Day 4.

lib.rkt

@@ -1,3 +1,4 @@
+
 #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 ;;
 

src/04.rkt

@@ -0,0 +1,83 @@
+#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)