Find 2 cells which are NC.
Prelims
a) R1C45 = {18/27/36/45}, no 9
b) R1C67 = {39/48/57}, no 1,2,6
c) R1C89 = {15/24}
d) R3C34 = {39/48/57}, no 1,2,6
e) R45C3 = {39/48/57}, no 1,2,6
f) R56C7 = {39/48/57}, no 1,2,6
g) R7C67 = {19/28/37/46}, no 5
h) R9C12 = {49/58/67}, no 1,2,3
i) R9C34 = {18/27/36/45}, no 9
j) R9C56 = {17/26/35}, no 4,8,9
k) 20(3) cage at R1C1 = {389/479/569/578}, no 1,2
l) 11(3) cage at R1C3 = {128/137/146/236/245}, no 9
m) 10(3) cage at R2C1 = {127/136/145/235}, no 8,9
n) 10(3) cage at R7C2 = {127/136/145/235}, no 8,9
1a. 45 rule on N1 2 outies R23C4 = 8 = [17/35/53], R3C3 = {579}
1b. 45 rule on N12 2 innies R13C6 = 6 = {39/48} (cannot be {57} which clashes with R23C4), clean-up: no 5,7 in R1C7
1c. 45 rule on N9 2 outies R78C6 = 15 = {69/78}, R7C7 = {1234}
1d. Killer pair 8,9 in R13C6 and R78C6, locked for C6
1e. 45 rule on N89 2 innies R79C4 = 8 = {17/26/35}, no 4,8,9
1f. R9C4 = {123567} -> R9C3 = {234678}
1g. Killer triple 5,6,7 in R79C4, R78C6 and R9C56, locked for N8
1h. 4 in N8 only in 14(3) cage at R7C5 = {149/248}, no 3
1i. 45 rule on N4 3 innies R6C123 = 11 = {128/137/146/236/245}, no 9
1j. 45 rule on R1 3 innies R1C123 = 18 = {279/369/468/567} (cannot be {189/378} which clash with R1C67, cannot be {459} which clashes with R1C89), no 1
1k. 45 rule on R1 1 outies R2C2 = 1 innie R1C3 + 2, no 8 in R1C3, no 3 in R2C2
1l. 45 rule on R9 1 outie R8C8 = 1 innie R9C7 + 1, no 1 in R8C8, no 9 in R9C7
1m. R1C45 = {18/27/36} (cannot be {45} which clashes with R1C89), no 4,5
1n. 12(3) cage at R2C8 = {138/156/237/246} (cannot be {129/147/345} which clash with R1C89), no 9
1o. Killer pair 1,2 in R1C89 and 12(3) cage, locked for N3
1p. 45 rule on N6 3 innies R4C789 = 12 = {129/138/147/156/237/246} (cannot be {345} which clashes with R56C7)
1q. 45 rule on N9 3 innies R789C7 = 12 = {129/138/147/156/237/246} (cannot be {345} which clashes with R56C7)
1r. 45 rule on N6 1 outie R3C9 = 1 innie R4C7 + 6, R3C9 = {789}, R4C7 = {123}
1s. 45 rule on N4 1 outie R7C1 = 1 innie R6C3 + 4, R6C3 = {12345}, R7C1 = {56789}
1t. 45 rule on N1 3 innies R123C3 = 15 = {249/258/267/456} (cannot be {168/348} because R3C3 only contains 5,7,9, cannot be {159} = [519] because 11(3) cage at R1C3 cannot contain both of 1,5, cannot be {357} which clashes with 10(3) cage at R2C1), no 1,3, clean-up: no 5 in R2C2
1u. R3C3 = {579} -> no 5,7 in R12C3, clean-up: no 7,9 in R2C2
1v. 1 in C3 only in R678C3, locked for 27(6) cage at R6C3, clean-up: no 7 in R9C4, no 2 in R9C3
2a. R1C45 (step 1m) = {18/27/36}, R23C4 (step 1a) = [17]/{35} -> combined cage R1C45 + R23C4 = {18}{35}/{27}/{35}/{36}[17], 3 locked for N2, clean-up: no 9 in R13C6 (step 1b), no 3,9 in R1C7
2b. Naked pair {48} in R1C67, locked for R1, clean-up: no 1 in R1C45, no 2 in R1C89, no 6 in R2C2 (step 1k)
2c. Naked pair {48} in R13C6, locked for C6 and N2, clean-up: no 7 in R78C6 (step 1c), no 2,3 in R7C7
2d. Naked pair {15} in R1C89, locked for N3, 5 locked for R1
2e. Naked pair {69} in R78C6, locked for N8, 6 locked for C6, clean-up: no 2 in R79C4 (step 1e), no 2 in R9C56, no 3,7 in R9C4
2f. Naked quad 1,3,5,7 in R2379C4, locked for C4, clean-up: no 2,6 in R1C5
2g. Naked pair {26} in R1C34, 6 locked for R1
