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(defun 03/parse-bin-char (x) (case x (#\1 1) (#\0 0)))
(defun 03/parse-bin-char-inv (x) (case x (1 #\1) (0 #\0)))
;; Turn the input file into whatever form you will use for both parts
;; (get-file-lines) and (get-file-string) will be useful
(defun 03/parse-input-direct (input)
(mapcar (lambda (x) (mapcar #'03/parse-bin-char (coerce x 'list))) input))
(defun 03/parse-input (input-file)
(03/parse-input-direct (get-file-lines input-file)))
(defun 03/is-more (h l)
(mapcar (lambda (x) (if (< x h) 0 1)) l))
(defun 03/is-less (h l)
(mapcar (lambda (x) (if (>= x h) 0 1)) l))
(defun 03/not-list (l)
(mapcar (lambda (x) (if (= x 0) 1 0)) l))
(defun 03/to-dec (l)
(parse-integer (coerce (mapcar #'03/parse-bin-char-inv l) 'string) :radix 2))
(defun 03/find-most-common (parsed-input)
(let ((half-length (/ (list-length parsed-input) 2)))
(03/is-more half-length (apply (partial #'mapcar #'+) parsed-input))))
(defun 03/find-least-common (parsed-input)
(let ((half-length (/ (list-length parsed-input) 2)))
(03/is-less half-length (apply (partial #'mapcar #'+) parsed-input))))
(defun 03/part-a (parsed-input)
(let* ((l (03/find-most-common parsed-input))
(gamma (03/to-dec l))
(epsilon (03/to-dec (03/not-list l))))
(* epsilon gamma)))
(defun 03/recursive-b (f input out)
(if (member nil input) out
(let* ((common (car (funcall f input)))
(rest-tmp (mapcar #'cdr (remove-if-not (lambda (x) (equalp (car x) common)) input)))
(rest (if rest-tmp rest-tmp
(progn
(setf common (car (car input)))
(mapcar #'cdr input)))))
(03/recursive-b f rest (append out (list common))))))
(defun 03/part-b (parsed-input)
(* (03/to-dec (03/recursive-b #'03/find-most-common parsed-input nil))
(03/to-dec (03/recursive-b #'03/find-least-common parsed-input nil))))
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