src/2021/days/day-05.lisp @ 68bbcb0ce4f7
2020/14
author |
Steve Losh <steve@stevelosh.com> |
date |
Tue, 14 Dec 2021 20:18:56 -0500 |
parents |
dd27f6b2d778 |
children |
(none) |
(advent:defpackage* :advent/2021/05)
(in-package :advent/2021/05)
(defun parse (stream)
(iterate (for line :in-stream stream :using #'read-line)
(collect (ppcre:register-groups-bind ((#'parse-integer x1 y1 x2 y2))
("(\\d+),(\\d+) -> (\\d+),(\\d+)" line)
(cons (complex x1 y1) (complex x2 y2))))))
(defun delta (line)
(let-complex ((x1 y1 (car line))
(x2 y2 (cdr line)))
(complex (signum (- x2 x1)) (signum (- y2 y1)))))
(defun orthogonalp (line)
(= (abs (delta line)) 1.0))
(defun add-line (board line)
(iterate (with (a . b) = line)
(for i :from a :by (delta line))
(incf (gethash i board 0))
(until (= i b))))
(defun count-overlaps (data &aux (board (make-hash-table)))
(map nil (curry #'add-line board) data)
;; (print-hash-table-map board :flip-y t :default #\.)
(count-if (curry #'<= 2) (alexandria:hash-table-values board)))
(define-problem (2021 5) (data parse) (5585 17193)
(values (count-overlaps (remove-if-not #'orthogonalp data))
(count-overlaps data)))
#; Scratch --------------------------------------------------------------------