dailysudoku.com

[Guest]

Have got this far and just cannot work out what to do next. I would appreciate an explanation (in simple language) from a helpful person please.



5 . 2367. 67. 139. 13689. 1268. 134789. 1348. 1278.

4. 23. 1. 39. 7. 28. 389. 5. 6.

9. 2367. 8. 4. 136. 5. 137. 13. 127.

2. 1. 67. 57. 456. 3 . 478. 9. 578.

38. 78. 5. 2. 14. 9. 6. 134. 17.

36. 4. 9. 8. 156. 167. 137. 2. 157

18. 89. 2. 6. 189. 4. 5. 7. 3.

7. 59. 3. 159. 2. 18. 18. 6. 4.

168. 568. 4. 1357. 1358. 178. 2. 18. 9[/img][/list]

[chobans]

You need X-Wing for this.

By looking at the grid, 8 has a X-Wing at r2c6,r2c7,r8c6 and r8c7. So you can eliminate 8 at r1c6, r1c7, r4c7 and r9c6.

See if you can solve it after those eliminations.

[Guest]

Thankyou. Would you mind explaining X Wing as I do not understand it.

[chobans]

http://www.simes.clara.co.uk/programs/sudokutechnique6.htm

That site has some great methods with easy to understand explanation. I possibly can't explain better than he did.

[alanr555]

I do not see that XY-wing is necessary to solve this one.
The key area is in column 2
(2367,23,2367;1,378,4;89,59,568)

The first three cells in the column include an embedded triplet
{236,23,236} so that the digit 7 may be removed from rows 1
and 3 in this column - leaving row 5 as the only possibility for
the location of the digit 7.

Having set r5c2 to '7' the rest of the puzzle resolves quite easily.

I do not know if this is a valid method or whether I have just made
a lucky guess. Perhaps someone else can elaborate the rule?

Where THREE cells within a row, column or box contain THREE digits
forming a triplet PLUS other digits, can any conclusion be drawn?

A suggestion has been made theat XY-wing applies. OK, if it does, we
need to know which cells are involved. I looked for one as a pattern
of the cells containing just two values but did not find one. The search
was for three cells (each containing only a pair of values) which form
a right-angled pattern with only three unique values within them
(eg 12,23,13). It would then be possible to learn something about the
cell in the opposite corner of the rectangle formed by the three cells - but
in this case I found no such pattern.

Two questions:
Is my elimination of 7 from r1c2 and r3c2 (described above) correct?
What cells are involved in the XY-wing?

Alan Rayner BS23 2QT

[chobans]

[Guest]

Thankyou for your efforts! I have in fact solved this puzzle but am not satsified with my method. I took one pair 8,3 (R5,C1) ...selected one of them and followed through from there. With the 3 it did not work, with the 8 it all came out fine. Not a very satisfying method, there surely must be a more logical one.

"The first three cells in the column include an embedded triplet
{236,23,236} so that the digit 7 may be removed from rows 1
and 3 in this column - leaving row 5 as the only possibility for
the location of the digit 7."

I understood that to be a triplet there must be three digits ONLY in three cells.

"A suggestion has been made that XY-wing applies. OK, if it does, we
need to know which cells are involved. I looked for one as a pattern
of the cells containing just two values but did not find one. The search
was for three cells (each containing only a pair of values) which form
a right-angled pattern with only three unique values within them
(eg 12,23,13). It would then be possible to learn something about the
cell in the opposite corner of the rectangle formed by the three cells"

I have found the cells referred to by Chobans: 2,8 (R2,C6); 1,8 (R8,C7); 1,8 (R8,C and 3,8,9 (R2,C7) but still cannot understand what this tells me. Please explain!!

Thanks

[Guest]

Oops! The smiley face above is supposed to be C6!

[chobans]

[David Bryant]

[Guest]

Thankyou both David and Chobans. Got it!!