(solve the-challange the-words)

Midje test

(ns challange.test.core
  (:use [challange.core] :reload)
  (:use [midje.sweet]))

(fact 
 (solve "AA" ["A"]) => ""
 (solve "ABA" ["A" "B"]) => "" 
 (solve "AB" ["A" "X"]) => "B")

(fact
 (solve the-challange the-words) => "CITERUSLOVESTALENT")

Solve the challange

(ns challange.core
  (:require [clojure.set :as set]))

(def the-challange "VOCDIITEIOCRUDOIANTOCSLOIOCVESTAIOCVOLIOCENTSU")

(def the-words (map str '(TDD, DDD, DI, DO, OO, UI, ANT, CV, IOC, LOC, SU, VO)))

(defn reduce-by [^String s words]
  "For each word, tries to remove it from the first string.
   Returns the candidates that turned out shorter"
  (let [len (.length s)
        candidates (map #(reduce str (.split s %)) words)]
    (filter (fn [^String c] (< (.length c) len)) candidates)))

(def m-reduce-by (memoize reduce-by))

(declare m-reduce-replace)

(defn reduce-replace [challange words]
  (let [replacements (m-reduce-by challange words)]
    (conj (set/union (set replacements)
                     (apply set/union (map #(m-reduce-replace % words) replacements)))
          challange)))

(def m-reduce-replace (memoize reduce-replace))

(defn solve [challange words]
  (let [comp (fn [& params] (apply < (map count params)))]
    (first (sort comp (reduce-replace challange words)))))