dailysudoku.com

[Johan]

After using X-wing on 7, I think i found an XY-chain length 8.
Starting with [4] in R7C7(1) = [9] in R7C4(2) = [1] in R7C1(3) = [7] in R1C1(4) = [1] in R1C7(5) = [6] in R3C7(6) = [7] in R3C9(7) = [2] in R6C9(8, chain end).
This means I think that 2 can only exist in R7C7 or in R6C9, which eliminates the 2's in R6C7,R4C7 and R9C9, because both cells [R7C7,R6C9] can see the other 2's in R6C7,R4C7, and R9C9. Therefore R9C9 is left with a single 6.
Can anyone confirm this please, because i'm not certain of the chain end.
The chain can also ends in R9C9.
Length 8 [24] [49] [91] [17] [71] [16] [67] [72]
Length 9 [24] [49] [91] [17] [71] [16] [67] [72] [26]

[Asellus]

Johan,

Your length 8 chain is correct and solves the puzzle completely.

The length 9 chain is of no use that I can see.

On the other thread for this puzzle, there is length 6 XY chain that eliminates <1> in R1C1 and also solves the puzzle, as an alternative to your chain. Quite a day for XY chains, it seems.