day 2: cheese

2.rkt

@@ -5,49 +5,23 @@
 ;; solution for day 2
 
 (define (part1 input)
-  (for/sum ([x (in-list input)])
-    (match-define (list x1 x2) x)
-    (+ (match x2
-         ["X" 1]
-         ["Y" 2]
-         ["Z" 3])
-       (match* (x1 x2)
-         [("A" "X") 3]
-         [("A" "Y") 6]
-         [("A" "Z") 0]
-         [("B" "X") 0]
-         [("B" "Y") 3]
-         [("B" "Z") 6]
-         [("C" "X") 6]
-         [("C" "Y") 0]
-         [("C" "Z") 3]))))
-
+  (for/sum ([line (in-list input)])
+    (+ 1 (second line)
+       (~> (- (second line) 2 (first line))
+           (modulo 3)
+           (* 3)))))
 
 (define (part2 input)
-  (for/sum ([x (in-list input)])
-    (match-define (list x1 x2) x)
-    (+ (match x2
-         ["X" 0]
-         ["Y" 3]
-         ["Z" 6])
-       (match* (x1 x2)
-         [("A" "X") 3]
-         [("A" "Y") 1]
-         [("A" "Z") 2]
-         [("B" "X") 1]
-         [("B" "Y") 2]
-         [("B" "Z") 3]
-         [("C" "X") 2]
-         [("C" "Y") 3]
-         [("C" "Z") 1]))))
+  (for/sum ([line (in-list input)])
+    (+ (* (second line) 3)
+       (~> (+ (second line) (first line) 2)
+           (modulo 3)
+           (add1)))))
 
 (define (parse fname)
-  (for/list ([x (in-list (file->lines fname))])
-    (string-split x " ")))
-
-(module+ test
-  (require rackunit)
-  (displayln "no tests :("))
+  (for/list ([line (in-list (file->lines fname))])
+    (map #{hash-ref (hash "A" 0 "B" 1 "C" 2 "X" 0 "Y" 1 "Z" 2) %}
+         (string-split line " "))))
 
 (module+ main
   (define input (parse "inputs/2"))