- Code: Select all
`6 . . . . 9 8 . .`

. 5 . . 3 . . . .

. . 2 5 . . . . 7

. . 7 . . . . . 9

. 1 . . . . . 2 .

4 . . . . . 3 . .

3 . . . . 8 6 . .

. . . . 4 . . 8 .

. . 9 7 . . . . 1

My solution :

(1) ... (denotes use of SSTS, here including elimination of 3e6 by colouring).

(2) ?7f6...(?3a3...??)-3a3...-8f5(MC), -8e5(MC),

(?3a2...(?8b4...??) -8b4, 8c5...(?8f9...??) -8f9, 5f9...??)

-3a2, 4a2...?? -7f6.

(3) ?7h7...(?3a2...??) -3a2, 4a2...?? -7h7...

(4) ?3a3... -2g4(MC)...(?9g4, -5e6(MC), -5e9(MC)...(?8f3...??) -8f3,

6f3...??) -9g4, 1g4...?? -3a3, 4a3...

(5) ?3a8...?? -3a8...

(6) ?1c1...?? -1c1, 9c1, -4d4(MC).

(7) ?2g2...(?5g3...??) -5g3, 1g3...?? -2g2, 4g2, -4e6(X-Wing), -5k6(colours), -8e5(XY-Wing 568e1f39)...-6ce6(colours)...End.

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Comments: No trial steps rejected. I resorted to sub-sub-nets as this was the quickest and easiest way to go.

The use of these sub-sub-nets underlies the difficulty of this puzzle, which I found about equal to that of Fluid Drive #1.