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diff --git a/racket/aoc2020/day-16/day-16.rkt b/racket/aoc2020/day-16/day-16.rkt
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+++ b/racket/aoc2020/day-16/day-16.rkt
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+#lang racket
+
+(require racket/struct
+         advent-of-code
+         fancy-app
+         relation
+         threading
+         rebellion/base/range)
+
+(struct field-rule (name range1 range2) #:transparent)
+
+(define (make-lines strs)
+  (string-split strs "\n"))
+(define (seperate-fields strs)
+  (~>> (string-split strs ",") (map ->number)))
+
+(define (process-rules str)
+  (match str
+    [(regexp
+      #px"(.+): (\\d+)-(\\d+) or (\\d+)-(\\d+)"
+      (list _ name (app ->number min1) (app ->number max1) (app ->number min2) (app ->number max2)))
+     (field-rule name (closed-range min1 max1) (closed-range min2 max2))]))
+
+(match-define (list (app (λ~>> make-lines (map process-rules)) ticket-rules)
+                    (app (λ~>> make-lines second seperate-fields) your-ticket)
+                    (app (λ~>> make-lines rest (map seperate-fields)) other-tickets))
+  (~> (fetch-aoc-input (find-session) 2020 16 #:cache #true) (string-split "\n\n")))
+
+;; part 1
+(define (fails-all-checks? field rules)
+  (define rule-list (~>> rules (map (λ~> struct->list rest)) flatten))
+  (for/and ([rule (in-list rule-list)])
+    (not (range-contains? rule field))))
+
+(define (ticket-scanning-error-rate tickets rules)
+  (for*/sum
+   ([ticket (in-list tickets)] (field (in-list ticket)) #:when (fails-all-checks? field rules))
+   field))
+
+(ticket-scanning-error-rate other-tickets ticket-rules)
+
+;; part 2
+(define valid-tickets (filter (ormap (fails-all-checks? _ ticket-rules) _) other-tickets))
+
+(define fields (apply map list valid-tickets))
+
+(for/list ([field (in-list fields)])
+  (for*/list (
+              [rule (in-list ticket-rules)]
+              #:unless (not (or (range-contains? (field-rule-range1 rule) value)
+                                (range-contains? (field-rule-range2 rule) value))))
+    (field-rule-name rule)))