advent-2025/p9/p9.org

Solution to p9

  (with-temp-buffer
    (insert-file-contents "input")
    (advent/replace-multiple-regex-buffer
     '(("," . " ")
       ("^" . "(")
       ("$" . ")")))
    (goto-char (point-min))
    (insert "(setq data '(")
    (goto-char (point-max))
    (insert "))")
    (eval-buffer))

Find max area

  (defun area (el)
    (let ((a (car el))
  	(b (cdr el)))
      (abs (* (- (car a) (car b) -1)
  	    (- (cadr a) (cadr b) -1)))))

  (defun symmetric-pairs (list)
   (apply #'append (--map-indexed (-map (lambda (other) (cons it other))
                         (-drop (1+ it-index) list))
                   list)))

  (-max (-map 'area (symmetric-pairs data)))

4737096935