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112 lines
3.1 KiB
112 lines
3.1 KiB
#+title: Solution to p12 |
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Load the file into a list of lines |
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#+begin_src emacs-lisp |
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(require 'dash) |
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(with-temp-buffer |
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(insert-file-contents "input") |
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(goto-char (point-min)) |
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(replace-regexp "^" "\"") |
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(goto-char (point-min)) |
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(replace-regexp "$" "\"") |
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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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#+RESULTS: |
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and split into a list of list of chars |
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#+begin_src emacs-lisp :no-results |
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(setq data-chars (-map (lambda (str) (--map (string-to-char it) (split-string str "\\|.+" t))) |
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data) |
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height (length data-chars) |
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width (length (car data-chars))) |
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#+end_src |
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#+RESULTS: |
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: 140 |
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#+begin_src emacs-lisp :results silent |
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(defun acceptable-p (p) |
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(let ((x (car p)) |
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(y (cadr p))) |
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(and (>= x 0) (>= y 0) (< x width) (< y height)) )) |
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(defun neighbours (p) |
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(let ((x (car p)) |
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(y (cadr p))) |
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(-map (lambda (q) (list (+ x (car q)) (+ y (cadr q)))) '((+1 0) (-1 0) (0 1) (0 -1))))) |
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(defun acceptable-neighbours (p) |
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(-filter #'acceptable-p (neighbours p))) |
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(defun plant (p) |
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(if (not (acceptable-p p)) ?. |
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(nth (car p) (nth (cadr p) data-chars)))) |
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#+end_src |
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collect all plants type and return a list of list of positions |
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#+begin_src emacs-lisp :results none |
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(setq plants (-distinct (-mapcat #'identity data-chars))) |
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(setq groups (-map (lambda (pl) |
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(-map #'cadr |
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(--filter (eq (car it) pl) |
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(-mapcat #'identity |
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(-map-indexed (lambda (y l) (-map-indexed (lambda (x el) (list el (list x y))) l)) data-chars))))) |
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plants)) |
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#+end_src |
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now we need to split each group into regions |
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ACC is a list of regions. The function |
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#+begin_src emacs-lisp :results none |
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(defun agglomerate (acc el) |
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(let ((nbhs (acceptable-neighbours el))) |
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(cons (-mapcat #'identity (cons (list el) (--filter (-intersection it nbhs) acc))) |
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(--filter (not (-intersection it nbhs)) acc)) |
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) |
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) |
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(setq regions (--mapcat (-reduce-from #'agglomerate nil it) groups)) |
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#+end_src |
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#+begin_src emacs-lisp |
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(defun count-fence (el) |
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(let ((i (plant el)) |
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(pos el)) |
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(length (--filter (not (eq i it)) (-map #'plant (neighbours pos)))))) |
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(defun vertex-p (el dir) |
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(let* ((x (car el)) |
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(y (cadr el)) |
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(a (car dir)) |
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(b (cadr dir)) |
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(opposite (list (+ x a) (+ y b))) |
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(adjh (list (+ x a) y)) |
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(adjv (list x (+ y b)))) |
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(or (and (not (eq (plant el) (plant adjh))) |
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(not (eq (plant el) (plant adjv)))) |
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(and (eq (plant el) (plant adjh)) |
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(eq (plant el) (plant adjv)) |
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(not (eq (plant el) (plant opposite)))))) |
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) |
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(defun count-vertices (el) |
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(length (-non-nil (--map (vertex-p el it) '((1 1) (1 -1) (-1 1) (-1 -1))))) |
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) |
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(-reduce #'+ (--map (* (car it) (cdr it)) |
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(-zip-pair (-map #'length regions) |
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(-map (lambda (region) (-reduce #'+ (-map #'count-fence region))) regions)))) |
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(-reduce #'+ (--map (* (car it) (cdr it)) |
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(-zip-pair (-map #'length regions) |
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(-map (lambda (region) (-reduce #'+ (-map #'count-vertices region))) regions)))) |
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#+end_src |
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#+RESULTS: |
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: 859494 |
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