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Techniques
Double Block Line
Double Block Line is similar to Block Line except... doubled! With this technique,
two
blocks and
two
lines are taken into account.
Consider the sudoku below.
4
4
4
4
4
4
8
6
5
2
3
4
4
4
4
4
In
the left and right blocks
, the value 4 can only exist in
the cells marked with a small 4
.
If a 4 exists in
the top row of the left block
, then there must be a 4 in
the bottom row of the right block
. Alternatively, if
the bottom row of the left block
contains a 4, then there must be a 4 in
the top row of the right block
.
Wherever the two 4s are, we know that
the top and bottom rows of the center block
cannot contain a 4. So we can remove 4 as a possible value for those cells.
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Last Updated: 2/20/2019 1:59:00 PM CST