(ql:quickload :cl-ppcre)

(defun parse-input (input)
  (cl-ppcre:split "\\n" (uiop:read-file-string input)))

(defun get-score (c)
  (cond ((lower-case-p c) (- (char-code c) 96))
	((upper-case-p c) (- (char-code c) 38))))

(defun calc-score-one (rucksack)
  (let* ((c1 (subseq rucksack 0 (/ (length rucksack) 2)))
	 (c2 (subseq rucksack (/ (length rucksack) 2) (length rucksack))))
    (loop :for c :across c1 :if (find c c2) :return (get-score c))))

(defun part-one (input)
  (reduce '+ (mapcar #'calc-score-one (parse-input input))))

(defun calc-score-two (rucksacks)
  (let* ((r1 (first rucksacks))
	 (r2 (second rucksacks))
	 (r3 (third rucksacks)))
    (loop :for c :across r1 :if (and (find c r2) (find c r3)) :return (get-score c))))

(defun part-two (input)
  (reduce '+ (loop :for (r1 r2 r3)
		     :on (parse-input input)
		       :by 'cdddr
		   :collect (calc-score-two (list r1 r2 r3)))))