update example solution

exercises/practice/allergies/.meta/src/example.clj

@@ -3,22 +3,13 @@
 (def ^:private allergens
   [:eggs :peanuts :shellfish :strawberries :tomatoes :chocolate :pollen :cats])
 
-(defn- flagged?
-  [flags index]
-  (-> (bit-shift-right flags index)
-      (bit-and 1)
-      (pos?)))
-
-(defn allergies
-  "Given an 8-bit bitmap of flags, return the list of matching allergens."
-  [flags]
-  (keep-indexed (fn [index allergen]
-                  (when (flagged? flags index)
-                    allergen))
-                allergens))
+(def ^:private allergen->power
+  (zipmap allergens (range (count allergens))))
 
 (defn allergic-to?
-  "Given an 8-bit bitmap of flags and an allergen, return a boolean
-  indicating whether or not the patient is allergic to the given allergen."
-  [flags allergen]
-  (some #{allergen} (allergies flags)))
+  [score allergen]
+  (bit-test score (allergen->power allergen)))
+
+(defn allergies
+  [score]
+  (keep-indexed #(if (bit-test score %1) %2) allergens))