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9 x 9 Tuesday May 3rd https://www.calcudoku.org/forum/viewtopic.php?f=16&t=785 
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Author:  paulv66 [ Wed May 04, 2016 11:48 pm ] 
Post subject:  9 x 9 Tuesday May 3rd 
I have been on this site for about two months and it is rare for a puzzle to totally stump me. It can take me a lot of time and perseverance on occasion and sometimes I run out of time because of other commitments. But Tuesday's 9 x 9 has me totally stumped. I've been unable to find a way to unlock it and have spent quite a lot of time unsuccessfully trying to figure it out. So, I would be very grateful if anyone could tell me how they solved it. I'm clearly missing something, but I've no idea what it is. 
Author:  sjs34 [ Thu May 05, 2016 3:14 am ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
I also thought that this was as difficult a puzzle as I can remember and did not find any remarkably useful keys. I used an awful lot of trial and error, particularly focussing on the center 108x cross and the lower left 38+ dogleg. 
Author:  paulv66 [ Thu May 05, 2016 11:40 am ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
Thanks. I also focussed on the lower left 38 dogleg. I concluded that A7 and A8 were either 59 or 79 (in either order) that B9 was 9 and that A9 was 6 or 8 and C9 was 5 or 7. But I didn't get much further. Maybe I should have concentrated on the middle cross. The fact that there was no 4 in it limited the number of combinations, but there were still quite a few options. I take it from your response that you managed to solve it. Any idea how long it took you? 
Author:  paulv66 [ Thu May 05, 2016 11:44 am ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
I've just looked at the solution and I see that I was wrong about A9 and C9. Not sure how I arrived at the wrong conclusion for these cells, but I guess it might have helped solving the puzzle if I'd had the correct options in those cells. 
Author:  sjs34 [ Thu May 05, 2016 1:17 pm ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
I did solve it it but not until the last possible option for the cross. No 4s did help but 1st I tried all options without a 9, then 96211, and only then did I successfully get to 93221. It is irritating to need so much trial and error. It took over 2 hours. I share your wondering if anyone found better keys. My way felt more like chopping the door down. 
Author:  jpoos [ Thu May 05, 2016 2:29 pm ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
I used the fact that the 3 fives in the bottom 3 rows could only be in 4 places; It boiled down to whether there was a five in the 38+ or not. From there it still took some guessing to solve it, but it worked in the end. 
Author:  jaek [ Thu May 05, 2016 3:47 pm ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
After filling in the easy/obvious cells, I also focused on the bottom three rows. I spent a while figuring out the options for the 38+ on the bottom left. The fact that there could only be one 8, and on the bottom row, limited things a bit. Next I worked out several possibilities for what the 168x and 180x could be. (Not in my head, btw. I often use text edit or notepad to keep track of things for more difficult puzzles.) I don't remember the specifics of my solution, but say that the 9s required for the 38+ and 7 across the bottom preclude {1,1,4,5,9} and {1,2,2,5,9} as possibilities for the 180x on the bottom right. So that leaves {1,1,5,6,6}, {1,2,3,5,6}, {1,3,3,4,6} and {2,2,3,3,6} as options. Then, I did a similar thing with the three rightmost columns. Between those two comparisons, all of the options with two of the same number fell away, leaving {1,2,3,5,6}. I did a similar process for each corner. I think the 108x in the center of the puzzle was one of the last pieces I filled in. There were just too many permutations for me to track, even with a digital scratch pad. I know that's not a step by step solution, but I hope it helps a little. 
Author:  pnm [ Thu May 05, 2016 3:59 pm ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
paulv66 wrote: I have been on this site for about two months and it is rare for a puzzle to totally stump me. It can take me a lot of time and perseverance on occasion and sometimes I run out of time because of other commitments. But Tuesday's 9 x 9 has me totally stumped. I've been unable to find a way to unlock it and have spent quite a lot of time unsuccessfully trying to figure it out. So, I would be very grateful if anyone could tell me how they solved it. I'm clearly missing something, but I've no idea what it is. Note that Tuesday's 9x9 is traditionally the hardest puzzle of the week 
Author:  paulv66 [ Thu May 05, 2016 5:14 pm ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
Thanks for all the replies folks. 
Author:  pnm [ Thu May 05, 2016 5:55 pm ] 
Post subject:  Re: 9 x 9 Tuesday May 3rd 
Interestingly, this puzzle is maybe harder than the "world's hardest Calcudoku" (see http://www.calcudoku.org/hardest_logic_ ... #calcudoku and http://www.calcudoku.org/en/20130402/9/3) The one from April 2, 2013 was solved on time by 48 people (out of about 840 "monthly active users"). The one from this past Tuesday by 50 people (out of about 1050 monthly active users). I'll wait for clm's verdict 
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