Add q84

src/ex/q084.clj

@@ -0,0 +1,20 @@
+;; https://4clojure.oxal.org/#/problem/084
+
+(ns ex.q084)
+
+(defn link? [a b] (= (second a) (first b)))
+(defn link [a b] [(first a) (second b)])
+(defn links
+  [coll]
+  (loop [start (first coll) tail (rest coll) conns (set coll)]
+    (if (nil? start)
+      conns
+      (recur (first tail) (rest tail) (into conns (map #(link start %) (filter #(link? start %) coll)))))))
+
+(defn ans
+  "Problem 84, Transitive Closure"
+  [coll]
+  (loop [accum coll conns nil]
+    (if (= accum conns)
+      conns
+      (recur (links accum) accum))))

test/ex/q084_test.clj

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+;; https://4clojure.oxal.org/#/problem/084
+
+(ns ex.q084-test
+  (:require [clojure.test :as t]
+            [ex.q084 :as sut]))
+
+(t/deftest test-q84
+  (t/testing "Problem 84, Transitive Closure"
+    (t/is (= #{[4 2] [8 4] [8 2] [9 3] [27 9] [27 3]}
+             (sut/ans #{[8 4] [9 3] [4 2] [27 9]})))
+    (t/is (= #{["cat" "man"] ["cat" "snake"] ["man" "snake"]
+               ["spider" "cat"] ["spider" "man"] ["spider" "snake"]}
+             (sut/ans #{["cat" "man"] ["man" "snake"] ["spider" "cat"]})))
+    (t/is (= #{["father" "son"] ["father" "grandson"]
+               ["uncle" "cousin"] ["son" "grandson"]}
+             (sut/ans #{["father" "son"] ["uncle" "cousin"] ["son" "grandson"]})))))