day 3

1 files changed, 46 insertions, 0 deletions

diff --git a/03/2.scm b/03/2.scm
new file mode 100644
index 0000000..96eda29
--- /dev/null
+++ b/03/2.scm
@@ -0,0 +1,46 @@
+(import (chicken io))
+(import regex)
+(import matchable)
+(import (chicken string))
+
+(define in-str
+  (with-input-from-file "input" read-string))
+
+;; (display in-str)
+(define re
+  "mul\\([0-9]+,[0-9]+\\)|do\\(\\)|don't\\(\\)")
+
+(define matched
+  (let loop ((start 0) (result '()))
+    (define search-ret (string-search re in-str start))
+    (if (not search-ret)
+        (reverse result)
+        (loop (cadar (string-search-positions re in-str start))
+              (cons (car search-ret) result)))))
+
+(define (extract-numbers str)
+  (define nums-str (substring str 4 (- (string-length str) 1)))
+  (map string->number (string-split nums-str ",")))
+
+(define (process-instr str)
+  (cond ((string-search "mul" str) (extract-numbers str))
+        ((string-search "do\\(" str) 'do)
+        (else 'dont)))
+
+(define (calculate str)
+  (define vals (extract-numbers str))
+  (* (car vals) (cadr vals)))
+
+(define sum
+  (let loop ((is-do #t)
+             (lst (map process-instr matched))
+             (ret 0))
+    (match lst
+      (() ret)
+      (('do . r) (loop #t r ret))
+      (('dont . r) (loop #f r ret))
+      (((a b) . r) (if is-do
+                  (loop is-do r (+ ret (* a b)))
+                  (loop is-do r ret))))))
+
+(display sum)