I try to include sudokus every time I write a puzzle set. I don’t like how the fame of sudoku means it often get excluded in “puzzles” in general. My first project consisting of just sudokus came a couple of months after Puzzle Cruise. A staff of a local high school was hosting a sudoku contest hoping to include some variants that programs from the internet couldn’t spew out.
Tackling the job of writing variants were myself and sinchai4547, the current top 2 sudoku solvers in the nation. For a country that has never seen much beyond classic sudoku, we had to be modest with the level of difficulty.
The tournament featured 5 preliminary rounds and the top 20 moves on. After rounds 6 and 7 the remaining top 5 advance to the finals. Here is one puzzle from round 7:
Quadruple Sudoku: Enter digits 1-9 in each row, column and outlined 3×3 boxes. The groups of 4 numbers indicate the contents of that particular 4 boxes.