The last missing digit is the easiest pattern to spot in Sudoku.
Understanding the Concept
When a row, column, or box has 8 numbers filled, only one digit is missing.
Simply identify which number from 1-9 isn't present.
This technique is also called "Last Free Cell" or "Single Empty Cell".
It's the most basic solving technique and requires no complex logic.
Always scan for these easy wins before using harder techniques.
In easy puzzles, you can often solve many cells using just this technique.
Examples
Last Digit in Row 0
Row 0 has 8 numbers filled: 5,3,4,6,7,8,9,1. The missing digit is 2, which goes in the empty cell (green).
5
3
4
6
7
8
9
1
6
7
2
1
9
5
3
4
8
1
9
8
3
4
2
5
6
7
8
5
9
7
6
1
4
2
3
4
2
6
8
5
3
7
9
1
7
1
3
9
2
4
8
5
6
9
6
1
5
3
7
2
8
4
2
8
7
4
1
9
6
3
5
3
4
5
2
8
6
1
7
9
Solution
Last Digit in Box 8
The bottom-right box has 8 digits filled. The missing digit 6 goes in the highlighted cell.
5
3
4
6
7
8
9
1
2
6
7
2
1
9
5
3
4
8
1
9
8
3
4
2
5
6
7
8
5
9
7
6
1
4
2
3
4
2
6
8
5
3
7
9
1
7
1
3
9
2
4
8
5
6
9
6
1
5
3
7
2
8
4
2
8
7
4
1
9
3
5
3
4
5
2
8
6
1
7
9
Solution
Pro Tips
- •Scan all rows, columns, and boxes for this pattern
- •This should always be your first technique to try
- •Easy puzzles have many last missing digit opportunities
- •Check again after placing each number - new opportunities appear
Practice Exercise
Find the last missing digits! Each highlighted row or box has just one cell to fill.
5
3
4
6
7
8
9
1
2
6
7
2
1
9
5
3
4
8
1
9
8
3
4
2
5
6
7
8
5
9
7
6
1
4
2
3
4
2
6
8
5
3
7
9
1
7
1
3
9
2
4
8
5
6
9
6
1
5
3
7
2
4
2
8
7
4
1
9
6
3
5
3
4
5
2
6
1
7
9
