Re: Suggested method for returning a string from a C program?

Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:

Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
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Michael S <already5chosen@yahoo.com> writes:
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On Tue, 18 Mar 2025 21:38:55 -0400
DFS <nospam@dfs.com> wrote:
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I'm doing these algorithm problems at
https://cses.fi/problemset/list/
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For instance:  Weird Algorithm
https://cses.fi/problemset/task/1068

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It is not an interesting programming exercise.  But it looks to me
as a challenging math exercise.  I mean, how could we give a not
too pessimistic estimate for upper bound of length of the sequence
that starts at given n without running a full sequence?  Or
estimate for maximal value in the sequence?  So far, I found no
answers.

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You may console yourself with the knowledge that no one else
has either, even some of the most brilliant mathematicians
of the last hundred years.  In fact it isn't even known that
all starting points eventually terminate;  as far as what has
been proven goes, some starting points might just keep going
up forever.

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I think someone has mentioned that this is called the Collatz
Conjecture.  According to Wikipedia, it's been shown to hold for
all positive integers up to 2.95e20 (which is just under 2**68).

Yes it is sometimes called the Collatz Conjecture, and sometimes
called the 3n+1 problem, and also is known by several other names.
I first heard the problem in the early 1980s (at that time it was
known as the (3n+1)/2 problem), and worked on it on and off for ten
years or so.  I would be astonished if anyone disproved it.