optimisation

longest-common-subsequence.clj

(defn lcs [xr yr]
  ((fn inner-lcs [x y]
   (cond
    (or (zero? (count x)) (zero? (count y))) nil
    (= (first x) (first y)) (cons (first x) (inner-lcs (rest x) (rest y)))
    :else (let [xx (inner-lcs (rest x) y)
                yy (inner-lcs x (rest y))]
            (if (> (count xx) (count yy)) xx yy)))) xr yr))

> (print "result:" (lcs "Stathis Georgiou Sideris" "Stathis Sideris") "\n")
result: (S t a t h i s   S i d e r i s) 

> (print "list result:" (prn-str (lcs [1 2 3 4 5 6 7] [-1 -2 3 4 7 8 9])))
list result: (3 4 7)

Executes in 13% of the previous time