The New Sudoku Players' Forum

[emm]

However, on c1r2, how did you manage to get rid of the candidate 3?

There is a naked pair 63 in c7 => remove all other 6s and 3s in c7
Now the only place for a 3 in box 3 is r2 => remove all other 3s in row 2 = c1r2
=> a naked quad 2567 in box 1 => remove all other 2567 in box 1


The puzzle can be solved with singles alone from here but since you asked about Xwing here’s one that you could use

Xwing of 2s r36c24 => remove 2s from r1c24, r5c4, r7c2

Code: Select all

*--------------------------------------------------------------------*
 | 349    2567   349    | 257    567    2567   | 49     1      8      |
 | 57     567    8      | 4      9      1      | 36     2      3567   |
 | 49     2*567  1      | 2*57   3      8      | 49     567    567    |
 |----------------------+----------------------+----------------------|
 | 159    4      59     | 13579  1567   5679   | 8      356    2      |
 | 6      3      259    | 2589   58     259    | 7      4      1      |
 | 8      12*5   7      | 12*35  156    4      | 36     9      356    |
 |----------------------+----------------------+----------------------|
 | 1237   1278   23     | 6      4      79     | 5      378    379    |
 | 457    9      456    | 578    2      3      | 1      678    467    |
 | 13457  15678  3456   | 15789  1578   579    | 2      3678   34679  |
 *--------------------------------------------------------------------*

[Bigtone53]

Another way of reaching the same answer is to note that the 4 and 9 in box 9 can only be in column 9. They therefore fill r1c7 and r3c7, meaning that the 3 in box 3 is in r2. There are often a number of ways of skinning the same cat, and pencilling in all the alternatives should not be necessary except for very complicated puzzles (although I appreciate that it may prove quicker)

As an aside, unless you ask specifically for the answer, the practice on this site seems to be to give clues and guidance. Every once in a while, this seems to cause offence but there you go

[Pi]

the 3 is gone because the hidden pair in box 3 (4,9) removes the 3 from c7r1 This puts a locked candidate of 3's on c1r1 and c3 r1. the three is then removed from the cell in question

[Cec]

The blue cells form the naked quad. This means that the 2 5 6 and 7 must be in those blue cells. Therefore, you can remove all candidate 2 5 6 and 7 from the yellow squares.

Well done Lardarse - so easy to follow your explanation when presented this way. Can you explain please how this is done?
Cec

[Lardarse]

Thanks. However, on c1r2, how did you manage to get rid of the candidate 3?

You mean r2c1 ? ok...

r2c7 and r6c7 are a naked pair (36) removing the 3 from r1c7
This leaves all of the candidate 3s in b3 on r2, so all other candidate 3s in r2 can be removed.

And no, it doesn't matter, it just becomes a naked quad.

Cec: I use Simple Sudoku to take a screenshot, and then i upload it.

LA

PS: Weird, the Susser finds a naked quad in row 1 instead of box 1...

[Cec]

Cec: I use Simple Sudoku to take a screenshot, and then i upload it.

Thanks LA. "screenshot" and "upload" are new terms to me. Does this mean the normal "cut-copy-paste" routine which I've tried without success. You're further help would be appreciated.
Cec

[Pat]

I use Simple Sudoku to take a screenshot, and then i upload it.

"screenshot" and "upload" are new terms to me.
Does this mean the normal "cut-copy-paste" routine which I've tried without success?

you can paste any text into your post,
but not an image.

you'd have to post (upload) the image to some other web-site (e.g. ImageShack)
in order to be able to mention such image in a post on our Forum.

- Pat

[Cec]

"..in order to be able to mention such image in a post on our Forum".

Thanks Pat. Hope I can work out how to do this - I'm still learning computer technique. I'm not clear when you refer to "our" forum. If I do 'sus' this out are you saying I'm restricted not to do this in the "Times" forum? Sorry for being confused about this.
Cec

[Pat]

---in order to be able to mention such image in a post on our Forum.

I'm not clear when you refer to "our" forum -
are you saying I'm restricted not to do this in the "Times" forum?

my fault for not being clear.

we cannot post an image anywhere in the Sudoku Players Forum.

the image must be placed somewhere else on the www
(e.g. ImageShack),
and then our posts can refer to it.

- Pat

[Cec]

Thanks Pat for your help again. Hope I can work this out .
Cec