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Swordfish

Expert

When a digit lines up in three parallel , and three opposite lines, we can safely remove candidates in the opposite lines.

How it works

7
2
6
3
1
5
8
9
1
8
9
1
5
8
9
6
8
5
4
7
3
8
2
4
8
7
3
7
1
4
5
6
8
9
1
2
4
6
8
9
1
5
6
8
9
2
5
1
4
6
8
9
4
6
7
8
9
6
8
9
1
4
6
8
9
5
1
3
6
8
9
1
4
9
6
8
3
6
8
7
6
8
2

Find the first Row

Digit 8 appears in two or three cells in this Row.

7
2
6
3
1
5
8
9
1
8
9
1
5
8
9
6
8
5
4
7
3
8
2
4
8
7
3
7
1
4
5
6
8
9
1
2
4
6
8
9
1
5
6
8
9
2
5
1
4
6
8
9
4
6
7
8
9
6
8
9
1
4
6
8
9
5
1
3
6
8
9
1
4
9
6
8
3
6
8
7
6
8
2

Find another matching Row

This Row also has 8 in two or three cells, and in the same Columns.

7
2
6
3
1
5
8
9
1
8
9
1
5
8
9
6
8
5
4
7
3
8
2
4
8
7
3
7
1
4
5
6
8
9
1
2
4
6
8
9
1
5
6
8
9
2
5
1
4
6
8
9
4
6
7
8
9
6
8
9
1
4
6
8
9
5
1
3
6
8
9
1
4
9
6
8
3
6
8
7
6
8
2

Find the third matching Row

This Row lines up too. All three Rows share exactly three Columns.

7
2
6
3
1
5
8
9
1
8
9
1
5
8
9
6
8
5
4
7
3
8
2
4
8
7
3
7
1
4
5
6
8
9
1
2
4
6
8
9
1
5
6
8
9
2
5
1
4
6
8
9
4
6
7
8
9
6
8
9
1
4
6
8
9
5
1
3
6
8
9
1
4
9
6
8
3
6
8
7
6
8
2

Only possible outcomes

We know 8 must land once in each Row.

7
2
6
3
1
5
8
9
1
8
9
1
5
8
9
6
8
5
4
7
3
8
2
4
8
7
3
7
1
4
5
6
8
9
1
2
4
6
8
9
1
5
6
8
9
2
5
1
4
6
8
9
4
6
7
8
9
6
8
9
1
4
6
8
9
5
1
3
6
8
9
1
4
9
6
8
3
6
8
7
6
8
2

Spot the relationship

No matter which order we place 8 in the Rows, each of the Columns will have one 8 too.

7
2
6
3
1
5
8
9
1
8
9
1
5
8
9
6
8
5
4
7
3
8
2
4
8
7
3
7
1
4
5
6
8
9
1
2
4
6
8
9
1
5
6
8
9
2
5
1
4
6
8
9
4
6
7
8
9
6
8
9
1
4
6
8
9
5
1
3
6
8
9
1
4
9
6
8
3
6
8
7
6
8
2

Eliminate other cells

We can safely remove other 8 from the Columns.

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