solver.clj

(ns doublets.solver
  (:require [clojure.java.io :as io]
            [clojure.edn :as edn]
            [clojure.set :as sets]))

(def words (-> "words.edn"
               (io/resource)
               (slurp)
               (read-string)))

(defn doublets [word1 word2]
  (letfn [(doublets-rec [from visited available to]
            (cond
              (= from to) visited
              (empty? available) []
              :else (let [neighbours (-> available
                                         (map (fn [x] [x (diff from x)]))
                                         (filter #(= (% 0) 1))
                                         (map #(% 1)))]
                      (apply concat
                             (map
                              #(doublets-rec % (conj visited %)
                                             (sets/difference available %) to)
                              neighbours)))))]
    (doublets-rec word1 [] (into #{} words) word2)))

(defn diff [w1 w2]
  "Positionally compares the given collections and returns the number of differing elements."
  (+ (Math/abs (- (count w1) (count w2)))
     (count (filter #(not (= (% 0) (% 1))) (map #(into [] %&) w1 w2)))))