general algorithm + ackermann question

Hi, I am working on an assignment and I'm a bit confused and stuck.

I am to write an Ackermann function using recursion which was no
problem and dynamic version as well. The dynamic version is giving me
crap.

1st off according to this Wikipedia article,
http://en.wikipedia.org/wiki/Recursion#Functional_recursion

"A famous recursive function is the Ackermann function which, unlike
the Fibonacci sequence, cannot be expressed without recursion."

2nd thing, can a function be dynamic, yet also be recursive? Example:

int ackDyn(int m, int n)
{

switch (m)
{
case 0:
return n + 1;
case 1:
return n + 2;
case 2:
return 2 * n + 3;
case 3:
return (int)Math.Pow(2, n + 3) - 3;
default:
if (n == 0)
{
return ackDyn(m - 1, 1);
}
else
{
return ackDyn(m - 1, ackDyn(m, n - 1));
}
}

}

I attempted to rework it with no self-calls, based on some info that I
found on the Ackerman function combined with the code above, which
resulted in:

long dynAck(long m, long n)
{
long result = 2;
long stop = n + 3;
switch (m)
{
case 0:
return n + 1;
case 1:
return n + 2;
case 2:
return 2 * n + 3;
case 3:
return (int)Math.Pow(2, n + 3) - 3;
default:
if (n == 0)
{
stop = 4;
}
for (int i = 1; i < stop; i++)
{
result = (long)Math.Pow(2, result);
}
return result - 3;
}

}

It seems to almost work, but not quite.


Thanks,

Jason
.

Relevant Pages

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