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(load "~/quicklisp/setup.lisp")
(ql:quickload "uiop")
(defun get-file-lines (name)
(uiop:read-file-lines name))
(defun parse-bin-char (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 parse-input (input-file)
(mapcar (lambda (x) (mapcar #'parse-bin-char (coerce x 'list))) (get-file-lines input-file)))
;; Loops through two item windows on input and counts each time the first is less than the second
(defun partial (func &rest args1)
(lambda (&rest args2)
(apply func (append args1 args2))))
(defun is-less (h l)
(mapcar (lambda (x) (if (< x h) 0 1)) l))
(defun not-list (l)
(mapcar (lambda (x) (if (= x 0) 1 0)) l))
(defun range (max &key (min 0) (step 1))
(loop :for n :from (- max 1) :above (- min 1) :by step
:collect n))
(defun to-dec (l)
(apply #'+ (mapcar (lambda (a b) (* a (expt 2 b))) l (range (list-length l)))))
(defun part-a (parsed-input)
(let* ((half-length (/ (list-length parsed-input) 2))
(l (is-less half-length (apply (partial #'mapcar #'+) parsed-input)))
(gamma (to-dec l))
(epsilon (to-dec (not-list l))))
(* epsilon gamma)))
;; Similar to part a, but with four item windows, comparing the sum of the first 3 with the next 3
(defun part-b (parsed-input)
(loop for (w x y z) on parsed-input until (null z) if (< (+ w x y) (+ x y z)) count w))
(time (format t "part 1: ~a~%" (part-a (parse-input "../inputs/03.txt"))))
;;(time (format t "part 1: ~a~%" (part-a (parse-input "test.txt"))))
;;(time (format t "part 1: ~a~%" (part-b (parse-input "../inputs/01.txt"))))
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