How to solve Hitori: what to shade and what to keep
5 min read ·
Hitori starts with a grid full of numbers, many of them repeated. Your job is to shade cells until no number appears twice in any row or column, while keeping the rest of the board open and connected.
Each Hitori has one solution, and a few patterns decide most of it before you ever have to think hard. This guide shows them in order.
The rules
- Shade cells so that no number appears twice among the unshaded cells of any row or column.
- Shaded cells never touch side by side (diagonal contact is fine).
- All unshaded cells form one connected group.
Patterns that decide cells at once
- Sandwich: a cell between two equal numbers (5 x 5) stays white. If it were shaded, both 5s beside it would have to stay white, leaving two 5s in the line.
- Adjacent pair: two equal numbers side by side (4 4): one of them is shaded, so every other 4 in that row or column must be shaded, because it would clash with whichever 4 stays white.
- Three in a row: three equal numbers next to each other (3 3 3): the middle one stays white and both outer ones are shaded, since shading the middle would leave the outer two as a duplicate.
Around every shaded cell
Shaded cells can't touch side by side, so all four neighbours of a shaded cell are white. Circle them. Each of those white cells then forces its own duplicates elsewhere in its row and column to be shaded, and the shading spreads.
Keep the white cells connected
The connection rule decides the hardest cells. Before shading a cell, check that the white cells around it can still reach each other another way. A shade that would cut off a white cell or a white corner is impossible, so that cell is white and its duplicate is the one to shade.
Corners and edges are where this happens most: two shaded cells diagonal to each other next to a corner can trap the corner cell, so at most one of them can be shaded.
A solving routine
- Circle every sandwiched cell, and shade the extra copies next to adjacent pairs.
- Around every shaded cell, circle the four neighbours.
- For every circled cell, shade its duplicates in the same row and column.
- Check connectivity before every new shade, especially near edges and corners.
- Repeat until every row and column has unique numbers.
Practise
On Puzzimo, tap a cell to circle it ○ as white (tap again to clear), double-tap to shade it ■, and drag to mark many cells at once. Shading a cell that the solution keeps white counts as a mistake: it's shown and corrected, and the third ends the round. Grids come in 6×6, 8×8 and 10×10, with a 6×6 daily challenge.
Frequently asked questions
What's the first move in Hitori?
Look for sandwiches, a cell between two equal numbers, and circle it as white. Then look for adjacent equal pairs, which force every other copy of that number in the line to be shaded.
Can shaded cells touch in Hitori?
Not side by side. They may touch diagonally, as long as the white cells still form one connected group.
Why does connectivity matter so much?
Because it rules out shades that the number rules alone would allow. A shade that would isolate a white cell can never be right, so its duplicate must be shaded instead.