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"the World's hardest logic/number puzzles" https://www.calcudoku.org/forum/viewtopic.php?f=24&t=463 
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Author:  main [ Fri Aug 09, 2013 11:33 am ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
This is how I discovered your website, through the duplicate post you published on conceptis puzzles from July 25th. I've been glad I found calcudoku.org ever since. Great way to burn some free time! 
Author:  pnm [ Fri Aug 09, 2013 11:38 am ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
main wrote: This is how I discovered your website, through the duplicate post you published on conceptis puzzles from July 25th. I've been glad I found calcudoku.org ever since. Great way to burn some free time! Good to hear, thanks It also got copied to "gizmodo": http://gizmodo.com/canyousolvethe10 ... 1064112665 Patrick 
Author:  nicow [ Fri Aug 09, 2013 3:28 pm ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
Crazydad nr8 is not difficult. After applying simple logic, this puzzles is solved applying Ariadne's Threat in order to eliminate faulty candidates. And more: the first 3 (!) numbers are quite simple to find. So nr8 is only of medium difficulty. I agree with CLM that it's not clear wether a puzzle is more difficult than an other one or not. Because at first there has to be consent to the measuring method. My system solves the 21122012 puzzle in nearly 8 hours (!), after applying Adriadne's Threat, using a search tree. As Dutch men say: "Het is de kift!" Ha ha. 
Author:  pnm [ Sun Aug 11, 2013 9:16 am ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
nicow wrote: Crazydad nr8 is not difficult. After applying simple logic, this puzzles is solved applying Ariadne's Threat in order to eliminate faulty candidates. And more: the first 3 (!) numbers are quite simple to find I never knew that "Ariadne's threat" meant guessing & backtracking... (shouldn't it be "thread" ?) nicow wrote: My system solves the 21122012 puzzle in nearly 8 hours (!), after applying Adriadne's Threat, using a search tree There must be some strategies that can reduce this. For example, my solver works with linear equations of up to 3 unknowns, which can of course be extended to 4, etc. nicow wrote: As Dutch men say: "Het is de kift!" Ha ha. Ik denk het 
Author:  nicow [ Sun Aug 11, 2013 7:11 pm ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
pnm wrote: I never knew that "Ariadne's threat" meant guessing & backtracking... (shouldn't it be "thread" ?) Ariadne's thread (indeed with a 'd'), is trying a candidate, and if the result is a faulty solution, this candidate is faulty. Trying all candidates is elaborate, but for a computer that doesn't matter. It is an easy way to clean up all candidates, and many times a good solution is found in the meantime(!). pmn wrote: nicow wrote: My system solves the 21122012 puzzle in nearly 8 hours (!), after applying Adriadne's Threat, using a search tree There must be some strategies that can reduce this. For example, my solver works with linear equations of up to 3 unknowns, which can of course be extended to 4, etc. Mine does the same, but in an other way, and up to 8 unknowns; this level can be set; 4 happens to be fast, but 6 is more secure in my solver. Of course there can be more strategies implemented. But I search for an optimum: the easy puzzles (and all up to 8x8) are solved within a second or few seconds, so why building in extra logic? But I am building in Row/blockinteraction now for the larger puzzles. I'm curious... 
Author:  pnm [ Sun Aug 11, 2013 8:02 pm ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
nicow wrote: But I am building in Row/blockinteraction now for the larger puzzles. I'm curious... What do you mean by that? (maybe that's already in my solver, maybe not..) Patrick 
Author:  nicow [ Mon Aug 12, 2013 11:49 am ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
pnm wrote: nicow wrote: But I am building in Row/blockinteraction now for the larger puzzles. I'm curious... What do you mean by that? (maybe that's already in my solver, maybe not..) Patrick In today's sudoku, candidate 3 in A3 is to be wiped out bij column/block interaction. Here is how: H8=3 so B8 and A8 cannot be a 3. B6=3 so B8 cannot be a 3 So, in block 7 value 3 only occurs in row A (A7 and A9) That is why A3 cannot be a 3: in the intersection of row A and block 7 , the value 3 only exists. (By turning the puzzle 90°, column/block is the same as row/block) (edited) 
Author:  pnm [ Mon Aug 12, 2013 6:49 pm ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
Interesting, thanks, I'll have to check if I'm already doing this. (thread is going a bit offtopic..) nicow wrote: In today's sudoku, candidate 3 in A3 is to be wiped out bij column/block interaction. Here is how: H8=3 so B8 and A8 cannot be a 3. B7=3 so B8 cannot be a 3 You mean B6=3 so B9 cannot be a 3? 
Author:  danaburns [ Fri Aug 16, 2013 8:05 pm ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
Is the link in a bad location for anyone else? I have a hard time avoiding it when using the input popup thingie. This is only an issue when I use a small screen device such as a phone. 
Author:  pnm [ Fri Aug 16, 2013 10:38 pm ] 
Post subject:  Re: "the World's hardest logic/number puzzles" 
danaburns wrote: Is the link in a bad location for anyone else? I have a hard time avoiding it when using the input popup thingie. This is only an issue when I use a small screen device such as a phone. Thanks for letting me know, I'll check this, and maybe remove the link for small devices. Patrick 
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