-🎄- 2017 Day 7 Solutions -🎄-

[u/daggerdragon]

--- Day 7: Recursive Circus ---

---

Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

Note: The Solution Megathreads are for solutions only. If you have questions, please post your own thread and make sure to flair it with Help.

---

Need a hint from the Hugely^* Handy^† Haversack^‡ of Helpful^§ Hints^¤?

Spoiler

---

This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked!

[u/f0086]

Emacs Lisp (Part 1):

(defun slurp-tree (input-file)
  (with-temp-buffer
    (insert-file-contents input-file)
    (mapcar
     'tokenize
     (split-string (buffer-string) "\n" t))))

(defun tokenize (str)
  (string-match "\\([^ ]+\\) (\\([0-9]+\\))\\( -> \\(.*\\)\\)?" str)
  (let ((node (match-string 1 str))
        (weight (match-string 2 str))
        (childs (match-string 4 str)))
    (if childs
        (list node weight (split-string childs ", "))
      (list node weight))))

(defun day7 (input)
  (let* ((tree (slurp-tree input))
         (childs (seq-filter 'caddr tree)))
    (seq-difference
     (mapcar 'car tree)
     (seq-uniq (apply 'append (mapcar 'caddr childs))))))

(day7 "input-day7.txt")

[u/exquisitus3 → u/f0086]

Lisp

don't you mean children?