Secret santa

secret-santa.clj

(ns secret-santa.core
  (require [clojure.set :refer [difference]]))

;; note: only works if each person is in a single constraint

(def people #{:carole :ben :andrew :hillary :tom :dick :harry :barry})

(def constraints '([:carole :ben] [:andrew :hillary]))

(defn split
  [people]
  (let [constrained (flatten constraints)
        list        (apply conj constrained (difference people (set constrained)))
        split-list  (apply interleave (split-at (/ (count list) 2) list))]
    (apply conj
           [[(last split-list) (first split-list)]]
           (for [[a b] (partition 2 1 split-list)]
             [a b]))))

(split people)