79
Techniques · Hard
Y-Wing
A pivot cell with two candidates, say A/B, sees two pincer cells: one holds A/C and the other B/C. If the pivot is A, the first pincer is C; if it is B, the second pincer is C. Either way one pincer is C, so C can be removed from any cell that sees both pincers.
How to spot it
Look at cells with exactly two notes. Find one that shares a unit with two other two-note cells, each sharing one digit with it and one common digit with each other. Remove that common digit where both pincers can see.
Example
1
4
8
59
579
2
3
6
3
25
79
69
1
2679
49
459
8
25
6
8
4
3
29
1
59
7
2569
25
1
3569
4
8
39
7
239
69
7
3
1
2
69
5
8
4
259
8
4
359
7
59
6
1
239
4
3
2
79
89
1
789
6
5
8
1
5
279
6
4
379
29
39
7
9
6
25
58
3
48
24
1
Pivot r3c6 (2/9) with pincers r3c1 (2/5) and r6c6 (5/9): one pincer must be 5, so 5 can be removed from cells that see both pincers (Y-Wing).
the pattern cells that lose a candidate (crossed out)