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1 files changed, 37 insertions, 0 deletions

diff --git a/racket/aoc2023/day-24/day-24b.rkt b/racket/aoc2023/day-24/day-24b.rkt
new file mode 100644
index 0000000..b106b30
--- /dev/null
+++ b/racket/aoc2023/day-24/day-24b.rkt
@@ -0,0 +1,37 @@
+#lang rosette
+
+(require advent-of-code
+         threading)
+
+(struct hail (posn vel))
+(struct posn (x y z))
+(struct vel (x y z))
+
+(define input (fetch-aoc-input (find-session) 2023 24 #:cache #true))
+
+(define (->struct f str)
+  (~> str (string-split _ ",") (map (λ~> string-trim string->number) _) (apply f _)))
+
+(define (parse-hail-record str)
+  (match-define (list p v) (string-split str " @ "))
+  (hail (->struct posn p) (->struct vel v)))
+
+(define hail-paths
+  (for/list ([hail (in-list (string-split input "\n"))] ;
+             [_ (in-range 3)])
+    (parse-hail-record hail)))
+
+;; part 1 - see day-24a.rkt
+;; part 2
+
+(define-symbolic px py pz vx vy vz integer?)
+
+(define sol
+  (solve ;
+   (for ([path (in-list hail-paths)])
+     (define-symbolic* t integer?)
+     (assert (= (+ px (* vx t)) (+ (~> path hail-posn posn-x) (* (~> path hail-vel vel-x) t))))
+     (assert (= (+ py (* vy t)) (+ (~> path hail-posn posn-y) (* (~> path hail-vel vel-y) t))))
+     (assert (= (+ pz (* vz t)) (+ (~> path hail-posn posn-z) (* (~> path hail-vel vel-z) t)))))))
+
+(evaluate (+ px py pz) sol)