1 files changed, 58 insertions, 0 deletions
diff --git a/2024/puzzle-3.lisp b/2024/puzzle-3.lisp
new file mode 100644
index 0000000..cca2f43
--- /dev/null
+++ b/2024/puzzle-3.lisp
@@ -0,0 +1,58 @@
+(load "util.lisp")
+
+(defparameter input (uiop:read-file-string "3-input"))
+
+(defun is-good-mul (str)
+  (let* ((delimiter (search "," str))
+         (end (search ")" str)))
+    (if (or (null delimiter) (null end)
+            (> delimiter end)
+            (not (eq #\( (char str 3))))
+        nil
+        (let* ((first-arg (subseq str 4 delimiter))
+               (second-arg (subseq str (1+ delimiter) end)))
+          (and (every #'digit-char-p first-arg)
+               (every #'digit-char-p second-arg))))))
+
+(defun trim-mul (str)
+  (subseq str 0 (1+ (search ")" str))))
+
+(defun parse-mul (str)
+  (let ((start (search "(" str))
+        (middle (search "," str))
+        (end (search ")" str)))
+    (list (parse-integer (subseq str (1+ start) middle))
+          (parse-integer (subseq str (1+ middle) end)))))
+
+(defun parse-input-muls (line)
+  (let ((possible (search-all "mul" line)))
+    (--> (cdr possible)
+         (append _ (list (length line)))
+         (mapcar (lambda (z1 z2) (cons z1 (subseq line z1 z2))) possible _)
+         (remove-if-not (lambda (x) (is-good-mul (cdr x))) _)
+         (mapcar (lambda (x) (cons (car x) (trim-mul (cdr x)))) _)
+         (mapcar (lambda (x) (cons (car x) (parse-mul (cdr x)))) _))))
+
+(format t "Round 1: ~a~%"
+        (loop for (pos x y) in (parse-input-muls input)
+              sum (* x y)))
+
+(defun parse-input-conds (input)
+  (let ((dos (search-all "do()" input))
+        (donts (search-all "don't()" input)))
+    (cons
+     '(do . 0)
+     (sort (append (mapcar (lambda (x) (cons 'do x)) dos)
+                   (mapcar (lambda (x) (cons 'dont x)) donts))
+           (lambda (x y) (< (cdr x) (cdr y)))))))
+
+(defun current-cond (pos conds)
+  (caar (last (remove-if (lambda (x) (> (cdr x) pos)) conds))))
+
+(format t "Round 2: ~a~%"
+        (let ((conds (parse-input-conds input))
+              (muls (parse-input-muls input)))
+          (loop for (pos x y) in muls
+                for current = (current-cond pos conds)
+                if (eq current 'do)
+                  sum (* x y))))