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Techniques · Expert
Swordfish
The X-Wing with three lines. A digit has two or three places in each of three rows, and all those places fall within the same three columns. The digit takes one cell in each of those columns from these rows, so it can be removed from the rest of the three columns. It also works with columns and rows swapped.
How to spot it
Pick a digit and list the rows where it has two or three places. Three rows that between them use only three columns make a Swordfish.
Example
3
7
24
89
6
48
5
1
6
4
8
13
13
5
9
2
7
29
1
5
24
7
89
48
3
6
4
6
2
38
5
7
1
9
38
38
5
9
6
4
1
37
78
2
38
7
1
389
2
389
5
6
4
5
2
34
189
13689
389
367
478
89
7
8
6
5
39
4
2
1
39
1
9
34
7
368
2
36
48
5
In rows 2, 4 and 8, 3 can only go in columns 4, 5 and 9, so 3 can be removed from the rest of columns 4, 5 and 9 (Swordfish).
the pattern cells that lose a candidate (crossed out)