X-Git-Url: http://git.jkinsey.net/?p=adventofcode2020.git;a=blobdiff_plain;f=src%2Fday02.lisp;fp=src%2Fday02.lisp;h=fb93f03ffa3f4108fc08f2416f8ec0e0da280929;hp=0000000000000000000000000000000000000000;hb=e69214f6f0191786d2e782af3f79831b44bb5178;hpb=63a814f25cb8eff79f8f566f75b7b5fdac549f5f

diff --git a/src/day02.lisp b/src/day02.lisp
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+(in-package #:adventofcode2020)
+
+(defun valid-password-count? (pw-spec)
+  (destructuring-bind (count-str char-str passwd) (split " " pw-spec)
+    (let ((countp (destructuring-bind (count-low count-high) (mapcar #'parse-integer (split "-" count-str))
+                    (lambda (n)
+                      (<= count-low n count-high))))
+          (char-count (loop with char = (char char-str 0)
+                            for c across passwd
+                            summing (if (char= c char) 1 0))))
+      (funcall countp char-count))))
+
+(defun valid-password-index? (pw-spec)
+  (destructuring-bind (index-str char-str passwd) (split " " pw-spec)
+    (let* ((indices (mapcar (compose #'1- #'parse-integer) (split "-" index-str)))
+           (char (char char-str 0))
+           (get-char (lambda (n) (char passwd n))))
+      (->> (mapcar get-char indices)
+           (remove char)
+           (length)
+           (= 1)))))
+
+(day 02 input
+  (let ((pws-and-specs (list-from input)))
+    (part1 (->> pws-and-specs
+                (remove-if-not #'valid-password-count?)
+                (length)))
+    (part2 (->> pws-and-specs
+                (remove-if-not #'valid-password-index?)
+                (length)))))
+
+(def-suite day02)
+(in-suite day02)
+
+(test valid-password-count?
+  (is (equal
+        '(t nil t)
+        (mapcar #'valid-password-count?
+                '("1-3 a: abcde" "1-3 b: cdefg" "2-9 c: ccccccccc")))))
+
+(test valid-password-index?
+  (is (equal 
+        '(t nil nil) 
+        (mapcar #'valid-password-index? 
+                '("1-3 a: abcde" "1-3 b: cdefg" "2-9 c: ccccccccc")))))
+
+(run! 'day02)