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2020
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Day 4.

This commit is contained in:
Jonathan Chan 2020-12-03 22:45:29 -08:00
parent bbdc3cd4e8
commit 1203dc4a1d
3 changed files with 1109 additions and 1 deletions
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1009
input/04.txt Normal file
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18
lib.rkt
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#lang racket
(require
@ -5,9 +6,11 @@
make-queue
enqueue!)
(only-in 2htdp/batch-io
read-lines))
read-lines
read-file))
(provide problem-input
problem-input-all
show-solution
make-vector-grid
@ -23,6 +26,7 @@
sum
!= nchar=?
char-alphanumeric?
nzero?
negate
pos-or-zero
@ -66,6 +70,13 @@
[path (string-append "../input/" filename ".txt")])
(read-lines path)))
;; problem-input-all : number? -> string?
;; Return contents of input file input/xx.txt as a single string.
(define (problem-input-all n)
(let* ([filename (~a n #:min-width 2 #:align 'right #:left-pad-string "0")]
[path (string-append "../input/" filename ".txt")])
(read-file path)))
;; show-solution : a -> b -> void
;; Print part1 and part2 on separate lines.
(define (show-solution part1 part2)
@ -132,6 +143,11 @@
(define (nchar=? c1 c2)
(not (char=? c1 c2)))
;; char-alphanumeric? : char -> boolean
(define (char-alphanumeric? c)
(or (char-alphabetic? c)
(char-numeric? c)))
;; Number helpers ;;

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src/04.rkt Normal file
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#lang racket
(require "../lib.rkt")
(define input (problem-input-all 4))
(define test
"ecl:gry pid:860033327 eyr:2020 hcl:#fffffd
byr:1937 iyr:2017 cid:147 hgt:183cm
iyr:2013 ecl:amb cid:350 eyr:2023 pid:028048884
hcl:#cfa07d byr:1929
hcl:#ae17e1 iyr:2013
eyr:2024
ecl:brn pid:760753108 byr:1931
hgt:179cm
hcl:#cfa07d eyr:2025 pid:166559648
iyr:2011 ecl:brn hgt:59in")
(define fields '(byr iyr eyr hgt hcl ecl pid)) ;; except 'cid
(define ecls '(amb blu brn gry grn hzl oth))
(define (passports in)
(define (interp-value field value-string)
(match field
['byr (string->number value-string)]
['iyr (string->number value-string)]
['eyr (string->number value-string)]
['hgt (cond
[(string-suffix? value-string "in")
(cons 'in (string->number (string-trim value-string "in")))]
[(string-suffix? value-string "cm")
(cons 'cm (string->number (string-trim value-string "cm")))]
[else (cons 'na (string->number value-string))])]
['hcl (string->list value-string)]
['ecl (string->symbol value-string)]
['pid (string->list value-string)]
['cid value-string]))
(let* ([passport-strings (map (λ (p) (string-replace p "\n" " "))
(string-split in "\n\n"))]
[passport-entries (map (λ (p) (map (curryr string-split ":")
(string-split p " ")))
passport-strings)]
[passport-hashes (map (λ (p)
(for/hash ([entry p])
(let* ([field (string->symbol (first entry))]
[value (interp-value field (second entry))])
(values field value))))
passport-entries)])
passport-hashes))
(define part1
(count (λ (p) (andmap (∂ hash-has-key? p) fields))
(passports input)))
(define part2
(count
(λ (p)
(and (andmap (∂ hash-has-key? p) fields)
(match-let ([byr (hash-ref p 'byr)]
[iyr (hash-ref p 'iyr)]
[eyr (hash-ref p 'eyr)]
[`(,unit . ,hgt) (hash-ref p 'hgt)]
[`(,hash ,hex ...) (hash-ref p 'hcl)]
[ecl (hash-ref p 'ecl)]
[pid (hash-ref p 'pid)])
(and (<= 1920 byr 2002)
(<= 2010 iyr 2020)
(<= 2020 eyr 2030)
(match unit
['cm (<= 150 hgt 193)]
['in (<= 59 hgt 76)]
[else #f])
(char=? #\# hash)
(= (length hex) 6)
(andmap (curry char-alphanumeric?) hex)
(member ecl ecls)
(= (length pid) 9)))))
(passports input)))
(show-solution part1 part2)