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Difficult Killer Sudoku for 16 Sept 2012
http://www.calcudoku.org/forum/viewtopic.php?f=19&t=326
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Author:  pharosian  [ Sun Sep 16, 2012 7:17 pm ]
Post subject:  Difficult Killer Sudoku for 16 Sept 2012

Hi,

Does anyone who solved today's difficult Killer Sudoku have any tips for solving it? I am nearly always able to solve all three puzzles, but this one has me stumped. I got a couple of cells figured out, but either I'm missing something or this puzzle is FAR more difficult than others with a similar rating.

Did anyone else struggle with this one?

Thanks for any help.

Author:  picklepep  [ Sun Sep 16, 2012 7:24 pm ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

pharosian wrote:
Hi,

Does anyone who solved today's difficult Killer Sudoku have any tips for solving it? I am nearly always able to solve all three puzzles, but this one has me stumped. I got a couple of cells figured out, but either I'm missing something or this puzzle is FAR more difficult than others with a similar rating.

Did anyone else struggle with this one?

Thanks for any help.


Yeah this one was pretty difficult. Alot of T&E. I think my breakthrough came when I realized that some of the cages were isomorphic(i.e. they must have the same numbers in them no matter which block they are in{I think my language here is bad :)})

Try starting on the right, top than middle

Author:  pnm  [ Sun Sep 16, 2012 8:01 pm ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

pharosian wrote:
Does anyone who solved today's difficult Killer Sudoku have any tips for solving it? I am nearly always able to solve all three puzzles, but this one has me stumped. I got a couple of cells figured out, but either I'm missing something or this puzzle is FAR more difficult than others with a similar rating.

It's nice to see this confirmed in the new solver: it rates it considerable
harder than that killersudokuonline sample puzzle
(from this thread)

Patrick

Author:  pharosian  [ Sun Sep 16, 2012 11:06 pm ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

Thanks, picklepep! [thumbup]

Author:  bram  [ Mon Sep 17, 2012 3:16 am ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

I agree: Yesterday's difficult killer sudoku was indeed a killer! Because I had said just the day before that I was able to solve the difficult killer sudokus at calcudoku.org "on-screen, memorizing candidate numbers when necessary and doing the calculations in my head", I felt obliged to try to do so even if it was fiendishly difficult and I ended up using hours [sad]

Surprisingly, more than 50 puzzlers have actually managed the 16 Sept difficult killer sudoku so far, which must be a sign that this site is gaining traction with hardcore puzzlers [cool]

pnm wrote:
It's nice to see this confirmed in the new solver: it rates it considerable
harder than that killersudokuonline sample puzzle

Hmm, I actually half-suspected you of having cranked up the level just to punish my hubris, going, "I, Min ze Merciless, have forged a most eevil keeller sudoku! Mwahahaha!" in your secret (virtual?) Dutch lair. [scared] Today, 17 Sept, the difficult killer sudoku was no more difficult than usual, though. It may actually have been slightly easier. [smile]

Author:  pnm  [ Tue Sep 18, 2012 1:40 pm ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

bram wrote:
Hmm, I actually half-suspected you of having cranked up the level just to punish my hubris, going, "I, Min ze Merciless, have forged a most eevil keeller sudoku! Mwahahaha!" in your secret (virtual?) Dutch lair. [scared] Today, 17 Sept, the difficult killer sudoku was no more difficult than usual, though. It may actually have been slightly easier. [smile]

Soon the difficulty level should be more consistent (making many improvements to the solver).

And yes, at some point I'll punish people by showing a different puzzle depending on who's logged in:
bram -> Killer Ultra
everybody else -> normal difficult Killer
[biggrin]

Author:  bram  [ Wed Sep 19, 2012 3:56 am ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

pnm wrote:
And yes, at some point I'll punish people by showing a different puzzle depending on who's logged in:
bram -> Killer Ultra
everybody else -> normal difficult Killer
[biggrin]

Wow, you surely wasted no time in implementing that bit! :-) I only managed today's Dee-Kay because I tested a wild assumption that yielded such a promising-looking set of constraints that I figured it was probably "to good to be true". However, I didn't run into any contradictions and soon the puzzle was solved. (Hint for other solvers who got stuck solving the 19 Sept difficult killer: In the top middle 3x3 section, I had found that 8 and 9 go into the two cells of the "23" cage that are in that section. Then I noticed that if 7 does not go into the "18" cage, then 3, 4, 5 and 6 go into that cage while 1, 2 and 7 go into the three remaining cells in the section.)

pnm wrote:
Soon the difficulty level should be more consistent (making many improvements to the solver).

Yes, a rating of 176 is quite realistic, indicating that this is indeed a bad-ass puzzle [thumbup]

Author:  pharosian  [ Wed Sep 19, 2012 5:19 pm ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

bram wrote:
I only managed today's Dee-Kay because I tested a wild assumption that yielded such a promising-looking set of constraints that I figured it was probably "to good to be true". However, I didn't run into any contradictions and soon the puzzle was solved. (Hint for other solvers who got stuck solving the 19 Sept difficult killer: In the top middle 3x3 section, I had found that 8 and 9 go into the two cells of the "23" cage that are in that section. Then I noticed that if 7 does not go into the "18" cage, then 3, 4, 5 and 6 go into that cage while 1, 2 and 7 go into the three remaining cells in the section.)

Wow, that was incredibly helpful! Thanks!

I'd already got the 8 and 9 in the 23 cage and knew the other three corners had a sum of 10, but after that I was stuck, even knowing a fair bit about the left 3 columns of the puzzle. With what I already had, your clue gave me the "leg up" I needed to get the rest of the way. [thumbsup]

Author:  bram  [ Thu Sep 20, 2012 1:26 am ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

pharosian wrote:
Wow, that was incredibly helpful! Thanks!

I'd already got the 8 and 9 in the 23 cage and knew the other three corners had a sum of 10, but after that I was stuck, even knowing a fair bit about the left 3 columns of the puzzle. With what I already had, your clue gave me the "leg up" I needed to get the rest of the way. [thumbsup]

You're very welcome. I'm a great fan of clm's impressive contributions to the solving strategies and tips section and tried to do something similar to this recent clue for a harder-than-difficult killer sudoku at another site. Nice to know it was useful.

Author:  pnm  [ Thu Sep 20, 2012 4:14 pm ]
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012

pnm wrote:
Soon the difficulty level should be more consistent (making many improvements to the solver).

More improvements to the solver, and the rating of killer sudokus :-)
(it solves an "outrageous" puzzle on the killersudokuonline site in about a second now).

So now I know which of the upcoming difficult puzzles will be harder than usual:
- Sunday Sep 23
- Tuesday Sep 25 (but not as bad as Sep 23, 19, and 16)(comparable to the ones on Sep 1 and Sep 5)
- Sunday Sep 30

So you've been warned [scared]

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