Sudoku Sudoku is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 sub-grids (called boxes) ...

First, a data structure to store a Sudoku cell: A set of possible values. When this set is reduced to a single value, the cell is solved. Cells are immutable. The rules of Sudoku are applied ...