refactor advent of code 2023 day 02 from c to racket

1 files changed, 63 insertions, 0 deletions

diff --git a/advent-of-code/2023/02/1.rkt b/advent-of-code/2023/02/1.rkt
new file mode 100644
index 0000000..4382a66
--- /dev/null
+++ b/advent-of-code/2023/02/1.rkt
@@ -0,0 +1,63 @@
+#lang racket
+
+(define fp (open-input-file "input"))
+
+(define (get-lines fp)
+  (let loop ((lines '()))
+    (define l (read-line fp))
+    (if (eof-object? l)
+      (reverse lines)
+      (loop (cons l lines)))))
+
+(define lines (get-lines fp))
+
+(define (extract-game line)
+  (define game-str (cadr (string-split line ":")))
+  (define sets-str (string-split game-str ";"))
+  (set! sets-str (map string-trim sets-str))
+  (map extract-set sets-str))
+
+(define (extract-set str)
+  (define r 0)
+  (define g 0)
+  (define b 0)
+  (define balls (string-split str ","))
+  (set! balls
+    (map (lambda (s)
+           (define pair (map string-trim (string-split s " ")))
+           (list (string->number (car pair)) (cadr pair)))
+         balls))
+  (let loop ((balls balls))
+    (if (null? balls)
+      '()
+      (let ()
+        (define ball (car balls))
+        (define number (car ball))
+        (define color (cadr ball))
+        (cond ((string=? "red" color) (set! r number))
+              ((string=? "green" color) (set! g number))
+              ((string=? "blue" color) (set! b number)))
+        (loop (cdr balls)))))
+  (list r g b))
+
+(define (possible? game)
+  (if (null? game)
+    #t
+    (let ()
+      (define head (car game))
+      (if (or (> (car head) 12)    ; r
+              (> (cadr head) 13)   ; g
+              (> (caddr head) 14)) ; b
+        #f
+        (possible? (cdr game))))))
+
+(define (enumerate lst)
+  (let loop ((i 1) (ret '()) (remain lst))
+    (if (null? remain)
+      (reverse ret)
+      (loop (+ 1 i) (cons (list (car remain) i) ret) (cdr remain)))))
+
+(apply + (map cadr
+              (filter (lambda (game)
+                        (possible? (car game)))
+                      (enumerate (map extract-game lines)))))