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61 lines
1.7 KiB
61 lines
1.7 KiB
#+title: Solution to p7 |
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Yay, another 2D problem |
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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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'(("^\\(.*\\)$" . "\"\\1\" "))) |
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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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(setq data-char (-map #'advent/split-string-into-char-list data) |
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width (length (car data-char)) |
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height (length data-char)) |
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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 position-valid-p (pos) |
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(and (and (>= (car pos) 0) (< (car pos) width)) |
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(and (>= (cadr pos) 0) (< (cadr pos) height)))) |
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(advent/char-at '(-1 0) data-char) |
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(defun tachyon-step (el) |
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(if (not (position-valid-p el)) (list el) |
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(let ((down (advent/neighbour el '(0 1)))) |
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(if (or (not (position-valid-p down)) |
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(not (eq ?^ (advent/char-at down data-char)))) |
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(list down) |
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(push down splits) |
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(--map (advent/neighbour el it) '((-1 0) (1 0))))))) |
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(setq tachyons (advent/coordinates-of ?S data-char)) |
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(setq splits nil) |
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(length (--fix (-distinct (-mapcat 'tachyon-step it)) tachyons)) |
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(length (-distinct splits)) |
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#+end_src |
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#+RESULTS: |
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: 1507 |
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#+begin_src emacs-lisp |
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(defun tachyon-step-freq (el) |
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(--map (cons it (cdr el)) (tachyon-step (car el)))) |
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(setq tachyons (cons (car (advent/coordinates-of ?S data-char)) 1)) |
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(defun compress (li) |
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(--map (cons it (-sum (-map #'cdr (-filter (lambda (x) (equal it (car x))) li)))) (-distinct (-map #'car li)))) |
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(-sum (-map #'cdr (--fix (compress (-mapcat 'tachyon-step-freq it)) (list tachyons)))) |
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#+end_src |
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#+RESULTS: |
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: 1537373473728
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