SUDOKU
Write a number from 1 to 9 into each empty square in the grid so that every number from 1 to 9 appears exactly once in each horizontal row, each vertical column, and each 3×3 block.
4
9
5
9
3
1
7
1
8
2
3
4
6
8
4
6
1
7
2
6
8
4
9
3
7
4
** Moderate