blob: 062e4418e071efd741bc65cf7a442a259a7ea8fc (
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
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
|
(ql:quickload '(fiveam uiop arrows trivia))
(defun parse-instructions (str &optional (start 0))
(multiple-value-bind (action str-pos)
(case (aref str start)
(#\R 'right)
(#\L 'left)
(t (parse-integer str :start start :junk-allowed t)))
(let ((next (or str-pos (1+ start))))
(if (= next (length str))
(list action)
(cons action (parse-instructions str next))))))
(defun create-field (filename)
(let* ((data (uiop:read-file-lines filename))
(map (butlast data 2))
(instructions (car (last data)))
(rows (length map))
(columns (reduce (lambda (a r) (max a (length r))) map :initial-value 0))
(field (make-array (list rows columns) :initial-element nil)))
(loop for row in map
for i from 0
do (loop for entry across row
for j from 0
do (setf (aref field i j)
(ecase entry
(#\. 'free)
(#\# 'wall)
(#\Space nil)))))
(values field (parse-instructions instructions))))
(defun get-start (field)
(loop for i from 0
until (aref field 0 i)
finally (return i)))
(defstruct state
x-pos y-pos direction)
(defun advance (field state)
(destructuring-bind (height width) (array-dimensions field)
(with-slots (direction x-pos y-pos) state
(destructuring-bind (new-x new-y)
(ecase direction
(north (list x-pos (mod (1- y-pos) height)))
(south (list x-pos (mod (1+ y-pos) height)))
(east (list (mod (1+ x-pos) width) y-pos))
(west (list (mod (1- x-pos) width) y-pos)))
(let ((new-state (make-state :x-pos new-x :y-pos new-y :direction direction)))
(if (aref field new-y new-x)
new-state
(advance field new-state)))))))
(defun new-direction (current-direction turn &optional (directions #(north east south west)))
(svref directions
(mod
(+
(ecase turn
(left -1)
(right 1))
(position current-direction directions))
4)))
(defun walk (field state steps)
(if (zerop steps)
state
(let ((new-state (advance field state)))
(with-slots (x-pos y-pos) new-state
(ecase (aref field y-pos x-pos)
(free (walk field new-state (1- steps)))
(wall state))))))
(defun decode-state (state)
(with-slots (x-pos y-pos direction) state
(+ (* 1000 (1+ y-pos))
(* 4 (1+ x-pos))
(ecase direction
(east 0)
(south 1)
(west 2)
(north 3)))))
(defun solver (filename)
(multiple-value-bind (field instructions) (create-field filename)
(let ((state (make-state :x-pos (get-start field) :y-pos 0 :direction 'east)))
(dolist (move instructions)
(if (numberp move)
(setf state (walk field state move))
(setf (state-direction state) (new-direction (state-direction state) move))))
(decode-state state))))
;;; part 2
;;; Cube face layout
;;; 1
;;; 234
;;; 56
;;; face coords
;;; 1=2 0
;;; 2=0 1
;;; 3=1 1
;;; 4=2 1
;;; 5=2 2
;;; 6=3 2
(defparameter +face-label+
'((1 . (2 0))
(2 . (0 1))
(3 . (1 1))
(4 . (2 1))
(5 . (2 2))
(6 . (3 2))))
(defun coord->face (x-face y-face)
(car (rassoc (list x-face y-face) +face-label+ :test #'equal)))
(defun face->coord (face)
(cdr (assoc face +face-label+ :test #'eq)))
(defun reduced-coords (state face-length)
(with-slots (x-pos y-pos) state
(multiple-value-bind (x-face x-coord)
(floor x-pos face-length)
(multiple-value-bind (y-face y-coord)
(floor y-pos face-length)
(list (coord->face x-face y-face) x-coord y-coord)))))
(defun place-state (face x y direction face-length)
(destructuring-bind (x-face y-face) (face->coord face)
(make-state :x-pos (+ x (* x-face face-length))
:y-pos (+ y (* y-face face-length)) :direction direction)))
(defun face-jump (face direction fl)
"fl is face-length"
(ecase face
