AtCoder Beginner Contest 268 B

https://atcoder.jp/contests/abc268/tasks/abc268_b

部分文字列はこんな感じで取れるようです。

    let sub = &T[..S.len()];

// Prefix?
#![allow(non_snake_case)]

fn read<T: std::str::FromStr>() -> T {
    let mut line = String::new();
    std::io::stdin().read_line(&mut line).ok();
    line.trim().parse().ok().unwrap()
}

fn is_prefix(S: &String, T: &String) -> bool {
    if S.len() > T.len() {
        return false
    }
    let sub = &T[..S.len()];
    S == sub
}

fn main() {
    let S: String = read();
    let T: String = read();
    println!("{}", if is_prefix(&S, &T) { "Yes" } else { "No" })
}