(ql:quickload :cl-ppcre)

(defun parse-input (input)
  (ppcre:split "\\n" (uiop:read-file-string input)))

(defun get-height (trees line pos)
  (digit-char-p (char (nth line trees) pos)))

(defun visible-p (trees line pos)
  (cond ((zerop pos) 1)
	((= pos (- (length (nth line trees)) 1)) 1)
	((zerop line) 1)
	((= line (- (length trees) 1)) 1)
	(t
	 (let ((sum 0)
	       (height (get-height trees line pos))
	       (left (get-height trees line (- pos 1)))
	       (top (get-height trees (- line 1) pos))
	       (right (get-height trees line (+ pos 1)))
	       (bottom (get-height trees (+ line 1) pos)))
	   (cond ((> height left) (+ sum 1))
		 ((> height top) (+ sum 1))
		 ((> height right) (+ sum 1))
		 ((> height bottom) (+ sum 1)))))))

(defun count-visible (trees)
  (let ((sum 0))
    (loop :for line :from 0 :to 98 :do
      (loop :for pos :from 0 :to 98 :do
	(if (visible-p trees line pos) (incf sum))))
    sum))