True! Apart from an easy start it does resist for a long time. The Assassins continue to get harder each time.Ruud wrote:This is a strange killer. It keeps resisting almost till the very end.
Here is my walkthrough. Any comments or suggested improvements to the solving method are welcome. As with all my walkthroughs, this is essentially in the order that I solved the puzzle.
Step 1
30(4) cage in N568 = {6789}, 45 rule on N9 2 outies = 17 -> R89C6 = [89], R89C7 = [15], R67C6 = {67}, R6C57 = {89}, 45 rule on N3 1 outie = 1 -> R2C6 = 1, R5C12 = {89}, R89C1 = {69/78}, killer pair {89} in R589C1 so no 8 or 9 in rest of C1
Step 2
45 rule on C89 2 outies = 12 -> R17C7 = {39/48}, killer pair {89} in R167C7 -> no 8 or 9 in rest of C7, R23C7 = {37/46}, killer pair {34} in R1237C7 -> no 3 or 4 in rest of C7, R45C7 = {267} with 2 in N6 locked in C7
Step 3
45 rule on R89 innie/outie -> R7C3 = R8C9, 18(5) cage in N56 must contain {12} with the 1 in C45, R1345C6 = {2345} so R34C6 is 9 max -> R4C7 = {67}, R5C7 = 2 (hidden single in C7) -> no other 2 in 18(5) cage in N56, R34C6 = {3/4 5}, R5C6 = {34}, R1C6 = 2, R6C4 = 2 (hidden single in N5), 2 in N8 locked in R89C5 -> 9(3) cage in N8 = {126/234}, 18(5) cage in N56 cannot contain 9 and this is blocked from R5 -> R6C57 = [98] (hidden single 9 in N5), 8 in N5 locked in R4C45 so 18(5) cage in N56 must contain {12348}, R5C4 = {67}, R4C6 = 5, R17C7 = {39}, R23C7 = {46}, R4C7 = 7, R35C6 = [34], R45C9 = {36/45}, 19(4) cage in N6 contains 1 and 9 -> R4C8 = 9
Step 4
R7C45 = {47/56}, killer pair {67} in R7C456 -> no 6 or 7 in rest of R7 or N8 -> 9(3) cage in N8 = {234} with the 2 in C5, R9C4 = 1 (hidden single in N8), R7C45 = {56}, R67C6 = [67], R5C4 = 7, 24(4) cage in N9 = {3489} because the other candidate groups {2679} and {3678} contain both 6 and 7 which are blocked from R7C89, 15(3) cage in N9 = {267}
Step 5
45 rule on R6789 4 outies = 27, already have R4C8 = 9 and R5C4 = 7, 2 remaining outies = 11 -> R5C38 = {56} (7, 8 and 9 already blocked in R5) -> R5C5 = 1 (hidden single in R5) -> R45C9 = [63] (hidden single 3 in R5) -> R5C38 = [65], R6C3 = 3, R6C89 = {14}, R6C12 = {57}, R7C12 = {12}, 45 rule on R89 1 innie/1 outie R7C3 = R8C9 = {49}, R89C2 = {37/46}, R8C3 = 5 (hidden single in N7), R79C3 = [48], R8C9 = 4, R9C5 = 4, R8C45 = [32], R4C45 = [83], R89C2 = [73], R89C1 = [96], R5C12 = [89], R6C12 = [75], R8C8 = 6, R6C89 = [41]
Step 6
R4C123 = {124}, 45 rule on N1 outies – innies = 6 -> R3C3 = 1, R1C8 = 1 (hidden single in N3), R4C3 = 2, R12C3 = {79}, R1C12 = {36/45}, 8 in N1 locked in R23C2 -> 17(4) cage in N14 must contain {1268} -> R4C12 = 1, R23C2 = {68}, R4C1 = 4, R1C12 = [54], R23C1 = [32]
Step 7
9 in N2 cannot be in 20(4) cage (all possible candidates for the remaining 2 cells are blocked) -> R3C4 = 9, R23C5 = {57}, R1C5 = 8, R12C4 = [64], R23C7 = [64] , R23C2 = [86], R7C45 = [56]
Step 8
8 in N3 must be in R3C89 -> 17(3) cage = {278} -> R2C8 = 2, R3C89 = {78} and carry on, the rest is filling in the remaining candidates and simple elimination
Thanks to sudokuEd for some useful suggestions off-forum. They have helped to make this more logical and readable.
I don't think I've ever seen so many Killer Pairs in a puzzle. Ruud, was that your intention when you composed this Assassin?
Andrew