Superior 10 02/10/2005

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Superior 10 02/10/2005

I'm currently stuck at:

31-|-47|--6
--6|-3-|1-7
87-|691|-53

-5-|-23|679
7-3|916|5--
69-|75-|-31

-3-|16-|7-5
--7|-8-|3--
2--|37-|---

I've found the X-Wing (2) in rows 3,6 columns 3,7 which has eliminated the 2 from r1c7

Can see no other X-Wings or triples from here.
Thanks
Alan
alanh

Posts: 6
Joined: 18 September 2005

There are two Hidden Pairs, one in Box 7 and one in Box 9. When you find them, that only leaves one place for a '9' in Row 8.

After that, look for a few Candidates Locked in a Row set-ups and you're there.
Karyobin

Posts: 396
Joined: 18 June 2005

Thanks
I'm not sure if the X-Wing actually helps.
Having said I can see no triples, I think there is one in Column 8 (289) which places the 4 in r5c8.
From there it solved quite easily, but I'd hate to think it was just a lucky guess!

Alan
alanh

Posts: 6
Joined: 18 September 2005

The X-wing does help, and I'll explain why.

There is no Naked Triple {2,8,9} in Column 8. There is a Naked Quad {2,4,8,9}, but this only serves to identify the Hidden Pair {1,6} in that column. By identifting the Hidden Pair {1,5} in Box 7, you lock the 9's in Row 7 into that box. From this you can exclude the 9 as a candidate from r7c6 and r7c8, leaving the remaining two 9's having to be in r9c7 and r8c6.

Remember the X-wing? That allowed you to remove a candidate 2 from r1c7. Now, the 9 you just placed in r9c7 allows you to do the same with the candidate 9, leaving r1c7 to be 8.

The next step was to find candidate 8's locked in a row in Box 6, allowing you to remove a candidate 8 from r5c2, resulting in a Hidden Pair {2,4} in Column 2. See the 6?

The rest, as people round here have started saying, is trivial.
Karyobin

Posts: 396
Joined: 18 June 2005

Cheers karyobin
This is beyond my Sudoku skills (as yet)
But thanks for the insights
Until I saw these forums I hadn't worked out X wings...still working on the swordfish!
alanh

Posts: 6
Joined: 18 September 2005

One final hint: I have never used a swordfish. Puzzles exist that do require them, but in my experience they are few and far between.
Karyobin

Posts: 396
Joined: 18 June 2005

I always look for swordfish. Because they are few, it's really cool to find one!
emm

Posts: 987
Joined: 02 July 2005

What is a "swordfish"? I have figured out "X wing" at last (thanks Alan for your very specific post) and managed to complete the Sunday superior after that.

I have never knowlingly used the swordfish technique, despite having completed almost all the fiendish puzzles (except for a couple of the earlier ones).
bridgarw

Posts: 5
Joined: 25 September 2005

These two sites have excellent explanations, along with diagrams, to explain both of these techniques and more.

http://www.angusj.com/sudoku/hints.php
http://www.simes.clara.co.uk/programs/sudokutechniques.htm
Shazbot

Posts: 220
Joined: 24 September 2005

Could somebody with Sundays paper do a quick check for me please and confirm that the one published does match the one now posted to the Times website at http://www.timesonline.co.uk/article/0,,2092-1793864,00.html

I'm totally stumped, I finally loaded it into the software I've just downloaded from angusj's website and it says it is asymmetrical with multiple solutions; I am hoping it has been mis-transcribed and it is not me!

cheers
b00sfuk

Posts: 2
Joined: 04 October 2005

Yeah, that one on the website is certainly asymmetrical, and has multiple solutions at least according to the Susser. Odd, since Pappocom's program specifically doesn't generate asymms.
PaulIQ164

Posts: 533
Joined: 16 July 2005

Could somebody with Sundays paper do a quick check for me please and confirm that the one published does match the one now posted to the Times website

The Times has now posted a revised grid that has some more numbers filled in. I'm optimistic my sanity will return now I know it was not me!
b00sfuk

Posts: 2
Joined: 04 October 2005