Day 6; some refactoring to use new problem-input-grouped and $.

lib.rkt

@@ -11,6 +11,7 @@
 
 (provide problem-input
          problem-input-all
+         problem-input-grouped
          show-solution
 
          make-vector-grid
@@ -95,6 +96,12 @@
          [path     (string-append "../input/" filename ".txt")])
     (read-file path)))
 
+;; problem-input-grouped : number? -> (listof string?)
+;; Return contents of input file input/xx.txt as a list of strings,
+;; where each string is a group of lines separated by newlines.
+(define (problem-input-grouped n)
+  (string-split (problem-input-all n) "\n\n"))
+
 ;; show-solution : a -> b -> void
 ;; Print part1 and part2 on separate lines.
 (define (show-solution part1 part2)

src/04.rkt

@@ -2,7 +2,7 @@
 
 (require "../lib.rkt")
 
-(define input (problem-input-all 4))
+(define input (problem-input-grouped 4))
 
 (define test
   "ecl:gry pid:860033327 eyr:2020 hcl:#fffffd
@@ -52,7 +52,7 @@ iyr:2011 ecl:brn hgt:59in")
                                          (∂r string-split ":")))
                                  (∂r string-split " ")
                                  (∂r string-replace "\n" " "))
-                                (string-split in "\n\n"))]
+                                in)]
          [passports (map (∂ foldl passport-set default-passport)
                          passport-entries)]
          [valid-raw? (struct/c passport string? string? string? string? string? string? string? any/c)]

src/05.rkt

@@ -9,8 +9,8 @@
 (define input (map string->seat (problem-input 5)))
 
 (define-values (part1 part2)
-  (let* ([minimum (apply min input)]
+  (let* ([minimum ($ min input)]
-         [maximum (apply max input)]
+         [maximum ($ max input)]
          [seats (list->set (range minimum (add1 maximum)))]
          [filled (list->set input)])
     (values maximum (set-first (set-subtract seats filled)))))

src/06.rkt

@@ -0,0 +1,16 @@
+#lang racket
+
+(require racket/set
+         "../lib.rkt")
+
+(define (parse group)
+  (map (∘ list->set string->list) (string-split group "\n")))
+
+(define input (map parse (problem-input-grouped 6)))
+
+(define-values (part1 part2)
+  (let* ([any-counts (map (∘ set-count ($ set-union)) input)]
+         [all-counts (map (∘ set-count ($ set-intersect)) input)])
+    (values (sum any-counts) (sum all-counts))))
+
+(show-solution part1 part2)