2016 day 1 part 1

1 files changed, 38 insertions, 0 deletions

diff --git a/aoc2016/day-01/day-01.rkt b/aoc2016/day-01/day-01.rkt
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+++ b/aoc2016/day-01/day-01.rkt
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+#lang racket
+
+(require advent-of-code
+         threading)
+
+(struct posn (x y) #:transparent)
+(struct dir (x y) #:transparent)
+
+(define/match (left _d)
+  [((dir 0 1)) (dir -1 0)]
+  [((dir -1 0)) (dir 0 -1)]
+  [((dir 0 -1)) (dir 1 0)]
+  [((dir 1 0)) (dir 0 1)])
+
+(define/match (right _d)
+  [((dir 0 1)) (dir 1 0)]
+  [((dir 1 0)) (dir 0 -1)]
+  [((dir 0 -1)) (dir -1 0)]
+  [((dir -1 0)) (dir 0 1)])
+
+(define/match (go _from _d _dist)
+  [((posn x y) (dir dx dy) dist) (posn (+ x (* dx dist)) (+ y (* dy dist)))])
+
+(define input (~> (fetch-aoc-input (find-session) 2016 1 #:cache #true) string-trim (string-split ", ")))
+
+;; part 1
+(for/fold ([p (posn 0 0)]
+           [d (dir 0 1)]
+           #:result (+ (abs (posn-x p)) (abs (posn-y p))))
+          ([instruction (in-list input)])
+  (displayln (~a p " " d))
+  (match instruction
+    [(regexp #rx"L(.*)" (list _ n)) (values (go p (left d) (string->number n))
+                                            (left d))]
+    [(regexp #rx"R(.*)" (list _ n)) (values (go p (right d) (string->number n))
+                                            (right d))]))
+
+;; part 2