day 2: 2 shonk 2 furious

2.rkt

@@ -0,0 +1,31 @@
+#lang racket
+
+(require "scripts/aoc.rkt")
+
+;; solution for day 2
+
+(define (password-valid-part1? lmin lmax char password)
+  (<= lmin (count (curry char=? char) (string->list password)) lmax))
+
+(define (password-valid-part2? a b char password)
+  (define pwd-chars (string->list password))
+  (xor (char=? (string-ref password (sub1 a)) char)
+       (char=? (string-ref password (sub1 b)) char)))
+
+(define (calculate valid-proc input)
+  (for/sum ([line (in-list input)])
+    (match line
+      [(pregexp #px"^([0-9]+)\\-([0-9]+) (.): (.*?)$" (list _ lmin lmax char password))
+       (if (valid-proc (string->number lmin) (string->number lmax)
+                       (string-ref char 0) password) 1 0)]
+      [_ (error "failed to parse" line)])))
+
+(module+ main
+  (define input (file->lines "inputs/2"))
+  ;; part 1
+  (answer 2 1 (calculate password-valid-part1? input))
+
+  ;; part 2
+  (answer 2 2 (calculate password-valid-part2? input))
+
+  (displayln "meow"))