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(use-package 'cl-ppcre)
(use-package 'trivia)
(defun 05/parse-input-direct (input)
(mapcar (lambda (i)
(map 'list #'parse-integer
(multiple-value-bind (a b)
(scan-to-strings "(.*),(.*) -> (.*),(.*)" i) b)))
input))
(defun max-coord (c1 c2)
(match (list c1 c2)
((list (list x1 y1) (list x2 y2))
(list (max x1 x2) (max y1 y2)))))
(defun find-max (l)
(fold-left #'max-coord '(0 0)
(mapcar
(lambda (x)
(match x
((list x1 y1 x2 y2)
(list (max x1 x2) (max y1 y2))))) l)))
(defun 05/parse-input (input-file)
(05/parse-input-direct (get-file-lines input-file)))
(defun draw-line-x (arr y x1 x2)
(let ((nx1 (min x1 x2))
(nx2 (max x1 x2)))
(loop :for x :from nx1 :to nx2
:do (incf (aref arr y x)))))
(defun draw-line-y (arr x y1 y2)
(let ((ny1 (min y1 y2))
(ny2 (max y1 y2)))
(loop :for y :from ny1 :to ny2
:do (incf (aref arr y x)))))
(defun draw-line-diag (arr x1 y1 x2 y2)
(if (< x1 x2)
(if (< y1 y2)
(loop for y from y1 upto y2
for x from x1 upto x2
do (incf (aref arr y x)))
(loop for y from y1 downto y2
for x from x1 upto x2
do (incf (aref arr y x))))
(if (< y1 y2)
(loop for y from y1 upto y2
for x from x1 downto x2
do (incf (aref arr y x)))
(loop for y from y1 downto y2
for x from x1 downto x2
do (incf (aref arr y x))))))
(defun draw-line (b arr coords)
(match coords
((list x1 y1 x2 y2)
(if (equalp x1 x2)
(draw-line-y arr x1 y1 y2)
(if (equalp y1 y2) (draw-line-x arr y1 x1 x2)
(when b (draw-line-diag arr x1 y1 x2 y2)))))))
(defun 2d-array-to-list (array)
(loop for i below (array-dimension array 0)
collect (loop for j below (array-dimension array 1)
collect (aref array i j))))
(defun 05/part-a (parsed-input)
(let ((lines (make-array (match (mapcar #'1+ (find-max parsed-input)) ((list a b) (list b a)))))
(overlapping 0))
(loop for x in parsed-input do (draw-line nil lines x))
(mapcar (lambda (x) (mapcar (lambda (y) (when (> y 1) (incf overlapping))) x))
(2d-array-to-list lines))
overlapping))
(defun 05/part-b (parsed-input)
(let ((lines (make-array (match (mapcar #'1+ (find-max parsed-input)) ((list a b) (list b a)))))
(overlapping 0))
(loop for x in parsed-input do (draw-line t lines x))
(mapcar (lambda (x) (mapcar (lambda (y) (when (> y 1) (incf overlapping))) x))
(2d-array-to-list lines))
overlapping))
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