2016 d16 p2

2016/day16/lang.rkt

@@ -10,7 +10,7 @@
 
 (define-macro (mb SIZE INIT)
   #'(#%module-begin
-     (display (list->string (checksum (fill-disk (string->list INIT) (string->number SIZE)))))))
+     (time (display (list->string (checksum (fill-disk (string->list INIT) (string->number SIZE))))))))
 
 (define (dragonize cs)
   (append cs '(#\0)
@@ -25,14 +25,15 @@
         (take cs size)
         (loop (dragonize cs)))))
 
-(require sugar/list)
 (define (checksum cs)
-  (let loop ([cs cs])
+  (define cvec (list->vector cs))
-    (if (odd? (length cs))
+  (let loop ([cvec cvec])
-        cs
+    (match (vector-length cvec)
-        (loop
+      [(? odd?) (vector->list cvec)]
-         (for/list ([match (in-list (slice-at cs 2))])
+      [len
-           (if (member match '((#\0 #\0) (#\1 #\1)))
+       (define newvec (make-vector (/ len 2) #\0))
-               #\1
+       (for ([idx (in-range 0 (vector-length cvec) 2)]
-               #\0))))))
+             #:when (char=? (vector-ref cvec idx) (vector-ref cvec (add1 idx))))
+            (vector-set! newvec (/ idx 2) #\1))
+       (loop newvec)])))