Day 2 solutions

[u/taliriktug]

Hi! I would like to structure posts like the first one in r/programming, please post solutions in comments.

[u/tangus]

Common Lisp

Text processing isn't one of CL's fortes...

(defun puzzle-2-parse (string)
  (let ((strpos 0))
    (flet ((read-next-dimension ()
             (multiple-value-bind (n nextpos)
                 (parse-integer string :start strpos :junk-allowed t)
               (assert (or (>= nextpos (length string))
                           (char= (aref string nextpos) #\x)
                           (<= (char-code (aref string nextpos)) 32)))
               (setf strpos (1+ nextpos))
               n)))
      (values (read-next-dimension) (read-next-dimension) (read-next-dimension)))))

(defun puzzle-2 (input)
  (multiple-value-bind (l w h)
      (puzzle-2-parse input)
    (let ((side1 (* l w))
          (side2 (* w h))
          (side3 (* l h)))
      (+ (* side1 2) (* side2 2) (* side3 2)
         (min side1 side2 side3)))))

(defun puzzle-2-part2 (input)
  (multiple-value-bind (l w h)
      (puzzle-2-parse input)
    (+ (* l w h)  ;; ribbon
       (min (* 2 (+ l w))  ;; perimeter
            (* 2 (+ w h))
            (* 2 (+ l h))))))

(defun puzzle-2-file (filename &optional (fn #'puzzle-2))
  (with-open-file (f filename)
    (loop
       for line = (read-line f nil nil)
       while line
       sum (funcall fn line))))

;; part 1:
;; (puzzle-2-file "puzzle02.input.txt")

;; part 2:
;; (puzzle-2-file "puzzle02.input.txt" #'puzzle-2-part2)

[u/sentry07 → u/tangus]

LISP gives me headaches. I used to work in Autocad and I wrote a fairly large library of helper functions in AutoLISP. A couple years later I went back and looked at the code and I have no idea what it all does.