blob: bec30f45f2d7c868912ab423ebe9b4fa3d6f9b46 (
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
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
#!/usr/bin/sbcl --script
(defun main (filename)
(loop for numbers in (parse-input filename)
sum (solve numbers)))
(defun parse-input (filename)
(with-open-file (stream filename)
(let ((contents (make-string (file-length stream))))
(read-sequence contents stream)
(loop for paragraph in (split-string contents (format nil "~%~%"))
collect (extract-numbers-from-string paragraph)))))
(defun extract-numbers-from-string (string)
(loop with number-count = 6
with numbers = (make-array number-count)
for i from 0 below number-count
for start = (position-if #'digit-char-p string)
for end = (position-if-not #'digit-char-p string :start start)
do (setf (aref numbers i) (parse-integer (subseq string start end))
string (subseq string (or end 0)))
finally (return numbers)))
(defun split-string (string delimiter)
(loop with delimiter-length = (length delimiter)
for end = (search delimiter string)
unless (eq end 0)
collect (subseq string 0 end) into parts
unless end
return parts
do (setq string (subseq string (+ end delimiter-length)))))
(defun solve (numbers)
;; ⎡ a0 b0 ⎢ c0 ⎤
;; ⎣ a1 b1 ⎢ c1 ⎦
(let* ((a0 (aref numbers 0))
(a1 (aref numbers 1))
(b0 (aref numbers 2))
(b1 (aref numbers 3))
(c0 (aref numbers 4))
(c1 (aref numbers 5))
;; START PART 2
(c0 (+ 10000000000000 c0))
(c1 (+ 10000000000000 c1))
;; END PART 2
(D-bar (determinant a0 b0 a1 b1))
(Dx-bar (determinant c0 b0 c1 b1))
(Dy-bar (determinant a0 c0 a1 c1))
(x (/ Dx-bar D-bar))
(y (/ Dy-bar D-bar)))
(if (and (integerp x)
(integerp y))
(+ (* x 3) y)
0)))
(defun determinant (a b c d)
(- (* a d)
(* b c)))
(format t "~d~%" (main "input"))
|
