d11

2017/d11/main.rkt

@@ -0,0 +1,24 @@
+#lang reader "../aoc-lang.rkt"
+(provide (rename-out [#%mb #%module-begin]))
+
+(define-macro (#%mb (STARS) (HEX ...) ...)
+  #'(#%module-begin
+     ((if (eq? 'STARS '★) one-star two-star) (list HEX ...)) ...))
+
+(define origin '(0 0 0))
+(define ne '(1 0 -1)) (define sw '(-1 0 1))
+(define n '(0 1 -1)) (define s '(0 -1 1))
+(define nw '(-1 1 0)) (define se '(1 -1 0))
+(provide ne sw n s nw se)
+
+(define (dist h1 h2) (/ (apply + (map abs (map - h1 h2))) 2))
+
+(define (one-star hexes) (dist origin (apply map + hexes)))
+
+(define (two-star hexes)
+  (for/fold ([sum origin]
+             [max-dist 0]
+             #:result max-dist)
+            ([h (in-list hexes)])
+    (define this-sum (map + h sum))
+    (values this-sum (max max-dist (dist origin this-sum)))))

2017/d11/test1.rkt

@@ -0,0 +1,5 @@
+#lang reader "main.rkt" ★
+ne,ne,ne ; is 3 steps away.
+ne,ne,sw,sw ; is 0 steps away (back where you started).
+ne,ne,s,s ; is 2 steps away (se,se).
+se,sw,se,sw,sw ; is 3 steps away (s,s,sw).

2017/d11/test2.rkt

@@ -0,0 +1,5 @@
+#lang reader "main.rkt" ★★
+ne,ne,ne ; is 3 steps away.
+ne,ne,sw,sw ; is 0 steps away (back where you started).
+ne,ne,s,s ; is 2 steps away (se,se).
+se,sw,se,sw,sw ; is 3 steps away (s,s,sw).