Code shared from the Rust Playground

playground.rs

fn main() {
    println!("{:?}", series("92017", 0));
}

fn series(digits: &str, len: usize) -> Vec<String> {
    let mut result: Vec<String> = Vec::new();
    if len <= digits.len() && len != 0 {
        result = digits
            .as_bytes()
            .windows(len)
            .map(|sl| String::from_utf8(sl.to_vec()).unwrap())
            .collect::<Vec<String>>();
    } else if len == 0 {
        result = vec!["".to_string(); digits.len()+1];
    }
    result
}