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