Solving methods — Hitori

The different methods for solving a Hitori. Know more of them? Send me an e-mail.

Once you have set a circle, you can mark every other cell with the same number in its row and column as black.

Once you have set a black cell, every cell next to it must be marked white.

If you have set a black in the corner, the other one must be a circle.

If you have set two blacks along the edge, the third must be a circle.

If circling a cell leads to an impossibility, the cell must be black.

If the combinations mean a cell must be circled no matter what, we know it has to be circled.

If you have a corner with two equal numbers, you can set a circle.

If you have a corner with three equal numbers.

If you have a corner with four equal numbers, you know the black cells must run out from the corner.

If you have two equal numbers with one in between, you can mark the one in between.

If you have three equal in a row, you know how they must be marked.

If you have a double and a single of a number, you can mark the single.

If you find two doubles wrapped around a single, the single must be black.

Look for two pairs.

Look for two pairs and see whether you find the numbers between them.

If you have two doubles along the edge, you can mark some circles.

If you have three doubles along the edge, you can mark some circles.

Look for doubles along the edge — it can pay off.

Look for doubles in the middle — it can pay off.

You are not allowed to split the board in two with black cells.

If you have set three blacks in the middle of the board, the last one must be a circle.

Four equal numbers in the middle have only two solutions — we can exploit that.