Rust Practice

main.rs

fn dna_to_rna(dna: &str) -> String {
//  dna.chars().map(|c|   match c { 'T' => 'U', _ => c  }   ).collect()
//  dna.chars().map(|c| { match c { 'T' => 'U', c => c, } } ).collect()
    dna.replace("T", "U")
}

// https://www.codewars.com/kata/reviews/5824a92c5ce9e05d7700000e/groups/5be0706b2934eb31570049b1
// https://www.codewars.com/kata/reviews/5824a92c5ce9e05d7700000e/groups/5b7aba0b0da8ff76920006e4

main2.rs

fn count_red_beads(n: u32) -> u32 {
    if n==0 { 0 } else { (n-1)*2 }
}

//----
// https://www.codewars.com/kata/reviews/5b76e825a20d72759f001f5b/groups/5b7733d957c6b9f88e0012ad
fn count_red_beads(n: u32) -> u32 {
    if n <= 2 {
        return 0
    }
  
    (n - 1) * 2
}
//=================

fn count_red_beads(n: u32) -> u32 {
    match n {
    0 | 1 => 0,
    _     => (n-1)*2
    }
}

fn count_red_beads(n: u32) -> u32 {
    match n {
    n if n < 2 => 0,
    _          => (n-1)*2,
    }
}

fn count_red_beads(n: u32) -> u32 {
    match n {
    n if n > 1 => (n - 1) * 2,
    _          => 0
  }
}

//==========

fn count_red_beads(n: u32) -> u32 {
    2 * n.checked_sub(1).unwrap_or(0)
}

fn count_red_beads(n: u32) -> u32 {
    n.checked_sub(1).map(|n| n * 2).unwrap_or(0)
}

fn count_red_beads(n: u32) -> u32 {
    2 * n.saturating_sub(1)
}