區間數獨
4
6
9
1
4
7
5
7
9
1
3
2
6
1
5
4
3
1
6
9
7
1
6
4
3
3
5
8
4
7
1
5
7
8
6
8
7
3
線上的數字必須嚴格落在兩個端點值之間
什麼是 區間數獨？
線之間數獨繪製帶有圓形端點的線。沿線的每個數字（不包括端點本身）必須嚴格大於較小的端點並嚴格小於較大的端點。如果端點是2和8，線上的每個中間單元格必須是3、4、5、6或7之一。端點值越接近，中間單元格越受約束。
一覽
| 約束類型 | 線條約束 |
| 典型給定數 | 20–28 |
| 難度評分 | ★★★☆☆ 3/5 |
| 平均解題時間 — 簡單 | 8分鐘 |
| 平均解題時間 — 中等 | 18分鐘 |
| 平均解題時間 — 困難 | 36分鐘 |
| 平均解題時間 — 專家 | 64分鐘 |
如何解 區間數獨
| 技巧 | 它的作用 | 等級 |
|---|---|---|
| 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}. | 進階 |
| Endpoint Ordering | The endpoint values have no fixed order — the constraint is that all middle cells are strictly between the minimum and maximum endpoint. | 進階 |
| 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. | 進階 |
| 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. | 進階 |
平均解題時間
簡單
8分鐘
中等
18分鐘
困難
36分鐘
專家
64分鐘
常見問題
什麼是 Between Lines Sudoku？
Between Lines Sudoku is a variant where lines with circular endpoints are drawn on the grid. Every digit along a line (excluding the endpoint circles) must be strictly between the two endpoint values. The endpoints themselves are placed during solving — only the line positions are given.
How do I read the between-line clues?
The two circles at the ends of each line are the boundary values. Every cell between them must be strictly greater than the smaller endpoint and strictly less than the larger one. You deduce which endpoint is larger as part of the solve.
Can the endpoints be any digits?
Yes. Endpoint circles are not pre-filled — you place digits in them during solving. The only rule is that every cell along the line (excluding endpoints) must sit strictly between whatever ends up in the two circles.
What is the best strategy for Between Lines Sudoku?
Look for short between-lines — a single cell between two endpoints is tightly constrained. Combined with row, column, and box rules, the valid range for that cell is often very small. Also look for lines where available candidates in a given row or column form a narrow range.
Is Between Lines Sudoku hard to learn?
The concept is straightforward but the deductions require careful range analysis. Tracking the minimum and maximum possible values for each endpoint and inferring the valid range for in-between cells is the core skill. Easy puzzles make this very accessible.
How long does Between Lines Sudoku take to solve?
Easy puzzles take 8–18 minutes. Medium puzzles run 18–35 minutes. Hard puzzles average 35–65 minutes and expert puzzles can take over 90 minutes. Solve time scales with the number of overlapping lines and the complexity of range interactions.