2020 Advent of Code

2020-12-01.clj

(defn find-sum
  "O(n^2)"
  [sum nums]
  (set (for [x nums
             y nums
             :when (and (not= x y)
                        (= sum (+ x y)))]
         (* x y))))

(defn find-sum
  "O(4n^2)"
  [sum nums]
  (->> (for [x nums y nums]
         #{x y})
       (filter #(and (= (+ (first %) (second %)) sum)
                     (= 2 (count %))))
       (map #(* (first %) (second %)))
       (set)))