Attempt 2, day 2, a

aoc.org

@@ -1360,3 +1360,47 @@ How many passwords are valid according to their policies?
 Hmmm, I'm too high.  Besides, this has a lot of issues with cleaning up the input; I'll keep trying tomorrow.  But for now, to bed!
 
 Okay, I lied.  I tried 740 as well -- since the last row was giving me such trouble I thought I could've got a false positive there.  Oh well.
+**** Attempt 2
+
+I think I've formatted the regex wrong; I also need to throw an error if there are too /many/ of the character!  So the regex for =2-7 b= should look more like ... =^[^b]*b.*b.*b?.*b?.*[^b]*$=
+
+#+begin_src emacs-lisp :var input=input-2
+  (defun build-pw-regex (spec)
+    (let* ((thing (split-string spec "[- ]"))
+           (min (string-to-number (or (car thing) "0")))
+           (max (string-to-number (or (cadr thing) "0")))
+           (chr (caddr thing))
+           (regex-begin (concat "^[^" chr "]*"))
+           (regex-end (concat "[^" chr "]*$"))
+           (min-regex (concat chr ".*"))
+           (max-regex (concat chr "?.*"))
+           (min-full-regex "")
+           (max-full-regex ""))
+      (dotimes (n min min-full-regex)
+        (setq min-full-regex (concat min-full-regex min-regex)))
+      (dotimes (x (- max min) max-full-regex)
+        (setq max-full-regex (concat max-full-regex max-regex)))
+      (concat regex-begin min-full-regex max-full-regex regex-end)))
+
+  (let* ((strlist (split-string input "\n+"))
+         (alist)
+         (valid-count 0))
+    (dolist (line strlist alist)
+      (let* ((thing (split-string line ": "))
+             (regex (build-pw-regex (car thing))))
+        (setq alist (cons (list regex (cadr thing)) alist))))
+    ;; test the regexen
+    (dolist (a alist valid-count)
+      (message "%s '%s' '%s'"
+               (string-match (or (car a) "") (or (cadr a) ""))
+               (car a) (cadr a))
+      (if (string-match (or (car a) "") (or (cadr a) ""))
+          (setq valid-count (1+ valid-count)))))
+#+end_src
+
+#+RESULTS:
+: 741
+
+Well tits.
+
+Okay, tomorrow (really this time!), I'm going to look for a =count= style function.