xmas gift swap

map_names.clj

(require '[clojure.string :as str])
(require '[clojure.set :as set])
(require '[clojure.pprint :as pp])

(defn map-names [names]
  (first
   (reduce
    (fn [mem n1]
      (let [avail (set/difference names (get mem 1))
            sel (->> avail shuffle (some #(when (not= n1 %1) %1)))]
        (-> mem
            (assoc-in [0 n1] sel)
            (update-in [1] conj sel))))
    [{} #{}] names)))

(pp/pprint (map-names #{"barney" "fred" "wilma" "betty" "pebbles" "dino" "bamm bamm" "baby puss" "hoppy"}))