All Sudoku Variants
9×9 · Constraint

Nabner Sudoku

Also known as Nabner Lines

On a Nabner line every digit is different and no two are consecutive — the opposite of a Renban run.

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An example Nabner puzzle: every digit on the line is different and no two are consecutive — here 2, 4, 6, 8.

Nabner Sudoku draws lines with a two-part rule: along a Nabner line, every digit is different, and no two of them are consecutive. It is the exact opposite of a Renban line, which demands a run of consecutive digits — here consecutive digits are banned outright.

The rule: all different, none consecutive

Two conditions hold for the whole line at once. First, no value repeats. Second, no two values anywhere on the line differ by exactly 1 — so if a 4 is on the line, neither a 3 nor a 5 may appear on it. Below, the line reads 2, 4, 7, 9: all different, and every pair is at least 2 apart.

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2, 4, 7, 9 — all different, and no two are consecutive (each pair differs by at least 2).

A worked example, step by step

Take a five-cell Nabner line where one cell is already a 4.

4

Step 0. One cell on the line is a 4.

Step 1 — knock out the neighbours. Because no two line digits may be consecutive, having a 4 on the line forbids both 3 and 5 from anywhere else on that line — not just the cells next to the 4.

4no 3,5no 3,5no 3,5no 3,5

Step 1. A 4 on the line bans 3 and 5 from every other line cell.

Step 2 — see what's left. With 4 taken (no repeats) and 3 and 5 banned, the other cells can only be 1, 2, 6, 7, 8 or 9 — and each of those, once placed, will knock out its neighbours too, cascading down the line.

1267891267891267891267894

Step 2. The remaining cells are limited to {1, 2, 6, 7, 8, 9}.

Solving strategy

  • Each placement bans two values. A digit d on the line removes d−1 and d+1 from the whole line — sweep them out at once.
  • The middle digits bite hardest. A 5 bans 4 and 6; the extremes 1 and 9 ban only one neighbour each.
  • Watch the length. A long Nabner line needs many well-spaced digits, which quickly forces the extremes and gaps.
  • Feed the grid. Each digit fixed on the line behaves like a given for its row, column and box.

Common mistakes

  • Only checking neighbours. The no-consecutive rule spans the whole line, not just adjacent cells.
  • Allowing a repeat. Every digit on a Nabner line is distinct as well as non-consecutive.
  • Confusing it with Renban. Renban wants a consecutive run; Nabner forbids consecutive pairs entirely.
  • Forgetting ordinary Sudoku. Line cells still can't repeat within a row, column or box.

Can I play it here?

Not yet — Nabner Sudoku isn't one of the puzzle types SudokuStreak generates for now. But you can learn its rules above, and there's plenty here to sink your teeth into meanwhile: