day15

2016/day15/input-b.rkt

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+#lang reader "lang.rkt"
+Disc #1 has 5 positions; at time=0, it is at position 2.
+Disc #2 has 13 positions; at time=0, it is at position 7.
+Disc #3 has 17 positions; at time=0, it is at position 10.
+Disc #4 has 3 positions; at time=0, it is at position 2.
+Disc #5 has 19 positions; at time=0, it is at position 9.
+Disc #6 has 7 positions; at time=0, it is at position 0.
+Disc #7 has 11 positions; at time=0, it is at position 0.

2016/day15/input.rkt

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+#lang reader "lang.rkt"
+Disc #1 has 5 positions; at time=0, it is at position 2.
+Disc #2 has 13 positions; at time=0, it is at position 7.
+Disc #3 has 17 positions; at time=0, it is at position 10.
+Disc #4 has 3 positions; at time=0, it is at position 2.
+Disc #5 has 19 positions; at time=0, it is at position 9.
+Disc #6 has 7 positions; at time=0, it is at position 0.

2016/day15/lang.rkt

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+#lang br/quicklang ;; http://adventofcode.com/2016/day/15
+(require openssl/md5)
+(provide read-syntax
+         (rename-out [mb #%module-begin]))
+
+(define (read-syntax path port)
+  (strip-bindings
+   #`(module mod "lang.rkt"
+       #,@(for/list ([line (in-list (string-split (port->string port) "\n"))])
+            `(disc ,@(map string->number (regexp-match* #px"\\d+" line)))))))
+
+(define-macro (mb . DISCS)
+  #'(#%module-begin
+     (solve . DISCS)))
+
+(define-macro (solve . DISCS)
+  (with-pattern ([(DISC# ...) (generate-temporaries #'DISCS)]
+                 [(DISC-SLOTS ...) #'DISCS])
+  #'(for/or ([DISC# (in-cycle DISC-SLOTS)] ...
+             [i (in-naturals)]
+             #:when (= DISC# ...))
+      i)))
+
+(require sugar/list)
+(define-macro (disc TIME-OFFSET SIZE _ START)
+  #'(shift (range SIZE) (modulo (- (+ START TIME-OFFSET)) SIZE) #f #t))
+(provide disc)

2016/day15/test.rkt

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+#lang reader "lang.rkt"
+Disc #1 has 5 positions; at time=0, it is at position 4.
+Disc #2 has 2 positions; at time=0, it is at position 1.