The Box/Line Reduction
technique is similar to the Hidden Single
. In the Hidden Single technique, we are looking for a number that appears as a possible candidate only in one cell for the whole box, row, or column. In the Box/Line Reduction
technique, we are looking for a number that appears as a possible candidate in several cells, but only in one box for the whole row or column. We can remove this candidate from all cells in the box, except the cells that belong to the specified row or column.
A picture on the left shows an example of Box/Line Reduction
in a row. The number '1'
in cells C2 and C3 (marked yellow) appears in the list of possible candidates in row C only in box (1*1). The number 1 can be removed from all cells in box (1*1) except cells in row C. We are removing candidate '1'
in the cells A2 and B3 (marked red).