The New Sudoku Players' Forum

[juanwang]

I'm currently documenting the steps to solving a fiendish 9x9 Sudoku puzzle. See here for an image of where I'm at:
http://sudoku.meganvu.com/?p=16
Any one want to have a go at working out the next step?

[udosuk]

Here is the puzzle in text format (in future please include your puzzle in formats like this instead of a pic or a link, for the convenience of others):

Code: Select all

Original puzzle:
 *-----------*
 |...|.13|2.9|
 |4..|2..|3..|
 |.9.|5..|.7.|
 |---+---+---|
 |.6.|...|4.7|
 |2..|7.8|..6|
 |..7|...|.3.|
 |---+---+---|
 |.7.|..2|.1.|
 |..9|..7|..4|
 |..1|96.|...|
 *-----------*

Your current state:
 *-----------*
 |7..|.13|249|
 |41.|279|3..|
 |392|5..|.71|
 |---+---+---|
 |.6.|3..|4.7|
 |2..|7.8|1.6|
 |..7|...|.3.|
 |---+---+---|
 |67.|..2|91.|
 |..9|1.7|..4|
 |..1|96.|7..|
 *-----------*

Refer to the post below to see a simple way to solve this puzzle.

[wintder]

One xy-wing unravels it nicely.

Code: Select all

.---------------------.---------------------.---------------------.
| 7      58     568   |*68     1      3     | 2      4      9     |
| 4      1      568   | 2      7      9     | 3      568    58    |
| 3      9      2     | 5      48    *46    | 68     7      1     |
:---------------------+---------------------+---------------------:
| 1589   6      58    | 3      259    15    | 4      2589   7     |
| 2      345    345   | 7      459    8     | 1      59     6     |
| 1589   458    7     | 46     2459   1456  | 58     3      258   |
:---------------------+---------------------+---------------------:
| 6      7      3458  |*48     3458   2     | 9      1      358   |
| 58     2358   9     | 1      358    7     | 568    2568   4     |
| 58     23458  1     | 9      6      5-4   | 7      258    2358  |
'---------------------'---------------------'---------------------'

[Para]

It's kinda strange that the 9 in R1C9 and the 7 in R4C9 are given in this puzzle. They are both singles when taken away(7 is immediately a hidden single and the 9 is a hidden single after placing a 4 in R1C8(hidden single)) and ruin the symmetric givens pattern. Just feels like they are added from the original puzzle but that could only be my opinion.

Para

[juanwang]

Thanks wintder! i've added the next step using your xy-wing tip

Juanwang