Various Algorithms

misc.txt

;;; Lisp - top 2 in a list

(defun top-2 (a)
	   (let ((ls (reduce 
		      #'(lambda (vs n)
			  (if (null (third vs))
			      (list
			       n
			       (second vs)
			       n)
			      (let* ((m1 (first vs))
				     (m2 (second vs))
				     (p (third vs))
				     (mx (max m1 n p))
				     (my (cond
					   ((= mx n) (max p m2))
					   ((= mx p) (max n m2))
					   (t (max n p m2)))))
				(list mx my n))))
		      a
		      :initial-value '(-999 -999 nil))))
	     (list (first ls)
		   (second ls))))
		   
;; Top - 2 algorithm in Clojure

(defn top-2
  [ns]
  (let [rs (reduce
            (fn [vs n]
              (cond
                (nil? (vs 2)) [n (vs 1) n]
                :else (let [m1 (vs 0)
                            m2 (vs 1)
                            p (vs 2)
                            mx (max m1 n p)
                            my (cond
                                 (= mx n) (max p m2)
                                 (= mx p) (max n m2)
                                 :else (max n p m2))]
                        [mx my n])))
            [Integer/MIN_VALUE
             Integer/MIN_VALUE
             nil]
            ns)]
    [(rs 0)
     (rs 1)]))