Renban Sudoku
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How to play Renban Sudoku
Standard Sudoku rules apply. Each purple line must contain a set of consecutive digits in any order. The line length tells you exactly how many consecutive numbers are needed - E.g. a 4-cell line might contain 3,6,4,5.
Full guide →
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
What is Renban Sudoku?
Renban Sudoku is a variant where purple lines are drawn across the grid. Every purple line must contain a set of consecutive digits (in any order along the line). For example, a 4-cell renban line might hold 3,4,5,6 or 6,4,5,3 — any arrangement, as long as the set forms a run of consecutive numbers. Standard Sudoku rules apply.
Do renban digits have to be in order?
No. The digits on a renban line must form a set of consecutive numbers, but they can appear in any order along the line. A 3-cell renban line holds three consecutive digits arranged in any sequence — it's the set that matters, not the sequence.
Can digits repeat on a renban line?
No. Because the digits must form a consecutive set and each digit in a set is unique, no digit can repeat on a renban line. This is an implicit constraint: a 4-cell renban line always contains exactly four distinct consecutive digits.
How do I start solving Renban Sudoku?
Start with the shortest lines and look for lines that share cells with highly constrained rows, columns, or boxes. A 2-cell renban line can only hold adjacent digit pairs (1&2, 2&3, ..., 8&9). Identifying which consecutive set fits each line, then cross-referencing with standard Sudoku constraints, is the core technique.
Is Renban Sudoku harder than regular Sudoku?
Easy and medium renban puzzles are comparable in difficulty to classic Sudoku at the same level. Hard and expert puzzles become significantly harder because you must track which consecutive sets are possible for multiple overlapping lines simultaneously, which requires combinatorial thinking on top of standard Sudoku logic.
How long does Renban Sudoku take to solve?
Easy puzzles take 8–18 minutes. Medium puzzles run 18–35 minutes. Hard puzzles average 35–60 minutes and expert puzzles can take over an hour. Solve time is most affected by the number and length of renban lines — more lines mean more interacting constraints.