Prelims
a) R1C78 = {17/26/35}, no 4,8,9
b) R4C23 = {29/38/47/56}, no 1
c) R4C78 = {16/25/34}, no 7,8,9
d) R67C2 = {16/25/34}, no 7,8,9
e) R67C8 = {49/58/67}, no 1,2,3
f) R89C4 = {17/26/35}, no 4,8,9
g) R89C5 = {69/78}
h) R89C6 = {49/58/67}, no 1,2,3
i) R9C23 = {19/28/37/46}, no 5
j) R9C78 = {18/27/36/45}, no 9
k) 8(3) cage at R7C9 = {125/134}
l) 13(4) cage at R1C1 = {1237/1246/1345}, no 8,9
m) 13(4) cage at R3C5 = {1237/1246/1345}, no 8,9
n) 28(4) cage at R4C6 = {4789/5689}, no 1,2,3
Steps resulting from Prelims
1a. 8(3) cage at R7C9 = {125/134}, 1 locked for C9 and N9, clean-up: no 8 in R9C78
1b. R9C78 = {27/36} (cannot be {45} which clashes with 8(3) cage), no 4,5 in R9C78
1c. Killer pair 2,3 in 8(3) cage and R9C78, locked for N9
1d. R9C23 = {19/28/46} (cannot be {37} which clashes with R9C78), no 3,7 in R9C23
1e. R89C6 = {49/58} (cannot be {67} which clashes with R89C5), no 6,7 in R89C6
1f. Killer pair 8,9 in R89C5 and R89C6, locked for N8
1g. 13(4) cage at R1C1 = {1237/1246/1345}, 1 locked for N1
1h. 13(4) cage at R3C5 = {1237/1246/1345}, 1 locked for C5
1i. 28(4) cage at R4C6 = {4789/5689}, CPE no 8,9 in R5C4
2. Variable hidden killer pair 8,9 in 22(4) cage at R7C6 and R7C8 for N9, R7C8 cannot contain more than one of 8,9 -> 22(4) cage must contain at least one of 8,9) = {1489/…/3568} (cannot be {4567} which doesn’t contain 8 or 9)
2a. 1,2,3 only in R7C6 -> R7C6 = {123}
3. 45 rule on C1 2 innies R12C1 = 8 = {17/26/35}, no 4
3a. 45 rule on C1 2 outies R1C23 = 5 = {14/23}
3b. R1C23 + R1C78 = 13 = {1237/1246/1345}, 1 locked for R1, clean-up: no 7 in R2C1
4. 45 rule on N1 2 innies R3C13 = 17 = {89}, locked for R3 and N1
5. 45 rule on N3 2 innies R3C79 = 6 = [15/24/42]
6. 45 rule on C9 2 innies R12C9 = 15 = {69/78}
6a. 45 rule on C9 3 outies R2C78 + R3C8 = 16 = {169/178/349/358} (cannot be {268/367} which clash with R12C9, cannot be {259/457} which clash with R3C79), no 2
7. 45 rule on N2 2 outies R3C37 = 1 innie R3C5 + 3
7a. Min R3C37 = 9 -> min R3C5 = 6
7b. Max R3C37 = 10 -> R3C37 = [81/82/91], no 4 in R3C7, clean-up: no 2 in R3C9 (step 5)
[With hindsight I could have reduced R3C9 to {45} more directly using 45 rule on R123 3 innies R3C159 but I didn’t spot that 45 until later.]
7c. Killer pair 6,7 in R3C5 and R89C5, locked for C5
7d. Killer pair 4,5 in R3C9 and 8(3) cage at R7C9, locked for C9
8. R3C5 = {67} -> 13(4) cage at R3C5 = {1237/1246} (cannot be {1345} which doesn’t contain 6 or 7), no 5, 1,2 locked for C5 and N5
9. Hidden killer pair 2,3 in R456C9 and 8(3) cage at R7C9 for C9, 8(3) cage contains one of 2,3 -> R456C9 must contain one of 2,3
9a. Hidden killer triple 1,2,3 in R4C78, R456C9 and R6C7 for N6, R4C78 contains one of 1,2,3, R456C9 contains one of 2,3 -> R6C7 = {123}
10. 45 rule on N8 3 innies R7C456 = 9 = {135/234} (cannot be {126} because R7C5 only contains 3,4,5), no 6,7, 3 locked for R7 and N8, clean-up: no 4 in R6C2, no 5 in R89C4
10a. 45 rule on N7 1 outie R7C4 = 1 innie R7C2 + 1, no 5,6 in R7C2, no 1,4 in R7C4, clean-up: no 1,2 in R6C2
10b. R7C456 = {135/234}
10c. 2 of {234} must be in R7C4 (R7C456 cannot be [342] which clashes with R7C24 = [23], IOD blocker), no 2 in R7C6
10d. 2 in N8 only in R789C4, locked for C4
11. Naked quint {12345} in R7C24569, locked for R7, clean-up: no 8,9 in R6C8
12. 45 rule on N9 1 innie R7C8 = 1 outie R7C6 + 6, R7C6 = {13} -> R7C8 = {79}, R6C8 = {46}
12a. 5 in N6 only in R45C78, CPE no 5 in R4C6
13. Hidden killer pair 8,9 in R12C9 and R456C9 for C9, R12C9 contains one of 8,9 -> R456C9 must contain one of 8,9
13a. Hidden killer pair 8,9 in R456C9 and R5C78 for N6, R456C9 contains one of 8,9 -> R5C78 must contain one of 8,9
13b. Hidden killer pair 8,9 in R45C6 and R5C78 for 28(4) cage at R4C6, R5C78 contains one of 8,9 -> R45C6 must contain one of 8,9
13c. Killer pair 8,9 in R45C6 and R89C6, locked for C6
[Just spotted that I hadn’t looked deeply enough in step 3.]
