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16 x 16 broken?

Submitted by: barclay

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 Another repeat. |  |
 9:18 Maen |  |
 8.42 |  |
 It is too easy for hard.... |  |
 Happy day/night, everyone! |  |
 in China? It look like main gate of the antiquity city in China. Nice ... |  |
 Possible proof of too easy sudoku of 09 27 06: (specifically ignoring the AUR's and xy wings... seeking some density in some step...) 1) Start at 23 filled - the given puzzle. Unique Possibilities to 27 filled. (UP 27).2) Hidden triplet 239 at h178 forbids h1=78,h7=4,h8=457 UP More... |  |
 The idea of proofs, for those who are wondering, is not to post a solution, but rather to reveal a path towards solution. The paths we take are certainly not unique, and the exposure of these differing paths can be quite interesting - and perhaps also an avenue towards learning how to better tackle the truly tough puzzles here. |  |
 Possible proof of too easy sudoku of 09 27 06:Specifically trying to keep it simple...1) Start at 23 filled - the given puzzle. Unique Possibilities to 27 filled. (UP 27).2) Hidden triplet 239 at h178 forbids h1=78,h7=4,h8=457 UP 303a) Hidden pair 56 at ad3 forbids a3=8, More... |  |
 1.How many unique completed Sudoku grids are there (9x9)?2.And how many of those are just a result of switiching numbers? (For example, if you take a completed grid and just switch the 3s and 9s, it might be thought of as a new grid.)3.Lastly, what is the minimum number of cells required to ensure a unique solution (Does such a simple rule exist?) |  |
 Great picture. |  |
 It's amazing to me how one wrong choice can snowball into a dozen wrongly placed numbers. I hate to use check moves unless I get stuck - after all, there is no such thing on paper! Another scene from a fascinating place. |  |
 Nice pic, my mother has one of her standing outside during ww2, she visited the Forbidden City then and it was completely empty as the communists discouraged anyone from visiting it then. |  |
 Hi paul!Probably you can google the answers to your questions, but given one puzzle, there are quite a few representations of the same puzzle (ignoring chances for symetry) available just by switching numbers (9!), 90 degree rotation (2),rows and columns of boxes (3!**2), rows and columns More... |  |
 solved with a guess |  |
 Good afternoon to all. The pictures are getting to be like re-runs on the television. |  |
 good morning... |  |
 maEn all |  |
 Good Maen |  |
 Paul: Google 'Sudoku' and have a look at Wikipedia. It tells you most of what you want to know. |  |
 Good maeN. |  |
 2) Hidden triplet 239 at h178 forbids h1=78,h7=4,h8=457 UP 30?? How? no 9 in h8 due to A8=9 |  |
 Hi Steve!If one has three cells , two of which are 239, and the third is 23 - we still have a hidden triplet - much like one would still have a naked triplet even with 3 pairs 23 39 29. The idea is that the 2's, 3's, and 9's are limited to those three cells. Hopefully this helps. In any event, there is also a naked quad - as always there is a naked set with a hidden set. |  |
 In this case, of course - the 2's are limited to h178, the 3's are limited to h178, the 9's are limied to h17. If something other then 2,3,9 were to occur in any of those three cells, then there would no longer be enough places for 239 in column h. |  |
 OK, whatever. |  |
 05:49. |  |
 Wow... ?! 5:49 = 349s (second), that mean need only 6s to fix a cell : 4.5s for thinking and 1.5s for click the mouse. How can you do this, YARALE? you are very very smart Hhhh, you can remember all ... I can't believe, you are master of master! |  |
 to Steve: just for something to do, since this toughisn't worth proving, I managed to find a depth 4(not sure) proof of 6/26/06 tough in archive - you submitted a depth 7 proof. |  |
 to Steve: typo - make that the 6/22/06 tough. |  |
 23:51 |  |
 Dec. 3, 2007. 04/Dec/07 5:39 AM |  |
 SE=4.2 05/Sep/10 10:05 PM |  |

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