Hitori Strategy Tips
To solve hitori puzzles, there are many tips and strategies that you can look to implement.
Here are a few strategy hints and tips to help you solve hitori:
Look for the same number three times continuously
If a number occurs in three consecutive cells in a row or a column, for instance 1  1  1, then you know that the middle one must be a white cell and the other two cells filled in and marked accordingly.
This is because we know that a number can only occur once in a row or column. If the middle of the three cells were filled black, then the two surrounding cells would have to be white, meaning the same number would have to occur twice in that row or column  against the rules.
Therefore a pattern like 1  1  1 can be instantly completed using this method.
Look for a number three times, with two occurrences together
For instance, in one row: 1  2  2  3  5  2  1
We know here that one of the two '2's together must be black, and therefore the other one white. They can't both be filled black because then two black filled cells would touch which is against the rules. Therefore we know that the '2' on it's own in this row must be crossed out, and we can mark this accordingly.
Look for a pattern like 1  2  1
In other words, any time you see a number, a different number and then the first number again, then you can mark the middle cell as white.
That's because one of the number that is the same (here, a '1'), must be marked black as otherwise the same number would occur twice in the same row or column.
Marking cells
Just a practical point on marking cells: if a cell is definitely white, then circle it. If it is filled, mark this clearly by shading it in grey  but don't completely obliterate the cell so that you don't obscure the number that was in the cell.
With our online player, you can mark a cell as yellow rather circling it to show it must be white; to do this press the up arrow, and mark as filled by pressing 'the down arrow.
Look for this pattern in the corner of the puzzle
1  2
1  2
If you have a pattern like this at the corner of the puzzle, then you can cross out the top left and bottom right of these as the filled cells. If it were the other way around, you would have an isolated white cell at the top left, which would be against the rules.
Using these hitori strategies, you will be able to solve the majority of hitori puzzles.
As you play harder puzzles and get more experienced, you will notice more patterns that you can use to help you solve hitori puzzles  part of the fun is finding these for yourself.
One interesting point to consider with harder puzzles is that you will sometimes have to look a few moves ahead to see if one move, then another and then another will lead you to block in and isolate a group of white cells, in other words to create a wall around them.
Whilst often there will be other rules you can apply, it is worth bearing in mind this strategy as it is usually the one to apply when you can't seem to make any progress by applying any of the other rules listed here. Remember you should never have to guess, should always be able to deduce with certainty whether a cell is filled or not, and there should only be one valid solution to each hitori puzzle. Good luck!
