http://adventofcode.com/2017/day/2

day2.el

(defun read-numbers-from-file (file-path)
  (with-temp-buffer
    (insert-file-contents file-path)
    (mapcar
     (lambda (arg) (mapcar 'string-to-number(split-string arg)))
     (split-string (string-trim (buffer-string)) "\n" t)
     )
    )
  )

(read-numbers-from-file "./input.txt")

(defun find-max-min (compar list)
  (let ((res (nth 0 list)))
    (dolist (x list)
      (when (apply compar (list x res)) (setq res x))
      )
    res
    )
  )


(find-max-min '< '(-1 2 3))

(defun calculate-checksum (list2d)
  "Solution for Part #1 http://adventofcode.com/2017/day/2"
  (let (res (min 0) (max 0))
    (dolist (list list2d)
      (setq min (find-max-min '< list))
      (setq max (find-max-min '> list))
      (push (- max min) res)
      )
    (apply '+ res)
    )
  )

(setq input '((5 1 9 5)
              (7 5 3)
              (2 4 6 8)))

(calculate-checksum input) ;; 18

(calculate-checksum (read-numbers-from-file "./input.txt"))

(defun find-evenly-devided (list)
  (let ((n (length list)) val next j res)
    (dotimes (i (- n 1))
      (dotimes (jj (- n i 1))
        (setq j (+ jj i 1))
        (setq val (nth i list))
        (setq next (nth j list))
        (when (= (% val next) 0) (setq res (/ val next)))
        (when (= (% next val) 0) (setq res (/ next val)))
        )
      )
    res
    )
  )


(defun calculate-checksum1 (list2d)
  "Solution for Part #2 http://adventofcode.com/2017/day/2"
  (let (res step)
    (dolist (list list2d)
      (setq step (find-evenly-devided list))
      (when step (push step res))
      )
    (apply '+ res)
    )
  )

(setq input1 '((5 9 2 8)
              (9 4 7 3)
              (3 8 6 5)))

(calculate-checksum1 (read-numbers-from-file "./input.txt"))

(find-evenly-devided (nth 2 input1)) ;; 9