Chouser · January 29, 2019 22:46 · Jan 29, 2019
diff --git a/0031b.clj b/0031b.clj
@@ -0,0 +1,24 @@
+; In England the currency is made up of pound, £, and pence, p, and
+; there are eight coins in general circulation:
+;
+;    1p, 2p, 5p, 10p, 20p, 50p, £1 (100p) and £2 (200p).
+;
+; It is possible to make £2 in the following way:
+;
+;    1×£1 + 1×50p + 2×20p + 1×5p + 1×2p + 3×1p
+;
+; How many different ways can £2 be made using any number of coins?
+
+; 0031b.clj, but cleaned up for "modern" clojure and idioms
+
+(defn countpence
+  ([] (countpence 0 [200 100 50 20 10 5 2 1]))
+  ([sum opts]
+    (cond
+      (== sum 200) 1
+      (>  sum 200) 0
+      (not opts)   0
+      :else (+ (countpence sum (rest opts))
+               (countpence (+ sum (first opts)) opts)))))
+
+(prn (countpence))
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