Sudoku Solving

Sudoku solvers are near and dear to my heart. They’re my go to problem when learning a new programming language because they’re just complex enough to exercise a whole bunch of different language features. I built this when I wanted to learn Swift and dip my toe into machine learning: https://twitter.com/braddwyer/status/910030265006923776?s=21

Why did I do this? As computer security expert Ben Laurie has stated, Sudoku is "a denial of service attack on human intellect". My wife was infected by the virus, and I wanted to convince her that the problem had been solved and didn't need any more of her time. Very true.

Another way to solve Sudoku is to understand that it is an instance of the Exact Cover problem [1]. Basically, solving a 3x3 Sudoku grid is nothing more than finding 9 "sheets" of each number which superimpose exactly on top of the grid. For example (2x2 sudoku = 4 sheets): 1324 3142 4213 2431 is: 1... .2.. .3.. ...4 .1.. ...2 3... ..4. ..1. + .2.. + ...3 + 4... ...1 2... ..3. .4.. or even: x... .x.. .x.. ...x…

I've seen this article every now and then, and it's always fun to read. Something jumped out at me this time, though: > As computer security expert Ben Laurie has stated, Sudoku is "a denial of service attack on human intellect". Several people I know (including my wife) were infected by the virus, and I thought maybe this would demonstrate that they didn't need to spend any more time on Sudoku. Ah, yes... remember the halcyon days of 2006, when…