Initial commit

2018/day08/day08.ss

@@ -0,0 +1,46 @@
+(import :gerbil/gambit/ports)
+(import :std/pregexp)
+(import :std/srfi/1)
+(import :std/iter)
+
+(export main)
+
+(defstruct node (children metadata))
+
+(def (parse-node lst)
+  (match lst
+    ([m n . rest]
+     (let*-values (((children rest) (parse-children rest m))
+		   ((metadata rest) (split-at rest n)))
+       (values (make-node children metadata) rest)))))
+
+(def (parse-children lst m)
+  (if (= m 0)
+    (values [] lst)
+    (let*-values (((children rest) (parse-children lst (1- m)))
+		  ((child rest) (parse-node rest)))
+      (values (cons child children) rest))))
+
+(def (dfs node f g)
+  (if (null? (node-children node))
+    (f (node-metadata node))
+    (g (cons (f (node-metadata node))
+	     (map (lambda (n) (dfs n f g)) (node-children node))))))
+
+(def (node-value node)
+  (if (null? (node-children node))
+    (apply + (node-metadata node))
+    (apply + (for/collect ((m (node-metadata node)))
+	       (if (and (> m 0) (< (1- m) (length (node-children node))))
+		 (node-value (list-ref (reverse (node-children node)) (1- m)))
+		 0)))))
+
+(def (main . args)
+  (def example-lst [2 3 0 3 10 11 12 1 1 0 1 99 2 1 1 2])
+  (define-values (example _) (parse-node example-lst))
+  (displayln (dfs example (lambda (m) (apply + m)) (lambda (m) (apply + m))))
+  (displayln (node-value example))
+  (def lst (map string->number (pregexp-split " " (call-with-input-file "input.txt" read-line))))
+  (define-values (tree _) (parse-node lst))
+  (displayln (dfs tree (lambda (m) (apply + m)) (lambda (m) (apply + m))))
+  (displayln (node-value tree)))