Ch133 (Clojure): Task 2

2 files changed, 43 insertions, 4 deletions

diff --git a/challenge-133/tyler-wardhaugh/clojure/src/tw/weekly/c133/t2.clj b/challenge-133/tyler-wardhaugh/clojure/src/tw/weekly/c133/t2.clj
index ad200456c8..ed11beff5a 100644
--- a/challenge-133/tyler-wardhaugh/clojure/src/tw/weekly/c133/t2.clj
+++ b/challenge-133/tyler-wardhaugh/clojure/src/tw/weekly/c133/t2.clj
@@ -1,15 +1,39 @@
-(ns tw.weekly.c132.t2
-  (:require [clojure.edn :as edn]
-            [clojure.pprint :refer [cl-format]]))
+(ns tw.weekly.c133.t2
+  (:require [clojure.edn :as edn]))
 
 ;;;
 ; Task description for TASK #2, Smith Numbers
 ;;;
 (def DEFAULT-INPUT [10])
 
+; based on source: https://rosettacode.org/wiki/Prime_decomposition#Clojure
+(defn prime-factors
+  "Return a list of factors of n."
+  ([n]
+   (prime-factors n 2 (list)))
+  ([n k acc]
+   (cond
+     (= 1 n) acc
+     (zero? (rem n k)) (recur (quot n k) k (cons k acc))
+     :else (recur n (inc k) acc))))
+
+(defn sum-digits
+  "Sum the individual digits of n."
+  [n]
+  (transduce (map #(Character/getNumericValue %)) + (str n)))
+
+(defn smith?
+  "Returns true if n is a Smith Number."
+  [n]
+  (let [pfs (prime-factors n)]
+    (and (< 1 (count pfs))
+         (= (sum-digits n) (transduce (map sum-digits) + pfs)))))
+
+(def smiths (->> (iterate inc 1) (filter smith?)))
+
 (defn -main
   "Run Task 2 with a given input N, defaulting to the first
   example from the task description."
   [& args]
   (let [[N] (or (some->> args (map edn/read-string)) DEFAULT-INPUT)]
-    ))
+    (run! println (take N smiths))))
diff --git a/challenge-133/tyler-wardhaugh/clojure/test/tw/weekly/c133/t2_test.clj b/challenge-133/tyler-wardhaugh/clojure/test/tw/weekly/c133/t2_test.clj
new file mode 100644
index 0000000000..424873cbea
--- /dev/null
+++ b/challenge-133/tyler-wardhaugh/clojure/test/tw/weekly/c133/t2_test.clj
@@ -0,0 +1,15 @@
+(ns tw.weekly.c133.t2-test
+  (:require [clojure.test :refer [deftest is testing]]
+            [tw.weekly.c133.t2 :refer [smiths]]))
+
+; source: https://oeis.org/A006753/list
+(def oeis-smith-numbers
+  [4,22,27,58,85,94,121,166,202,265,274,319,346,355,
+   378,382,391,438,454,483,517,526,535,562,576,588,
+   627,634,636,645,648,654,663,666,690,706,728,729,
+   762,778,825,852,861,895,913,915,922,958,985,1086,
+   1111,1165,1219])
+
+(deftest first-10
+  (testing "Verify the first 10 Smith Numbers"
+    (is (= (take 10 oeis-smith-numbers) (take 10 smiths)))))