Add q82.. difficult, some external resources used

src/ex/q082.clj

@@ -0,0 +1,23 @@
+;; https://4clojure.oxal.org/#/problem/082
+
+(ns ex.q082)
+
+(defn ans
+  "Problem 82, Word Chains"
+  [words]
+  (letfn [(tail [w] (->> w rest (apply str)))
+          (lev
+            [a b]
+            (cond
+              (= 0 (count b)) (count a)
+              (= 0 (count a)) (count b)
+              (= (first a) (first b)) (lev (tail a) (tail b))
+              :else (+ 1 (min (lev (tail a) b) (lev a (tail b)) (lev (tail a) (tail b))))))
+          (link? [a b] (<= (lev a b) 1))
+          (chain
+            [[word :as curr-chain] remaining]
+            (if (empty? remaining)
+              [curr-chain]
+              (apply concat (keep #(when (or (nil? word) (link? word %))
+                                     (chain (cons % curr-chain) (disj remaining %))) remaining))))]
+    (boolean (some #(= % words) (map set (chain () words))))))

test/ex/q082_test.clj

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+;; https://4clojure.oxal.org/#/problem/082
+
+(ns ex.q082-test
+  (:require [clojure.test :as t]
+            [ex.q082 :as sut]))
+
+(t/deftest test-q82
+  (t/testing "Problem 82, Word Chains"
+    (t/is (= true (sut/ans #{"hat" "coat" "dog" "cat" "oat" "cot" "hot" "hog"})))
+    (t/is (= false (sut/ans #{"cot" "hot" "bat" "fat"})))
+    (t/is (= false (sut/ans #{"to" "top" "stop" "tops" "toss"})))
+    (t/is (= true (sut/ans #{"spout" "do" "pot" "pout" "spot" "dot"})))
+    (t/is (= true (sut/ans #{"share" "hares" "shares" "hare" "are"})))
+    (t/is (= false (sut/ans #{"share" "hares" "hare" "are"})))))