Tough Sudoku for 2/February/2006

Party animal!

Sweetie - in case gb doesn't see your question - I think he means consider 1's in column g to eliminate f7=1....(g7=1, f7 <>1; g4=1,h6=9, f6=1, f7 <>1); BTW, I didn't get the remote pairs either.

Sweetie - the comment above was from me - didn't mean to be anonymous!

Eeek. Maybe this time my name will show up

i know dogs like beer
cats are a new one for the suds
good mAen all

6.52

3:41 I taut I saw a puddycat!!! I d-i-d, I d-i-d!
Remember: 'Miller... High Life... the Champagne of Bottled Beerssssss!' It's the Cat in the Pack!! Good to see a cat again.

Easy to:
7 1 9 4 _ _ _ 6 _
5 8 4 2 _ 6 3 7 _
6 2 3 7 _ _ _ 4 _
3 4 5 8 2 _ 7 _ 6
1 _ 7 _ 4 _ _ _ _
8 _ 2 _ _ 7 _ _ 4
2 5 8 _ 7 4 6 _ _
9 3 1 5 6 8 4 2 7
4 7 6 _ _ 2 5 8 _
FC: (h6=9)==(f6=9)--(f6=1)==(f7=1)--(g7=1)== (g7=9)--(g4=9); g4=1 ez to end

Thats a great joke!

Haven't done tough jet. Only manage them sometimes without guessing. Hard is nearly always sure without guessing.

Save game never works for me on one of my computers, not sure why. I do not use the ARP as often as I used to, so not sure about that.

Over 30 minutes! This one was very Tough. I couldn't get it. I guess after the others being so easy, I had to make up for it. Nice picture, I wonder if he had to drink his way in there? See you all tomorrow.

Merci Christina, Thanks Mike! That made sense once it was spelled out for me :))

Only 13, serious butt-kicker - 8.34 on the tough - lol :) I also got second best recorded score on the easy!!!!

This was very tough for me, and took over two hours. Sometimes I go like crazy, but today was a brain freeze!!

There's an end to that cat!

7:26 total time (with one interruption from my boss); 4:23 setup, so 3:03 for solving.

complete graphic solution in sandbox.

Mike from Iowa : I try to make a difference between easy fillings and eliminations. The ground level for sudokus could be defined as those needing only easy fillings. Then we can measure level-1 puzzles by the number of sets needed considering to perform the eliminations leading to new easy fillings.

'(g5=8)==(i5=8) forbids {f5=8, e5=8, d5=8}'

is a very easy elimination, but it's not a cell filling so I count it for 1 set. cont...

Alistair, my brother used to tell that joke as: Q. What's the difference between a duck? A. One leg is both the same.

The whole elimination effort in that puzzle is :

'(g5=8)==(i5=8) forbids {f5=8, e5=8, d5=8}' (locked cand)-->31 filled
(c1=3)==(c7=3)--(c7=6)==(c1=6) forbids {c1=4} (hidden pair)
(a3=2)==(b3=2)--(b3=5)==(a3=5) forbids {a3=9} (hidden pair)
(f6=1)==(h6=1)--(g4=1)==(g7=1) forbids {f7=1} (colors).

so : 7 sets examined and depth (max number of sets used to perform an elimination)=2.

Your chain has depth 3 and needs previous (easy) eliminations, so we may consider your solution as heavier.

Nurn : that's too short ! my version was (to be spoken veeeryyy sloooww) : 'There's no difference between a duck , it has the two legs the same, especially the left'.

Mike, the 'save game' worked for a while for me, then not, then mysteriously for a few days, but now it's gone again. I tried changing IExplorer to 'allow intersession cookies' but no change...'

If I am understanding correctly, if it is a simple box/line/column elimination it does not count as a set. You then count the number of total strong to weak links(set), and then multiply that by the most sets used in a single step. The chain I used required depth three, and had two additional sets. I would have then used 9 sets with depth 3 for a total of 27. Correct?

This puzzle is fairly easy - not sure it is worth the effort to find the easiest solution. If one does pair eliminations after 52 filled, then cells evaluate to 19. There are remote pairs here, and they let 19 be eliminated further from f7 & e4. This solution seems a bit too complicated, though for such an easy puzzle.

If at 52 filled I do no eliminations, colors on 1's trivially solves h6=9, easy to end.

gb - yeah, I like your version better!

Mike :
when there's only one value left in a column/row/box/cell, you fill that value : that's what I call easy fillings.

what sets to count ? those who need to be checked as 'thick' on the grid. Once checked, the proof can be read without further examining of the grid, e.g :

(f6=1)==(h6=1)--(g4=1)==(g7=1)

W e must check on the grid that either f6 or h6=1 (ie the set of possible 1s in row 6 reduces to {f6=1, h6=1}) and that either g4 or g7=1. Then we no more need the grid to tell that o

... Then we no more need the grid to tell that one among f6,g7 is 1 : if f6 is not 1, then h6=1, g4 is not 1, g7=1, which forbids f7=1.

In other words : thin links can be checked on the fc without looking at the grid.

And there's no multiplying...

Sarah, loved the joke!!! Not even goimg to attempt the puzzle. Good maeN everyone!!!!

OOps - seems I mistyped my last comment, but if you're all clever enough to do this one, then I'm sure you'll figure out what I meant. Bye!!

Thanks for the further explanation. I understand it now. I really love the forbidding chain technique. It is basically a catch-all for all other techniques. I looked at some of your proofs in the sandbox on the 14th of January and then it finally started to make sense. Before I had only looked at the beginners section and had not looked at any of the proofs. It opened up a brand new set of possibilities to solve. It is starting to click now, so I like the idea of searching for efficiency.

liked the joke. good maen to all

you know what I love about this site? Nobody is mean.

39:48 'nough said. Hi to all.

Hi everyone!

Hey howardl -- Who asked you?!!!

my cat loves boxes too. she also eats rubber bands. so don't think her taste counts for much. it must be why she licks he bum, to get the rubber taste out of her mouth.

no timer

10:43...Pass me a Miller please Good meaN to all

Very, very tough for me for some reason. Time wasn't worth talking about. I'll check the site cb mentioned as I don't know about 'remote pairs' or 'locked pairs'.

gb
can you finish after f7 is not 1? cant seem to finish from there