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(load "lib")
(defparameter input (uiop:read-file-string "8-input"))
(defparameter lines (get-lines input))
;; Just converts every line into a sequence of integral digits
(defparameter trees
(mapcar (lambda (line) (mapcar (lambda (char) (parse-integer (string char))) (string-to-clist line)))
lines))
;; Size of a row or column
(defparameter n-trees (length trees))
(defun get-column (x)
(loop for row in trees
collect (nth x row)))
(defun get-row (y)
(nth y trees))
(defun get-tree (x y)
(nth x (nth y trees)))
(defun is-visible? (x y)
(if (or (= x 0) (= x (- n-trees 1))
(= y 0) (= y (- n-trees 1)))
t
(let* ((tree (get-tree x y))
(lt-tree? (lambda (a) (< a tree)))
(row (get-row y))
(row-left (subseq row 0 x))
(row-right (subseq row (+ x 1)))
(col (get-column x))
(col-top (subseq col 0 y))
(col-bottom (subseq col (+ y 1))))
(or
(all lt-tree? row-left)
(all lt-tree? row-right)
(all lt-tree? col-top)
(all lt-tree? col-bottom)))))
(defun how-many-visible ()
(loop
for x from 0 to (- n-trees 1)
sum
(reduce
#'+
(loop
for y from 0 to (- n-trees 1)
if (is-visible? x y)
collect 1
else
collect 0))))
(format t "round 1: ~s~%" (how-many-visible))
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