3,4,3,1,2

(ql:quickload "split-sequence")
(defun read-data (path)
  (with-open-file (stream path)
                  (loop for line = (read-line stream nil)
                        while line collect line)))
(defparameter *input-source*
  (cadr *posix-argv*))
;; Useful in testing
;; (defparameter *input-source* "example_input")
;; (defparameter *input-source* "input")
(defun parse-input (lines)
  (map 'list #'parse-integer
       (split-sequence:split-sequence #\, (car lines))))
(defun preprocess-input (numbers)
  (let ((arr (make-array 9)))
    (dolist (n numbers)
      (setf (aref arr n) (1+ (aref arr n))))
    arr))
(defparameter *data*
  (parse-input (read-data *input-source*)))
(defun solution (data days)
  (let ((working (preprocess-input data)))
    (dotimes (n days)
      (let ((zeroes (aref working 0)))
        (loop for x from 1 to 8
              do (setf (aref working (1- x)) (aref working x)))
        (setf (aref working 8) zeroes)
        (setf (aref working 6) (+ zeroes (aref working 6)))))
    (loop for x from 0 to 8 sum (aref working x))))
(defun part1 (data)
  (solution data 80))
(defun part2 (data)
  (solution data 256))
(format t "===== Part 1 =====")
(format t "Result: ~A~%~%" (time (part1 *data*)))
(format t "===== Part 2 =====")
(format t "Result: ~A~%" (time (part2 *data*)))