day09

2016/day09-test.rkt

@@ -0,0 +1,2 @@
+#lang aoc-racket/2016/day09
+(27x12)(20x12)(13x14)(7x10)(1x12)A

2016/day09.rkt

@@ -0,0 +1,55 @@
+#lang br/quicklang
+(require racket/string)
+
+(module+ reader (provide read-syntax))
+(define (read-syntax path port)
+  (strip-bindings
+   #`(module mod "day09.rkt"
+       #,@(for/list ([str (in-lines port)]
+                     #:when (not (equal? str "")))
+            `(solve ,(string-trim str))))))
+
+(provide solve #%module-begin)
+(define (solve str)
+  (for-each displayln
+            (let (#;[decomp-result (decomp str)]
+                  [decomp2-result (decomp2 str)])
+              (list #;decomp-result #;(string-length decomp-result)
+                    decomp2-result))))
+
+(define (decomp str)
+  (define p (open-input-string str))
+  (define decompressor-pat "\\((\\d+)x(\\d+)\\)")
+  (let loop ([bstrs empty][decompressor #f])
+    (define cur-pat (if decompressor
+                        (pregexp (format ".{~a}" (car decompressor)))
+                        (pregexp (format "~a|." decompressor-pat))))
+    (define match (let ([result (regexp-try-match cur-pat p)])
+                    (and result (car result))))
+    (cond
+      [(not match) (string-append* (map ~a (reverse (flatten bstrs))))]
+      [decompressor (loop (cons (make-list (cadr decompressor) match) bstrs) #f)]
+      [else
+       (define maybe-decompressor (regexp-match (pregexp decompressor-pat) match))
+       (if maybe-decompressor
+           (loop bstrs (map (compose1 string->number ~a) (cdr maybe-decompressor)))
+           (loop (cons match bstrs) #f))])))
+
+(define (decomp2 str)
+  (define p (open-input-string str))
+  (define decompressor-pat "\\((\\d+)x(\\d+)\\)")
+  (let loop ([sum 0][decompressor #f])
+    (define cur-pat (if decompressor
+                        (pregexp (format ".{~a}" (car decompressor)))
+                        (pregexp (format "~a|." decompressor-pat))))
+    (define match (let ([result (regexp-try-match cur-pat p)])
+                    (and result (car result))))
+    (cond
+      [(not match) sum]
+      [decompressor (loop (+ sum (* (cadr decompressor) (decomp2 (~a match)))) #f)]
+      [else
+       (define maybe-decompressor (regexp-match (pregexp decompressor-pat) match))
+       (if maybe-decompressor
+           (loop sum (map (compose1 string->number ~a) (cdr maybe-decompressor)))
+           (loop (+ sum (string-length (~a match))) #f))])))
+