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+#lang racket
+
+(require advent-of-code
+ threading
+ (only-in relation ->list ->set)
+ (only-in algorithms sliding))
+
+(define buffer (~> (fetch-aoc-input (find-session) 2022 6)))
+
+(define (find-marker data type)
+ (define n
+ (match type
+ ['start-of-packet 4]
+ ['start-of-message 14]))
+ (for/first ([chunk (in-list (sliding (->list data) n))]
+ [i (in-naturals n)]
+ #:when (= n (~> chunk remove-duplicates length)))
+ i))
+
+;; part 1
+(find-marker buffer 'start-of-packet)
+
+;; part 2
+(find-marker buffer 'start-of-message)