I have to tell you, this has kept me up nights with worry.
It’s an obvious worry. You go in the bookstore, and you see hundreds of Sudoku books, many of them written by Will Shortz. Surely, you think, there’s a limit to Sudoku. Isn’t there?
Turns out there’s not. There are 5.5 billion possible unique (that is, with only one solution) Sudoku puzzles.
Eight of the nine numbers need to be on the initial grid, otherwise there will be multiple solutions. I’ve always wondered about that.
So, now I can rest easy. No Sudoku shortage is in the offing.