Sudoku Rules

Sudoku is a logic-based 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 that compose the grid (also called "boxes", "blocks", "regions", or "sub-squares") contains all of the digits from 1 to 9.

The same single integer may not appear twice:

• in the same 9x9 playing board row
• in the same 9x9 playing board column or
• in any of the nine 3x3 subregions of the 9x9 playing board