About Hitori
Hitori starts with a grid full of numbers, often with duplicates in the same row or column. The goal is to shade cells so that no number repeats in any row or column — but with two extra constraints: no two shaded cells can be adjacent, and every unshaded cell must stay connected into one single group. It's a Nikoli classic that rewards careful, methodical elimination.
The Rules
Shade cells to remove every duplicate number from each row and column, without shading two adjacent cells, and keeping all unshaded cells connected.
Step by Step
- Start with a grid where numbers can repeat within a row or column.
- Shade cells so that no number appears more than once in any row or column.
- Two shaded cells can never be directly adjacent (horizontally or vertically).
- Every unshaded cell must be reachable from every other unshaded cell — no isolated pockets allowed.
- The puzzle is solved when all three rules hold at once.
Tips & Strategy
- If you see three or more of the same number in a row or column, shading the right ones is more constrained — start there.
- If shading a cell would isolate another cell from the rest of the grid, that cell can't be shaded — leave it white instead.
- A number that appears only once in its row and column can never be shaded, since shading it wouldn't fix a duplicate.
- Work from the most duplicated rows and columns first — they narrow the rest of the grid the fastest.
Frequently Asked Questions
Can two shaded cells be diagonally adjacent?
Yes — the no-adjacency rule only applies horizontally and vertically. Diagonal shaded neighbors are fine.
What does 'connected' mean for the unshaded cells?
You must be able to travel between any two unshaded cells by moving up, down, left, or right through other unshaded cells — no shaded cell can cut the grid into separate islands.
Is Hitori solvable without guessing?
Yes — every generated puzzle has a unique solution reachable through pure logical deduction.
