Add q39

src/ex/q039.clj

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+;; https://4clojure.oxal.org/#/problem/039
+
+(ns ex.q039)
+
+(defn ans
+  "Problem 39, Interleave Two Seqs. restriction: interleave"
+  [coll1 coll2]
+  (let [c1 (seq coll1) c2 (seq coll2)]
+    (if (and c1 c2)
+      (cons (first c1) (cons (first c2) (ans (rest c1) (rest c2))))
+      [])))

test/ex/q039_test.clj

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+;; https://4clojure.oxal.org/#/problem/039
+
+(ns ex.q039-test
+  (:require [clojure.test :as t]
+            [ex.q039 :as sut]))
+
+(t/deftest test-q39
+  (t/testing "Problem 39, Interleave Two Seqs"
+    (t/is (= '(1 :a 2 :b 3 :c) (sut/ans [1 2 3] [:a :b :c])))
+    (t/is (= '(1 3 2 4) (sut/ans [1 2] [3 4 5 6])))
+    (t/is (= [1 5] (sut/ans [1 2 3 4] [5])))
+    (t/is (= [30 25 20 15] (sut/ans [30 20] [25 15])))))