Add q74 and q75

src/ex/q074.clj

@@ -0,0 +1,17 @@
+;; https://4clojure.oxal.org/#/problem/074
+
+(ns ex.q074)
+
+(defn ans
+  "Problem 74, Filter Perfect Squares"
+  [s]
+  (letfn [(square? [x]
+            (cond
+              (< x 1) false
+              (let [y (int (Math/sqrt x))] (= (* y y) x)) true))]
+    (->> s
+         (re-seq #"\d+")
+         (map #(Integer/parseInt %))
+         (filter square?)
+         (interpose ",")
+         (apply str))))

src/ex/q075.clj

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+;; https://4clojure.oxal.org/#/problem/075
+
+(ns ex.q075)
+
+(defn ans
+  "Problem 75, Euler's Totient Function"
+  [x]
+  (letfn [(gcd [x y]
+            (loop [x x y y]
+              (if (= x y) x (recur (- (max x y) (min x y)) (min x y)))))
+          (coprime? [x y] (= 1 (gcd x y)))
+          (coprimes [y] (filter #(coprime? y %) (range 1 y)))]
+    (if (< x 2) 1 (count (coprimes x)))))

test/ex/q074_test.clj

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+;; https://4clojure.oxal.org/#/problem/074
+
+(ns ex.q074-test
+  (:require [clojure.test :as t]
+            [ex.q074 :as sut]))
+
+(t/deftest test-q74
+  (t/testing "Problem 74, Filter Perfect Squares"
+    (t/is (= "4,9" (sut/ans "4,5,6,7,8,9")))
+    (t/is (= "16,25,36" (sut/ans "15,16,25,36,37")))
+    (t/is (= "1,9,100" (sut/ans "1,2,5,6,9,11,20,30,100,101")))))

test/ex/q075_test.clj

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+;; https://4clojure.oxal.org/#/problem/075
+
+(ns ex.q075-test
+  (:require [clojure.test :as t]
+            [ex.q075 :as sut]))
+
+(t/deftest test-q75
+  (t/testing "Problem 75, Euler's Totient Function"
+    (t/is (= 1 (sut/ans 1)))
+    (t/is (= (count '(1 3 7 9)) 4 (sut/ans 10)))
+    (t/is (= 16 (sut/ans 40)))
+    (t/is (= 60 (sut/ans 99)))))