Mathematics9

Q9. Write a method to generate the nth Fibonacci number. Try both recursive and iterative function.
Fibonacci Function: f(0) = 0, f(1) = 1, f(n) = f(n - 1) + f(n - 2)

Answer:

public class Mathematics9 {
    public static int fibonacciRecursive(int n) {
        if (n == 0) {
            return 0;
        } else if (n == 1) {
            return 1;
        } else if (n > 1) {
            return fibonacciRecursive(n - 1) + fibonacciRecursive(n - 2);
        } else {
            // return error code to show that Fibonacci is not
            // defined for given input
            return -1;
        }
    }

    public static int fibonacciIterative(int n) {
        if (n == 0) {
            return 0;
        } else if (n == 1) {
            return 1;
        } else if (n > 1) {
            int tn_2 = 0;
            int tn_1 = 1;
            int tn = 0;

            for (int i = 2; i <= n; i++) {
                tn = tn_1 + tn_2;
                tn_2 = tn_1;
                tn_1 = tn;
            }
            return tn;
        } else {
            // return error code to show that Fibonacci is not
            // defined for given input
            return -1;
        }
    }

    public static void main(String[] args) {
        for (int i = 0; i <= 10; i++) {
            System.out.print(fibonacciRecursive(i) + " ");
        }

        System.out.println();

        for (int i = 0; i <= 10; i++) {
            System.out.print(fibonacciIterative(i) + " ");
        }
    }
}