Decabit Software
X-Wing

If two rows have a candidate in exactly two cells that lie on the same two columns, then the candidate can be eliminated from all other cells in the those columns.

Consider the Sudoku below.

1
1
1
1
1
2 3
1
1
1
1
1
1
1
1
1
1
8 9
1
1

In rows 2 and 8, the candidate 1 exists twice in each row and lies in exactly 2 columns. The candidate 1 must exist in either the top-left and bottom-right cells or the top-right and bottom-left cells. In either case, we can eliminate the candidate 1 from all other cells in columns 2 and 6.

Note: You can swap columns and rows when performing this technique.
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Last Updated: 8/5/2017 12:27:29 PM CST