Day 04: Use entire file instead of splitting input beforehand.

input/04-example.txt

@@ -1,17 +0,0 @@
-22 13 17 11  0
- 8  2 23  4 24
-21  9 14 16  7
- 6 10  3 18  5
- 1 12 20 15 19
-
- 3 15  0  2 22
- 9 18 13 17  5
-19  8  7 25 23
-20 11 10 24  4
-14 21 16 12  6
-
-14 21 17 24  4
-10 16 15  9 19
-18  8 23 26 20
-22 11 13  6  5
- 2  0 12  3  7

input/04-order.txt

@@ -1 +0,0 @@
-6,69,28,50,36,84,49,13,48,90,1,33,71,0,94,59,53,58,60,96,30,34,29,91,11,41,77,95,17,80,85,93,7,9,74,89,18,25,26,8,87,38,68,5,12,43,27,46,62,73,16,55,22,4,65,76,54,52,83,10,21,67,15,47,45,40,35,66,79,51,75,39,64,24,37,72,3,44,82,32,78,63,57,2,86,31,19,92,14,97,20,56,88,81,70,61,42,99,23,98

input/04.txt

@@ -1,3 +1,5 @@
+6,69,28,50,36,84,49,13,48,90,1,33,71,0,94,59,53,58,60,96,30,34,29,91,11,41,77,95,17,80,85,93,7,9,74,89,18,25,26,8,87,38,68,5,12,43,27,46,62,73,16,55,22,4,65,76,54,52,83,10,21,67,15,47,45,40,35,66,79,51,75,39,64,24,37,72,3,44,82,32,78,63,57,2,86,31,19,92,14,97,20,56,88,81,70,61,42,99,23,98
+
 22 59  7 10  6
 33 36 96 55 23
 13 85 18 29 28

src/04.rkt

@@ -2,21 +2,22 @@
 
 (require "../lib.rkt")
 
+(define input (problem-input-grouped 4))
+
 (define order
-  (~> (problem-input 4 "-order")
+  (string-csv (first input) string->number))
-      first
-      (string-split ",")
-      (map string->number _)))
 
 (define boards
-  (~> (problem-input-grouped 4)
+  (for/list ([board (rest input)])
-      (map string-lines _)
+    (for/list ([row (string-lines board)])
-      (map #{map string-words %} _)
+      (for/list ([cell (string-words row)])
-      (map #{map #{map string->number %} %} _)))
+        (string->number cell)))))
 
 (define (winner? board)
   (or (ormap #{andmap false? %} board)
-      (ormap #{andmap (λ (row) (false? (list-ref row %))) board} (range 5))))
+      ;; IMO this is the more aesthetic but less efficient version
+      #;(ormap #{andmap false? %} (transpose board))
+      (ormap #{not (ormap (∂r list-ref %) board)} (range (length board)))))
 
 (define (blot board n)
   (for/list ([row board])
@@ -27,36 +28,26 @@
 (define (score board)
   (sum (filter number? (apply append board))))
 
-(define-values (winner n)
+(define part1
   (for/fold ([boards boards]
              [winner #f]
              [winning #f]
-             #:result (values winner winning))
+             #:result (* (score winner) winning))
             ([n order]
              #:break winner)
     (define boards*
-      (for/list ([board boards])
+      (map #{blot % n} boards))
-        (blot board n)))
+    (values boards* (findf winner? boards*) n)))
-    (define winner
-      (findf winner? boards*))
-    (values boards* winner n)))
-
-(define-values (loser m)
-  (for/fold ([boards boards]
-             [losing #f]
-             #:result (values (first boards) losing))
-            ([m order]
-             #:break (and (singleton? boards)
-                          (winner? (first boards))))
-    (define boards*
-      (for/list ([board (filter (∘ not winner?) boards)])
-        (blot board m)))
-    (values boards* m)))
-
-(define part1
-  (* n (score winner)))
 
 (define part2
-  (* m (score loser)))
+  (for/fold ([boards boards]
+             [loser #f]
+             [losing #f]
+             #:result (* (score loser) losing))
+            ([m order]
+             #:break (empty? boards))
+    (define boards*
+      (map #{blot % m} boards))
+    (values (filter (∘ not winner?) boards*) (first boards*) m)))
 
 (show-solution part1 part2)