I might be missing something here. Can someone help? Take bottom left conner as the origin (0,0) of a normal coordinate system, then position (4,1), (4,3), (7,1) and (7,3) can have interchangeable values of "1" or "9". Is that nor true?
Posted 24th Jul 2018 at 09:53 Last edited by Elisabeth 24th Jul 2018 at 09:54
Elisabeth Daily subscriber Has not played this puzzle yet
SlowBurn, using your coordinates, (6, 3) is a 4 and so the 1 cannot be alongside it, as 4+1 = 5 and no v so must be the 9 which fixes the others. Easy to miss!
Posted 24th Jul 2018 at 09:54
bergensbest Daily subscriber Has not played this puzzle yet
SlowBurn, if you interchange the 9s and 1s as you say then a 1 appears in the position (7,3) which is next to the 4 in position (6,3)
Posted 25th Jul 2018 at 07:13 Last edited by SlowBurn 25th Jul 2018 at 07:26
SlowBurn Has not played this puzzle yet
Thanks Elisabeth & bergensbest. Indeed I was just being blind. It seems logical that the fewer clues a puzzle contains the more challenging it will be (desirable). However, if we keep reducing the number of clues there will come a point when the solution is no longer unique (undesirable). Can someone point me to some references about this interesting subject for a casual learner please?
Posted 25th Jul 2018 at 20:49 Last edited by awesomeusername 25th Jul 2018 at 20:50
awesomeusername Has not played this puzzle yet
Here's an article I found. Turns out the fewest number of clues you can have is 17, at least for a standard 9x9 grid.
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Take bottom left conner as the origin (0,0) of a normal coordinate system, then position (4,1), (4,3), (7,1) and (7,3) can have interchangeable values of "1" or "9". Is that nor true?
Last edited by Elisabeth 24th Jul 2018 at 09:54
Last edited by SlowBurn 25th Jul 2018 at 07:26
It seems logical that the fewer clues a puzzle contains the more challenging it will be (desirable). However, if we keep reducing the number of clues there will come a point when the solution is no longer unique (undesirable). Can someone point me to some references about this interesting subject for a casual learner please?
Last edited by awesomeusername 25th Jul 2018 at 20:50
https://www.technologyreview.com/s/426554/mathematicians-solve-minimum-sudoku-problem/
EDIT: An even better resource: https://en.wikipedia.org/wiki/Mathematics_of_Sudoku
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