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(defvar input (with-input-from-string (s (uiop:read-file-string "6-input"))
(read-line s nil)))
(defun is-unique (lst)
(or (null lst)
(and (not (member (car lst) (cdr lst)))
(is-unique (cdr lst)))))
(defun string-to-list (str)
(loop for char across str collect char))
(defun first-round (input)
(defun calculate-position (nth)
"Calculate the actual position of the nth item."
(if nth
(+ nth 4)
nil))
(let* ((char-list (string-to-list input))
(unique-check (mapcar (lambda (x y z w) (is-unique (list x y z w))) char-list (cdr char-list) (cdr (cdr char-list)) (cdr (cdr (cdr char-list))))))
(calculate-position (position t unique-check))))
(format t "First round: ~a~%" (first-round input))
(defun successive-by (lst n)
"Returns consecutive subsequences of size N in LST."
(loop
for item in lst
for i from 0
collect
(if (> (+ n i) (length lst))
nil
(subseq lst i (+ n i)))))
(defun second-round (input)
(defun calculate-position (nth)
"Calculate the actual position of the nth item."
(if nth
(+ nth 14)
nil))
(let* ((char-list (string-to-list input))
(unique-check (mapcar #'is-unique (successive-by char-list 14))))
(calculate-position (position t unique-check))))
(format t "Second round: ~a~%" (second-round input))
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