solve day 12 part 1

1 files changed, 33 insertions, 0 deletions

diff --git a/12/1.rkt b/12/1.rkt
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+++ b/12/1.rkt
@@ -0,0 +1,33 @@
+#lang racket
+
+(require "../lib/utils.rkt")
+
+(define lines
+  (call-with-input-file "input"
+    (λ (fp)
+      (get-lines fp))))
+
+(define (parse-line line)
+  (define line-splited (string-split line))
+  (define arr-list (string->list (car line-splited)))
+  (define conds (map string->number (string-split (cadr line-splited) ",")))
+  (cons arr-list conds))
+
+(define (arr-match? lst conds)
+  (define str (list->string (reverse lst)))
+  (equal? conds (filter (λ (n) (not (= 0 n))) (map string-length (string-split str ".")))))
+
+(define (possible-arr-num instance)
+  (define conds (cdr instance))
+  (define (impl scanned unscanned)
+    (if (null? unscanned)
+      (if (arr-match? scanned conds) 1 0)
+      (let ()
+        (define head (car unscanned))
+        (if (not (char=? head #\?))
+          (impl (cons head scanned) (cdr unscanned))
+          (+ (impl (cons #\. scanned) (cdr unscanned))
+             (impl (cons #\# scanned) (cdr unscanned)))))))
+  (impl '() (car instance)))
+
+(apply + (map possible-arr-num (map parse-line lines)))
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