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82 lines
2.4 KiB
82 lines
2.4 KiB
#+title: Solution to p8 |
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#+begin_src emacs-lisp :results none |
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(with-temp-buffer |
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(insert-file-contents "input") |
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(advent/replace-multiple-regex-buffer |
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'(("," . " ") |
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("^" . "(") |
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("$" . ")"))) |
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(goto-char (point-min)) |
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(insert "(setq data '(") |
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(goto-char (point-max)) |
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(insert "))") |
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(eval-buffer)) |
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#+end_src |
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First of all, sort the pair of boxes by means of their distance. |
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#+begin_src emacs-lisp :results none |
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(defun square (x) |
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(* x x)) |
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(defun distance-squared (el) |
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(let ((a (car el)) |
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(b (cdr el))) |
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(+ (square (- (car a) (car b))) |
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(square (- (cadr a) (cadr b))) |
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(square (- (caddr a) (caddr b)))))) |
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(defun symmetric-pairs (list) |
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(apply #'append (--map-indexed (-map (lambda (other) (cons it other)) |
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(-drop (1+ it-index) list)) |
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list))) |
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(setq sorted-pairs |
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(--sort (< (distance-squared it) (distance-squared other)) (symmetric-pairs data))) |
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#+end_src |
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This is for part 1 |
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#+begin_src emacs-lisp |
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(defun insert-pair (circuits el) |
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(let* ((list (list (car el) (cdr el))) |
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(ind-a (--find-index (-contains-p it (car el)) circuits)) |
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(ind-b (--find-index (-contains-p it (cdr el)) circuits))) |
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(cond |
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((not (or ind-a ind-b)) (cons list circuits)) |
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((and ind-a ind-b (not (eq ind-a ind-b))) |
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(-remove-at ind-b (-replace-at ind-a |
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(-union (nth ind-a circuits) |
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(nth ind-b circuits)) |
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circuits))) |
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(t (-replace-at (or ind-a ind-b) |
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(-union list (nth (or ind-a ind-b) circuits)) |
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circuits))))) |
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(setq circuits |
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(-reduce-from #'insert-pair nil (-take 1000 sorted-pairs))) |
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(-product (-take 3 (-sort '> (-map #'length circuits)))) |
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#+end_src |
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#+RESULTS: |
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: 81536 |
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This is for part 2. Will it explode? |
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#+begin_src emacs-lisp |
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(let ((sorted-pairs sorted-pairs) |
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(circuits nil) |
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(last-junction nil)) |
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(while (or (> 1 (length circuits)) |
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(> (length data) (length (apply 'append circuits)))) |
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(setq last-junction (pop sorted-pairs) |
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circuits (insert-pair circuits last-junction))) |
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last-junction |
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;(* (caar last-junction) (cadr last-junction)) |
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) |
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#+end_src |
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#+RESULTS: |
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| (84981 85692 23226) | 91121 | 84159 | 34357 |
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