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;; Advent of Code 2020 - Day
(require 'cl-lib)
(require 'dash)
(require 'f)
(require 's)
(setq day8/input
(apply #'vector
(-map (lambda (s)
(pcase-let ((`(,op ,val) (s-split " " s t)))
(cons (intern op) (string-to-number val))))
(s-lines (s-chomp (f-read "/tmp/aoc/day8.txt"))))))
(defun day8/step (code position acc)
(let ((current (aref code position)))
(aset code position nil)
(pcase current
('() (cons 'final acc))
(`(nop . ,val) (cons (+ position 1) acc))
(`(acc . ,val) (cons (+ position 1) (+ acc val)))
(`(jmp . ,val) (cons (+ position val) acc)))))
;; Puzzle 1
(message "Solution to day8/1: %s"
(let ((code (copy-sequence day8/input))
(position 0)
(acc 0))
(cl-loop for next = (day8/step code position acc)
when (equal 'final (car next)) return (cdr next)
do (setq position (car next))
do (setq acc (cdr next)))))
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