Fibonacci Series with Rust

fibonacci.rs

use std::io;

fn main() {
    let mut number = String::new();

    println!("\nEnter a positive integer: ");

    io::stdin().read_line(&mut number)
        .expect("Failed to read line");

    let number: u32 = match number.trim().parse() {
        Ok(num) => num,
        Err(_) => 0,
    };

    println!("{}", fibonacci(number));
}


fn fibonacci(n: u32) -> u32 {
    match n {
        0 => 1,
        1 => 1,
        _ => fibonacci(n-1) + fibonacci(n-2),
    }
}

// O(n)
pub fn fib2(n: usize) -> i32 {
    let mut vec = vec![0, 1];
    for val in 2..=n {
        let result = vec[val - 1] + vec[val - 2];
        vec.push(result);
    }
    vec[n]
}