src/2021/days/day-12.lisp @ 2848a4548adf
2023/01 and 2022/01 Also start porting my test data to the new account, since Twitter imploded and apparently it's impossible for a website to store a goddamn username and password in The Year of Our Lord 2023 so everyone just outsources auth all the time, ugh.
| author | Steve Losh <steve@stevelosh.com> |
|---|---|
| date | Fri, 01 Dec 2023 11:05:43 -0500 |
| parents | 6614131d7b10 |
| children | (none) |
(advent:defpackage* :advent/2021/12) (in-package :advent/2021/12) (defun edge (graph from to) (push to (gethash from graph)) (push from (gethash to graph))) (defun parse (stream) (iterate (with-result graph = (make-hash-table)) (for line :in-stream stream :using #'read-line) (for (from to) = (str:split #\- line)) (edge graph (intern from :advent/2021/12) (intern to :advent/2021/12)))) (defun bigp (cave) (upper-case-p (char (symbol-name cave) 0))) (defun restrict-small-1 (node path) (member node path)) (defun used-small-twice (path) ;; todo do something faster than this (iterate (for (a . rest) :on path) (unless (bigp a) (dolist (b rest) (thereis (eql a b)))))) (defun restrict-small-2 (node path) (cond ((member node '(|start| |end|)) (member node path)) ((used-small-twice path) (member node path)) (t (member node (rest (member node path)))))) (defun neighbors (graph path &key restriction) (iterate (for node :in (gethash (first path) graph)) (when (or (bigp node) (not (funcall restriction node path))) (collect node)))) (defun paths (graph &key restriction) (recursively ((path '(|start|))) (if (eql '|end| (first path)) 1 (iterate (for next :in (neighbors graph path :restriction restriction)) (summing (recur (cons next path))))))) (define-problem (2021 12) (graph parse) (5254 149385) (values (paths graph :restriction #'restrict-small-1) (paths graph :restriction #'restrict-small-2))) #; Scratch --------------------------------------------------------------------