Hidden singles will be a technique used in virtually every sudoku puzzle you solve and are one of the basic steps that you will be looking for all the time to allow you to input a number into the grid. This is easier to spot than a naked single if you are not using candidates and is easily found by using scanning and cross-hatching techniques.
Knowing that a number can't be repeated in any row, column or box, this allows you to determine sometimes that there is only one cell left in a particular house in which a particular number can go.
Finding hidden singles in boxes is the easiest out of all the houses. It's quite easy to see how all the same number intersect with box.
If you are using candidates then it's a case of scanning that box to see if there is a particular number that only appears once.
This is the same principle as with boxes, but the house is either a row or column.
A row works exactly the same as a column, only that it is rotated by 90°. In this case you will see that in column 3 there is only one remaining cell in which number 8 can go.
If you are using candidates then it's a case of scanning that row or column to see if there is a particular number that only appears once. If you are not using candidates then these are more tricky to spot than with a box because you have to look for intersections along the length of a row or column from all areas of the grid.
The Full House | Naked Singles
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