题解 | #斐波那契数列#

use std::io::Write;

fn get_user_input() -> String {
    let mut user_input = String::new();
    std::io::stdin().read_line(&mut user_input).unwrap();
    return user_input;
}

fn fibnoacci(number : i32) -> i32 {
    let mut a : i32 = 1;
    let mut b : i32 = 1;
    let mut i : i32 = 0;
    if number <= 2 {
        return a;
    }
    loop {
        let c = a + b;
        a = b;
        b = c;
        i = i + 1;
        if i + 2 >= number {
            return c;
        }
    }
} 

fn main() {
    let user_input : i32 = get_user_input().trim().parse().expect("want a number.");
    let result : i32 = fibnoacci(user_input);

    std::io::stdout().write(format!("{}", result).as_bytes()).unwrap();
}