(require :uiop)
(load (sb-ext:posix-getenv "ASDF"))
(asdf:load-system 'str)

(defun bank-max-joltage (bank)
  (let ((batt-len (- (length bank) 1)))
  (apply #'max
    (loop for batt-first from 0 to (- batt-len 1)
      collect (apply #'max
        (loop for batt-last from (+ batt-first 1) to batt-len
          collect (let (
            (first-char (subseq bank batt-first (+ batt-first 1)))
            (last-char (subseq bank batt-last (+ batt-last 1))))
            (parse-integer (format nil "~A~A" first-char last-char)))))))))
(bank-max-joltage "987654321111111")


(defun array-total-joltage (bank-list)
  (reduce #'+
    (mapcar #'bank-max-joltage bank-list)))

(array-total-joltage (uiop:read-file-lines "03example.txt"))
(array-total-joltage (uiop:read-file-lines "03data.txt"))