65 lines
1.4 KiB
Common Lisp
65 lines
1.4 KiB
Common Lisp
(load (merge-pathnames "../common.lisp" *load-truename*))
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(defconstant test-data
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'(
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"abc"
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""
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"a"
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"b"
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"c"
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""
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"ab"
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"ac"
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""
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"a"
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"a"
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"a"
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"a"
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""
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"b"
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))
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(defun array-to-list (array)
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(map 'list #'identity array))
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(defun character-counts (group)
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(loop for answers in group
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with counts = (make-array 26)
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do (loop for answer across answers
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do (incf (aref counts (- (char-code answer) (char-code #\a)))))
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finally (return (array-to-list counts))))
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(defun answered-yes (group)
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(length (remove-if #'zerop (character-counts group))))
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(defun all-answered-yes (group)
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(let ((group-size (length group)))
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(length (remove-if-not (lambda (e) (= e group-size)) (character-counts group)))))
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(let ((input '("abcx" "abcy" "abcz")))
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(assert (= 6 (answered-yes input)))
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(assert (= 3 (all-answered-yes input))))
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(defun groups (input)
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(loop for x = 0 then (1+ j)
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as j = (position "" input :start x :test #'string=)
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collect (subseq input x j)
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while j))
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(defun solve (input f)
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(apply '+ (mapcar f (groups input))))
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(defun part1 (input)
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(solve input #'answered-yes))
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(defun part2 (input)
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(solve input #'all-answered-yes))
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(assert (= 11 (part1 test-data)))
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(assert (= 6 (part2 test-data)))
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(let ((input (read-data)))
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(format t "Part 1: ~A~%" (part1 input))
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(format t "Part 2: ~A~%" (part2 input)))
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