Exercise: Fibonacci

The Fibonacci sequence begins with [0,1]. For n>1, the n’th Fibonacci number is calculated recursively as the sum of the n-1’th and n-2’th Fibonacci numbers.

Write a function fib(n) that calculates the n’th Fibonacci number. When will this function panic?

fn fib(n: u32) -> u32 {
    if n < 2 {
        // The base case.
        return todo!("Implement this");
    } else {
        // The recursive case.
        return todo!("Implement this");
    }
}

fn main() {
    let n = 20;
    println!("fib({n}) = {}", fib(n));
}