Code Jam Japan Prelim Problem C

gcjj_pC.clj

(require '[clojure.contrib.io :as io])

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;; Main funcs

;; find digits pair for a and b
;; returns [<total bit count> <carry>]

(defn check-one-digit [tgt-digit carry is-msb]
  (if (zero? carry)
    (if (zero? tgt-digit)
      [2 1]      ;; carry 0, digit 0 -> 1 1
      [1 0])     ;; carry 0, digit 1 -> 1 0
    (if (zero? tgt-digit)
      [1 1]      ;; carry 1, digit 0 -> 1 0
      (if is-msb
	[0 0]    ;; carry 1, digit 1, msb yes -> 0 0
	[2 1]))));; carry 1, digit 1, msb no -> 1 1

;; Get last digit
(defn lsb [n]
  (rem n 2))

;; Top digit or not
(defn msb? [n]
  (= n 1))

;; Main func
(defn gcj-pC [n]
  (loop [tgt-n n
	 bit-count 0
	 carry 0]
    (if (zero? tgt-n)
      bit-count
      (let [[bits carr] (check-one-digit (lsb tgt-n) carry (msb? tgt-n))]
	(recur (bit-shift-right tgt-n)
	       (+ bit-count bits)
	       carr)))))

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;; Support funcs 

;; get args from the question file.
;; returns them as 
;;      ((1 N1) (2 N2) ........))
(defn get-gcj-args-list [file-name]
  (map list
       (iterate inc 1)
       (map (fn [line-dat]
	      (map (fn [s] (BigInteger. s))
		   (.split line-dat " ")))
	    (drop 1 (io/read-lines file-name)))))


(defn gcj-get-ans [file-name f]
  (pmap (fn [[num args]] [num (apply f args)]) 
	(get-gcj-args-list file-name)))


;; Get answer : for 1 line data
(defn gcj-create-ans [in-file out-file f]
    (with-open [bw (io/writer out-file)]
      (io/with-out-writer bw
	(dorun
	 (for [[num ans] (gcj-get-ans in-file f)]
	   (println (str "Case #" num ": " ans)))))))


;;(gcj-create-ans "C-large-practice.in" "C-large_practice.out" gcj-pC)
;; "Elapsed time: 67.20944 msecs"