Collatz Conjecture

[Dexter]

In a programming book, I found this recursive algorithm which always
returns 1 regardless of the value of the input parameter

=============== ===

int collatz (int n) {
if (n == 1)
return 1;
else{
if ( n%2 == 1)
return collatz(3*n+1);
else
return collatz(n/2);
}
}

=============== ===

The author of the book asserts its unproven that it will indeed always
return 1

[Antoninus Twink]

Re: Collatz Conjecture

On 26 Apr 2008 at 18:16, Dexter wrote:

In a programming book, I found this recursive algorithm which always
returns 1 regardless of the value of the input parameter

Here's a *non*-recursive algorithm which always returns 1 regardless of
the value of the input parameter:

int f(int n)
{
return 1;
}

[Lew Pitcher]

Re: Collatz Conjecture

In comp.lang.c, Dexter wrote:

In a programming book, I found this recursive algorithm which always
returns 1 regardless of the value of the input parameter
>
=============== ===
>
int collatz (int n) {
if (n == 1)
return 1;
else{
if ( n%2 == 1)
return collatz(3*n+1);
else
return collatz(n/2);
}
}
>
=============== ===
>
The author of the book asserts its unproven that it will indeed always
return 1

In at least one case, it will not return 1

If n == 0 then it will never return at all.

--
Lew Pitcher

Master Codewright & JOAT-in-training | Registered Linux User #112576
http://pitcher.digitalfreehold.ca/ | GPG public key available by request
---------- Slackware - Because I know what I'm doing. ------

[santosh]

Re: Collatz Conjecture

Dexter wrote:

In a programming book, I found this recursive algorithm which always
returns 1 regardless of the value of the input parameter
>
=============== ===
>
int collatz (int n) {
if (n == 1)
return 1;
else{
if ( n%2 == 1)
return collatz(3*n+1);
else
return collatz(n/2);
}
}
>
=============== ===
>
The author of the book asserts its unproven that it will indeed always
return 1

See:

<http://mathworld.wolfr am.com/CollatzProblem. html>
<http://en.wikipedia.or g/wiki/Collatz_conject ure>
<http://www.numbertheor y.org/php/collatz.html>

There is an ongoing thread over in comp.programmin g on this problem.

[christian.bau]

Re: Collatz Conjecture

On Apr 26, 7:16 pm, Dexter <yousaf.a...@gm ail.comwrote:

In a programming book, I found this recursive algorithm which always
returns 1 regardless of the value of the input parameter
>
=============== ===
>
int collatz (int n) {
  if (n == 1)
    return 1;
  else{
    if ( n%2 == 1)
       return collatz(3*n+1);
    else
       return collatz(n/2);
  }
>
}
>
=============== ===
>
The author of the book asserts its unproven that it will indeed always
return 1

If he or she makes that claim, then the author is completely wrong.

On many implementations , calling this function will result in a stack
overflow whenever the function argument is a negative number. It will
also result in stack overflow on many implementations if the argument
is an odd integer between INT_MAX / 3 and INT_MAX / 3 * 2.