blob: 91397ec53355792867a15c5d12ea30f992941322 (
plain)
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
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
|
(ql:quickload '(fiveam uiop))
(defun distance-1 (a b)
(apply #'+
(mapcar (lambda (e1 e2)
(abs (- e1 e2))) a b)))
(fiveam:test distance
(fiveam:for-all* ((n (fiveam:gen-integer :min 1 :max 10))
(a (fiveam:gen-list :length (lambda () n)))
(b (fiveam:gen-list :length (lambda () n)) (not (equal a b)))
(c (fiveam:gen-list :length (lambda () n))))
(fiveam:is (zerop (distance-1 a a)))
(fiveam:is (plusp (distance-1 a b)))
(fiveam:is (= (distance-1 a b) (distance-1 b a)))
(fiveam:is (<= (distance-1 a b) (+ (distance-1 a c) (distance-1 c b))))))
(defun surface (cubes)
(loop for a in cubes
sum (- 6 (loop for b in cubes
count (= 1 (distance-1 a b))))))
(defun parse-coords (filename)
(mapcar (lambda (l)
(mapcar #'parse-integer (uiop:split-string l :separator ",")))
(uiop:read-file-lines filename)))
(defun bounding-corner (points edge)
(reduce (lambda (edges point)
(mapcar edge edges point))
points))
(defun box-surface (min-point max-point)
(* 2
(loop for (a . rest) on (mapcar #'- max-point min-point)
sum (loop for b in rest
sum (* a b)))))
(defconstant +neighbor-dirs+ '((1 0 0) (0 1 0) (0 0 1)
(-1 0 0) (0 -1 0) (0 0 -1)))
(defun spread-steam (next allowedp)
(loop for dir in +neighbor-dirs+
for nbg = (mapcar #'+ next dir)
when (funcall allowedp nbg)
collect nbg))
(defun available-p (cubes min-point max-point)
(lambda (point)
(and (every #'<= min-point point max-point)
(not (member point cubes :test #'equal)))))
(defun fill-outside (queue outer-region cubes min-point max-point)
(reduce (lambda (out voxel)
(let ((next-queue (spread-steam voxel
(available-p
(append out cubes) min-point max-point))))
(fill-outside next-queue
(append next-queue out)
cubes min-point max-point)))
queue
:initial-value outer-region))
(defun exterior-surface (cubes)
(let* ((min (mapcar #'1- (bounding-corner cubes #'min)))
(max (mapcar #'1+ (bounding-corner cubes #'max)))
(outer (list min)))
(- (surface
(fill-outside outer outer cubes min max))
(box-surface min (mapcar #'1+ max)))))
(fiveam:test solutions
;; part 1
(fiveam:is (= 64 (surface (parse-coords "eg-in"))))
(fiveam:is (= 4474 (surface (parse-coords "input"))))
;; part 2
(fiveam:is (= 58 (exterior-surface (parse-coords "eg-in"))))
(fiveam:is (= 2518 (exterior-surface (parse-coords "input")))))
|
