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;;; https://gitlab.com/Syndamia/senzill
(require :senzill)
(use-package :senzill.collections)
(use-package :senzill.io)
(ask-for-stream (prog-input)
(let ((forest '()))
(doread-lines (inpt :read-line-options (prog-input NIL))
(push-back (map 'list
(lambda (x) (cons x 0)) ; Each tree is a (cons) pair of (<TREE_HEIGHT> . <IS_VISIBLE>)
(integer-to-list (parse-integer inpt)
:min-length (length (first forest)))) ; Doesn't handle if very first digit(s) is zero
forest))
(defun loop-on-row (row)
(setf (cdr (first row)) 1) ; Edge, we always see it
(loop for col on row
maximize (car (first col)) into max-height
while (cdr col)
if (< max-height (car (second col)))
do
(setf (cdr (second col)) 1)))
;;; Checks every row
(loop for row in forest
do
;; Iterate from left to right
(loop-on-row row)
;; Iterate from right to left
(loop-on-row (reverse row)))
;;; Checks every column
(loop for i from 0 to (- (length (first forest)) 1)
for col = (loop for row in forest
collect (nth i row))
do
;; Iterate top to bottom
(loop-on-row col)
;; Iterate bottom to top
(loop-on-row (reverse col)))
(loop for row in forest
sum (loop for tree in row
count (= 1 (cdr tree))) into result
finally (print result))))
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