Pro Tip

Box-Line Reduction: if all candidates for a digit in a row or column are within one box, eliminate that digit from the rest of the box.

Pro Tip
✓ Completed! 👍
3
1
6
8
2
7
9
8
6
4
7
5
2
9
8
5
4
6
1
6
3
2
5
Math Insight

The minimum number of clues (17) needed for a unique Sudoku was proved by exhaustive computer search in 2012.

Math Insight