2023-07-01 11:58:00 -04:00
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(defun hailstone (n)
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(cond ((= n 1) '(1))
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((evenp n) (cons n (hailstone (/ n 2))))
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(t (cons n (hailstone (+ (* 3 n) 1))))))
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2026-04-30 12:34:36 -04:00
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(defun longest-hailstone (n)
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2023-07-01 11:58:00 -04:00
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(let ((k 0) (l 0))
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(loop for i from 1 below n do
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(let ((len (length (hailstone i))))
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(when (> len l) (setq l len k i)))
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finally (format t "Longest hailstone sequence under ~A for ~A, having length ~A." n k l))))
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