The lightning speed of his observing standard rules across the board is impressive but expected after months of practice. The agility with which he picks up new rules and starts working with them is sign of a beautiful mind. This was a pleasure to watch.
Yeah, the guy is a genius at solving sudokus and makes it look easy. It is amazing how he fast can develop new "algorithms" and the explanation for the for new rules he encounters. And the way he develops/explains those algorithms
I though that too at first but actually they seem well practiced too. Eg other sudoku-style puzzles also have knight move rules. The main trick I missed is the forking one (if I put a 3 here then it reaches here and here by knight’s move therefore it can’t go here).
That said It is still impressive and I think practice is not sufficient to explain how fast he is at it.
> (if I put a 3 here then it reaches here and here by knight’s move therefore it can’t go here)
A possibly-simpler way to look at it is the inverse. Putting a 3 here or here (where it must go) both block this other place, so we know this other place is blocked either way.
Yes, that’s something I tried thinking about but computing the intersection of two or more quite large regions turns out to be harder than using the symmetry to only look at one region. There are also tricks one can learn for eg dominos.
