Fibonacci2.cpp

Code

/*
    Fibonacci2.cpp
    CIS 250
    Dave Klick
    2008-03-24
   
    This program uses recursion to calculate Fibonacci numbers,
    and allows the series to start with any two integers.
*/
#include <iostream>
#include <cassert>
using std::cout;
using std::endl;
using std::cin;

long fib(long a, long b, long n);

int main(void) {
    long a, b, n;
    cout << "This program calculates Fibonacci numbers\n";
    cout << "Please enter the first number in the series: ";
    cin >> a;
    cout << "Please enter the second number in the series: ";
    cin >> b;
    cout << "Please enter the position of the Fibonacci number you want: ";
    cin >> n;
    cout << "The answer is " << fib(a,b,n) << endl;
    return 0;
}

long fib(long a, long b, long n) {
    assert (n > 0);
    if (n == 1) return a;
    if (n == 2) return b;
    return fib(a,b,n-1) + fib(a,b,n-2);
}