(1 (case direction
(> (list 6 '< (lambda (_ y) (declare (ignore _)) (list (1- fl) (- fl y 1)))))
(v (list 4 'v (lambda (x _) (declare (ignore _)) (list x 0))))
(< (list 3 'v (lambda (_ y) (declare (ignore _)) (list y 0))))
(^ (list 2 'v (lambda (x _) (declare (ignore _)) (list (- fl x 1) 0))))))
(2 (case direction
(> (list 3 '> (lambda (_ y) (declare (ignore _)) (list 0 y))))
(v (list 5 '^ (lambda (x _) (declare (ignore _)) (list (- fl x 1) (1- fl)))))
(< (list 6 '^ (lambda (_ y) (declare (ignore _)) (list (- fl y 1) (1- fl)))))
(^ (list 1 'v (lambda (x _) (declare (ignore _)) (list (- fl x 1) 0))))))
(3 (case direction
(> (list 4 '> (lambda (_ y) (declare (ignore _)) (list 0 y))))
(v (list 5 '> (lambda (x _) (declare (ignore _)) (list 0 (- fl x 1)))))
(< (list 2 '< (lambda (_ y) (declare (ignore _)) (list (1- fl) y))))
(^ (list 1 '> (lambda (x _) (declare (ignore _)) (list 0 x))))))
(4 (case direction
(> (list 6 'v (lambda (_ y) (declare (ignore _)) (list (- fl y 1) 0))))
(v (list 5 'v (lambda (x _) (declare (ignore _)) (list x 0))))
(< (list 3 '< (lambda (_ y) (declare (ignore _)) (list (1- fl) y))))
(^ (list 1 '^ (lambda (x _) (declare (ignore _)) (list x (1- fl)))))))
(5 (case direction
(> (list 6 '> (lambda (_ y) (declare (ignore _)) (list 0 y))))
(v (list 2 '^ (lambda (x _) (declare (ignore _)) (list (- fl x 1) (1- fl)))))
(< (list 3 '^ (lambda (_ y) (declare (ignore _)) (list (- fl y 1) (1- fl)))))
(^ (list 4 '^ (lambda (x _) (declare (ignore _)) (list x (1- fl)))))))
(6 (case direction
(> (list 1 '< (lambda (_ y) (declare (ignore _)) (list (1- fl) (- fl y 1)))))
(v (list 2 '> (lambda (x _) (declare (ignore _)) (list 0 (- fl x 1)))))
(< (list 5 '< (lambda (_ y) (declare (ignore _)) (list (1- fl) y))))
(^ (list 4 '< (lambda (x _) (declare (ignore _)) (list (1- fl) (- fl x 1)))))))))
(defun cube-advance (state face-length)
(destructuring-bind (face x-coord y-coord) (reduced-coords state face-length)
(with-slots (direction) state
(let ((new-x (+ x-coord (case direction (< -1) (> 1) (t 0))))
(new-y (+ y-coord (case direction (^ -1) (v 1) (t 0)))))
(if (and
(< -1 new-x face-length)
(< -1 new-y face-length))
(place-state face new-x new-y direction face-length)
(destructuring-bind (new-face new-direction pos-fn) (face-jump face direction face-length)
(destructuring-bind (new-x new-y) (funcall pos-fn x-coord y-coord)
(place-state new-face new-x new-y new-direction face-length))))))))
(defun around-corner-test (start-face face-length)
(let* ((orig (place-state start-face 0 0 '^ face-length))
(state (copy-structure orig)))
(dolist (move '(1 left 1 left 1 left))
(if (numberp move)
(setf state (cube-advance state face-length))
(setf (state-direction state) (new-direction (state-direction state) move #(^ > v <))))
;; (print state)
)
(equalp orig state)))
(fiveam:test preparation
(fiveam:is (eq 'south (new-direction 'east 'right)))
(fiveam:is (eq 'west (new-direction 'north 'left)))
(fiveam:is (equal
(parse-instructions "10R5L5R10L4R5L5" )
'(10 RIGHT 5 LEFT 5 RIGHT 10 LEFT 4 RIGHT 5 LEFT 5)))
(fiveam:is (= 1 (coord->face 2 0)))
(fiveam:is (= 6 (apply #'coord->face (face->coord 6)))))
;; (let* ((field (create-field "eg-in"))
;; (face-length (floor (array-dimension field 0) 3)))
;; (fiveam:is
;; (equalp (place-state 2 3 0 'v 4)
;; (cube-advance (place-state 1 0 0 '^ face-length) face-length))))
(fiveam:test around-corner
(dotimes (i 6)
(fiveam:is (around-corner-test (1+ i) 4))))
(fiveam:test solutions
(fiveam:is (= 6032 (solver "eg-in")))
(fiveam:is (= 159034 (solver "input"))))
|
