Decabit Software
Swordfish

This technique is similar to the X-Wing technique, except it looks at three rows and columns. If three rows have a candidate in up to three cells that lie on the same three columns, then the candidate can be eliminated from all other cells in the those columns.

Consider the partial Sudoku below with the candidate 4 in the following cells.

4
4
4
4
4
4
4
4

In rows 2, 4, and 7, the candidate 4 exists up to three times in each row and lies in exactly three columns. This arrangement of cells must contain a 4 in each column of the Swordfish. So, we can eliminate the candidate 4 from all other cells in columns 1, 3, and 6.

Note: You can swap columns and rows when performing this technique.
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Last Updated: 10/23/2017 6:36:11 PM CST