Code shared from the Rust Playground

playground.rs

use std::collections::HashSet;
use std::str::FromStr;

fn main() {
    let alphabets = String::from_str("ABCDEFGHIJKLMNOPQRSTUVWXYZ").unwrap();
    let alpha_set: HashSet<_> = alphabets.split("").filter(|x| x.len() != 0).collect();

    let keyword = String::from_str("SECRET").unwrap();
    let keyword_set: HashSet<_> = keyword.split("").filter(|x| x.len() != 0).collect();
    
    let diffset: HashSet<_> = alpha_set.difference(&keyword_set).collect();
    
    let mut rem_alphas: Vec<_> = diffset.clone().into_iter().collect();
    rem_alphas.sort_by_key(|&x| alphabets.find(x));
    
    let mut keyword_sort: Vec<_> = keyword_set.clone().into_iter().collect();
    keyword_sort.sort_by_key(|&x| keyword.find(x));
    
    println!("{:?}", rem_alphas);
    println!("{:?}", keyword_sort);
}