+
| 3    5    6    | 9    2    4    | 7    8    1    |
| 79   279  29   | 1    8    3    | 5    6    4    |
| 1    4    8    | 6    7    5    | 3    9    2    |
+----------------+----------------+----------------+

There is also a w-wing 89 with strong link for 8 in row 6:
Either 8 is in r6c2 and 9 in r2c2,
or 8 is in r6c7 and 9 in r3c7
In both cases 9 cannot be in r2c9.

[mseno]

Thank you! I've solved it. Never heard of the skyscraper technique until today.