14. R1C23 + R1C78 (step 3b) = {1237/1246/1345} = {1237}, locked for R1 or R1C23 = {14}, locked for N1 -> R12C1 (step 3) = {26/35} (cannot be [71], killer locking-out cages)
14a. 1 in N1 only in R1C23 (step 3a) = {14}, locked for R1 and N1, clean-up: no 7 in R1C78
14b. Killer pair 2,5 in R1C78 and R3C79, locked for N3
15. 14(3) cage at R7C1 = {149/158/167/347} (cannot be {239/257/356} which clash with R12C1, cannot be {248} which clashes with R7C2 + R9C23, killer ALS block), no 2
15a. 8,9 of {149/158} must be in R7C1 -> no 8,9 in R89C1
15b. 14(3) cage = {149/158/167}, 1 locked for N7 or 14(3) cage = {347} => killer pair 1,2 in R7C2 + R9C23, locked for N7 -> 1 in 14(3) cage + R7C2 + R9C23, locked for N7
16. 8 in N9 only in 22(4) cage at R7C6
16a. 22(4) cage = {1489/3478/3568} (cannot be {1678} which clashes with R9C78)
16b. Consider combinations for R7C456 (step 10) = {135/234}
16c. R7C456 = {135} = {35}1 => 22(4) cage = {1489}
or R7C456 = {234} = [243] => 2 in N7 only in R9C23 => R9C78 = {36}, locked for N9 => 22(4) cage = {3478}
-> 22(4) cage = {1489/3478}, no 5,6, 4 locked for R8 and N9, clean-up: no 9 in R9C6
16d. 6 in N9 only in R9C78 = {36}, locked for R9 and N9, clean-up: no 4 in R9C23, no 2 in R8C4, no 9 in R8C5
[Cracked. The rest is straightforward.]
17. Naked triple {125} in 8(3) cage at R7C9, locked for C9 -> R3C9 = 4, R3C7 = 2 (step 5), clean-up: no 6 in R1C78, no 5 in R4C8
17a. 3 in C9 only in R456C9, locked for N5 -> R6C7 = 1, R4C8 = 2 (hidden single in N6), R4C7 = 5, R1C78 = [35], R9C78 = [63], clean-up: no 3,5 in R2C1, no 6,9 in R4C23
18. 45 rule on R123 2 remaining innies R3C15 = 16 -> R3C1 = 9, R3C5 = 7, R3C3 = 8, clean-up: no 3 in R4C2, no 8 in R89C5, no 2 in R9C2
18a. R89C5 = [69], R1C5 = 8, clean-up: no 7 in R2C9 (step 6), no 1 in R9C23, no 4 in R9C6
18b. R9C23 = [82], R89C6 = [85], R9C9 = 1, R9C4 = 7, R8C4 = 1, R7C456 = [243], R7C2 = 1, R6C2 = 6, R6C8 = 4, R7C8 = 9, R7C7 = 8 (hidden single in N9), R8C78 = [47]
19. Naked pair {26} in R12C1, locked for C1 and N1 -> R7C1 = 7, R9C1 = 4, R8C1 = 3 (cage sum)
19a. R1C23 = [41], R4C2 = 7, RR4C3 = 4
19b. Naked pair {35} in R23C2, locked for C2 and N1 -> R2C3 = 7
19c. Naked pair {26} in R1C16, locked for R1 -> R1C4 = 9, R1C9 = 7, R2C9 = 8 (step 6)
20. R5C78 = [78] (hidden pair in N6) = 15 -> R45C6 = 13 = [94]
21. R2C5 = 5 (hidden single in C5), R23C4 = [43] (hidden pair in N2), R3C6 = 6 (cage sum)
22. R6C67 + R7C5 = [714] = 12 -> R6C34 = 11 = [38]
and the rest is naked singles.