Hitori Puzzle
Hitori flips the usual puzzle formula on its head. Instead of filling in empty cells, you start with a grid that's already full of numbers — and your job is to figure out which ones to blacken out. The goal: no row or column should have the same number appearing twice among the white (unshaded) cells. It sounds straightforward, but two extra constraints make things interesting. Black cells can never touch each other side-to-side, and every white cell must connect to every other white cell through adjacent neighbors.
Hitori
5×5 — Small grids where basic coloring rules handle everything. Good for learning the ropes.
Standard play. Timer runs. Hints available.
What is Hitori?
Hitori is a Japanese logic puzzle created by Nikoli, the same company behind Sudoku, Kakuro, and dozens of other pencil-and-paper puzzles. It first appeared in Puzzle Communication Nikoli No. 29 back in 1990. The name comes from “hitori ni shite kure” (ひとりにしてくれ), meaning “leave me alone” — each number in the solved grid stands alone in its row and column without any matching neighbors.
What makes Hitori unusual is the elimination mechanic. Most logic puzzles ask you to fill in missing information. Hitori does the opposite: everything is already there, and you need to decide what to remove. That mental shift — thinking in terms of what should go rather than what should stay — is what gives Hitori its distinct feel.
The Three Rules
Every Hitori puzzle follows the same three constraints, regardless of grid size:
- No duplicate unshaded numbers. Each row and each column can contain any given number at most once among its white cells.
- No adjacent black cells. Shaded cells cannot touch each other horizontally or vertically. Diagonal is fine.
- White cells stay connected. All unshaded cells must form one continuous group — you should be able to travel from any white cell to any other by stepping through adjacent white cells.
The connectivity rule is what separates Hitori from a simple duplicate-elimination exercise. Without it, you could just shade every duplicate and call it done. The requirement that white cells stay connected forces you to think about the spatial layout of your shading — and that's where the real puzzle lives.
For a deeper look at solving strategies, check the rules & strategy guide.
How to Play
Each cell cycles through three states when you click or tap it:
- Unmarked — default state, not yet decided
- Black (shaded) — you believe this cell should be eliminated
- White (circled) — you've confirmed this cell is definitely not black
The white/circled state is a solving aid, not a rule requirement. It helps you track cells you've already reasoned about. Think of it like pencil marks in Sudoku — not part of the answer, but useful while working things out.
Difficulty Levels
| Level | Grid | What to Expect |
|---|---|---|
| Easy | 5×5 | Small grids where basic coloring rules handle everything. Good for learning the ropes. |
| Medium | 7×7 | Larger boards that need connectivity reasoning on top of standard deductions. |
| Hard | 9×9 | Full-size puzzles requiring what-if analysis. You'll need to test assumptions. |
| Expert | 12×12 | Multi-step what-if chains across a 144-cell grid. Patience required. |
| Einstein | 15×15 | The biggest grids with deep deduction chains. Solvable by logic alone — no guessing. |
Key Strategies at a Glance
The sandwich rule is usually the first technique you'll learn: when three identical numbers appear consecutively in a row or column, the middle one must stay white. Why? If the middle were black, you'd need to shade both outer cells too (they duplicate each other), and that would make the outer blacks adjacent to the middle — breaking rule two.
Beyond that, keep an eye on cells next to existing blacks — they must be white. And if a number appears only once in its row and column, it can't be shaded. For trickier puzzles, you'll need what-if analysis: assume a cell is black, propagate consequences, and check whether you hit a contradiction.
Frequently Asked Questions
What is hitori?
A number-elimination logic puzzle from Nikoli. Start with a filled grid, shade cells to remove duplicates in each row and column while keeping all white cells connected.
Is hitori harder than sudoku?
At the same grid size, Hitori can feel harder because you're removing rather than placing numbers, and the connectivity constraint adds spatial reasoning. A 5×5 Hitori is simpler than most Sudoku, though — it depends on the size and difficulty tier.
What does “hitori” mean?
Short for “hitori ni shite kure” — Japanese for “leave me alone.” Each unshaded number stands alone in its row and column after solving.
What is the sandwich rule?
When three identical numbers sit next to each other in a line, the middle one must be white. Shading it would force both outer cells shaded too, and adjacent black cells aren't allowed.
Can hitori puzzles have multiple solutions?
A well-formed Hitori puzzle has exactly one solution. Every puzzle on ThePuzzleLabs is verified by our solver to have a unique answer.
Related Puzzles
If you enjoy Hitori, you might like these:
Binairo
Another binary-state puzzle — fill cells with 0s and 1s instead of shading them.
Sudoku
Nikoli's most famous creation. Fill numbers so each row, column, and box contains 1–9 exactly once.
Star Battle
Place stars in a grid with row, column, and region constraints. Uses a shading-like placement mechanic.
Minesweeper
Grid deduction using numbered clues and adjacency logic. If you like reasoning about neighbors, you'll feel at home.