http://www.coderloop.com/puzzles/topfive

topfive.clj

(ns topfive.topfive
  (:import
    (java.io BufferedReader FileReader)
    (java.util Hashtable)))

(def filename
  (if (nil? *command-line-args*)
    (str "topfive/topfive-a.in")
    (first *command-line-args*)))

(defn process-file [file-name]
  (let [histogram (new Hashtable)]
    (with-open [rdr (BufferedReader. (FileReader. file-name))]
      (doseq [line (line-seq rdr)]
        (let [query (second (re-find #"query=(.+)]" line))]
          (if (.get histogram query)
            (.put histogram query (inc (.get histogram query)))
            (.put histogram query 1))))) histogram))

(time (let [results (process-file filename)]
  (doseq [top (take 5 (sort-by #(.get results %) > (keys results)))]
    (println top))))