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janet/examples/3sum.janet
Calvin Rose 2d7df6b78e Many changes for adding dynamic (fiber-level) scope.
- Allow passing a table to fibers, which make fiber level scope easier.
- Add fiber/getenv, fiber/setenv, dyn, and setdyn
- Remove meta, *env*, and *doc-width*
- Some functions changed dignatures, and no longer take an env
2019-04-16 15:41:45 -04:00

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(defn sum3
"Solve the 3SUM problem in O(n^2) time."
[s]
(def tab @{})
(def solutions @{})
(def len (length s))
(for k 0 len
(put tab (s k) k))
(for i 0 len
(for j 0 len
(def k (get tab (- 0 (s i) (s j))))
(when (and k (not= k i) (not= k j) (not= i j))
(put solutions {i true j true k true} true))))
(map keys (keys solutions)))
(def arr @[2 4 1 3 8 7 -3 -1 12 -5 -8])
(printf "3sum of %P: " arr)
(printf "%P\n" (sum3 arr))