Write a recursive function called fibor

Hello, I got a question as a below figure

My approach is as the following code:

function output = fibor(n)
a = 0; b = 1;
output = recursive_tail(n,a,b);
end

function out =  recursive_tail(n,a,b)
if n == 0
    out = a;
elseif n == 1 
    out = b;
else
    out = [b recursive_tail(n-1,b,a+b)];
end
end

(Source: Tail Recursion for Fibonacci - GeeksforGeeks)

The result is good (3/4 test cases), but the last one, the Grade External Tool does not eccept it as a recursive solution, I guest that because I call back the function "recursive_tail" instead of "fibor". Could you guys check the code for me, or any suggestions for the solution? I would appreciate it so much. Thank you guys.

[Jan]

"the Grade External Tool does not eccept it as a recursive solution" - do you get a corresponding message? If so, sharing it with the readers is a good idea. Otherwise it could be possible, that it is only a guess, what the problem is.

[Duong Nguyen]

My mistake, it says that I must include recursive call to the function. Here it is:

I hope it is helpful for other learners too.

Answer 1

[Jan]

If it is really the problem, that you use two functions, simply join then to one function:

function out = fibor(n, a, b)
if nargin == 1
    out = fibor(n, 0, 1);
else  % Here the "recursive tail":
    if n == 0
        out = a;
    elseif n == 1 
        out = b;
    else
        out = [b, fibor(n-1, b, a+b)];
    end
end
end

[Duong Nguyen]

It works very well, thank you.

[Dhairya]

How did using 3 input arguments prevent the server from timing out? How does it prevent making large number of stacks?

[Dyuman Joshi]

"How did using 3 input arguments prevent the server from timing out?"

What makes you think that using 3 (or more) input arguments will lead to the server being timed out?