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.
1
5
8
4
7
1
2
6
6
3
1
7
8
5
2
2
4
5
3
2
6
7
1
9
** Moderate