Code Jam Japan Problem A

gcjj_pA.clj

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

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;; Main funcs

;; step back
;; get previous position of the target card
(defn un-shuffle [W ab-list]
  (let [[A B] ab-list]
    (cond (<= W B) (+ W (- A 1))
	  (and (> W B) 
               (<= W (+ B A -1))) (- W B)
	  :else W)))

;; step back all the way
(defn gcj-pA [key-arg cut-list]
  (let [[_ _ W] key-arg]
    (loop [rev-cut-list (reverse cut-list)
	   w W]
      (if (empty? rev-cut-list)
	w
	(recur (next rev-cut-list)
	       (un-shuffle w (first rev-cut-list)))))))



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;; Support funcs 

;; get args from the question file.
;; returns them as 
;;      ((1 ((M T W) ((A1 B1)(A2 B2)...))) (2 ........))
(defn get-gcj-args-list-pA [file-name]
  (let [tmptmp
	(reduce (fn [[tmp-dat res] dat]
		  (cond (= (count dat) 3) [[dat []] (conj res tmp-dat)]
			(= (count dat) 2) [[(first tmp-dat) (vec (conj (second tmp-dat) dat))] res]
			:final  (vec (conj (second tmp-dat) dat))))
		[[] []]
		(map (fn [line-dat]
		       (map (fn [s] (BigInteger. s))
			    (.split line-dat " ")))
		     (drop 1 (io/read-lines file-name))))]
    (map list
	 (iterate inc 1)
	 (conj (vec (drop 1 (second tmptmp))) (first tmptmp)))))
	  
;; get answar list with answer function f
(defn gcj-get-ans-pA [file-name f]
  (pmap (fn [[num args]] [num (apply f args)]) 
	(get-gcj-args-list-pA file-name)))

;; create answar file from question file with answer function f
(defn gcj-create-ans-pA [in-file out-file f]
    (with-open [bw (io/writer out-file)]
      (io/with-out-writer bw
	(dorun
	 (for [[num ans] (gcj-get-ans-pA in-file f)]
	   (println (str "Case #" num ": " ans)))))))



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;; invoke
(time (gcj-create-ans-pA 
           "A-large-practice.in"
           "A-large-practice.out" 
            gcj-pA))