advent-2025/p6/p6.org

Solution to p6

First load the data as a list of cons cells (start . end)

  (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))

This is for part 1. Quite straightforward

  (-sum (-map #'eval (apply #'-zip-lists (-rotate 1 data))))

4412382293768

For part 2, we need a different approach. let's transpose the whole buffer

  (with-temp-buffer
    (insert-file-contents "input")
    (goto-char (point-max))
    (beginning-of-line)
    (kill-line)
    (backward-delete-char 1)
    (goto-char (point-min))
    (yank) (insert "\n")
    (advent/replace-multiple-regex-buffer
     '(
       ("^" . "\"")
       ("$" . "\"")
       ))
    (goto-char (point-min))
    (insert "(setq data '(")
    (goto-char (point-max))
    (insert "))")
    (eval-buffer)
    (with-temp-buffer 
      (apply #'insert (--map (apply 'string it) (apply #'-zip-lists (-map #'advent/split-string-into-char-list data))))
      (advent/replace-multiple-regex-buffer
       '(("\\([*+]\\)" . ") (\\1 "))
       )
      (goto-char (point-max))
      (insert ")))")
      (goto-char (point-min))
      (insert "(setq data2 '(")
      (delete-char 1)
      (eval-buffer)))

Then do the math

(-sum (-map #'eval  data2))

7858808482092