amalloy-4clojure-solution101.clj

;; amalloy's solution to Levenshtein Distance
;; https://4clojure.com/problem/101

(letfn [(iters [n f start]
          (take n (map second
                       (iterate f start))))]
 (fn [s t]
   (let [m (inc (count s)), n (inc (count t))
         first-row (vec (range m))
         matrix (iters n (fn [[j row]]
                           [(inc j)
                            (vec (iters m (fn [[i col]]
                                            [(inc i)
                                             (if (= (nth s i)
                                                    (nth t j))
                                               (get row i)
                                               (inc (min (get row i)
                                                         (get row (inc i))
                                                         col)))])
                                        [0 (inc j)]))])
                       [0 first-row])]
     (last (last matrix)))))