day 19: the import solution version

19.rkt

@@ -3,103 +3,47 @@
 (require "scripts/aoc.rkt")
 
 ;; solution for day 19
-(struct basic [value] #:transparent)
-(struct alias [target] #:transparent)
-(struct concat [left right] #:transparent)
-(struct orr [left right] #:transparent)
 
-(define (rule-match? rules line [rulenum 0])
-  (define rule (hash-ref rules rulenum))
-  (cond
-    [(basic? rule)
-     (cond
-       [(zero? (length line)) (values #f '())]
-       [(char=? (basic-value rule) (first line)) (values #t (list (rest line)))]
-       [else (values #f '())])]
-    [(alias? rule) (rule-match? rules line (alias-target rule))]
-    [(orr? rule)
-     (define-values [p1 p2] (rule-match? rules line (orr-left rule)))
-     (define-values [q1 q2] (rule-match? rules line (orr-right rule)))
-     (cond
-       [(and p1 q1) (values #t (append p2 q2))]
-       [p1 (values #t p2)]
-       [q1 (values #t q2)]
-       [else (values #f '())])]
-    [(concat? rule)
-     (define-values [p1 p2] (rule-match? rules line (concat-left rule)))
-     (cond
-       [p1
-        (define rst '())
-        (define m? #f)
-        (for ([sub (in-list p2)])
-          (define-values [q1 q2] (rule-match? rules sub (concat-right rule)))
-          (when q1
-            (set! rst (append rst q2))
-            (set! m? #t)))
-        (values m? rst)]
-       [else (values #f '())])]))
+;; MEGA CHEATING
+(define (run-part defs-in lines)
+  ;; add the #lang and the top rule
+  (define defs
+    (string-append "#lang brag\ntop: r0\n"
+                   ;; replace all the rule numbers N with rN otherwise brag has issues
+                   (regexp-replace* #px"\\d+" defs-in (lambda (x) (format "r~a" x)))))
+  ;; create a temporary file with the parser contents for brag
+  (define file (make-temporary-file))
+  (call-with-output-file file (lambda (out) (write-string defs out)) #:exists 'truncate)
+  ;; require it
+  (define parse (dynamic-require file 'parse))
+  ;; yeeeeet
+  (for/sum ([line (in-list lines)])
+    (with-handlers ([exn:fail? (lambda (_) 0)]) ;; catch parse error and just add 0
+      (parse line)
+      1)))
 
 (define (part1 input)
   (match-define (cons rules lines) input)
-  (for/sum ([line (in-list lines)])
-    (define-values [m? r] (rule-match? rules (string->list line)))
-    ; (printf "~a: ~a\n" line m?)
-    (if (and m? (member '() r)) 1 0)))
+  (run-part rules lines))
 
 (define (part2 input)
   (match-define (cons rules lines) input)
-  (define c2 (gensym))
-  (hash-set! rules 8 (orr 42 c2))
-  (hash-set! rules c2 (concat 42 8))
-
-  (define c3 (gensym))
-  (define c4 (gensym))
-  (define c5 (gensym))
-  (hash-set! rules 11 (orr c3 c4))
-  (hash-set! rules c3 (concat 42 31))
-  (hash-set! rules c4 (concat 42 c5))
-  (hash-set! rules c5 (concat 11 31))
-
-  (for/sum ([line (in-list lines)])
-    (define-values [m? r] (rule-match? rules (string->list line)))
-    ; (printf "~a: ~a\n" line m?)
-    (if (and m? (member '() r)) 1 0)))
+  ;; replace the lines for 8 and 11 with their replacements, then run it
+  (run-part
+    (string-join
+      (for/list ([line (in-list (string-split rules "\n"))])
+        (match line
+          [(pregexp #px"^8:") "8: 42 | 42 8"]
+          [(pregexp #px"^11:") "11: 42 31 | 42 11 31"]
+          [x x]))
+      "\n")
+    lines))
 
 ;; parse input file
 (define (parse fname)
-  (define sn string->number)
-  (match-define (list rules-lines input) (string-split (file->string fname) "\n\n"))
-  (define rules (make-hash))
-  (for ([line (in-list (string-split rules-lines "\n"))])
-    (match line
-      [(pregexp #px"^(\\d+): \"(.)\"$" (list _ num char))
-       (hash-set! rules (sn num) (basic (string-ref char 0)))]
-      [(pregexp #px"^(\\d+): (\\d+)$" (list _ num alias-to))
-       (hash-set! rules (sn num) (alias (sn alias-to)))]
-      [(pregexp #px"^(\\d+): (\\d+) (\\d+)$" (list _ num l r))
-       (hash-set! rules (sn num) (concat (sn l) (sn r)))]
-      [(pregexp #px"^(\\d+): (\\d+) (\\d+) (\\d+)$" (list _ num l r r2))
-       (define tmp (gensym))
-       (hash-set! rules (sn num) (concat (sn l) tmp))
-       (hash-set! rules tmp (concat (sn r) (sn r2)))]
-      [(pregexp #px"^(\\d+): (\\d+) \\| (\\d+)$" (list _ num l r))
-       (hash-set! rules (sn num) (orr (sn l) (sn r)))]
-      [(pregexp #px"^(\\d+): (\\d+) (\\d+) \\| (\\d+) (\\d+)$" (list _ num l1 l2 r1 r2))
-       (define ls (gensym))
-       (define rs (gensym))
-       (hash-set! rules ls (concat (sn l1) (sn l2)))
-       (hash-set! rules rs (concat (sn r1) (sn r2)))
-       (hash-set! rules (sn num) (orr ls rs))]
-      [_ (error "not shonks" line)]))
+  (match-define (list rules input) (string-split (file->string fname) "\n\n"))
   (cons rules (string-split input "\n")))
 
-
-
-(module+ test
-  (require rackunit)
-  ;; tests here
-  (displayln "no tests :("))
-
 (module+ main
   (define input (parse "inputs/19"))
   (answer 19 1 (time (part1 input)))