9 lines
300 B
Common Lisp
9 lines
300 B
Common Lisp
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;;; Recursive algorithm
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(defun factor (n)
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"Return a list of factors of N."
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(when (> n 1)
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(loop with max-d = (isqrt n)
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for d = 2 then (if (evenp d) (+ d 1) (+ d 2)) do
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(cond ((> d max-d) (return (list n))) ; n is prime
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((zerop (rem n d)) (return (cons d (factor (truncate n d)))))))))
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