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(load "util.lisp")
(defparameter input (uiop:read-file-string "3-input"))
(defun is-good-mul (str)
(let ((start (search "(" str))
(middle (search "," str))
(end (search ")" str)))
(and (not (null start)) (not (null middle)) (not (null end))
;; mul( <- 3 character
(eq start 3)
;; Simple to understand
(< start end)
(< start middle)
(< middle end)
;; Make sure the arguments are purely numbers
(every #'digit-char-p (subseq str (1+ start) middle))
(every #'digit-char-p (subseq str (1+ middle) end)))))
(defun parse-mul (str)
(let ((start (search "(" str))
(middle (search "," str))
(end (search ")" str)))
(list (parse-integer (subseq str (1+ start) middle))
(parse-integer (subseq str (1+ middle) end)))))
(defun parse-input-muls (line)
(let ((possible (search-all "mul" line)))
(--> (cdr possible)
(append _ (list (length line)))
;; index of mul -> (position substring)
(mapcar (lambda (z1 z2) (cons z1 (subseq line z1 z2))) possible _)
;; remove any bad muls
(remove-if-not (lambda (x) (is-good-mul (cdr x))) _)
;; parse muls
(mapcar (lambda (x) (cons (car x) (parse-mul (cdr x)))) _))))
(format t "Round 1: ~a~%"
(loop for (pos x y) in (parse-input-muls input)
sum (* x y)))
(defun parse-input-conds (input)
(let ((dos (search-all "do()" input))
(donts (search-all "don't()" input)))
(--> (append (mapcar (lambda (x) (cons 'do x)) dos)
(mapcar (lambda (x) (cons 'dont x)) donts))
(sort _ (lambda (x y) (< (cdr x) (cdr y))))
(cons '(do . 0) _))))
(defun current-cond (pos conds)
(caar (last (remove-if (lambda (x) (> (cdr x) pos)) conds))))
(format t "Round 2: ~a~%"
(let ((conds (parse-input-conds input))
(muls (parse-input-muls input)))
(loop for (pos x y) in muls
for current = (current-cond pos conds)
if (eq current 'do)
sum (* x y))))
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