Thanks a lot for your website - that was refreshing to see.

While I like the idea of using ARC3 to grade sudoku, I much prefer the approach developed by Andrew C. Stuart in [0], where they rely on the human techniques* needed to solve the sudoku. Indeed, Sudoku are small enough that a reasonable greedy algorithm is enough to solve them quasi instantly on modern hardware.

* techniques to solve the sudoku that can be applied by an human (as opposed to a computer).

[0]: https://www.sudokuwiki.org/Sudoku_Creation_and_Grading.pdf