day 21: revised clean solution

21.rkt

@@ -4,78 +4,43 @@
 
 ;; solution for day 21
 
+(struct line [is as] #:transparent)
+(struct data [lines all-is all-as tainted] #:transparent)
+
 (define (part1 input)
-  ; (define edges
-  ;   (for/fold ([edges '()]) ([line (in-list input)])
-  ;     (match-define (cons ingreds allergs) line)
-  ;     (append edges (for*/list ([i (in-list ingreds)] [a (in-list allergs)])
-  ;                     (list i a)))))
-  ; (define G (undirected-graph edges))
-  ;(define matching (maximum-bipartite-matching G))
-  (define all-ingreds (for/fold ([all (set)]) ([line (in-list input)])
-                        (set-union all (list->set (car line)))))
-  (define all-allergs (for/fold ([all (set)]) ([line (in-list input)])
-                        (set-union all (list->set (cdr line)))))
-  (define tainted (mutable-set))
-  (for ([allerg (in-set all-allergs)])
-    (define necessary (for/fold ([necessary all-ingreds]) ([line (in-list input)] #:when (member allerg (cdr line)))
-                        (set-intersect necessary (list->set (car line)))))
-    (set-union! tainted necessary))
-  (define untainted (set-subtract all-ingreds tainted))
-  (for*/sum ([line (in-list input)] [ingred (in-list (car line))])
-    (if (set-member? untainted ingred) 1 0)))
+  (match-define (data lines all-is all-as tainted) input)
+  (define untainted (set-subtract all-is (apply set-union (hash-values tainted))))
+  (for*/sum ([l (in-list lines)] [i (in-set (line-is l))] #:when (set-member? untainted i))
+    1))
 
 (define (part2 input)
-  (define all-ingreds (for/fold ([all (set)]) ([line (in-list input)])
-                        (set-union all (list->set (car line)))))
-  (define all-allergs (for/fold ([all (set)]) ([line (in-list input)])
-                        (set-union all (list->set (cdr line)))))
-  (define tainted (mutable-set))
-  (for ([allerg (in-set all-allergs)])
-    (define necessary (for/fold ([necessary all-ingreds]) ([line (in-list input)] #:when (member allerg (cdr line)))
-                        (set-intersect necessary (list->set (car line)))))
-    (set-union! tainted necessary))
-
-  (define tainthash (for/hash ([a (in-set all-allergs)])
-                      (values a (for/fold ([is all-ingreds]) ([line (in-list input)] #:when (member a (cdr line)))
-                                  (set-intersect is (list->set (filter #{set-member? tainted %} (car line))))))))
-  (define edges (for*/list ([k (in-list (hash-keys tainthash))]
-                            [v (in-set (hash-ref tainthash k))])
+  (match-define (data lines all-is all-as tainted) input)
+  (define edges
+    (for*/list ([(k v*) (in-hash tainted)] [v (in-set v*)])
       (list k v)))
-
-  (pretty-write edges)
   (define G (undirected-graph edges))
   (define matching (maximum-bipartite-matching G))
-  (displayln matching)
-  (define mhash (for/hash ([item (in-list matching)]) (values (first item) (second item))))
-  (displayln mhash)
-  (define by-allergs (sort (hash-keys mhash) string<?))
+
   (string-join
-    (for/list ([key (in-list by-allergs)])
-      (hash-ref mhash key))
-    ",")
-
-  )
-
-; (part2 (parse "test"))
-; (error "not shonks")
+    (for/list ([val (in-list (sort matching #{string<? (first %1) (first %2)}))])
+      (second val))
+    ","))
 
 ;; parse input file
 (define (parse fname)
-  (define lines (file->lines fname))
-  (for/list ([line (in-list lines)])
-    (match line
-      [(pregexp #px"^([^\\(]+) \\(contains ([^\\)]+)\\)+"
-                (list _ p1 p2))
-       (define ingredients (string-split p1 " "))
-       (define allergens (string-split p2 ", "))
-       (cons ingredients allergens)]
-      [_ (error "not shonks" line)])))
+  (define-values [lines all-is all-as]
+    (for/fold ([lines '()] [all-is (set)] [all-as (set)]) ([l (in-list (file->lines fname))])
+      (match-define (list _ p1 p2) (regexp-match #px"^([^\\(]+) \\(contains ([^\\)]+)\\)+" l))
+      (define is (list->set (string-split p1 " ")))
+      (define as (list->set (string-split p2 ", ")))
+      (values (cons (line is as) lines) (set-union all-is is) (set-union all-as as))))
 
-(module+ test
-  (require rackunit)
-  ;; tests here
-  (displayln "no tests :("))
+  (define tainted
+    (for/hash ([a (in-set all-as)])
+      (values a (for/fold ([necessary all-is]) ([l (in-list lines)]
+                                                #:when (set-member? (line-as l) a))
+                  (set-intersect (line-is l) necessary)))))
+  (data lines all-is all-as tainted))
 
 (module+ main
   (define input (parse "inputs/21"))