Renban Sudoku
Purple lines must contain consecutive digits in any order
Easy
Renban Sudoku Easy
Medium
Renban Sudoku Medium
Hard
Renban Sudoku Hard
Expert
Renban Sudoku Expert
What is Renban Sudoku?
Renban Sudoku draws purple lines on the grid. The digits on any purple line must form a set of consecutive integers (like 3,4,5 or 7,8), though they can appear in any order along the line. The length of the line tells you exactly how many consecutive numbers are involved. This creates powerful range restrictions: a 5-cell Renban line can only span 5 consecutive values from the possible range 1–9.
At a Glance
| Constraint type | Line Constraints |
| Typical givens | 20–28 |
| Difficulty rating | ★★★★☆ 4/5 |
| Avg. solve time — Easy | 10 min |
| Avg. solve time — Medium | 22 min |
| Avg. solve time — Hard | 42 min |
| Avg. solve time — Expert | 72 min |
How to Solve Renban Sudoku
| Technique | What it does | Level |
|---|---|---|
| Length-Based Range | A Renban line of length L must contain L consecutive integers. The starting value is between 1 and 10−L, giving 10−L possible ranges. | Beginner |
| Shared Cell Intersection | If two Renban lines share a cell, that cell's value must fit both lines' consecutive ranges. Intersect the ranges to find valid values. | Intermediate |
| Single-Range Reduction | When a Renban line's valid range reduces to a single starting value, all cell values are fully determined (in some order). | Intermediate |
| Renban–Box Interaction | Digits on a Renban line within one box restrict the box's remaining cells. Use box uniqueness to narrow the line's range. | Advanced |
Average Solve Times
Easy
10 min
Medium
22 min
Hard
42 min
Expert
72 min
Frequently Asked Questions
Must the digits be in order along the line?
No — the digits must form a set of consecutive integers but can appear in any order along the line.
What is the minimum line length?
Our puzzles use lines of length 2–7. A 1-cell line would add no constraint.