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Hitori
Hitori, whose name means "alone" in Japanese, is a number-elimination puzzle published by Nikoli. You start with a full grid of numbers and black out cells to remove duplicates. Where Sudoku is about filling in, Hitori is about taking away.
Hitori Rules
The grid begins completely filled with numbers. You shade (black out) cells so that no number appears more than once in any single row or any single column among the unshaded cells.
Shaded cells may never be adjacent to one another horizontally or vertically — two blacked-out cells cannot share an edge, though they may touch at a corner.
All the remaining unshaded cells must stay connected as a single group, reachable from one another horizontally or vertically. When duplicates are gone, no shaded cells touch, and the white cells form one connected area, the puzzle is solved uniquely.
Hitori Strategy & Tips
Spot triplets in a line
If the same number appears three times in a row or column, the middle one must stay white (shading both ends, since shaded cells can't be adjacent). This is a reliable opening move.
Protect cells next to shaded ones
Because shaded cells can't touch, the moment you black a cell, its four neighbors must remain white. That instantly forces those duplicates to be removed elsewhere.
Keep white cells connected
Shading must never split the unshaded region. If blacking a cell would strand a white area, that cell must instead stay white — and its duplicate gets removed.
Use pairs sharing a neighbor
When two identical numbers sit two apart with a cell between them, often only one configuration avoids adjacent shading. Work these constrained clusters to cascade decisions.
Frequently Asked Questions
What is the objective of Hitori?
To shade cells so that no number repeats in any row or column, while keeping all unshaded cells connected and never letting two shaded cells touch edge to edge.
Can shaded cells touch in Hitori?
Not along an edge. Two shaded cells may never be horizontally or vertically adjacent, though they are allowed to touch diagonally at a corner.
What does Hitori mean?
Hitori is Japanese for "alone" — short for a phrase meaning "leave it alone" — reflecting how each surviving number stands alone in its row and column.
How is Hitori different from Sudoku?
Instead of filling empty cells, you eliminate numbers from a full grid by shading them, and you only need each value to be unique once duplicates are blacked out.