Why doesn't my fibonacci search work?

[stonedviper]

Hello?

I was messing around with the fibonacci sequence and it's implementation and I got the hang of it.
And I want to find which number from the fibonacci sequence is bigger than the one given but the problem is if it's a fibonacci number there's a logical error

unsigned fib(unsigned k)
{
	if (k == 0)return 0;
	else if (k == 1)return 1;
	else return fib(k - 1) + fib(k - 2);
}

unsigned which_fib( unsigned i, unsigned k=0 )
{
	if (fib(k) < i)
		return which_fib(i, k+1);

	if (fib(k) > i)
		return k;
}

int main()
{
	std::cout << which_fib(8) << "\n";/*<-this outputs 8 when it should
output 7*/

}

Can anyone tell me where is the problem please?

Thank you!

[tpb]

You have no branch for == in which_fib, so it drops through and returns garbage (your compiler should warn you about that possibility).
So the first test needs to be <=, and the second should just be an else.

//     n : 0 1 2 3 4 5 6  7  8  9 10
// fib(n): 0 1 1 2 3 5 8 13 21 34 55

#include <iostream>

typedef unsigned long ulong;

ulong fib(ulong k) {
    return (k < 2) ? k : fib(k - 1) + fib(k - 2);
}

ulong which_fib(ulong i, ulong k = 0) {
    return (fib(k) > i) ? k : which_fib(i, k + 1);
}

int main() {
    std::cout << which_fib(8) << "\n";
}

[stonedviper]

The compiler didn't warn me...

Still Thank you!

[tpb]

If the compiler didn't warn you then you need to turn up the warning level. In gcc and clang you can add the -Wall flag (as well as the -Wextra and -pedantic flags). Look up how to do it for other compilers. The warnings are really helpful.