Sudoku
Each row must contain the numbers 1 to 9; each column must contain the numbers 1 to 9; and each set of 3 by 3 boxes must contain the numbers 1 to 9.
Each row must contain the numbers 1 to 9; each column must contain the numbers 1 to 9; and each set of 3 by 3 boxes must contain the numbers 1 to 9.