Sudoku Players' Forum (clone)

Hi, please see attached puzzle. I have pencilmarked all candidates possible. I have used the "normal" solving techniques and also (I think) found a Y-Wing that eliminated 6 or r5c8. There is information about the X and Y wing in the first page of this magazine so I am guessing those should be sufficient to solve the puzzle. Thanks in advance for any help.

An XY Wing won't help here but a Skyscraper will :

Code: Select all

*--------------------------------------------------------------------------------*
| 5       1       9        | 3       8       4        | 2       7       6        |
| 8       2       4        | 16      7       16       | 9       3       5        |
| 3       6       7        | 2       5       9        | 8       4       1        |
|--------------------------+--------------------------+--------------------------|
| 67      378     38       | 5       4       23       | 1       26      9        |
|b69      35      1        | 7      a69      23       | 4       25      8        |
| 4       59      2        | 16-9    169     8        | 3       56      7        |
|--------------------------+--------------------------+--------------------------|
| 1       4       6        | 8       3       7        | 5       9       2        |
|c79      38      38       |d69      2       5        | 67      1       4        |
| 2       79      5        | 4       16-9    16       | 67      8       3        |
*--------------------------------------------------------------------------------*

It's in cells marked a-b-c-d. One of cell a or d must be 9, so you can remove the 9's as shown and the puzzle solves easily from there. You can read about Skyscrapers here.

Leren