clojure performance on badly performing code -


i have completed this problem on hackerrank , solution passes test cases not fast enough 4 out of 11 test cases.

my solution looks this:

(ns scratch.core   (require [clojure.string :as str :only (split-lines join split)]))  (defn ascii [char]   (int (.charat (str char) 0)))  (defn process [text]   (let [parts (split-at (int (math/floor (/ (count text) 2))) text)         left (first parts)         right (if (> (count (last parts)) (count (first parts)))                 (rest (last parts))                 (last parts))]      (reduce (fn [acc i]               (let [a (ascii (nth left i))                     b (ascii (nth (reverse right) i))]                 (if (> b)                   (+ acc (- b))                   (+ acc (- b a))))               ) 0 (range (count left)))))  (defn print-result [[x & xs]]   (prn x)   (if (seq xs)     (recur xs)))  (let [input (slurp "/users/paulcowan/downloads/input10.txt")       inputs (str/split-lines input)       length (read-string (first inputs))       texts (rest inputs)]   (time (print-result (map process texts))))

can give me advice should @ make faster?

would using recursion instead of reduce faster or maybe line expensive:

right (if (> (count (last parts)) (count (first parts)))                 (rest (last parts))                 (last parts))

because getting count twice.

you redundantly calling reverse on every iteration of reduce:

user=> (let [c [1 2 3]              noisey-reverse #(doto (reverse %) println)]          (reduce (fn [acc e] (conj acc (noisey-reverse c) e))                  []                  [:a :b :c])) (3 2 1) (3 2 1) (3 2 1) [(3 2 1) :a (3 2 1) :b (3 2 1) :c]

the reversed value calculated inside containing let, , need calculated once.

also, due way parts defined, doing linear time lookups each call nth. better put parts in vector , indexed lookup. in fact wouldn't need reversed parts, , arithmetic based on count of vector find item up.


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