Add q21

src/ex/q021.clj

@@ -0,0 +1,13 @@
+;; https://4clojure.oxal.org/#/problem/021
+
+(ns ex.q021)
+
+(defn ans
+  "Problem 21, Nth Element. restriction: nth"
+  [coll index]
+  (.get coll index))
+
+(defn ans2
+  "another take, using `drop`"
+  [coll index]
+  (->> coll (drop index) first))

test/ex/q021_test.clj

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+;; https://4clojure.oxal.org/#/problem/021
+
+(ns ex.q021-test
+  (:require [clojure.test :as t]
+            [ex.q021 :as sut]))
+
+(t/deftest test-q21-a
+  (t/testing "Problem 21, Nth Element"
+    (t/is (= 6 (sut/ans '(4 5 6 7) 2)))
+    (t/is (= :a (sut/ans [:a :b :c] 0)))
+    (t/is (= 2 (sut/ans [1 2 3 4] 1)))
+    (t/is (= [5 6] (sut/ans '([1 2] [3 4] [5 6]) 2)))))
+
+(t/deftest test-q21-b
+  (t/testing "Problem 21, Nth Element"
+    (t/is (= 6 (sut/ans2 '(4 5 6 7) 2)))
+    (t/is (= :a (sut/ans2 [:a :b :c] 0)))
+    (t/is (= 2 (sut/ans2 [1 2 3 4] 1)))
+    (t/is (= [5 6] (sut/ans2 '([1 2] [3 4] [5 6]) 2)))))