rust/theBook/chapter-3-variables-and-mutability/practice/fibonacci/src/main.rs


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use std::io;
use std::process;

fn main() {
    println!("Print nth Fibonacci number!");
    println!("");

    print_fibonacci();

    println!("done!");
}

fn print_fibonacci() {
    println!("Enter the n you want to print");

    let fib = read_input();

    println!("recursion_fibonacci:");
    println!("{}", recursion_fibonacci(fib));
    loop_fibonacci(fib);
}

fn loop_fibonacci(x: i32) {
    let mut num1 = 0;
    let mut num2 = 1;
    let mut next: i32;

    println!("loop_fibonacci:");

    for _i in 0..x {
        if _i <= 1 {
            next = _i;
        }   else {
            next = num1 + num2;
            num1 = num2;
            num2 = next;
        }
        println!("{next}");
    }
}

// Not recommend in rust
fn recursion_fibonacci(x: i32) -> i32 {
    if x <= 1 {
        return x;
    }   else {
        recursion_fibonacci(x-1) + recursion_fibonacci(x-2)
    }
}

fn read_input() -> i32 {
    let mut inp = String::new();

    io::stdin()
        .read_line(&mut inp)
        .expect("failed to read number");
    
    let inp: i32 = match inp.trim().parse() {
        Ok(inp) => inp,
        Err(_) => {
            println!("converting error");
            process::exit(1);
        },
    };

    inp
}