Hitori Solver, Step by Step
Type every number into its square. Shaded squares show dark, squares that stay white get a ring.
How to use the hitori solver
Set the width and height, then type every number of your puzzle into its square. Press Explain the next step: the solver shades the squares that must be shaded, rings the ones that must stay white, outlines what changed, and says why. Show the answer shades the whole grid at once and checks the solution is the only one.
The rules of hitori
Shade some squares so that no number appears more than once in any row or column among the squares left white. Shaded squares may not touch side by side, though they may touch at a corner. All the white squares must join up into one area, so you can walk from any white square to any other without crossing a shaded one.
How to solve hitori, step by step
Look for sandwiches. In a run like 3 5 3, the 5 stays white: shading it would force both 3s to stay, and they would repeat. Look for pairs. When two copies of a number sit side by side, one of them is shaded, so any third copy in that row or column is shaded too. Follow each shade. The squares beside a shaded square stay white, and a white number shades its copies in the same row and column. Keep the white joined. A square whose shading would wall off part of the grid stays white; corners and edges are where this bites first. When those run out, the solver tries a square both ways and keeps the one that does not break a rule.
How it was checked
The solver was run on all 150 puzzles of the daily hitori. It found each stored answer and found it to be the only one, and every step it explained was checked against those answers: it never shaded or kept a square wrongly. It was also run on larger grids up to 12 by 12.
More logic puzzles
There is a new daily hitori every day. The nurikabe solver also keeps an area joined up, and the Tango and binairo solver works with no-repeat rows the same way. For a puzzle you hold in your hands, see our brain teasers. There are more solvers on the puzzle tools page.
Frequently Asked Questions
How do you solve a hitori?
Start with the patterns: in a run like 3 5 3 the middle number stays white, and when two copies sit side by side any third copy in that line is shaded. After that, the squares beside a shaded one stay white, a white number shades its copies in the same row and column, and a square whose shading would cut the white area in two stays white.
What are the rules of hitori?
Shade squares so no number repeats in any row or column among the white squares. Shaded squares may not touch side by side, and all the white squares must join up into one area.
Can shaded squares touch diagonally in hitori?
Yes. Shaded squares may touch at a corner; they only may not share a side. Corner contact is often what walls a white square in, which is why the white squares have to be checked for joining up.
What does hitori mean?
Hitori ni shite kure, roughly "leave me alone", is the Japanese phrase the name comes from: each number must end up alone in its row and column.
Does every hitori have one solution?
A well-made one does. The solver checks, and says if the numbers you entered allow more than one.