1 files changed, 53 insertions, 0 deletions
diff --git a/racket/aoc2022/day-17/day-17.rkt b/racket/aoc2022/day-17/day-17.rkt
new file mode 100644
index 0000000..28e8763
--- /dev/null
+++ b/racket/aoc2022/day-17/day-17.rkt
@@ -0,0 +1,53 @@
+#lang racket
+
+(require advent-of-code
+         threading
+         fancy-app
+         data/collection)
+
+(define (relative-rock-coordinates rock)
+  (for*/hash ([(row y) (in-indexed (reverse rock))] [(_col x) (in-indexed row)])
+    (values (cons x y) #true)))
+
+(define rock-shapes
+  (~> (open-input-file "./2022/day-17/rock-shapes")
+      port->string
+      (string-split "\n\n")
+      (map (λ~> (string-split _ "\n") (map string->list _) relative-rock-coordinates) _)))
+
+(define gusts
+  (~> (fetch-aoc-input (find-session) 2022 17 #:cache #true)
+      string-trim
+      string->list
+      (map (match-lambda
+             [#\> 1]
+             [#\< -1])
+           _)))
+
+(define (place-new-rock rock elevation)
+  (for/hash ([(posn _) (in-hash rock)])
+    (match-define (cons x y) posn)
+    (values (cons (+ x 3) (+ y elevation 4)) #true)))
+
+(define (gust-move rock wind cave)
+  (define moved-rock
+    (for/hash ([(posn _) (in-hash rock)])
+      (match-define (cons x y) posn)
+      (define posn* (cons (+ x wind) y))
+      (if (hash-has-key? cave posn) (values 'collision #t) (values posn* #t))))
+  (if (hash-has-key? moved-rock 'collision) rock moved-rock))
+
+(for/fold ([cave (hash)]
+           [falling-rock #f]
+           [top-of-rocks 0]
+           [rock-cycle (cycle rock-shapes)]
+           [rock-number 0]
+           #:result top-of-rocks)
+          (#:break (> rock-number 2022) [gust (in-cycle gusts)])
+  (cond
+    [(not falling-rock)
+     (values cave
+             (~> (first rock-cycle) (place-new-rock top-of-rocks) (gust-move gust cave))
+             top-of-rocks
+             (rest rock-cycle)
+             (add1 rock-number))]))