Knuth Anagrams

anagrams.clj

(defn get-anagram-map
  "map of words keyed by letter-sorted 'words' (which all anagrams share)"
  [dict]
  (reduce (fn [acc w]
            (let [sw (apply str (sort w))]            
              (if-let [d (get acc sw)]
                (assoc acc sw (conj d w))
                (assoc acc sw (list w))))) {} dict))

(defn knuth-anagrams
  "what words in a dictionary are anagrams?"
  [dict]
  (->> (get-anagram-map dict)
       (filter #(> (count (second %)) 1))
       (map second)))

(knuth-anagrams ["lander", "earth", "antsier", "heart", "asterin", "randel"])

(defn all-anagrams
  "quickly find all anagrams given a dictionary and a word"
  [dict word]
  (let [am (get-anagram-map dict)        
        sw (apply str (sort word))]
    (get am sw)))

(all-anagrams ["lander", "earth", "antsier", "heart", "asterin", "randel"]
              "earth")