2026-08-21
first_word.rs
fn first_word(s: &str) -> &str {
// write this
}
Implement first_word: return the first whitespace-separated word of s, or the whole string if there's no whitespace.
Reference
fn first_word(s: &str) -> &str {
s.split_whitespace().next().unwrap_or("")
}
The returned slice borrows from s, which is why no explicit lifetime is needed — there's only one input reference for the elided output lifetime to match.