Expert Between Lines Sudoku
3
2
6
1
4
4
2
5
3
6
4
9
6
5
8
9
5
3
8
7
9
6
9
2
7
9
How to play Between Lines Sudoku
Standard Sudoku rules apply. Each line has two circle endpoints. All digits along the line (excluding the circles) must be strictly between the two endpoint values.
About Between Lines Sudoku
Difficulty
★★★☆☆
3/5
Constraint Type
Line Constraints
Typical Givens
20–28
Avg. Solve (Medium)
18 min
Between Lines Sudoku draws lines with circular endpoints. Every digit along the line (excluding the endpoints themselves) must be strictly greater than the smaller endpoint and strictly less than the larger endpoint. If the endpoints are 2 and 8, every middle cell on the line must be one of 3, 4, 5, 6, or 7. The closer the endpoints are in value, the more constrained the middle cells.
Solving Techniques
| Technique | Description | Level |
|---|---|---|
| Endpoint Gap Analysis | The gap between endpoint values must be large enough to accommodate all middle cells. If endpoints are 2 and 8, middle cells must come from {3,4,5,6,7}. | Beginner |
| Endpoint Ordering | The endpoint values have no fixed order — the constraint is that all middle cells are strictly between the minimum and maximum endpoint. | Beginner |
| Tight Endpoint Constraint | If endpoints would be consecutive (e.g., 3 and 4), no middle cell could satisfy the strict inequalities — use this to force endpoints apart. | Intermediate |
| Between-Line–Box Interaction | All middle cells sharing a box must satisfy the between constraint. Use the box to eliminate candidates outside the valid range. | Advanced |
Average Solve Time by Difficulty
Easy
8 min
Medium
18 min
Hard
36 min
Expert
64 min