【今日湯底】

Take 2 strings s1 and s2 including only letters from a to z. Return a new sorted string, the longest possible, containing distinct letters - each taken only once - coming from s1 or s2.

Examples:
a = "xyaabbbccccdefww"
b = "xxxxyyyyabklmopq"
longest(a, b) -> "abcdefklmopqwxy"

a = "abcdefghijklmnopqrstuvwxyz"
longest(a, a) -> "abcdefghijklmnopqrstuvwxyz"

（必須通過以下測試）

(ns longest.core-test
  (:require [clojure.test :refer :all]
            [longest.core :refer :all]))
(require '[clojure.string :as str])

(defn test-assert [act exp]
  (is (= act exp)))

(deftest a-test1
  (testing "longest"
    (test-assert(longest "aretheyhere", "yestheyarehere"), "aehrsty")
    (test-assert(longest "loopingisfunbutdangerous", "lessdangerousthancoding"), "abcdefghilnoprstu")
    (test-assert(longest "inmanylanguages", "theresapairoffunctions"), "acefghilmnoprstuy")  
))

【我的答案】

(ns longest.core)
(require '[clojure.string :as str])

(defn longest [s1 s2]
  (str/join (sort (distinct (str/join s1 s2))))
  )

【其他人的答案】

(ns longest.core)

(defn longest [& ss]
  (->> ss (apply concat) (apply sorted-set) (apply str)))