17recursion.cpp

#include<iostream>
using namespace std;

int factorial(int n)
{
    if (n == 0 || n == 1)
    {
        return 1;
    }
    else if(n < 0)
    {
        return 0;
    }
    else
    {
        return n * factorial(n-1);
    }
    
}

int fibonacci(int n)
{
    if (n == 0 || n == 1)
    {
        return n;
    }
    else
    {
        return fibonacci(n-1) + fibonacci(n-2);
    }
    
}
//Iterative approach is when the program is broken into simple operation codes
int fib_iterative(int n)
{
    int a = 0;
    int b = 1;
    for (int i = 0; i < n-1; i++)
    {
        b = a + b;
        a = b - a;
    }
    return a;
}
int main()
{
    //Recursions are functions that perform a task in broken down steps
    //for example a factorial function
    int num;
    cout<<"Enter a num"<<endl;
    cin>>num;
    cout<<"Factorial of "<<num<<" is "<<factorial(num)<<endl;
    cout<<"Fibonacci sequence of "<<num<<" is "<<fibonacci(num)<<endl;
    cout<<"Fibonacci sequence of "<<num<<" is "<<fib_iterative(num)<<endl;
    return 0;
}