http://www.reddit.com/r/dailyprogrammer/comments/1m1jam/081313_challenge_137_easy_string_transposition/

gistfile1.clj

(defn get-chars-at [seq count]
    (reduce (fn [accum next]
                (let [next-char (get next count)
                      char (if-not (nil? next-char) next-char " ")]
                      (str accum char)))
            "" seq))

(defn max-count [seq]
    (reduce (fn max-count [last line]
                (let [c (count line)]
                    (if (< last c) c last)))
            0 seq))

(defn transpose [str]
    (let [lines (clojure.string/split-lines str)
          max-length (max-count lines)]
        (clojure.string/join "\n"
                             (for [i (range max-length)]
                                 (get-chars-at lines i)))))