授業料もったいねーなぁ。ところでスタートとゴールの定義がわからねーんだけど。
それぞれ座標固定でいいの？

(defstruct maze size data)

(defun load-maze (file)
(with-open-file (stream file :direction :input)
(let ((size (read stream)))
(make-maze :size size
:data (make-array (list size size)
:initial-contents (loop for data = (read stream nil :eof) until (eq data :eof) collect data))))))

(defun print-maze (maze &aux (size (maze-size maze)))
(loop for row below size do
(loop for col below size do
(princ (if (eq (aref (maze-data maze) row col) 1) "+" " ")))
(terpri)))