解答

1. fn fib(n: u32) -> u32 {
2. if n <= 2 {
3. return 1;
4. } else {
5. return fib(n - 1) + fib(n - 2);
6. }
7. }

9. fn main() {
10. let n = 20;
11. println!("fib({n}) = {}", fib(n));
12. }