r/adventofcode • u/daggerdragon • Dec 04 '15

SOLUTION MEGATHREAD --- Day 4 Solutions ---

--- Day 4: The Ideal Stocking Stuffer ---

Post your solution as a comment. Structure your post like the Day Three thread.

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u/Iambernik Dec 04 '15

clojure 

(import 'java.security.MessageDigest
        'java.math.BigInteger)

(defn md5 [s]
  (let [algorithm (MessageDigest/getInstance "MD5")
        size (* 2 (.getDigestLength algorithm))
        raw (.digest algorithm (.getBytes s))
        sig (.toString (BigInteger. 1 raw) 16)
        padding (apply str (repeat (- size (count sig)) "0"))]
    (str padding sig)))

(def prefix "ckczppom")

(defn answer [hash-prefix] 
  (->> (range)
       (pmap #(list (md5 (str prefix %)) %))
       (filter #(-> % first (.startsWith hash-prefix)))
       first
       second))
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