4clojure solution to problem 82

82.clj

(defn chk-ins [w1 w2]
  (when (< (count w1) (count w2))
    (some #(= w1 %)
          (for [i (range (count w2))]
            (str (subs w2 0 i) (subs w2 (inc i))))
    )
  ))

(defn chk-subs [w1 w2]
  (when (= (count w1) (count w2))
    (some #(= (first %) (second %))
          (for [i (range (count w1))]
        [(str (subs w1 0 i) (subs w1 (inc i)))
         (str (subs w2 0 i) (subs w2 (inc i)))]
        ))
    ))

(defn chk-del [w1 w2]
  (when (> (count w1) (count w2))
    (chk-ins w2 w1)))


(defn permutations [s]
  (lazy-seq
    (if (seq (rest s))
      (apply concat (for [x s]
                      (map #(cons x %) (permutations (remove #{x} s)))))
      [s])))

(defn is-connected [w1 w2]
  (or (chk-ins w1 w2)
      (chk-del w1 w2)
      (chk-subs w1 w2)))

(defn word-chain [s]
  (true? (some #(every? (fn[pair] (is-connected (first pair) (second pair))) %)
        (map #(partition 2 1 %) (permutations s)))))