On 20.5.2011 3:38, Pascal J. Bourguignon wrote:
t...@sevak.isi.edu (Thomas A. Russ) writes:
"Pascal J. Bourguignon"<p...@informatimago.com> writes:
t...@sevak.isi.edu (Thomas A. Russ) writes:
This will only work if there is a backpointer to the parent.
No, you don't need backpointers; some cases have been mentionned in the
other answer, but in general:
(defun parent (tree node)
(if (member node (children tree))
tree
(some (lambda (child) (parent child node)) (children tree))))
Yes, the question wasn't about time complexity.
:-p
Um, this is a recursive function. Inside PARENT, there is another call
to PARENT.
Feel free to derecursive it.
In the general case, to derecursive a function necessitates programming
a stack, among other things.............
Antti "Andy" Ylikoski
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