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;; Advent of Code 2020 - Day 4
(require 'cl-lib)
(require 's)
(require 'dash)
(require 'f)
(cl-defstruct day4/passport
byr ;; Birth Year
iyr ;; Issue Year
eyr ;; Expiration Year
hgt ;; Height
hcl ;; Hair Color
ecl ;; Eye Color
pid ;; Passport ID
cid ;; Country ID
)
(defun day4/parse-passport (input)
(let* ((pairs (s-split " " (s-replace "\n" " " input) t))
(slots
(-map
(lambda (pair)
(pcase-let ((`(,key ,value) (s-split ":" (s-trim pair))))
(list (intern (format ":%s" key)) value)))
pairs)))
(apply #'make-day4/passport (-flatten slots))))
(defun day4/parse-passports (input)
(-map #'day4/parse-passport (s-split "\n\n" input t)))
(setq day4/input (day4/parse-passports (f-read "/tmp/aoc/day4.txt")))
;; Puzzle 1
(defun day4/validate (passport)
"Check that all fields except CID are present."
(cl-check-type passport day4/passport)
(and (day4/passport-byr passport)
(day4/passport-iyr passport)
(day4/passport-eyr passport)
(day4/passport-hgt passport)
(day4/passport-hcl passport)
(day4/passport-ecl passport)
(day4/passport-pid passport)))
(message "Solution to day4/1: %s" (cl-loop for passport being the elements of day4/input
count (day4/validate passport)))
;; Puzzle 2
(defun day4/year-bound (min max value)
(and
(s-matches? (rx (= 4 digit)) value)
(<= min (string-to-number value) max)))
(defun day4/check-unit (unit min max value)
(and
(string-match (rx (group (+? digit)) (literal unit)) value)
(<= min (string-to-number (match-string 1 value)) max)))
(defun day4/properly-validate (passport)
"Opting for readable rather than clever here."
(and
(day4/validate passport)
;; byr (Birth Year) - four digits; at least 1920 and at most 2002.
(day4/year-bound 1920 2002 (day4/passport-byr passport))
;; iyr (Issue Year) - four digits; at least 2010 and at most 2020.
(day4/year-bound 2010 2020 (day4/passport-iyr passport))
;; eyr (Expiration Year) - four digits; at least 2020 and at most 2030.
(day4/year-bound 2020 2030 (day4/passport-eyr passport))
;; hgt (Height) - a number followed by either cm or in:
;; If cm, the number must be at least 150 and at most 193.
;; If in, the number must be at least 59 and at most 76.
(or (day4/check-unit "cm" 150 193 (day4/passport-hgt passport))
(day4/check-unit "in" 59 76 (day4/passport-hgt passport)))
;; hcl (Hair Color) - a # followed by exactly six characters 0-9 or a-f.
(s-matches? (rx ?# (= 6 hex)) (day4/passport-hcl passport))
;; ecl (Eye Color) - exactly one of: amb blu brn gry grn hzl oth.
(-contains? '("amb" "blu" "brn" "gry" "grn" "hzl" "oth")
(day4/passport-ecl passport))
;; pid (Passport ID) - a nine-digit number, including leading zeroes.
(s-matches? (rx line-start (= 9 digit) line-end)
(day4/passport-pid passport))
;; cid (Country ID) - ignored, missing or not.
))
(message "Solution to day4/2: %s"
(cl-loop for passport being the elements of day4/input
count (day4/properly-validate passport)))
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