Tough Sudoku

Another non-winter day in Toronto.

round and round we go.

19:59. London's Eye again?

7:20 Maen

A proof for tough sudoku of 12 29 06:
1) Start at 23 filled - the given puzzle. Unique Possibilities to 28 filled. (UP 28).
2a) Locked 6's at g12 forbids g49=6
2b) triple 178 at abc1 forbids a23,b2,dg1=1; b2,dfg1=7; c3f1=8
2c) triple 345 at a237 forbids a59=3, a9=45 UP 34
3) coloring:(See the blog, upper right corner of this page)
fc on 6's: h4 == h9 -- a9 == a5 forbids i5=6 UP 81

Sets: 1+2(3) + 2 = 9. Max depth 3. Rating: .18

I did not make it to yesterday's puzzle until very late, as my two youngest sons had a wrestling tournament all day.
Both placed second in their weight classes, which was quite exciting - for me anyway.
Unfortunately, they both wrestled in the finals at the exact same time. Taping their final matches was thus a bit difficult.

12:41

On the River Thames in London.

Steve, been there and done that. Mama needs a Camera also.

Congratulations to your two, young ''rasslers,'' STEVE!

Thanks!

Almost the same thing occurred two weeks ago - only then one was wrestling for third place, the other for fifth place - and their matches were simultaneous again - only mats were further away from each other. Guess I should get another video camera...

BTW - have added a couple of pics from the tournament to my page.

Yep, that does indeed look like the eye with the parliament bldgs in the b'ground.

Good afternoon to all! Look closely... Kim and Gath are in the fourth car on the right. Just below them are two cats!

I am sick of this one. I have submitted a new Christmas picture to the Tough just recently! And I am still waiting for some from this year's Halloween to be shown!

Hi Steve,

Thanks for your proofs. Without them, I'd never finish (or learn anything about finishing) these tough ones.

Sorry if I've missed something, but I can't understand your proof for today's tough sudoku (step 2b).
I can understand how a triple 178 at abc1 would result in your specified forbids. However, how can a1 possibly be 178, when 7 is already allocated to a6?

(same thing applies with step 2c :- a3 cannot be part of a triple 345, since d5 is already equal to 5).

Cheers,
Andrew

4:53 and feeling good!

Very easy,

Andrew...Speaking for Steve, he is just using shorthand when he says 'triple 178 at abc1'. That is not to say that all three of those numbers are in all three of those cells, nor is it necessary. In this case just 1 & 8 were in a1. Same goes for the second triple.

Hi Andrew - Bob from Minnesota above answers your question. If you need further review, the idea is discussed in the blog. To get there, after clicking on the blog link at the upper right, look for the link to the blog page Pairs, Triples, Quads which should also appear in the right column towards the top.

makes me dizzy just looking at it....

w.w.

Nov. 10, 2007.

SE=6.6