Post the puzzle or solving technique that's causing you trouble and someone will help

Sudoku puzzle. Very hard
And how do you come to it.
Thanks
Javier

168 69 169 / 389 39 7 / 4 5 2
58 59 2 / 89 6 4 / 13 37 17
7 3 4 / 5 2 1 / 68 9 68
+-------------------+-----------------+-----------------+
4 1 569 / 2 39 8 / 7 36 569
36 679 79 / 4 1 5 / 368 2 689
235 259 8 / 39 7 6 / 35 1 4
+-------------------+----------------+------------------+
16 4 16 / 7 5 9 / 2 8 3
25 257 57 / 16 8 3 / 9 4 16
9 8 3 / 16 4 2 / 156 67 1567
+------------------+-----------------+-------------------+
The editing of this message is not correct , I know. How can I do it in a "readable" way
Javier Cia

Posts: 10
Joined: 02 January 2006

Did you read: New topics - How to ask for help? The first item in the second list shows a small procedure which you can follow to make it look better. (If you read it: was it too unclear on how to do it?)

Grid with corrected formatting:
Code: Select all
`168  69   169  | 389  39  7 | 4    5   258   59   2    | 89   6   4 | 13   37  177    3    4    | 5    2   1 | 68   9   68---------------+------------+---------------4    1    569  | 2    39  8 | 7    36  56936   679  79   | 4    1   5 | 368  2   689235  259  8    | 39   7   6 | 35   1   4---------------+------------+---------------16   4    16   | 7    5   9 | 2    8   325   257  57   | 16   8   3 | 9    4   169    8    3    | 16   4   2 | 156  67  1567`
Animator

Posts: 469
Joined: 08 April 2005

Take a really good look at the number 9. It should leave you to the next number. (Spoiler follows... if you don't want it: stop reading.)

X-Wing with number 9: If you look at the number 9 then you should see that the only possible place for it on row 2 is column 2 and column 4. Now there happens to be another row for which that it is the case (row 6).

This allows you to remove 9 as a candidate from r1c2, r5c2, r1c4.

Now you have your next number. 6 in r1c2.

[Update: this message has been updated to correct the r4c1 typo (as mentioned in the next post).]
Last edited by Animator on Mon Jan 09, 2006 6:22 pm, edited 2 times in total.
Animator

Posts: 469
Joined: 08 April 2005

Cannot see any 9 in r4c1
Javier Cia

Posts: 10
Joined: 02 January 2006

Javier Cia wrote:Cannot see any 9 in r4c1

Woops. That should have been r1c4.
Animator

Posts: 469
Joined: 08 April 2005

Even if you go for the several Box-Line eliminations available in succession (Row 1 & BOx 1,Row 1 & Box2, .....), you still need that X-wing in rows 2 & 6. It is straight forward from then

tarek

Posts: 2804
Joined: 05 January 2006