27 lines
820 B
Common Lisp
27 lines
820 B
Common Lisp
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; Split to list, remove duplicates, recombine
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(defun unique-string (str)
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(concatenate 'string (remove-duplicates (coerce str 'list))))
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; Returns the index of the first occurrence of a sequence of "len" different characters in "str"
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(defun unique-sequence (str len &optional (offset 0))
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(if (= len
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(length (unique-string (subseq str offset (+ len offset)))))
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offset
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(unique-sequence str len (+ offset 1))))
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; unique-sequence gives the index-of, but we want the index-after
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(defun part1 (str)
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(+ 4 (unique-sequence str 4)))
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(defun part2 (str)
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(+ 14 (unique-sequence str 14)))
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(let ((in (open "input.txt" :if-does-not-exist nil)))
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(when in
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(let ((str (read-line in nil nil)))
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(format t "Part 1: ~a~%" (part1 str))
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(format t "Part 2: ~a~%" (part2 str)))
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(close in)))
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