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[ArkieTech]

Code: Select all

 *-----------*
 |7..|.4.|...|
 |.5.|..1|3..|
 |..6|2..|.7.|
 |---+---+---|
 |..7|...|.2.|
 |9..|...|..8|
 |.3.|...|5..|
 |---+---+---|
 |.6.|..3|1..|
 |..2|7..|.6.|
 |...|.5.|..4|
 *-----------*


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[ArkieTech]

Code: Select all

 *-----------------------------------------------------------------------------*
 | 7       2       1389    | 3589    4       589     | 6       1589    159     |
 | 48      5       489     | 6       7       1       | 3      d48-9    2       |
 | 1348    1489    6       | 2       389     589     |c489     7       159     |
 |-------------------------+-------------------------+-------------------------|
 | 6       148     7       | 134589  1389    4589    | 49      2       139     |
 | 9       14      5       | 134     6       2       | 7       134     8       |
 | 2       3       148     | 1489    189     7       | 5       149     6       |
 |-------------------------+-------------------------+-------------------------|
 | 458     6       489     | 489     2       3       | 1      a589     7       |
 | 35      1489    2       | 7       189     489     |b89      6       35      |
 | 138     7       1389    | 189     5       6       | 2      b389     4       |
 *-----------------------------------------------------------------------------*
L-wing
9r79c8=(9-8)r8c7,r9c8=(8-4)r3c7=4r2c8 => -9r2c8; lclste

[David P Bird]

The notation should be:
(9)r79c8 = (9-8)r8c7 = (8-4)r3c7 = (4)r2c8 => r2c8 <> 9

But at this point there is a (9)Swordfish:r279c348 which is simpler to find.
This then leads to an (8)Swordfish down the line and no multi-digit chains are needed at all.

[Marty R.]

I felt fortunate to be able to solve this with five moves (could have been fewer had I noticed the Swordfish earlier).

Multi-coloring (9), from a kite with transport
XY-Wing (89-4)
Swordfish (9)
Swordfish (8)
XY-Wing (18-9)