2h. 9 in R1 only in R1C12, locked for N1, clean-up: no 3 in R3C4, no 5 in R2C4 (step 1a)
2i. Naked pair {57} in R3C34, locked for R3, clean-up: no 1 in R4C7 (step 1r)
2j. 1 in C7 only in R789C7, locked for N9
2k. R789C7 (step 1q) = {129/138/147} (cannot be {156} = 1{56} because 17(3) cage at R8C6 cannot contain both of 5,6), no 5,6
2l. 6 in C7 only in R23C7, locked for N3 and 29(6) cage at R2C7
2m. 2 in N3 only in 12(3) cage at R2C8 = {237}, 3,7 locked for N3, 7 locked for R2
2n. 4 in N3 only in R123C7, locked for C7 -> R7C7 = 1, R7C6 = 9, R8C6 = 6, clean-up: no 8 in R56C7
2o. R8C6 = 6 -> R89C7 = 11 = {29/38}, no 7
2p. R56C7 = {57} (hidden pair in C7), locked for N6
2q. 1 in N1 only in 10(3) cage at R2C1 = {136/145}, no 2
2r. 5 of {145} must be in R2C1 -> no 4 in R2C1
2s. 2 in N1 only in R12C3, locked for C3
2t. 11(3) cage at R1C3 = {128/236}, no 4
2u. 9 in C4 only in R456C4, locked for N5
2v. 18(3) cage at R3C9 = {189/468} (cannot be {369} = 9{36} which clashes with R3C9 + R4C7 = [93], step 1r), no 2,3
2w. 18(3) cage = {189/468}, CPE no 8 in R56C9
2x. 1 in R9 only in R9C456, locked for N8
2y. 2 in R9 only in R9C789, locked for N9, clean-up: no 9 in R9C7
2z. R45C3 = {39/48} (cannot be {57} which clashes with R3C3), no 5,7
3a. 17(3) cage at R7C8 = {368/458/467} (cannot be {359} which clashes with R89C7), no 9
3b. 16(3) cage at R8C8 = {259/358/367/457} (cannot be {268/349} which clash with R89C7)
4. Consider placement for 2 in R3
R3C5 = 2 => R1C4 = 6, R1C5 = 3, R1C12 = {79} => R2C2 = 4 (cage total)
or R3C8 = 2, R2C89 = {37}, 3 locked for R2 => R2C4 = 1, R12C3 = 10 = [28] => R2C2 = 4
-> R2C2 = 4, R1C12 = 16 = {79}, 7 locked for R1 and N1, R1C5 = 3, R1C4 = 6, R1C3 = 2, R2C4 = 1, R2C3 = 8 (cage sum), R3C34 = [57], clean-up: no 4 in R45C3, no 9 in R9C1
4a. Naked pair {35} in R79C4, locked for N8
4b. Naked pair {17} in R9C56, 7 locked for R9, clean-up: no 6 in R9C12
4c. Naked pair {39} in R45C3, locked for C3 and N4
4d. 7 in C3 only in R78C3, locked for N7 and 27(6) cage at R6C3
4e. 2,3 in N7 only in 10(3) cage at R7C2 = {235}, 5 locked for N7, clean-up: no 8 in R9C12
4f. R9C12 = [49], R1C12 = [97], R9C3 = 6 -> R9C4 = 3, R7C4 = 5, R678C3 = [471], clean-up: no 8 in R8C7 (step 2o)
4g. R678C3 = [471], R7C4 = 5 -> R6C45 = 10 = {28}, locked for R6 and N5
4h. R7C1 = 8 -> R6C12 = 7 = {16}, locked for R6 and N4
4i. Naked pair {39} in R6C89, locked for N6, 3 locked for R6
4j. R4C7 = 2, R9C7 = 8, R8C7 = 3 (cage sum)
4k. Naked pair {46} in R7C89, 4 locked for R7 and N9, R8C9 = 7 (cage sum), R7C25 = [32], R6C45 = [28], R8C45 = [84], R23C5 = [59], R2C6 = 2, R2C89 = [73], R3C8 = 2, R2C1 = 6, R3C12 = [31], R6C12 = [16], R6C89 = [39], R9C89 = [52], R8C8 = 9, R1C89 = [15], R123C7 = [496], R13C6 = [84],
4l. 45 rule on N5 2 remaining innies R4C56 = 8 = {17}, locked for R4 and N5 -> R4C12 = [58], R5C12 = [72], R8C12 = [25], R56C6 = [35], R45C3 = [39], R45C4 = [94], R56C7 = [57], R5C5 = 6, R5C89 = [81], R3C9 = 8
5a. R6C8 = 3 -> no 4 in R7C8 (NC), R7C8 = 6 -> R4C89 = [46], R7C9 = 6
5b. A choice of R4C7 = 2 -> no 1 in R4C6 (NC), R5C5 = 6 -> no 7 in R4C5 (NC), R8C6 = 6 -> no 7 in R9C6 (NC) or R9C7 = 8 -> no 7 in R9C6 (NC)
-> R4C56 = [17], R9C56 = [71]