src/2017/days/day-03.lisp @ cd781337a694
Restructure file layout, add 2017 days 14 & 15
author |
Steve Losh <steve@stevelosh.com> |
date |
Thu, 05 Dec 2019 20:45:46 -0500 |
parents |
src/2017/day-03.lisp@5b5c61ad8d2b |
children |
0a241f64eebb |
(defpackage :advent/2017/03 #.cl-user::*advent-use*)
(in-package :advent/2017/03)
(defun manhattan-distance (a b)
(let-complex ((ax ay a)
(bx by b))
(+ (abs (- ax bx))
(abs (- ay by)))))
(defun neighbors (coord)
(iterate (for (dx dy) :within-radius 1 :skip-origin t)
(collect (+ coord (complex dx dy)))))
(define-problem (2017 3) (data read) (552 330785)
(values
(manhattan-distance #c(0 0) (advent/spiral:number-coordinates data))
(iterate
(with memory = (make-hash-table))
(initially (setf (gethash #c(0 0) memory) 1))
(for n :from 2)
(for coord = (advent/spiral:number-coordinates n))
(for value = (summation (neighbors coord) :key (rcurry #'gethash memory 0)))
(finding value :such-that (> value data))
(setf (gethash coord memory) value))))