day 12

12.rkt

@@ -0,0 +1,66 @@
+#lang curly-fn racket
+
+(require "scripts/aoc.rkt")
+
+;; solution for day 12
+
+;; helper functions here
+
+(define (d->r deg)
+  (* (/ deg 180) pi))
+
+(define (part1 input)
+  (define-values [dir x y]
+  (for/fold ([dir 0] [x 0] [y 0]) ([ins (in-list input)])
+    (match-define (cons ltr num) ins)
+    (match ltr
+      ["N" (values dir x (+ y num))]
+      ["S" (values dir x (- y num))]
+      ["E" (values dir (+ x num) y)]
+      ["W" (values dir (- x num) y)]
+      ["L" (values (+ dir (d->r num)) x y)]
+      ["R" (values (- dir (d->r num))  x y)]
+      ["F" (values dir (+ x (* num (cos dir))) (+ y (* num (sin dir))))])))
+  (inexact->exact (floor (abs (+ x y)))))
+
+(define (part2 input)
+  (define (rot x y d)
+    (values
+      (- (* x (cos d)) (* y (sin d)))
+      (+ (* x (sin d)) (* y (cos d)))))
+  (define-values [sx sy wx wy]
+    (for/fold ([sx 0] [sy 0] [wx 10] [wy 1]) ([ins (in-list input)])
+      (match-define (cons ltr num) ins)
+      (match ltr
+        ["N" (values sx sy wx (+ wy num))]
+        ["S" (values sx sy wx (- wy num))]
+        ["E" (values sx sy (+ wx num) wy)]
+        ["W" (values sx sy (- wx num) wy)]
+        ["L"
+         (define-values [nwx nwy] (rot wx wy (d->r num)))
+         (values sx sy nwx nwy)]
+        ["R"
+         (define-values [nwx nwy] (rot wx wy (d->r (- num))))
+         (values sx sy nwx nwy)]
+        ["F"
+         (values (+ sx (* num wx)) (+ sy (* num wy)) wx wy)])))
+  (inexact->exact (floor (abs (+ (abs sx) (abs sy))))))
+
+(module+ test
+  (require rackunit)
+  ;; tests here
+  (displayln "no tests :("))
+
+(module+ main
+  (define input
+    (for/list ([line (in-list (file->lines "inputs/12"))])
+      (match line
+        [(pregexp #px"^(.)([0-9]+)$" (list _ dir (app string->number num)))
+         (cons dir num)])))
+  ;; part 1
+  (answer 12 1 (part1 input))
+
+  ;; part 2
+  (answer 12 2 (part2 input))
+
+  (displayln "meow"))