blob: 9e44aa06eb676a15524b56927f264ec52e84c2a9 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
|
;;; https://gitlab.com/Syndamia/senzill
(require :senzill)
(use-package :senzill.math)
(use-package :senzill.collections)
(use-package :senzill.pair)
(use-package :senzill.io)
(ask-for-stream (prog-input)
(let ((rhead '(0 . 0)) (rtail '(0 . 0)) (visited '((0 . 0))) (movec '()))
(flet ((p-longer-than-sqrt2 (c)
"If c is outside the 3x3 square"
(or (> (abs (car c)) 1) (> (abs (cdr c)) 1)))
(movement-vec (c1 c2)
(cons (- (car c2) (car c1)) (- (cdr c2) (cdr c1))))
(dir-to-pair (direction)
(cond ((char= direction #\R) '( 1 . 0))
((char= direction #\L) '(-1 . 0))
((char= direction #\U) '( 0 . 1))
((char= direction #\D) '( 0 . -1)))))
(doread-lines (inpt :read-line-options (prog-input NIL))
(pair+= rhead (*pair (digit-char-p (char inpt 2))
(dir-to-pair (char inpt 0))))
(setf movec (movement-vec rtail rhead))
(if (p-longer-than-sqrt2 movec)
(progn (setf movec (pair-round (dist-resize-by movec -1))) ; We dont want to move tail on the head, but behind it
(pair+= rtail movec)
(loop for intermvec = movec then (pair-round (dist-resize-by intermvec -1))
until (pair= intermvec '(0 . 0))
if (not (member (pair- rtail intermvec) visited))
do (push (pair- rtail intermvec) visited)))))
(print visited))))
|
