Day 4: Scratchcards

.dir-locals.el

@@ -1 +1 @@
-((scheme-mode . ((geiser-scheme . 'chicken))))
+((nil . ((geiser-scheme-implementation . 'chicken))))

chicken.org

@@ -1,7 +1,7 @@
 # -*- geiser-scheme-implementation: chicken -*-
 #+TITLE: Advent Of Code with Chicken Scheme
 #+AUTHOR: Daniel Ziltener
-#+PROPERTY: header-args:scheme :session *chicken*
+#+PROPERTY: header-args:scheme :session *chicken* :comments both
 
 * Prelude
 
@@ -2122,9 +2122,11 @@ card's id (it might be useful in part 2), the winning numbers, and the card's nu
 
 Since it could potentially be relevant, I also add a slot for the matches.
 
+/UPDATE: I also added a slot for the number of copies of the scratch card - relevant for part 2./
+
 #+NAME: day4-part1-scratchcard
 #+begin_src scheme :tangle day4.scm
-(define-record scratchcard id winning-numbers card-numbers match-numbers)
+(define-record scratchcard id winning-numbers card-numbers match-numbers copies)
 #+end_src
 
 **** Parsing The Input
@@ -2164,7 +2166,7 @@ statement.
                (string-split (irregex-match-substring match 'winning-numbers-str)))
           (map string->number
                (string-split (irregex-match-substring match 'card-numbers-str)))
-          '())
+          '() 1)
          seed))
       '() input-str))
 #+end_src
@@ -2179,13 +2181,10 @@ name ends with an ~!~.
 #+NAME: day4-part1-card-matching
 #+begin_src scheme :tangle day4.scm
   (define (calc-card-matches card)
-    (print "calculating matches for " (scratchcard-id card))
     (let ((winning-nums (scratchcard-winning-numbers card))
           (card-nums (scratchcard-card-numbers card)))
       (for-each (lambda (card-num)
-                  (print "\tCard number: " card-num)
                   (when (foldl (lambda (matches? winning-num)
-                                 (print "\t\tWinning number: " winning-num)
                                  (or matches?
                                      (= card-num winning-num)))
                                #f winning-nums)
@@ -2292,7 +2291,74 @@ the original set of scratchcards, *how many total scratchcards do you end up wit
 
 *** Puzzle Solution
 
-WIP...
+#+NAME: day4-part2-card-alist
+#+begin_src scheme :tangle day4.scm
+  (define (card-alist cards)
+    (foldl (lambda (alist card)
+             (calc-card-matches card)
+             (alist-update (scratchcard-id card)
+                           card
+                           alist))
+           '() (reverse cards)))
+#+end_src
+
+#+NAME: day4-part2-gen-copies
+#+begin_src scheme :tangle day4.scm
+  (define (generate-copies cardlist #!optional (index 1))
+    (let ((index-card (alist-ref index cardlist)))
+      (if index-card
+          (let* ((matches (scratchcard-match-numbers index-card))
+                 (copies  (scratchcard-copies index-card))
+                 (copy-indexes (foldl (lambda (indexes match)
+                                        (cons (+ 1 index (length indexes))
+                                              indexes))
+                                      (list) matches)))
+            (for-each (lambda (card-id)
+                        (let ((target-card (alist-ref card-id cardlist)))
+                          (scratchcard-copies-set!
+                           target-card
+                           (+ (scratchcard-copies target-card) copies))))
+                      copy-indexes)
+            (generate-copies
+             cardlist
+             (+ index 1)))
+        cardlist)))
+#+end_src
+
+#+NAME: day4-part2-count-scratchcards
+#+begin_src scheme :tangle day4.scm
+  (define (count-scratchcards cardlist)
+    (foldl + 0 (map (compose scratchcard-copies cdr) cardlist)))
+#+end_src
+
+#+NAME: day4-part2-calc
+#+begin_src scheme
+  (let ((cardlist (card-alist (input->cards input))))
+    (generate-copies cardlist)
+    (count-scratchcards cardlist))
+#+end_src
+
+#+NAME: day4-part2-calc-full
+#+begin_src scheme :var input=day4-input :noweb yes :exports results
+  (import (chicken string)
+          (chicken irregex))
+  <<day4-part1-scratchcard>>
+  <<day4-part1-card-irregex>>
+  <<day4-part1-card-fold>>
+  <<day4-part1-card-matching>>
+  <<day4-part2-card-alist>>
+  <<day4-part2-gen-copies>>
+  <<day4-part2-count-scratchcards>>
+  <<day4-part2-calc>>
+#+end_src
+
+#+RESULTS: day4-part2-calc-full
+: 5923918
+
+#+begin_src scheme :noweb yes :exports none :tangle day4.scm
+  (define (calc-part-2)
+    <<day4-part2-calc>>)
+#+end_src
 
 ** Puzzle Input