What Is Hitori?
Hitori first appeared in Puzzle Communication Nikoli issue 29 in March 1990. The Japanese title means something close to 'leave me alone,' which fits the goal: remove duplicate numbers until each row and column has no repeats. The twist is that shaded cells cannot touch side by side, and the remaining white cells must stay connected. That turns a simple duplicate check into a network puzzle. Start shading carefully and keep the grid in one piece.
How to Play Hitori
- Look for repeated numbers in each row and column.
- Shade cells so no number appears more than once in any row or column.
- Never shade two cells that touch horizontally or vertically.
- Keep every unshaded cell connected through side contact.
- Mark cells you know must stay white before shading around them.
- Finish when all duplicates are resolved and the white region remains connected.
Basic Rules
- Each row may contain only one visible copy of a number.
- Each column may contain only one visible copy of a number.
- Shaded cells may touch diagonally but not horizontally or vertically.
- All unshaded cells must form one connected group.
- Clue numbers do not change during play.
- A well-made Hitori puzzle has one logical solution.
Strategy Tips for Beginners
- When three identical numbers appear in a row with the middle copy between the other two, the middle often stays white so the outer pair can be shaded.
- If shading a cell would isolate a white region, that cell must stay white.
- After you shade a cell, mark its side neighbors as white immediately.
- Search for duplicate pairs that cross. A number repeated in both a row and column can force one cell's state.
- Use connectivity late in the puzzle. A legal duplicate choice can still fail if it cuts the white area apart.
Real Examples of Gameplay
Triple Pattern
A row contains 4, 4, 4 in three separated cells. If the middle 4 were shaded, the two outer 4s would both remain visible, so the middle 4 must stay white.
No Adjacent Shading
You shade a repeated 7. The cells above, below, left, and right of that 7 now must remain white.
Connectivity Check
A tempting shaded cell would split the lower-left corner from the rest of the grid. Since white cells must connect, that cell cannot be shaded.
Variations of Hitori
- Sudoku: Also uses rows and columns, but fills missing numbers instead of shading duplicates.
- Futoshiki: Adds inequality signs to Latin-square number placement.
- Nurikabe: Uses shaded cells and connectivity, but turns numbers into islands.
Why People Love Hitori
- The rules fit in a few lines.
- Every shaded cell has consequences for nearby cells.
- The connectivity rule gives the puzzle depth beyond duplicate removal.
- Small grids still produce satisfying logic chains.
Play Hitori Online for Free
Play Hitori online for free and practice duplicate removal with connectivity logic. Shade slowly, mark safe cells, and recheck the white region before committing to a risky move.
Comparison
| Version | Difficulty | Players | Typical Time |
|---|---|---|---|
| 5x5 Hitori | Easy | 1 | 5 to 10 min |
| 7x7 Hitori | Medium | 1 | 8 to 15 min |
| 9x9 Hitori | Hard | 1 | 12 to 25 min |
Frequently Asked Questions
What does Hitori mean?
The name comes from Japanese and is commonly translated around the idea of being alone or leaving one alone.
Can shaded cells touch diagonally?
Yes. The ban only applies to horizontal and vertical contact.
Why do white cells need to stay connected?
That rule prevents isolated islands of unshaded cells and creates many of the deeper deductions.
Start Playing Now
Hitori rewards careful local logic and whole-grid awareness. Remove duplicates, protect white connections, and use every shaded cell to force the next decision.