project euler 74

pe_74.clj

;; Problem 74  : 2011/12/14
;; "Elapsed time: 135291.687352 msecs"

(defn factorial [n]
  (reduce * (range 1 (inc n))))

(defn-memo sum-of-factorial [num-list]
  (reduce + (map factorial num-list)))

(defn exists [tgt col]
  (some #(= tgt %) col))

(defn get-loop [key col]
  (let [loops (drop-while #(not= key %) col)]
    (if (empty? loops)
      false
      [loops
       (take-while #(not= key %) col)])))

(let [mem (atom {})]
  
  (defn mem-set-count-loop! [loop-list]
    (let [loop-cnt (count loop-list)]
      (dorun (map #(swap! mem assoc % loop-cnt) loop-list))))
	     
  (defn mem-set-count-stem! [stem-list base]
    (dorun (map #(swap! mem assoc %1 (+ base %2))
		(reverse stem-list) (iterate inc 1))))

  (defn count-74-link [num prec-vec]
    (if-let [cnt (get @mem num)]
      (do (mem-set-count-stem! prec-vec cnt)
	  (+ cnt (count prec-vec)))
      (let [next-num (sum-of-factorial (sort (num-to-list num)))
	    new-vec  (conj prec-vec num)]
  	(if-let [[looping stem] (get-loop next-num new-vec)]
  	  (do (mem-set-count-loop! looping)
	      (mem-set-count-stem! stem (count looping))
  	      (count new-vec))
  	  (recur next-num new-vec)))))
)

(defn pe-74 [lmt]
  (count 
   (filter #(= 60 %)
	   (map #(do (count-74-link % [])) (range 1 (inc lmt))))))