こんな感じかな
fn fizzbuzz(s: &str) -> &str {
let last = s.bytes().next_back().unwrap();
let is_buzz = last == b'0' || last == b'5';
let sum = s.bytes().map(|n| n as u64).sum::<u64>();
let is_fizz = sum % 3 == 0;
if is_fizz {
if is_buzz {
"FizzBuzz"
} else {
"Fizz"
}
} else {
if is_buzz {
"Buzz"
} else {
s
}
}
}