Again a question about the very hard ones... I can solve a hard sudoku, but i get stuck in each very hard sudoku

I guess I need a technique or something...

Here's an example of a sudoku in which I am stuck, what do I miss?

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Again a question about the very hard ones... I can solve a hard sudoku, but i get stuck in each very hard sudoku

I guess I need a technique or something...

Here's an example of a sudoku in which I am stuck, what do I miss?

I guess I need a technique or something...

Here's an example of a sudoku in which I am stuck, what do I miss?

- Aiesh
**Posts:**3**Joined:**24 July 2005

Check the x-wing pattern with candidate 5 in columns 5 and 6. Let me know if you need more help.

Best,

Gil

Best,

Gil

- blackadder
**Posts:**2**Joined:**24 July 2005

Check the x-wing pattern with candidate 5 in columns 5 and 6.

Sorry, this is not an x-wing. You should find a true x-wing with candidate 2 on rows 2 and 4.

- blackadder
**Posts:**2**Joined:**24 July 2005

There is an X-Wing pattern for the value 8 in the cells (1,3) (1,7) (5,3) and (5,7). This eliminates the value 8 for cell (2,3).

==> The value 1 is the only candidate for cell (2,3)

Read more about X-Wings at:

http://daily-sudoku.tk

==> The value 1 is the only candidate for cell (2,3)

Read more about X-Wings at:

http://daily-sudoku.tk

- chabo
**Posts:**5**Joined:**23 July 2005

The left box in the middle, row 4,5 and 6, column 1,2 and 3, have 5 cells with a single value and 4 cells with a combination of two numbers. The box can be expressed in two different ways, alternative A setting cell (4.1) to the value of 2, or alternative B setting cell (4.1) to 5. The other cells will be determined accordingly for each of the two alternatives. Continue the Sudoku puzzle with alternative A (all cells having only one unique number) and see what it leads to for the other boxes. If you reach an impossible combination for one of the cells in the other boxes, then the alternative A is impossible, and you know that alternative B is the right one. Continue in this way and select alternatives only from boxes with cells having a combination of two numbers.

Regards Jan Otto

Regards Jan Otto

- Jan Otto
**Posts:**1**Joined:**25 July 2005

If anyone is still reading this - Jan Otto's suggestion above just looks like trial and error to me. I have been following this problem to try to improve my technique. I have looked at the excellent angusj.com web site. I kind of understand what X-wings are but I don't understand the theory behind them. I tried Chabo's advice about the X-wing for 8 but finding 1 for r2c3 didn't get me anywhere.

- tom375
**Posts:**5**Joined:**21 July 2005

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