diff --git a/16.rkt b/16.rkt
index d9fd096..238fa53 100644
--- a/16.rkt
+++ b/16.rkt
@@ -4,78 +4,58 @@
 
 ;; solution for day 16
 
-(struct note [name rule0 rule1] #:transparent)
+(struct note [name test] #:transparent)
 
-(define (invalid? notes val)
-  (not
-    (for/or ([n (in-list notes)])
-      (match-define (note name (cons a b) (cons c d)) n)
-      (or (and (>= val a) (<= val b)) (and (>= val c) (<= val d))))))
+(define (valid? notes val)
+  (ormap #{(note-test %) val} notes))
 
 (define (part1 input)
   (match-define (list notes yours others) input)
-  (for/sum ([tick (in-list others)])
-    (for/sum ([val (in-list tick)] #:when (invalid? notes val)) val)))
+  (for*/sum ([tick (in-list others)] [val (in-list tick)] #:unless (valid? notes val))
+    val))
 
 (define (part2 input)
   (match-define (list notes yours others) input)
-  (define (ticket-valid? tick)
-    (not (for/or ([val (in-list tick)]) (invalid? notes val))))
-  (define valid-tickets (filter ticket-valid? others))
+  (define valid-tickets (filter #{andmap #{valid? notes %} %} others))
 
-  (define mapping (make-hash))
-
-  (for ([idx (in-range (length yours))])
-    (define decided-note (mutable-set))
-    (for ([cand-note (in-list notes)])
-      (define shonks
-        (for/and ([tick (in-list valid-tickets)])
-          (not (invalid? (list cand-note) (list-ref tick idx)))))
-      (when shonks
-        (set-add! decided-note (note-name cand-note))))
-    (when (set-empty? decided-note) (error "couldn't decide..."))
-    (hash-set! mapping idx decided-note))
-
-  ; (displayln mapping)
+  (define mapping
+    (for/vector ([idx (in-range (length yours))])
+      (define matching-notes
+        (for/mutable-set ([cand-note (in-list notes)]
+                          #:when (andmap #{valid? (list cand-note) (list-ref % idx)} valid-tickets))
+          (note-name cand-note)))
+      (when (set-empty? matching-notes) (error "couldn't decide..."))
+      matching-notes))
 
   (let loop ()
-    (for ([(k v) (in-hash mapping)])
-      (when (= 1 (set-count v))
-        (define fst (set-first v))
-        (for ([k2 (in-list (hash-keys mapping))] #:unless (= k2 k))
-          (set-remove! (hash-ref mapping k2) fst))))
-    (when (for/or ([(k v) (in-hash mapping)])
-            (> (set-count v) 1))
-      (displayln "looping")
+    (define has-conflicts #f)
+    (for ([v (in-vector mapping)] [k (in-naturals)])
+      (cond
+        [(= 1 (set-count v))
+         (define fst (set-first v))
+         (for ([v2 (in-vector mapping)] [k2 (in-naturals)] #:unless (= k2 k))
+           (set-remove! v2 fst))]
+        [else (set! has-conflicts #t)]))
+    (when has-conflicts
       (loop)))
-  (displayln mapping)
 
-  (for/product ([val (in-list yours)] [idx (in-naturals)])
-    (define n (set-first (hash-ref mapping idx)))
-    (displayln n)
-    (if (string-contains? n "departure")
-      (begin (displayln val) val)
+  (for/product ([val (in-list yours)] [name-set (in-vector mapping)])
+    (if (string-contains? (set-first name-set) "departure")
+      val
       1)))
 
 ;; parse input file
 (define (parse fname)
-  (match-define (list notes yours others) (string-split (file->string fname) "\n\n"))
   (define sn string->number)
-  (define pnotes (for/list ([line (in-list (string-split notes "\n"))])
-                   (match line
-                     [(pregexp #px"^([^:]+): (\\d+)\\-(\\d+) or (\\d+)-(\\d+)$"
-                               (list _ name a b c d))
-                      (note name (cons (sn a) (sn b)) (cons (sn c) (sn d)))])))
-  (define pyours (map sn (string-split (second (string-split yours "\n")) ",")))
-  (define pothers (for/list ([line (in-list (rest (string-split others "\n")))])
-                    (map sn (string-split line ","))))
-
-  (list pnotes pyours pothers))
-
-(module+ test
-  (require rackunit)
-  ;; tests here
-  (displayln "no tests :("))
+  (match-define (list notes-in yours-in others-in) (string-split (file->string fname) "\n\n"))
+  (list (for/list ([line (in-list (string-split notes-in "\n"))])
+          (match line
+            [(pregexp #px"^([^:]+): (\\d+)\\-(\\d+) or (\\d+)-(\\d+)$"
+                      (list _ name (app sn a) (app sn b) (app sn c) (app sn d)))
+             (note name #{or (<= a % b) (<= c % d)})]))
+        (map sn (string-split (second (string-split yours-in "\n")) ","))
+        (for/list ([line (in-list (rest (string-split others-in "\n")))])
+          (map sn (string-split line ",")))))
 
 (module+ main
   (define input (parse "inputs/16"))