## help with Pappocom V Hard

Advanced methods and approaches for solving Sudoku puzzles

### help with Pappocom V Hard

I've reached this point on my first V Hard puzzle (am so pleased - I'd not get past a Medium without learning the techniques I've found here!)

Have looked for remaining naked/hidden singles/pairs/triplets/quads. I'm thinking I may need an X-wing but I can't see one. Or is there something very obvious I'm missing?

Code: Select all
GRID:

. 6 8 | 1 . . | 2 . .
2 9 7 | . 6 . | 5 . .
3 . 1 | . 2 . | 7 . 6
------+-------+------
6 . 5 | . 9 . | 3 2 .
. . 4 | 6 . 2 | 9 . 5
. . . | . 5 . | 4 6 7
------+-------+------
7 1 . | . 8 . | 6 . 3
. . 6 | . . . | 1 7 .
. . 3 | 7 1 6 | 8 5 .

CANDIDATES:

[45]    [6]     [8]    | [1]     [347]   [34579] | [2]     [349]   [49]
[2]     [9]     [7]    | [348]   [6]     [348]   | [5]     [1348]  [18]
[3]     [45]    [1]    | [59]    [2]     [4589]  | [7]     [489]   [6]
-----------------------+-------------------------+-------------------------
[6]     [78]    [5]    | [48]    [9]     [1478]  | [3]     [2]     [18]
[18]    [37]    [4]    | [6]     [37]    [2]     | [9]     [18]    [5]
[189]   [238]   [29]   | [38]    [5]     [138]   | [4]     [6]     [7]
-----------------------+-------------------------+-------------------------
[7]     [1]     [29]   | [259]   [8]     [459]   | [6]     [49]    [3]
[58]    [58]    [6]    | [29]    [34]    [349]   | [1]     [7]     [249]
[49]    [24]    [3]    | [7]     [1]     [6]     | [8]     [5]     [249]

Thanks.
Shazbot

Posts: 220
Joined: 24 September 2005

First step is the 4s are locked candidates in box 7 – they have to be in row 9 => remove the 4 from r9c9.

The Xwing of 4 is in r1c5 r8c5 and r1c9 r8c9.

For some reason I find it harder to visualise patterns down the columns as this one is and easier when it’s across the rows. Sometimes I turn the puzzle around if it’s on paper - it's probably a matter of training the eye.
emm

Posts: 987
Joined: 02 July 2005

I wasn't able to find any obvious answers. When I get to this point, I just try a number and see if it goes. I tried the very middle box with a 3 and it worked! Here is your answer if you want it:

568 179 234
297 463 518
341 528 796
685 497 321
174 632 985
932 851 467
719 285 643
856 349 172
423 716 859
Guest

Posts: 312
Joined: 25 November 2005

Thanks guys. Em, I know what you mean - you have to force yourself to work in columns. It's hard for me trying to find an X-wing as it is (don't think I've ever had to get one), let alone having to search by columns instead of rows.

I'll go try it again.
Shazbot

Posts: 220
Joined: 24 September 2005