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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:  pnm [ Sat Sep 22, 2012 10:24 pm ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
picklepep wrote: Btw Patrick, the Check now function doesn't work for this. Interesting, thanks Today I noted another small issue: if you manage to enter a valid grid for a Killer Sudoku, _except_ for the "no duplicates in box" (so your solution is valid, but maybe there are two 7s in a box, for example)(and necessarily also elsewhere), the puzzle will be submitted (!) It is then disqualified by the server, so you can't beat the system this way Still, another thing that should be fixed. 
Author:  pharosian [ Sun Sep 23, 2012 6:05 am ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
pnm wrote: rossiniman wrote: Boo. I say keep the difficult ones. Well, let me know what you think of tomorrow's difficult puzzle. I can then later also post the "dismissed" puzzles, for comparison. It took me 56 minutes to solve today's Difficult, which is about 20% longer than it normally takes me, and about 3x longer than it took me to solve the Medium. So even the replacement puzzle was more difficult (for me)... Not sure I'd even want to attempt the one that was removed. 
Author:  rossiniman [ Sun Sep 23, 2012 7:10 am ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
pnm wrote: rossiniman wrote: Boo. I say keep the difficult ones. Well, let me know what you think of tomorrow's difficult puzzle. I can then later also post the "dismissed" puzzles, for comparison. I'm not sure what's today and what's tomorrow, since the Sunday puzzles, for example, come up at 3 p.m. on Saturday here in the Western U.S. In any case, the Sep 23 K Sudoku was a challenge but definitely manageable. (I don't keep track of the time it takes (though I could probably count up the expletives I spend on each puzzle).) Btw, for us pacifists, the K Sudokus have been retitled Kindly Sudokus. 
Author:  arjen [ Sun Sep 23, 2012 9:31 am ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
Not sure if you are talking about the 20120923 difficult killer, but I found it not extreem difficult. It tooks me less than 20 minutes. Quickly solved the three 3x3 block on the right. +3 and +9 on the left was for me the key to solve the complete puzzle. 
Author:  clm [ Sun Sep 23, 2012 4:29 pm ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
rossiniman wrote: ... Btw, for us pacifists, the K Sudokus have been retitled Kindly Sudokus. This is a good idea, and I suggest this kind symbol to be used in the rankings when a puzzler finishes during the day all three K Sudokus (besides the gold star if this applies ... ). 
Author:  pnm [ Sun Sep 23, 2012 5:30 pm ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
arjen wrote: Not sure if you are talking about the 20120923 difficult killer, but I found it not extreem difficult. It tooks me less than 20 minutes. Yes, sorry, to be clear: I was talking about the difficult Killer Sudoku of Sunday 23 September 2012. 
Author:  pnm [ Mon Sep 24, 2012 3:31 pm ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
pnm wrote: Yes, sorry, to be clear: I was talking about the difficult Killer Sudoku of Sunday 23 September 2012. For the fanatical puzzlers, here is the difficult puzzle of Sunday the 23rd that was replaced: I'm not sure if it's even doable. 
Author:  clm [ Tue Sep 25, 2012 7:38 pm ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
pnm wrote: pnm wrote: Yes, sorry, to be clear: I was talking about the difficult Killer Sudoku of Sunday 23 September 2012. For the fanatical puzzlers, here is the difficult puzzle of Sunday the 23rd that was replaced: ... I'm not sure if it's even doable. I am very surprised at "the level of difficulty". Though the rating is not shown for this particular puzzle in my opinion it's not only doable but in fact even much more easier than many other book puzzles or than several daily difficult KSudokus. Consequently I do not understand very well the need for those replacements. Let's see: f1 = 7 is inmediate (column e); g3 + i3 = 15 (nonet 3) >>> [6,9] with g3 = 9, i3 = 6 (due to "24" = [7,8,9]) >>> i4 = 3, i1i2 = [4,5] >>> h2h3 = [1,7], "13" (g1g2h1) = [2,3,8]; also (inmediate and unique) i8 = 1 (h8 = 3), i9 = 2. And since i7 = g4 + 4 (from nonet 6: g4 + 3 + 19 + 3 + 24  i7 = 45) >>> g4 = 3 or 4 or 5 (later this is quickly determined to be a 5), so the 9 of column f goes to f8 or f9 and then the 9 of column d to d1 (unique, since there is another 9 in "16") and then a3 + c3 = 12, etc.. The puzzle is solved very quickly. Reedited 26 Sep 2012 to correct a mistake now it's Ok (g3 + i3 = 15) where it said (g7 + i7 = 15) (thanks to pharosian). 
Author:  pnm [ Tue Sep 25, 2012 7:43 pm ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
clm wrote: I am very surprised at "the level of difficulty". Though the rating is not shown for this particular puzzle in my opinion it's not only doable but in fact even much more easier than many other book puzzles or than several daily difficult KSudokus. Consequently I do not understand very well the need for those replacements. Hm, this may mean that I'm still missing an important solving strategy in my solver (I thought I had them all now ) I'll look at your solution steps to see if I'm missing something. Patrick 
Author:  pharosian [ Wed Sep 26, 2012 7:32 am ] 
Post subject:  Re: Difficult Killer Sudoku for 16 Sept 2012 
clm wrote: Let's see: f1 = 7 is inmediate (column e); g7 + i7 = 15 (nonet 3) >>> [6,9] ... I think you meant to say g3 + i3 = 15... But other than that, you lay out a solid case for why this puzzle wasn't as difficult as advertised. I missed a couple of the clues that seem so obvious once you point them out, but I did find several of them on my own. I'll be curious to hear what Patrick figures out with regard to the solver strategy. 
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