Hard Renban Sudoku

Digits on each purple line form a set of consecutive digits in any order. The line's length tells you the range.

Easy Medium Hard Expert

Hard Renban Sudoku. Longer lines, more possible sequences — expect systematic enumeration and multi-step eliminations.

4
7
9
3
4
6
3
4
9
4
1
9
2
7
8
5
6
7
8
6
4
4
5
7
8
3
2
Mistakes
0/3
Score
-
Time
00:00
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Progress0%

What is Renban Sudoku?

Difficulty
★★★★☆
4/5
Constraint Type
Line Constraints
Typical Givens
20–28
Avg. Solve (Hard)
42 min

Solving Techniques for Hard Level

Technique Description 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

Ready for the ultimate test? Try Expert Renban Sudoku — the hardest puzzles on Sudoku.by.

Techniques to Master at Hard

  • Hidden Pairs technique — Where two renban lines cross, the shared cell must fit both runs — the intersection maths strips candidates until pairs hide in the cells flanking the crossing.
  • X-Wing technique — Runs exclude 1 and 9 from most mid-grid lines, concentrating the extremes in off-line cells — hard renban X-Wings on 1 and 9 are the standard consequence.

Average Solve Time by Difficulty

Easy
10 min
Medium
22 min
Hard
42 min
Expert
72 min
Want a full walkthrough of rules, strategies, and solving steps? How to Play Renban Sudoku →

Related Variants

German Whispers

The mirror image of renban logic: lines that forbid close digits instead of requiring a consecutive run.

Palindrome Sudoku

Another line whose meaning is about the set of digits on it — here the line must read the same in both directions.

Between Lines Sudoku

Swaps the consecutive-run rule for a bounded-range rule anchored by two endpoint circles — kindred range reasoning.

Frequently Asked Questions — Hard Renban Sudoku

What makes hard Renban Sudoku so challenging?
Hard puzzles have longer renban lines with more possible consecutive sequences, and the lines are positioned so that initial constraints leave many candidates open. Resolving them requires cross-referencing multiple lines with box and row/column constraints simultaneously.
How do I handle a long renban line in hard difficulty?
Enumerate all valid consecutive sequences for the line length. Then use the row and column givens to eliminate specific digits from each cell position on the line. If enough candidates are eliminated, the sequence range narrows until only one is valid.
Should I use pencil marks for hard Renban Sudoku?
Yes — both standard digit candidates and notes about which consecutive sequences each line could hold. When you eliminate a sequence for one line, check whether that affects any adjacent or overlapping lines.
What is the hardest type of deduction in hard Renban Sudoku?
Sequence bifurcation: when a line has exactly two remaining possible sequences, you can sometimes prove that a specific digit must appear in a specific cell regardless of which sequence is correct — because both sequences place that digit in that position. This is the renban equivalent of a hidden single.
How long does hard Renban Sudoku take?
Expect 30–60 minutes. The hardest part is usually identifying which renban line is the key pivot — the one whose sequence gets fully determined first, unlocking chain placements across the grid.

More questions? See the full Renban Sudoku guide.