Question

I run this code using both gpp and microsoft compiler but in both case I’v got an exception
but I can’t understand why!
this is my code:

#include <iostream>
#include <map>

using namespace std;

map<int,int> fib;

int fibo(int i)
{
    if (!fib.count(i))
    {
        fib.insert(pair<int, int>(i,fibo(i-1)+fibo(i-2)));
    }

    return fib[i];
}

int r(int i)
{
    if(i<3)
    {
        return i;
    }
    else
    {
        return fibo(i)+r(i-2);
    }
}

int main()
{


    fib.insert(pair<int, int>(0,1));
    fib.insert(pair<int, int>(1,1));

    int a,b,n;
    cin>>a>>b;

    n=b-a;

    int fiba=fibo(a);
    int fibaa=fibo(a-1);

    cout << (r(n+1)*fiba)+(r(n)*fibaa);

    return 0;
}

can anyone help me?

I debugged this code and I found that fib.insert(pair<int, int>(i,fibo(i-1)+fibo(i-2))); doesn’t work.

Answer 1

I’ve got Stack Overflow exception when I ran your code, obviously because of too deep recursion.
You should either increase stack size (but you can later choose to input a larger number and get the same exception again), or convert this algorithm into a non-recursive one (for example see this one: http://www.codeproject.com/Tips/109443/Fibonacci-Recursive-and-Non-Recursive-C)