Question

1. Write an iterative C++ function that inputs a nonnegative integer n and returns the nth Fibonacci number.

2. Write a recursive C++ function that inputs a nonnegative integer n and returns the nth Fibonacci number.

Answer 1

#include <iostream>

using namespace std;

int fibonacci(int n) {
    int a = 0, b = 1, c;
    if (n <= 1)
        return n;
    for (int i = 2; i <= n; i++) {
        c = a + b;
        a = b;
        b = c;
    }
    return b;
}

int fibonacciRecursive(int n) {
    if (n <= 1) {
        return n;
    }
    return fibonacciRecursive(n-1) + fibonacciRecursive(n-2);
}

int main() {
    int n;
    cout << "Enter a value for n: ";
    cin >> n;
    cout << n << "th fibonacci number is " << fibonacci(n) << endl;
    cout << n << "th fibonacci number is " << fibonacciRecursive(n) << endl;
    return 0;
}