3
1
9
4
1
5
3
8
5
2
9
7
9
1
2
5
6
1
2
5
1
9
6
1
4
6
8
9
5
2
5
8
4
Keep a mental note of which digits are 'almost placed' — appearing 8 times on the board. One more elimination will solve them.
Keep a mental note of which digits are 'almost placed' — appearing 8 times on the board. One more elimination will solve them.
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.
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.