Puzzles/LCM
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Find an interesting use of *./ on a list of integers with length greater than 2.
Solution:
The LCM of the cycle lengths of a permutation p is period of p , the size of the subgroup generated by p . For example:
] p=: ?.~ 23 4 22 16 15 18 14 7 8 0 21 3 13 20 9 11 19 6 17 2 5 1 10 12 C. p ┌──┬─────────────────┬──────────────────────────┬──────────┐ │17│18 2 16 6 7 8 0 4│21 10 3 15 19 5 14 11 13 9│22 12 20 1│ └──┴─────────────────┴──────────────────────────┴──────────┘ #&> C. p 1 8 10 4 *./ #&> C. p 40 # ~. {/\ (100,#p)$p 40 p&{^:40 i.#p 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Contributed by Roger Hui.