advent-of-code-2024

My solutions to AoC 2024
Log | Files | Refs

day-3.lisp (1027B)

      1 (defpackage #:aoc/day-3
      2   (:use #:cl #:aoc/utils)
      3   (:export #:day-3))
      4 (in-package #:aoc/day-3)
      5 
      6 (defun try-read-number (stream)
      7   (loop while (digit-char-p (peek-char nil stream))
      8         collect (read-char stream) into bag
      9         finally (return (if bag
     10                             (parse-integer (coerce bag 'string))
     11                             nil))))
     12 
     13 (define-parser day-3-parser (stream)
     14     ((mul-enabled t)
     15      (num-1 0)
     16      (num-2 0)
     17      (task-1 0)
     18      (task-2 0))
     19   (#\d #\o #\( #\) (setf mul-enabled t))
     20   (#\d #\o #\n #\' #\t #\( #\) (setf mul-enabled nil))
     21   (#\m #\u #\l #\(
     22        (setf num-1 (try-read-number stream))
     23        #\,
     24        (setf num-2 (try-read-number stream))
     25        #\)
     26        (let ((result (* num-1 num-2)))
     27          (incf task-1 result)
     28          (when mul-enabled
     29            (incf task-2 result)))))
     30 
     31 (defun day-3 (input)
     32   (multiple-value-bind (mul-enabled num-1 num-2 task-1 task-2)
     33       (day-3-parser input)
     34     (declare (ignore mul-enabled num-1 num-2))
     35     (values task-1 task-2)))